Electricity in Texas: is 100% renewables feasible? Part I

by Peter Davies

Scenarios to understand how load, wind, solar PV and storage interact and whether a 100% renewable grid for Texas is technically feasible.

Given the stated policy of the new USA administration this might not seem the best time to explore whether renewable electricity generation can provide most of the USA’s electricity economically around 2030-40.  However, there is every sign that installation of wind and solar power in the USA is continuing. Texas has, not only plenty of wind and sunshine, but also by far the largest capacity of wind power installed of any US state. So Texas is a good place to start. If a 100% renewable grid won’t work for Texas then it won’t work anywhere else.

This article is the first of a pair and will cover non-financial aspects of the present and future Texas electricity grid. The aim is to present scenarios to understand how load, wind, solar PV and storage interact and whether a 100% renewable grid for Texas is technically feasible. The spreadsheet grid model used to analyse the scenarios is made available to enables checking of the findings of this article or investigation of alternative scenarios.

A second article will be based on a spreadsheet cost model providing ranges of costs. Future Texas price ranges are estimated from current prices, learning rates and other information.

Texas used more electricity than any other US state in 2015 – nearly 400 TWh (10% of the USA total) – followed by Florida and then California whose grids are half the size. ERCOT (the Electricity Reliability Council of Texas) manages more than 90% of the electricity in Texas. In this article the term “Texas” is often used loosely to mean the parts of Texas covered by the ERCOT grid. The ERCOT grid is largely isolated from the Western and Eastern USA grids and thus straightforward to analyse.

The simple spreadsheet model of the ERCOT grid will be introduced first. Then there is an outline of the current Texas grid, an analysis of the characteristics of Texas wind and solar PV (photovoltaic) generation and load and an exploration of scenarios with increasing renewable generation and storage. The same demand profile is used across all scenarios.

To keep things simple various low-carbon technologies are not considered here. The scenarios include no nuclear, solar thermal (using the heat of the sun to heat water to steam then used for generation), demand response (reducing demand when there is a deficit of renewable energy), hydro (Texas has only around 500 MW), biomass, offshore wind or rooftop solar. That does not mean they do not have a role to play, but to include them makes the analysis results more complex and more difficult to understand.

ERCOT grid model

The grid model and its manual are available to download from here. The grid model allows you to check the conclusions of this article or explore alternative scenarios.

Grid model scenarios are created by configuring peak demand, capacity of solar PV at 3 different locations and of total wind capacity. Other input options include grid battery storage size and losses and back-up gas turbine capacity. To investigate a 100% renewable solution renewable gas production, storage size and losses are included.  There is a supporting document explaining in some detail how to use the grid model.

The demand and renewables vary by hour based on the following public data for 2010 to 2012 :


The spreadsheet contains hourly load, expected solar generation and actual wind generation. It calculates the gaps in supply, the surplus generation, the effects of different tiers of storage and of back-up generation.

As the grid model uses only 3 years of hourly data the results should be treated as indicative rather than definitive. However, it should provide a first-cut estimate of the grid behaviour and is a good vehicle for exploring the interactions between load, renewable generation, storage and back-up.

Any specific issues or questions relating to the mechanics of the grid model should go here rather than on Judith’s site.

Texas Climate and Renewable Resources

Texas climate varies from arid desert in the West to humid and subtropical in the East, as in the global solar radiation map below.

The further west you go the better the solar power will be.

The Texas Panhandle region wind is part of the Great Plains wind system. Warm moist air from the Gulf of Mexico collides with frigid air from the arctic and strong winds blowing east off the Rocky Mountains giving wind speeds 2 m/s higher than the USA average.

The Current ERCOT Grid

The Texas 2016 grid consists of 46,000 miles of high voltage transmission, peak demand of 71 GW (which occurs in summer), average demand of 39.5 GW, and 570+ generating units capable of supplying 78 GW or more at the summer peak. It covers 90% of Texas load and supports 24 out of 27 million Texans. 2010 ERCOT summary data is here for comparison.

Capacity, Generation, Load Factor

The capacity at the end of 2016 and the generation in 2010 and 2016 are in the charts below.



Gas and wind equally have pushed coal firmly into second place while also providing a 33 TWh (10%) increase in generation between 2010 and 2016. Nuclear has made a stable contribution for some time.


The load factor for coal has fallen from 76% in 2010 to 59% in 2016. In the competitive Texas power market coal is losing out to cheap natural gas and wind power with PTC (production tax credit) federal subsidy. Both IEEFA and Brattle Group believe coal is economic and on the way out.

New generation

The ERCOT grid market is open to all generators. The generator pays for the spur to the nearest POI (point of interconnection) on the high-voltage transmission network, and for any upgrade to the POI substation equipment. ERCOT pays for any co-requisite upgrades to the high-voltage transmission network. The process goes through the four stages on the chart below with increasing chance of the new plant being built. Following connection contract signature, the new generation project has to pay a deposit before ERCOT will contract with suppliers for transmission line upgrades. The deposit is refunded once generation starts.

The December 2016 ERCOT interconnection queues contained the following proposed new generation.

The wind and solar PV on the queues dwarf the renewables already installed. Historically, 70-80% of wind projects in the queue drops out before installation. There’s less of a track record to judge solar drop outs. But with the PTC subsidy annual reductions and eventual expiry, the fraction of wind and solar projects dropping out now may be much lower than normal. Scenario 1 below shows that if everything in the current queues is installed the ERCOT grid would be more than 50% renewable generation.

CREZ Transmission Network

To support huge levels of wind and other power generation remote from the population centres ERCOT invested $6.7bn in a CREZ (Competitive Renewable Energy Zones) network upgrade. This supports transmission of up to 18GW of wind and solar power from the windy and sunny regions in West Texas and the Panhandle to the population centres in East Texas.

Texas variable renewables wind and solar PV?

Solar PV (photovoltaic)

ERCOT has only 500MW of utility solar PV installed at present, and most of this is in the less sunny regions close to the population centres rather than in Panhandle and West Texas areas with excellent sunlight. But there is a massive 13GW of solar PV in the interconnection queues! Recent Texas solar PV PPAs (purchase price agreements) are below 3.5 cents / kWh and exclude the PTC federal tax subsidy of 2.3 cents / kWh which is paid separately direct to the generator.   In other words the total cost is currently higher than 3.5 cents / kWh.

The grid model utility solar PV output assumes two-axis tracking of the sun i.e. during the day the solar panels always point at the sun. Thus generation is proportional to DNI (direct normal irradiance). Most new USA utility solar PV systems now use at least one-axis tracking. Two-axis tracking takes a little more space and costs a little more, for which the benefit is a higher CF (capacity factor) giving more revenue to the project.

The grid model assumes an ILR (inverter loading ratio) of 1.26, slightly lower than 1.31 for the typical recent USA utility solar PV system. This is the ratio of the maximum DC power output of the solar panels to the maximum AC power output of the inverters and grid connection.

The solar PV default grid model generation is based on 20% solar generation close to the eastern, less sunny population centres (averaging 27% CF) and 80% from the West Texas and Amarillo CREZ areas (34% CF). This results in an overall AC CF of 32.4% for solar PV for the grid model. The grid model is a little optimistic in the conversion of solar irradiance to AC power due to the method of averaging.

Let’s examine solar PV generation at noon.

50% of days Texas solar PV would generate at least 86% of the maximum possible AC grid power at midday. 75% of days it would generate at least 64% of the maximum. Clearly there is no generation at night and generation will be lower early and late in the day. Texas daytime solar PV power is reasonably, but not perfectly, reliable.

Wind power

West Texas is home to oil and gas drilling, and the rural population is typically conservative. But ranchers have embraced wind power to make a living out of land which might otherwise be only marginally profitable. Red-state Texas is the “Wild West of Wind” and installs wind power solely for economic reasons. Today it has nearly 21 GW installed, three times the installed wind capacity of Iowa which beats California in the race for second place.

The grid model uses actual hourly wind generation over all Texas between 2010 and 2012. Although individual wind farms do hit maximum rated power some of the time, the overall Texas wind power hourly capacity factor almost never exceeds 80% of the theoretical maximum.   The annual average wind CF factor for the Texas wind data is 32.5%, coincidentally very close to the solar PV CF of 32.4% above.

Most wind farms installed by 2010-12 were not in the CREZ zones which get the best wind.. More recent wind farms have mainly been installed in the CREZ zones. I have seen the results of a CF calculation based on actual hourly figures for 2010-2012 showing a wind CF of 49% in CREZ regions, but this more detailed data is not publicly available.

The trend since 2012 has been for US onshore wind turbines to have larger rotors, with a larger swept area (proportional to the square of the rotor diameter), without a corresponding increase in the generator size. Originally it was thought such turbines, designed for lower wind speed, could not cope with the turbulence of higher wind-speeds in places like Texas, but this has been shown not to be an issue. Clearly this has also contributed to higher CFs. From private correspondence with BNEF (Bloomberg New Energy Finance), the BNEF benchmark Texas onshore wind CF is also 49%.

At noon wind has more days with lower CF than with higher CFs. At midnight the higher CFs predominate. Thus wind power is more reliable at midnight than it is at noon. At 6 am and 6 pm the wind CF charts (not shown) are flatter as is the “all hours” wind output chart above.

Texas Load, wind and solar correlation coefficients

(Pearson) Correlation Coefficients
  Texas Load All Texas Wind Texas Solar
Texas Load 1.0 -0.23 0.39
All Texas Wind -0.23 1.0 -0.22
Texas Solar 0.39 -0.22 1.0

Correlation coefficients vary from 1.0 (e.g. high solar generation always occurs at time of high wind generation etc.) through 0.0 (wind and solar are completely independent of each other) through to -1.0 (high solar generation always occurs at times of low wind generation and vice versa).

During the day demand is highest, particularly on hot days when air conditioning is heavily used. Fortunately, as we saw above, solar is reasonably reliable at these times and in particular the grid model shows it is very reliable on hot days (no surprise here!) and this is reflected in the 0.39 correlation. With a negative -0.23 correlation wind will not help as much with peak daytime loads. It can’t be seen from the correlations, but night-time wind, though less reliable than daytime solar, does a reasonable job of meeting night-time demand.

The negative -0.22 correlation between wind and solar means that, while they can interfere with each other occasionally, high wind output tends to coincide with low solar output and vice versa. The inference is that a combination of wind and solar should provide a more consistent supply with fewer gaps than either wind or solar individually and the grid model will be used to check this. Similarly the CREZ network can be shared between wind and solar PV without large levels of interference between them. A CREZ network with the capacity of the larger of wind and solar capacities would thus avoid significant curtailment of either. For simplicity the transmission network is not explicitly included in the grid model.

Demand and Renewable Supply

This chart is based on the grid model spreadsheet set for 64GW of solar capacity, 60GW of wind, and load peaking at 71GW giving an average load of 39.5GW and matching average generation of 40GW.

Compare the blue (load) line with the purple (wind plus solar) line. On average, during the day there is excess solar generation until 6pm (the axis tick mark is before the number 18), followed by a big deficit until midnight and then a slightly smaller deficit until solar kicks in again. Additional wind and solar generation (creating a surplus) and large quantities of storage clearly have a role to play in minimising these gaps.

Remember that within the averages plotted on the chart there are large fluctuations as described above.

That’s probably as good an intuitive understanding of Texas load and renewable generation as charts alone can give us, so let’s now use the grid model to analyse some possible scenarios.

Scenario 1 – entire current interconnection queue gets installed

First we need to do some adjustments because of differing capacity factors.

The 26.7 GW of wind in the queues is likely to be installed mostly in CREZ regions with an expected CF (capacity factor) of 49%. This would be equivalent to 40 GW of extra wind capacity at the 32.5% CF of the grid model.   Add back 17 GW already installed at the end of 2016 for a total of 57 GW of wind at the grid model CF. This wouldn’t behave in precisely the same way as the real mixture of capacities and CFs, but will give a reasonable first approximation.

There is 13.7 GW of solar PV in the interconnection queues and 500MW installed, all with expected single-axis tracking with a lower CF of 26%. This is broadly equivalent to only 11.3 GW at the grid model CF of 32.4%.

Texas already has 48.4 GW of natural gas generation and there is another 18.6 GW on the queues, giving a total for this scenario of 67 GW.

Here are the grid model results :

Capacity Demand Coverage % (Surplus %)
Wind GW Solar GW No Storage Peak Deficit
57 11 54% (2%) 62 GW
0 11 9% (0%) 67 GW

Installing everything in the queues would move ERCOT to over 50% renewables generation with around 4% of the renewables generation (2% of average demand) as surplus.

On a simple view the unsatisfied peak load after subtracting wind and solar generation would be 62 GW. A high correlation between the air conditioning peak and a high level of solar generation is probably a safe assumption because they are likely both caused by hot sunny summer days. But with only three years of data it is not safe to bank on a minimum level of wind generation always coinciding with the summer air conditioning peak. Removing all the wind capacity changes the unsatisfied peak deficit to 67 GW. If all the gas generation in the queues gets installed too, there is exactly 67 GW of natural gas generation to cover the peak load gaps, although ERCOT would never operate on such tight margins.

It isn’t necessarily going to happen like this – some of the wind and solar capacity under investigation is bound to drop out of the queues before getting installed. But 50% renewable electricity is not necessarily that far off for ERCOT.

Interestingly, if all 57 GW of wind power (at 32.5% capacity factor) in the queues was installed it would break the back of the required wind capacity in the other scenarios below, at PTC-subsidy costs.

Scenario 2 – Maximum renewables with no more than 10% surplus

Each line represents multiple grid model settings to find the maximum percentage of generation (GWh) that has a surplus of no more than 10% of the renewable power generated.

Because the overall capacity factors for wind (32.5%) and solar PV (32.4%) just happen to be so similar (I didn’t fix it to come out like that!) then the same GW capacity for wind and solar will produce the same average GW actual generation. However, this generation will be at different times of day and with different seasonal variability.

Capacity Demand Coverage % (Surplus %)
Wind GW Solar GW No Storage 50 GWh Storage
0 52 39% (4%) 41% (2%)
36 45 60% (7%) 63% (3%)
45 41 64% (7%) 67% (4%)
54 37 67% (8%) 69% (5%)
60 31 68% (7%) 70% (5%)
66 25 67% (8%) 69% (5%)
75 0 56% (6%) 57% (4%)


Solar PV on its own can provide 39% of the total demand. Wind on its own does even better, satisfying 56% of demand.

A combination of both wind and solar does best. Without storage this potentially could provide up to 68% of total demand without wasting more than 10% of the renewables generation. Around a 2 to 1 ratio of wind to solar appears best, though the optimum is quite broad. This is the scenario Texas is naturally heading towards – plenty of existing and planned wind generation but with increasing amounts of solar in the ERCOT interconnection queues.

Storage and Grid Control

Grids require mechanisms to control frequency and voltage in the short and medium term, and also must ensure there is no shortage of supply to match demand at all longer time scales. In historical grids dominated by generators driven by coal or gas, the generators are rotating synchronously (at some simple fraction of the AC frequency) and have significant mechanical inertia (kinetic energy of rotation) which automatically damps fluctuations of up to a few seconds in frequency or voltage, whether caused by large short-term changes in demand or in supply. After a few seconds more (or less) input power to individual generators is supplied automatically through governors controlling medium-term stability of the electrical output.

Grids powered mainly by wind or solar do not have this automatic damping of short-term fluctuations. Although wind turbine rotors have mechanical inertia it is not synchronised with the AC frequency as the matching is done by electronic methods. Wind and solar PV farms can provide simulated inertia electronically but this requires them to be operating at less than optimum output levels most of the time.

Hourly load and generation numbers as used in the grid model hide any rapid changes in total renewable output within the hour and it is not possible to determine whether the back-up natural gas turbine generation can ramp up to required output immediately without undue thermal and mechanical stress. 50 GWh of grid battery storage would smooth renewable generation and demand and guarantee back-up generation can match demand to supply while minimising backup plant stress. Such battery storage would also enable short-term grid control and stability functions to be assumed by the battery storage systems, enabling wind and solar PV farms to operate at maximum possible output levels most of the time.

Solar contribution to reducing back-up capacity

The grid model also helps with the calculation of required back-up capacity. We have set the peak load to 71GW (for which the average load works out at 39.5 GW). The residual peak back-up requirement with 52 GW of solar generation comes down to 63 GW. You can use filtering on row 16 of the grid model spreadsheet to show that the 71 GW peak occurs during daytime solar generation, but that there is up to 63 GW of peak day demand between 8 and 10 pm with only a small dusk contribution from solar. So however much solar generation (without storage) there is it only shaves 8GW off residual summer peak demand

Let’s ask a different question. During the main solar generation period (say 9:00 to 16:00), what is the peak residual back-up requirement? This time the answer is 53 GW. Hot sunny summer days not only add 18 GW of air conditioning to the peak load but also guarantee a sufficiently high minimum solar generation capacity factor to satisfy the additional demand too.

Tier 1 grid battery storage

Texans like their trucks. The two most popular private use vehicles in Texas are trucks. For the whole of the USA cars occupy the four top slots before the Ford F150 truck gets a look in at number 5. Around 2030-40 most of the 9 million private vehicles in Texas could be electric vehicles with a range of 300 miles. Trucks requiring air conditioning would probably do considerably worse than 3 miles / kWh. 9 million x 100 kWh batteries represent 900 GWh of storage, dwarfing the 300GWh of ERCOT tier 1 grid storage required for scenario 3 below and certainly swamping the 50 GWh of storage suggested for this scenario. Such two-way power transfer is known as V2G (vehicle to grid) storage.

At a recent UK meeting I attended, arranged by the UK government, Eduardo Mascarell, head of V2G and Stationary Storage of Nissan Europe, forecast that vehicle manufacturers would allow V2G use with no reduction in battery warranty lifetimes. Nissan believes the additional degradation from V2G is small compared to normal use. He suggested that in exchange for V2G storage, grids might provide free charging of private vehicles, effectively providing free private travel for all local and some long-distance use.

Tier 1 battery storage needs to be efficient (good ratio of input to output energy) because it is used for significant fraction of demand (over 10%). Lithium ion or other battery technology is suitable as it has an efficiency of 80% or more, but it would be uneconomic if used to store more than a few hours of average load.

Scenario 3 – 100% renewables?

Is a 100% renewable solution technically feasible?

In the second part of this article we will look at the economics of a 100% renewable ERCOT grid, but will leave it to others to debate whether or not such a zero operational carbon solution is actually required.

The first use of the grid model in this scenario is to analyse how to cover over 90% of demand using a mix of renewable generation and relatively efficient tier 1 grid battery storage. The second is to work out how to close the remaining gap using much cheaper tier 2 storage.

155 GW of renewables split between wind and solar
(base for 100% renewable grid)
Generation Demand Coverage % (Surplus %)
Wind GW Solar GW No Storage 50 GWh Storage 100 GWh Storage 300 GWh Storage 94% Coverage Storage
0 155 52% (75%) 57% (70%) 62% (64%) 81% (41%) 700 GWh
65 90 80% (47%) 84% (42%) 88% (38%) 94% (31%) 300 GWh
75 80 82% (45%) 86% (40%) 89% (37%) 94% (31%) 300 GWh
85 70 84% (43%) 88% (39%) 90% (36%) 94% (32%) 300 GWh
95 60 85% (42%) 88% (38%) 91% (36%) 93% (33%)
105 50 85% (42%) 88% (38%) 90% (37%) 93% (34%)
155 0 77% (51%) 79% (48%) 81% (45%) 86% (40%) 8000 GWh


Providing 155 GW of capacity as all wind or all solar would be a complete waste. If you added 300 GWh of storage you could push the coverage up to 81% or 86%, while you can achieve 85% coverage with 95 GW of wind, 60 GW of solar PV and no storage at all!

And it is also hard to achieve 94% demand coverage using 155 GW capacity of just wind or just solar alone plus tier 1 storage. The more reliable solar would need 700 GWh of tier 1 grid battery storage. Wind would require 8,000 GWh (8 TWh) which would be hugely wasteful given that just 300 GWh of storage is enough with a sensible wind/solar mix.   This demonstrates that Texas wind and solar PV generation in the right locations complement each other well.

Is there enough suitable land in Texas for scenario 3?

The wind power density of the best locations in Texas averages around 2.5 W/m2. The average wind power required is 25GW. Thus 10bn square metres are required, which is 10,000 square km, or a grid 100km by 100km. The Panhandle and West Texas has many times this amount of suitable land.

Solar power in Texas requires about 5 acres per MW. An acre is about 4,000 square metres, so 1 MW is 20,000 square metres. 80GW of solar PV thus would require 80,000 (MW) x 20,000 (m2 per MW) = 1.6bn m2 or 1,600 square km, which would be a square 40km x 40 km. Again Texas has many times this amount of suitable land.

There is plenty of space on a wind farm to mount solar panels in between wind turbines so the required areas can overlap.

Tier 2 renewable gas storage

Though much cheaper per GWh stored, the proposed tier 2 storage is not very efficient during the charge and discharge cycle. So the gap it has to fill needs to be as low as possible to minimise total losses. 75 GW of wind, 80 GW of solar and 300 GWh of tier 1 grid battery storage would cover 94% of demand, leaving a 6% gap. Renewable generation would average 50GW while the load averages 39.5 GW, providing ample surplus (25%) to cover the tier 2 storage losses.

The deficit totalling 6% consists of gaps of one or more days up to one or more weeks. Based on the 2010-12 data the grid model shows that 14,000 GWh (14 TWh, two weeks of average load) of tier 2 storage would be sufficient. Although this quantity of lithium ion battery storage would be far too expensive, there are better solutions. The front runner is renewable gas chemical storage, described below.

Some options for long-term renewable gas storage for the Texas grid are :-


The efficiency figures are for power to gas and back to power. The low efficiencies of hydrogen and methane mean they cannot be used economically to fill gaps which are more than a small fraction (< 10%) of overall generation and supply. In this scenario tier 2 storage must fill a 6% gap which is comfortable.

The renewable hydrogen storage process uses electrolysis of water to produce stored hydrogen and discarded oxygen. The hydrogen is stored in tanks above ground or in underground salt caverns and used in fuel cells to provide back-up generation, though fuel cells are currently expensive for occasional (6%) use. As yet there are no hydrogen-compatible gas turbines.

The favoured option is renewable methane which also uses electrolysis of water. Hydrogen is converted to methane in a reactor using the industrial Sabatier process requiring a source of CO2 which could be stored exhaust from gas turbines when they provide backup power. The methane can then be used in expensive fuel cells or in cheaper standard gas turbine generators. All parts of this process have already been used at industrial scales, though not yet in an integrated long-term grid storage system.

The mixed methane and carbon monoxide process electrolyses water and carbon dioxide at the same time in the same solid oxide electrolysis cell at low temperatures and high pressures. Generation uses solid oxide fuel cells. Potentially the full process is 70% efficient – on a par with pumped storage hydro, and thus might also replace tier 1 battery storage. However, the technology is very early in the development cycle – much less mature than the renewable methane option preferred at this point.

Installation of sufficient wind, solar PV and tier 1 grid battery storage to cover 94% of demand cover will take a number of years. The mixed renewable gas storage process may thus be mature and economic enough by the time tier 2 storage is actually required.

A summary of the ERCOT grid configuration for the preferred renewable methane solution and the higher-risk renewable mixed gas solution is given below.

Component Renewable Methane Renewable Mixed Gas
Tier 2 storage efficiency 34% 70%
Wind 75 GW 72 GW
Solar PV 80 GW 75 GW
Tier 1 storage 300 GWh 200 GWh
Tier 1 inverters 60 GW 60 GW
Demand coverage (wind /solar/tier 1 storage) 94% 91%
Electrolysers 40 GW 30 GW
Gas turbine generation 40 GW
Fuel cells 40 GW
Tier 2 Storage 14,000 GWh 18,000 GWh
Losses + surplus 13%+14%=27% 6%+13%=19%


Reducing gas turbine back-up generation capacity

From the grid model “deficit” columns, scenario 3 (100% renewables) would seem to need 55 GW of peak back up gas turbine generation to satisfy 6% of total demand. But we have 300 GWh of storage and an average demand of 39.5 GW. If we can forecast in advance when peak gas generation will be needed, we can start gas generation earlier than absolutely necessary, charge the tier 1 grid battery storage in advance, and reduce the necessary gas turbine back up capacity by supplementing it with electricity from the batteries during peak times.

The grid model forecasting implemented is “perfect” in that it understands both future generation and load completely! It shows 30 GW is the lowest back-up gas turbine capacity that would achieve no supply deficit with perfect foresight – down from 55GW without using the battery storage. However, ERCOT will have to run the grid with real-world, imperfect forecasting, so an additional 10 GW has been assumed for a total of 40GW and a saving of 15GW. This clearly reduces the cost of the solution.


There are no obvious major technical show-stoppers for a 100% renewable electricity grid for ERCOT using wind, solar PV, tier 1 battery storage, low-risk tier 2 renewable methane long-term chemical storage and gas turbine generation back up.

75 GW of wind and 80 GW of solar PV at 32.4% CF, plus 300GWh of tier 1 battery storage can satisfy 94% of demand. The remaining 6% requires 40GW of electrolysers, Sabatier process plant, 14,000 GWh of methane storage and 40 GW of gas turbine backup generation. The required renewables over-generation of 27% of average demand covers storage losses and surplus (wasted) generation.

Part 2 of this article will examine the costs of such a solution and discuss some regulatory issues – can it be economically feasible?

Biosketch: Peter is a mature, part-time PhD student in the condensed matter theory physics group of Imperial College London.  He uses Schroedinger’s equation to model nano-scale capacitor technology to understand whether it can be developed for use in challenging environments such as jet engines and electricity grids.  In his youth he studied physics, maths , electrical science and computer science at Trinity College Cambridge.  He worked for IBM UK for over 30 years in IT systems design at customers including banks, government departments and energy companies.  Peter’s interests include energy and particularly electricity grids.

Moderation note:  As with all guest posts, please keep your comments civil and relevant.

206 responses to “Electricity in Texas: is 100% renewables feasible? Part I

  1. Pingback: Electricity in Texas: is 100% renewables feasible? Part I – Enjeux énergies et environnement

  2. Reblogged this on Climate Collections.

    • David Springer

      It’s possible to do it. However, the definition of feasible is “possible to do easily or conveniently”. It’s not feasibly possible to do it today. Maybe in the future with better/cheaper technology but today its simply not easy or convenient.

  3. Pingback: Electricity in Texas: is 100% renewables feasible? Part I – NZ Conservative Coalition

  4. Its not the annual totals that count. Its the daily min/max of solar/wind.

    How many GW of capacity do you need when solar+wind approach zero on a particular day and who pays for the all the standby capacity to sit around.

    • For example, Germany needs lots of coal to make the grid function when solar+wind approaches zero.


    • The customers pay and why should they pay for wind and solar that causes the total cost to be much higher, real costs or tax cost, we pay more for wind and solar with no benefits. It really makes no sense.

    • sunshinehours1, the results from the grid model are calculated on an hourly basis and supply has to meet demand, for all hours in the years 2010 to 2012. Have a play with the grid model – you can use the data filters to identify the hours when wind and solar generation are at their lowest, then see what proportion of the demand for those hours can be met from tier 1 battery storage and what has to be met by back up gas turbine generation.

      Specifically very low solar generation does not coincide with peak days because these are caused by increased air conditioning load on hot sunny days. For that reason, and because scenario 3 has batteries too, the estimate is that only 40 GW of back-up gas generation is required (or 30 GW if you could predict the future perfectly).

      Gas turbine generation back up is used only a small fraction of the time, but has to be paid for by users who require electricity during the times of low renewables generation. Gas turbine generation has the lowest capital costs. Some industrial users may be in a position to make savings by reducing their load at those times.

      • Peter Davies” “Some industrial users may be in a position to make savings by reducing their load at those times.”

        UK experience in DSR auctions suggest there are very few industrial users who can tolerate the disruption to their businesses by getting involved in this nonsense unless you compensate them sufficiently to cover the trouble and expense of installing back-up diesel generators.

        German experience suggests you need to exempt your industrial users from having to participate in green fantasies if you don’t want to risk tanking your economy.

        Nobody wants to play this silly game, which is why the only policy options available are compulsion or, if voluntary, stuffing participants mouths with gold (stolen from tax/rate-payers/consumers).

      • ERCOT has various demand response products offered to commercial and industrial users who can reduce load rapidly. An annual report can be found at http://mis.ercot.com/misapp/GetReports.do?reportTypeId=13244&reportTitle=Annual%20Report%20on%20ERCOT%20Demand%20Response&showHTMLView=&mimicKey . If my reading of it is correct, ERCOT have a few hundred MW they can call on in normal circumstances, and have agreements to share out the pain over participants. Page 4 says they got 927MW of demand reduction in a hurry when a large generator tripped, though the loads were able to be scheduled back online within a few minutes once the fault was cleared.

    • Wind and solar could be used to charge high capacity batteries to be plugged into the grid during peak usage to ease the burden. This would take the huge swings out of play and give a stable output. As for 100% solar/wind/renewables go, It’ll never work.

      • Maybe “It’ll never work” is a bit too strong. A more reasoned opinion might be “It might work”. For a guy with Tech in his name you seem oblivious to the exponential rate of change that technology can physically alter reality. And when I say ‘reality’ I’m including all life forms everywhere on the planet. Right now we are terraforming the planet without a blueprint. Currently the biosphere has had a few bumps and bruises but nothing too dramatic. Let’s hope our technology can improve to the point we can avoid serious problems.

      • Take a look at the grid model which uses real hourly data from Texas between 2010 to 2012. Have a play with changing the design, then decide whether or not it will work!

  5. Thanks for a very interesting essay.
    RE: two-axis tracking
    Just using single axis (E-W) really helps in late day power production and should be the default design for utility scale systems I hope.
    I have run tests with my system and I could have used 20% fewer panels with just one-axis (E-W) tracking. Looking at the available technologies available to perform tracking on a residential scale is slightly better than break even (at best) over the projected life span of the array but few people can take advantage of tracking systems unless they have ground mounted systems. One of the engineering strong points of solar is no moving parts and adding tracking diminishes that simplicity and reliability for small systems unfortunately.

    If any grid wants to really aim for 100% RE there really needs to be both a interactive demand response system and intelligent load management technologies like smart appliances and climate control. Things are moving in this direction because that’s what technology wants. We are following not leading these trends.

    • jacksmith4tx : “Things are moving in this direction because that’s what technology wants.”

      The last DSR auction in the UK required a price of £45/kW, and even at that level did not meet the capacity target. Last year’s rounds required a price of £27.50/kW on average – over 80% of which was switching from grid to local diesel generation. Again, the capacity target was not met.

      In the latest auction only ‘turn-down’ DSR was permitted (no generator substitution) – hence the price hike.

      An evaluation of the UK DSR scheme commissioned by the Department of Business, Energy and Industrial Strategy (BEIS) concluded: “it will make only a limited contribution to its objectives of increasing security of supply”

      The only trend I see is ever more expensive electricity.

    • OK. You are right about ‘Never”. We will have to develop alternate sources that meet our needs, but It’s a ways down the road.

  6. West Texas is home to oil and gas drilling, and the rural population is typically conservative. But ranchers have embraced wind power to make a living out of land which might otherwise be only marginally profitable.

    They only did that because of the tax credits and subsidies that robbed the taxpayers to pay for it. We elected Trump to stop this criminal activity.

  7. Are the capacity factors at the generator terminals (or at solar panels)?
    Are auxiliary loads included in capacity factors?
    Do capacity factors account for inverter losses as a result of high summer temperatures? Also impacts solar panel degradation.

    Reported data is a little wobbly on whether or not real world considerations are actually included. Appears in many cases capacity factors are not reported at the high-voltage grid connection.

    The point is you may be a bit optimistic by a few percent on what actually makes it to the end user.

    Also, while Texas is big, wind turbines and solar panels remove land from use while also adversely impacting wildlife. Might want to include some sort of deduct for amount of land realistically available (e.g. remove national, state & local grasslands, refuges, unsuitable land and fact some land owners simply do not want anything on their land. Few counties in Kansas have banned wind turbines because folks consider them a monumental eyesore – which they are.)

    Finally, ignoring financial practicality is kind of like saying we should generate all power with nuclear energy. Yes we could, but no one could afford to pay their electric bill.

    • kellermfk, The capacity factors used are AC capacity factors, so are measured after auxiliary loads, inverter losses, and most importantly the “inverter loading ratio” which means the inverter inputs are deliberately overloaded at times by overconfiguring the solar PV panels.

      Treat the model as indicative rather than definitive – it is indeed likely to be few percent out. As an example transmission losses are not included.

      There will be a follow-up article shortly on the economics.

      • Just out of curiosity, why are you so sure all the aux. loads and losses have been included?
        Capacity data reported by California and several Federal agencies is generally at generator terminals (wind turbines) or meters not located on the high voltage side of the grid – shows up when obscure and odd sounding footnotes are fully unearthed. Almost looks like renewable capacities are being inflated somewhat for PR purposes.

        Also, not entirely clear that power needs when not operational (including curtailments for unneeded power) are being included (e.g. freeze protection for wind turbines, which is a concern out here on the Great Plains where winters are long and hard). Further, with lots of panels & turbines, unexpected maintenance issues invariably arise.

        Power plants tend to be cantankerous from time-to-time and do not happily go along with rosey class-room expectations.

      • The ERCOT grid analysis has a time/generation profile @100% renewable energy much like California’s infamous Duck Chart profile, which leads to dumping excess solar power in late afternoon as Nat Gas has to kick in to bail out the renewable energy grid (wind typically doesn’t generate until early hours of mornings). So I would say this is an outsider’s analysis of the ERCOT grid and should not be taken as too realistic. See the profile data table marked “Demand and Renewable Supply” above for the “Duck Chart” profile. Renewable energy is redundant energy almost by definition. But none of the redundancies are shown in the above non-financial profile. Analysis is sort of an IT guys view of the ERCOT grid that I would not give too much credence to. By the way, where are his assumptions disclosed in his analysis? The numbers are no better than the assumptions. Garbage in, garbage out.

      • The history of the grid model is that it was originally run as a modification to a FORTRAN program (not a spreadsheet) written by Gene Preston who is a transmission adequacy consultant (i.e. a professional grid modeler), lives in Texas and works with ERCOT from time to time. He kindly ran a model for me with peak load capacity of both wind and solar and 560 GWh of battery storage, which showed only a 3% gap. But he didn’t have time to make the tweaks I needed, and his source data was not public. So I implemented his code as a spreadsheet instead with various tweaks and sourced with public data.

  8. There are no obvious major technical show-stoppers for a 100% renewable electricity grid for ERCOT using wind, solar PV, tier 1 battery storage, low-risk tier 2 renewable methane long-term chemical storage and gas turbine generation back up.

    It will cost a lot more, it will be much less reliable, it will not help anything, otherwise, it is ok, NOT!

  9. Curious George

    Peter, I am unsure what the Tier 2 renewable gas storage might be. Please elaborate.

    • Curious George

      I mean to say that your numbers feel rather optimistic. Are there any working installations? Same regarding the land use, where you consider a solar nameplate capacity. Running out of land seems to be a problem only when considering landfills.

    • CG, the reference is to the German Etogas pilot (5mw IIRC). I dissected it a while ago over at Euan Mearns blog Energy Matters. Goodle methane storage will take you there at about the fifth link. At best 31% rte (ruinous), which is why this guest post analysis correctly says secondary, and small total storage. The technical problem is the primary storage.

    • George, expanding on Rud’s response….

      Specifically the renewable gas storage comes into its own for gaps in supply or renewable power more than a day long which can be up to a few weeks. They aren’t very frequent, but they do exist and a reliable 100% renewables grid would have to handle them.

      To cover the 18% gaps in direct renewable supply for Texas with the specific wind and solar capacities needs a total of 14,300 GWh (14 TWh) of storage based on the grid model 2010-2012 figures. 14,300 GWh of costly but relatively efficient lithium-ion battery storage would cost far too much. 18% of demand going through cheap but inefficient (33%) renewable gas storage would need an additional 54% (3 x 18%) of excess renewable generation on top of the renewable generation used directly to meet demand and that would increase costs somewhat (though not as much as trying to do it all with battery storage).

      But if you split it into 300 GWh of battery storage and 14,000 GWh of renewable gas storage then 2/3 of the stored power (12% of supply) goes through the much smaller quantity of more efficient battery storage, leaving only 6% through inefficient renewable gas storage, so the additional renewable generation you need to make up for the storage losses is much reduced, while the limited battery storage capacity (300 GWh instead of 14,300 GWh) is now much more affordable.

      There aren’t any installations which cover the whole “power to gas and back to power” process as yet, and most likely none will be required much before 2030. For renewable methane the three separate parts are a) electrolysis of water to produce hydrogen, b) combining hydrogen with CO2 to produce methane (Sabatier process), c) storage and subsequent use of methane in gas turbine generators when required. Rud provided a reference to the first part in medium-scale production and the second and third parts are well-proven on an industrial scale. So it’s a low-risk approach to filling infrequent but long gaps in renewable supply.

      • Why bother with renewable methane? I assume this is taking place in the far future, you could inject hydrogen into an old gas field, or use a salt dome cavern.

        While I’m at it, I suspect that if you cover a very large area with wind turbines you will have a regional impact on wind speeds.

        And you had better plan for a January snow storm. See how that model works when the panels are covered with snow, the wind stopped blowing and it’s 5 degrees C below zero in Dallas.

    • George, the article calculates the land required for solar (1,600 sq km) which is a fraction of that required for wind (10,000 sq km).

      There is an NREL chart in the grid model manual showing many more times the land area being available for wind than is required. Direct link is https://www.dropbox.com/sh/oaco4isfl4dbkb2/AADfrbVS1bYStupKNGbj_jTra?dl=0&preview=Texas100%25RenewableGridModelManual.v1.0.pdf . See section 5.3.

  10. Finally, ignoring financial practicality is kind of like saying we should generate all power with nuclear energy. Yes we could, but no one could afford to pay their electric bill.

    No one is going to afford to pay their electric bill with wind and/or solar, or their bill will be low and they are not going to afford their tax bill to pay for it.

    Either way fossil fuel and nuclear are the only correct path for now and the foreseeable future.

    Nuclear, with multiple plants built with similar or identical plans, like done in France would give us power even lower cost than fossil fuel, if not soon, after it really is depleted. Wind and Solar have way too many problems to compete in an honest marketplace. Maybe, in some faraway places, but not for major US or World cities.

    • Seems unlikely nuclear will beat natural gas & coal in the US for a long time – we have lots of both. The capital cost of nuclear is just too high because of being so heavily over regulated by the NRC. That disadvantage cannot be overcome by standardization, as demonstrated by debacle with Westinghouse. However, renewables cannot compete either, absent subsides and forced mandates.

  11. PD, interesting to encounter you again in a non EEStor capacitor context. Greetings. Mature student of condensed matter physics at Imperial was a tell. EEStor has not turned out well, to say the least—just as I predicted back then.
    Interesting and complicated renewables grid analysis by you here now. There are a couple of simple difficulties you skim over that make your hopeful conclusion technically suspect, imho.
    1. Dedicated Grid storage on the scale required by your analysis assumes technology that does not exist yet, either technically or economically (your coming part 2). I have been active as an inventor, investor, or executive in energy storage since ~1994. Very tough, and see no path to possible needed breakthroughs EXCEPT Fisker Nanotech for EVs, guest post here concerning Vehicle Decarbonization 11/2/16. Dunno what that might mean for the grid, as insufficient technical info yet available (patent apps not yet published). Covered the grid storage waterfront in a guest post here titled Intermittent grid storage 7/1/15.
    2. Positing electric vehicles as a grid storage distributed solution doesn’t work, either. You see, if used for grid storage then they cannot at the same time be used as vehicles. Rather awkward for the vehicle owner. And vehicles parked at night, charging while owners sleep, are also useless for solar storage.
    KISS principle thinking.
    Stanford’s Prof Jacobson has published similar 100% renewable calculations, based on similar plus addtional fantasies and easily disproved.

    • Rud, you also wrote a comment on “Electricity in China” but maybe missed reading the author bio that time!

      EOS sell grid storage DC batteries right now for $160 / kWh, projected to last 15 years or 5,000 cycles (which would take more than 40 years based on scenario 3 use). https://www.eosenergystorage.com/products/. Those prices do not include grid inverters and other equipment but are substantially lower than anything available a few years ago. And Tesla’s gigafactory is gradually coming on stream. More on this in part 2.

      Private vehicle use is quite limited – utilisations are typically well below 10%, detracting very little from use as grid storage batteries. Solar power peaks at midday rather than at commuting times and if all parking places (home, office, shopping, leisure) are equipped with V2G connections it would matter little where the vehicle is charged and where discharged . That’s not to say it will definitely happen this way, but it definitely cannot be ruled out! See http://nissaninsider.co.uk/nissan-and-enel-launch-vehicle-to-grid-trial/

      Further, in the 2030/40 timeframe, when the owner gets bored after 7-10 years and replaces the vehicle those same batteries can then be “re-purposed” as cheap dedicated power storage. Nissan are already active in this space.

      • Curious George

        An average U.S. household consumes about 30 kWh per day, let’s assume that a half of it would come from a 15 kWh storage in EOS batteries. As these batteries have to be replaced after 15 years, that would add $160 per year to an electricity bill – but I am jumping the gun, you plan to analyze costs later.

        How to re-purpose old batteries is not immediately obvious. Probably a worthwhile research project.

      • PD, thanks for the EOS link. Went immediately to their tech spec for this zinc based startup. RTE 75%, cycle life ~10 years (their estimate, usually with favorable usage spin). Probably wont fly economically, but will wait for your analysis on that.
        The repurposed vehicle battery after vehicle life argument has been around for at least a decade of energy storage conferences I attend. Devil is in details like exponential decline in capacity/efficiency, control electronics, cooling systems. Doesn’t fly. Battery usually declared dead at 80% of original,capacity. Because the remainder disappears quickly with continued use.

      • CG, the grid model shows that direct supply of renewables to meet the load of over 80%. Hence less than 20% would come from the batteries and renewable gas storage, with less than 15% coming from the batteries.

      • Rud, EOS says “projected to last 5,000 cycles for a 15-year calendar life”. The 15 year life appears to be calculated from full daily cycling and a 5,000 cycle life. For the Texas grid model scenario 3 each full cycle averages 3.5 days, so you would expect much longer life than 10 or 15 years. I’ve emailed EOS for clarification. Let’s hope they respond.

        See https://www.fhwa.dot.gov/ohim/onh00/bar8.htm

        The average American drives 14,000 miles per year and presumably has their own car to do so many miles. Assume 3 miles/kWh (our Leaf around London gets 3.4 miles/kWh and on long journeys with little stop-start gets over 4 miles/kWh). That’s 4,666 kWh per year. With a battery of 100 kWh (as in some top-end Tesla models) that is 47 full cycles per year. An average vehicle lifetime of 10 years would use 470 full cycles.

        See http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

        In some tables you have to be a little careful to multiply the number of (partial) cycles by the DoD (depth of discharge) to get comparable figures for the lifetime expressed in full cycles.

        If the EV is normally charged only to a voltage of 4.1 volts then you get 80-85% capacity out of it. It can be charged to 100% in advance on the few occasions where you really need the range to be maximum. 80% normal maximum charge with manual override is an optional setting on our Leaf (which I will now start using!) Around town we recharge it when it drops below 50% capacity, so most of the cycling is between 80% and 50% (assuming zero charge on the display really does mean the battery is actually empty!!) With 100 kWh battery capacity the discharge and normal overnight charge rates are going to be less than 0.3C, causing very little stress on the battery apart from the occasional fast charge on a journey over 200 miles.

        From figure 6, the 80%-25% @20 degrees C case gives well over 4000 partial cycles equating to 2,200 full cycles, even with current technology. Using 470 of these in an EV leaves plenty of spare cycles for grid use afterwards at an excellent discount on the original battery price! It may depend on whether the EV battery would be kept cool in summer in Texas by a combination of air conditioned garages and in-car cooling.

      • Rud, mentally delete the bit above about whether batteries can be kept cool most of the time in Texas EVs. If Texas is too hot for good EV battery life time then “repurposed” EV batteries from other, cooler parts of the USA could provide Texan grid storage. The two locations need not be related.

      • Curious George

        “direct supply of renewables meets the load of over 80%”. That’s probably a statistical number. If your battery only supplies 20% of your needs, you get a short blackout once a day, on average.

      • CG, you said ‘“direct supply of renewables meets the load of over 80%”. That’s probably a statistical number. If your battery only supplies 20% of your needs, you get a short blackout once a day, on average.’

        It is an hour by hour analysis for three years of actual Texas data using a spreadsheet, not a statistical calculation.

        Specifically, in the model renewables generation directly met over 80% of the kWh (or MWh) of electricity demand. The batteries, renewable gas storage, and back up gas turbine generation were then sized to ensure that the other 20% of kWh were met. Using the spreadsheet enabled the system to be sized to meet all demand for every single hour of the three-year period (2010 to 2012). There are cells in the model on a particular row that report on the deficits and others reporting on surpluses. These two are not netted off against each other at any point. All deficits need to read zero before the system can be said to be the minimum size to meet demand. If there had been a gap (non-zero deficit) anywhere then one of the system components (renewable generation, storage, back up) could have been increased until there was no gap left!

        Further details are in the grid model manual https://www.dropbox.com/sh/oaco4isfl4dbkb2/AADfrbVS1bYStupKNGbj_jTra?dl=0&preview=Texas100%25RenewableGridModelManual.v1.0.pdf

        Have a play with the grid model for yourself! That’s the best way to understand how the approach works. And it could be fun too! It’s designed to be user-friendly with only input fields changeable and highlighted in yellow so they stand out.

      • Curious George

        I need a reliable electricity. A power that does not get interrupted after one cloudy, windless day. Or two, or a week. The spreadsheet seems to work with averages, not with worst cases. I want my power on in the worst case. I am willing to cope with 4 hours of power interruptions a year – not with 87 hours (a 99% reliable supply). My freezer only keeps food frozen for 5 hours.

      • Peter,

        I tend to agree with Rud on the practicality of using vehicle batteries for storage. Say it gets fully charged while sitting in the garage or parking lot at work. I drive it home and at night it discharges to make up the gap between load and wind/solar output. What happens to my truck when it is time for me to head into work the next morning?

    • I have to agree about using EV to backup the grid. Looking forward I can foresee much better integration with smart bi-directional charger/inverter designs. Nissan had a system deployed in Japan that uses a Leaf and a smart grid controlled inverter/charger design. They just announced a new system in the UK.

      As a Volt owner I don’t see the advantage of adding discharge/charge cycles to the most expensive part of my car.

      • Would your view of V2G (vehicle to grid power transfer) change if GM do what Nissan will and encourage V2G use with no battery warranty penalties?

      • I am very much in favor of V2G but I think my battery is a little too small to make the economic case. I would still hesitate to add more cycles to my battery pack because it would shorten the usable life of the battery. My answer might be different if I had a 500+ mile battery range and a 20yr warranty to begin with. The numbers look a lot better if the battery starts out with 60-100 KWH of capacity, 15yr warranty and the duty cycle is fairly moderate. Another factor would be the peak demand pricing. If I’m sitting on 60KWH of energy and the grid price spikes to 10x I would happy to be a V2G client.

      • Follow up to V2G.
        “New research from the Hawaii Natural Energy Institute at the University of Hawaii at Manoa. The extra cycling that accompanies use of an EV battery for grid balancing, even when at constant power, reduces EV battery cell performance significantly.
        To be more specific, the use of an EV with V2G tech could reduce the working lifespan of an EV battery pack to under 5 years time, according to the new work.
        The team concluded that a V2G step twice a day increased battery capacity loss by 75% and the resistance by 10%. This step once a day accelerated the capacity loss by 33% and the resistance increase by 5%. Forecasts based on the measurement results indicated that that V2G implementation would decrease the lifetime of the battery packs to under 5 years.”

        I’m sure there is other research that shows less degradation but using your (expensive) car battery for anything except emergency backup seems problematic.

      • jacksmith4tx, thanks for the link to the Hawaii Natural Energy Institute article. It is saying 33% faster EV battery degradation and 5% faster increase in resistance for 1 V2G cycle per day.

        Let’s go with their numbers as there aren’t that many out there.

        Cells O9 and Q9 of the grid model spreadsheet show that 11.8% of demand goes through the tier 1 batteries of 300 GWh. Assume that all of the 300 GWh of tier 1 storage is supplied by V2G-connected EV batteries.

        For the 71 GW configured peak load the average model load is just under 40 GW, and each day 40 x 24 = 960 GWh are supplied. 11.8% of this is 113 GWh per day through the batteries. We have 300 GWh of batteries, so V2G cycles the batteries once every 300/113 days = 2.6 days. Thus the increase in degradation is 33% / 2.6 = 13% from using the EV batteries for V2G, and the internal resistance increase (?) is 5% / 2.6 = 2%.

        The article estimate for total Texas EV battery capacity was 900 GWh. If 600 GWh rather than 300 GWh participated in V2G then they would get cycled on average once every 4.6 days (not double, because the additional 300 GWh increases coverage of demand from 94% to 96%), so the increase in degradation drops to 7% and 1% respectively.

        If the Nissan statement in the article is right then the deal would be free EV travel, maybe excluding fast charges on very long journeys. Lets say this was for 10,000 miles / year (out of the 14,000 miles / year average in USA). At 3 miles / kWh this would be 3,333 kWh free electricity at, maybe 8 cents / kWh for a total of $267 per year.

        So the deal is something like 7-13% faster degradation and negligible faster increase in internal resistance of your EV battery in exchange for $267 of free electricity per year, while retaining full EV battery warranty cover. The other significant benefit is that none of the V2G / charge points (except fast chargers on freeways) outside the home need a payment mechanism.

        What do you think?

  12. There are no obvious major technical show-stoppers for a 100% renewable electricity grid for ERCOT using wind, solar PV, tier 1 battery storage, low-risk tier 2 renewable methane long-term chemical storage and gas turbine generation back up.

    Yep, we could do it, but, we could not afford to do it. We elected Trump to stop the criminal subsidies and tax credits so we do not need to do it.
    Consider, people have much more to pay for than just “feel good junk that does no good”!

    • Roger Knights

      As Monckton said, ^If it’s affordable, it’s inadequate, and if it’s adequate, it’s unaffordable.^

  13. If any grid wants to really aim for 100% RE there really needs to be an effort for the people to move somewhere else before grid totally crashes. They are living in a really bad place at a really bad time. There may be rare exceptions to this, but not likely here in Texas where Fossil Fuel is King.

    • Properly locating the solar installations would be important because every year someplace in Texas gets pounded by a hundred-year storm. I was working in Fort Worth just after the area had been pounded by softball sized hail, killing several people at the factory I was working for, killing some caught out in the open, and destroying thousands of cars. Any large solar installation would have been totally obliterated.

    • Pope.

      In all seriousness…why do I need a grid if I can generate and store everything I need from my own property?

      • You would like (and so hopefully share in the costs of) the emergency services to pick up the phone, power their ER. For traffic lights to work, Frozen food distribution centers to stay cool. Grocery stores. Gas station pumps and services. Metro rails. Elevators. The internet. The industries that make all the stuff you use…

      • wijnand2015
        You just described a EMP event not a renewable energy crisis. Get a grip..

  14. Thanks for the detailed, informative and entertaining post.

    And here is where chaos enters the picture El Capitan. Hurst phenomenon guarantee there there will be clusters of events and rapid and extreme shifts (means and variance) between climate regimes. This will shift power supply under a 100% wind and solar scenario. It is utterly unpredictable but – on past behaviour – the next global climate shift is due in a 2018-2028 window. The natural variability of climate – even on short time frames – would suggest a potential for shortfalls in supply.

    Although a 100% wind and solar supply is technically feasible – the wisdom of putting all eggs in one basket is questionable. A 21st century energy transition is required for reasons that have little to do with global warming. It is economic reality that alternative technologies will continue to decline in cost and gas and coal will increasingly come up against supply and demand constraints in the global race to 15TW. Cheapest power maximizes critical global economic development.

    I am all in favour of the cheapest systems. This seems to require discounting of the moral panic of global warming. Changing the atmospheric composition has implications for ocean and atmospheric circulation, terrestrial hydrology and global ecologies. But the energy budget is at the base of the human ecology with far reaching implications in other dimensions.

    It all suggests that a optimal mix of energy sources – including wind and solar – is the rational option. The optimum mix is still up in the air.

    I’d suggest that a power to gas strategy is in the frame – along with fast neutron nuclear reactors.


    Hydrogen can be produced with excess supply of electricity – the technology is under intense development globally – and injected directly into gas lines or used in fuel cells and for fertilizers etc. Or converted to methane and liquid fuels for mobile uses. A system deliberately geared to excess supply – rather than load following – would be solid as a rock.

    Electric cars are fabulous – and they would tend to shift demand to off peak times. But I suspect that a linear generator range extender using some sort of fuel and a smaller battery pack would alleviate ‘range anxiety’.


    But on the bigger scale – would 100% wind and solar give us range anxiety?

  15. T. Boone Pickens tried to build the worlds largest wind farm in Texas a few years ago. It went bankrupt. As I recall Pickens blamed the failure on a lack of transmission lines. Does anyone have a comprehensive post mortem analysis of this failure?

    • Well maybe not comprehensive but some input anyway:


      • Thanks ordvic. I really didn’t phrase my original question too well. I had researched the trouble Pickens was having awhile back, all I found was superficial: lower NG prices undermining the venture, transmission issues, etc. There’s a few people here who are on the leading edge of the applied science and engineering for alternative energy build outs. I’m curious about the untold story to Pickens venture, relative to transmission difficulties from those who may be able to elaborate. I was never been able to ascertain if his problems were primarily a result of political red tape; technological hurdles; unexpected cost overruns caused by myriad reasons; or all the above.

      • Yes, It does seem like there is more to the story since T Boone was so enthusiastic at first.

  16. “Texas is the “Wild West of Wind” and installs wind power solely for economic reasons.”

    What a novel concept.
    Count moi as in favor of wind and solar when installed solely for economic reasons.
    When installed for gubment subsidized virtue signaling, not so much.

  17. The Sabatier reaction is CO2 + H4 yielding CH4 + H2O and heat. That would be 70% efficient, but making the renewable H4 to use is about 43% efficient I believe.

    • Efficiency only matters in terms of cost per unit – higher efficiency lower cost per unit. If you have a resource going to waste – as you do with wind and solar – then it matters only that you can sell the CH4 – plugged into the LNG infrastructure for transport – at a price high enough to be profitable and low enough to be competitive.


      • Robert, I am a big fan of using excess power to produce something of use instead of shutting down equipment with useful life remaining, but it is a bit like the vultures showing up to take advantage of someone else’s mistake.

    • CaptDallas. Making renewable H2 can be roughly 70% efficient, but then you have to burn it in a gas turbine at around 60% efficiency, giving the overall figure of 43%.

      The heat released in the Sabatier reaction reduces the energy obtainable from the methane output when compared to that obtainable from the hydrogen used as input. That’s indeed why the renewable methane cycle is less efficient.

      One reason the renewable mixed methane / carbon monoxide cycle can be 70% efficient is that the mixed electrolysis reaction is heat neutral – the heat released to get methane from hydrogen is absorbed by the hydrogen electrolysis to makes that part much more efficient – by design.

    • CD, did that math earlier for Energy Matters. Electrolysis makes 4% of commercial hydrogen today. Theoretical max efficiency is 88%, real world today is ~75% (btw, a typical theoretical/real ration ratio– best most expensive mono Si solar cells are similar). Significantly better than you supposed. Feed that hydrogen into the EtoGas published conversion to methane numbers, and the resulting methane is ~50% energy efficient based on their large scale pilot plant near Stuttgart (worse that Fischer Tropsch gas to liquids at Shell’s Pearl in Qatar at about 61%). Now, to regenerate electricity feed the synthetic methane into a 61% efficienct brand new CCGT. 0.5 * 0.61 is at best 0.31 round trip energy efficiency. Which is why PD’s system concepts try to minimize methane secondary storage. Ruinous from an energy EROEI perspective. That idea (worth your exploring, I am not a hard core believer) says anything less thn 4:1 is ruinous. EtoGas RTE is 0.3:1. Food for thought.

  18. There is a significant amount of power generated in co-generation plants that supply steam for industrial purposes to refineries and chemical plants. For example, one of our plants has four 187-MW gas turbines that can produce over 2 Million lbs per hour of high-pressure steam, along with a steam turbine that can produce 150 MW to handle swings in demand. I do not see how one can replace these plants with 100% renewables, and one must account for the fact that run 24/7.

    As a chemical engineer, and I can not imagine building a plant to convert perfectly good hydrogen to methane. You can burn hydrogen in gas turbines with sufficient steam dilution.

    • Robert,, co-generation is an issue. With increasing EV penetration the required refinery penetration will reduce, but there still needs to be a solution for chemical plants.

      My understanding is you get hydrogen embrittlement in normal gas turbines if fed with hydrogen. Presumably dilution with steam only slows it down, not stops it – you may care to comment. There were some DoE-funded research projects on hydrogen use a few years ago but there seems to be no output from them and the area has gone very quiet. I assumed the idea died a death, but perhaps it doesn’t matter so much if the plant is used only 6-10% of the time.

      • Peter, the problem with burning pure hydrogen is the flame temperature, not metal embrittlement, IIRC.

        This was an issue for the coal gasification plants that produce synthesis gas (a mixture of hydrogen, CO, and CO2) for power production. The carbon capture part required shifting the CO to CO2 and hydrogen, with subsequent removal of CO2. This produces a relatively pure hydrogen stream for use in a gas turbine. While it is true there are no gas turbines currently running pure hydrogen, there are plants that run some amount of hydrogen with steam dilution. The other issue with hydrogen is the NOx production due to the high flame temperatures, but again, steam dilution helps to reduce that problem. We actually looked at this technology as replacement for high-cost natural gas before fracking reduced the price of natural gas. :)

        I suspect if hydrogen storage became common that the manufacturers would find a way to handle it in gas turbines. Here are several presentations on hydrogen burning in gas turbines.



  19. A problem I see in the above non-financial analysis is that Texas has no need to shift to 100%, or 50%, or 10% renewable energy given it is a Plains State with only a singular spot atmospheric inversion layer that traps smog, as occurs in California – a Basin State. The solution to pollution is dilution, not renewable energy per se in a Plains State. The 10 worst cities in the U.S. for smog (ozone) are: 1) Los Angeles, 2) Bakersfield, CA, 3) Visalia, CA; 4) Fresno, CA; 5) Sacramento, CA; 6) Hanford, CA; 7) San Diego, CA; 8) Houston, TX; 9) Merced, CA; 10) Charlotte, NC
    Link: https://www.forbes.com/sites/morganbrennan/2011/04/28/list-americas-most-polluted-cities/3/#24d0a19824d0

    A case can be made for renewable in California, a Basin State with a topography comprised of many valleys that trap air. Texas has only 1 city of the list of worst cities for ozone concentrations.

    So-called “global warming” is a theoretical high atmospheric concentration of C02 in the Stratosphere, the second layer of earth’s atmosphere above the Troposphere and below the Mesosphere. So even California’s “Global Warming Solutions Act of 2006 has nothing to do with visible smog.

    The major causes of smog in Dallas and Houston are cars and plastics, oil and gas production. Most other Texans live in plains and plateaus where any potential toxic substances are dissipated quickly into the atmosphere. Texas is topographically greener than California despite its greater energy usage, but 12 million less population.

    Texas relies on coal fuel for 32 percent of its energy use, while California only depends on coal for 3.7 percent of its total energy usage (but 15.5 percent of its electricity usage). Texas imports coal fuel from Wyoming to run TXU power plants in Dallas, while California imports coal powered electricity from Utah to light up Los Angeles and about a dozen other cities in Southern California. Texas imports its pollution; California exports it. With a much higher usage percentage of so-called “dirty” coal-generated power than California, one would think that Texas would suffer from greater air pollution, incidence of asthma and lung cancer. But it doesn’t. Why?

    The answer is most Californians live in nine topographic basins along the coastline that serve as traps for smog. The major cause of smog in California cities is an inversion layer of warm air above cooler air that makes a toxic trap. Natural smog traps cause smog, not only man-made airborne substances. The solution to pollution is dilution.

    How many California environmentalists want to move to, say, West Texas to “save the planet?” My guess is none. It is easier to continue to live in the self-righteous cocoon of the Anti-Carbon Paradigm in California. And what makes up that cocoon is partly sociological, not scientific. In fact, most environmentalists have left the environment (the traps) out of environmental science. For example, sick buildings were created after energy tight-building codes were adopted which trapped toxic substances in buildings (asbestos, formaldehyde, radon, ricin, etc.), raising the issue of green iatrogenic disease.

    The same environmental trap phenomenon applies to water quality. Perchlorate is nearly everywhere. In Chile it occurs naturally in what California would call a toxic dose, but there are no measurable worse health from it. In West Texas perchlorate occurs naturally at low levels. In Southern California, with its many underground water basins, it occurs in what is considered toxic levels because it becomes concentrated in subsurface perc traps.

    Historically, California has been a post-modern (post-industrial) culture ever since it pushed the railroads out of controlling the state legislature. It has not merely demonized big railroads, big oil and big banks, it has also demonized the hard social processes of rationalization, mechanization, quantification, commodification, and industrialization (re: Max Weber). California’s cognitive elites want bucolic industrialization and with it green power at any price. It is important to understand the paradigms we live by and base policies on as well as the political-cultural environment that support it.

  20. What is the Armadillo Curve and why is ERCOT slightly worried about it?

    Ever heard of the Duck Curve? It was coined to describe a concern that California will use so much solar power that, in part due to the geography of the state, when the sun sets, there will be a gap in power supply as solar energy ramps down but demand is still high.

    Well, some Texas officials have tossed around the term “Armadillo Curve” to describe something similar, but less severe.

    The issue identified by ERCOT for the scenarios show a similar issue where there may be some hours of “unserved” energy in the early evenings after solar power drops off but before significant wind picks up to serve demand. The Armadillo Curve essentially resembles the ear of an Armadillo between about 7 and 10 PM before the wind power really picks up. ERCOT has started to refer to the Armadillo Curve in its presentations to distinguish it from the more traditional duck curve reference.

    While it will be years from now before this may be an issue, it points to the need to develop other resources like energy storage and demand response, which could quickly respond to such quick changes in power production and electric demand.

    Armadillo Curve Chart

  21. Wait. Is this *our* Peter Davies?

    • I don’t understand your question? What my above comment is pointing out is that the electricity load profile in Texas is in the shape of a duck or armadillo. A load profile shows the hour of the day and the various sources of power used each hour. Davies’ analysis doesn’t seem to address the load shaping of the Texas grid. I hope this answered your question.

      • > What my above comment is pointing out

        I wasn’t responding to your comment, WayneL. If I was responding to something specific in your comment, I would have quoted it and it would appear with some indentation.

        Sorry about that.

  22. Willard, my only other guest post here was “Electricity in China”. That probably means I’m not the same Peter Davies!

    • Thanks. The other Peter Davies was first and foremost a commenter. It’s been a while since we’ve seen him, so he *could* have decided to move to London and start a new gig.

      Good post, BTW. A little on the short side, but good.

      If Judy’s specialized in that kind of exposés, that’d be great to showcase what engineer-minded contrarians can bring to the table.

      • Willard: It will be dependability and cost. Such as the need of shedding load if the system frequency drops to 59.67 for more than 4 seconds. The cost problem is as the maximum capacity for the renewable system increases, the periodic dropouts increase to cause more system problems. What can be done? Load shedding and load sharing are currently used with generally 3 times the service area to act as a buffer. This means current system capabilities indicate a typical 17% real utilization factor for 50% renewable use. For 100% of the world’s systems going to RE, load sharing will not be available, and the cost of large corridors is expensive. As the RE increases how is overproduction paid for, and the cost of infrastructure that is 300% greater than the needs, while being less dependable? One hour is not the problem. It is that 4 to 6 seconds that can literally ruin modern systems such as manufacturing. It is the cost of having 3 times the infrastructure, and somehow maintaining an economy. Those are just the broad problems. I am sure others will bring up such items as the total life cycle of batteries, or chemical plants for chemical backup that have large environmental problems in the total life costs.

      • Don’t be such a pessimist, JP. Every solution has its load of problems, and if we listened to engineers for what to do, we’d never do anuthing. Just keep your napkin calculations going, and let the market create itself.

      • jfpittman, when the frequency goes down for a few seconds an alternative to load shedding is to increase generation. 300 GWh of batteries can do this extremely fast, provided some small capacity is kept charged for this contingency. You do not need to shed load fast. In fact batteries can respond within a fraction of a second. 7.5 hours of average load of battery storage will also give you plenty of time to bring up gas turbine back-up generation (whether fuelled by renewable gas or fossil fuel gas).

      • Willard, bringing up costs and problems is not being pessimistic. It is what they pay engineers to do. I do want the market to be allowed to create itself. I don’t want it to be forced, since that will likely be an expensive failure. Another item engineers do is life cycles. These appear to be as great or greater problem that the backup and infrastructure problems.

        PD, Yes, there are alternatives. Alternatives cost. Backups cost. The 5 to 10 years down the road has been a bit over 30 years for solar and wind for me. Just as solar and wind have made advances, so has much of everything else. The rate of improvement of solar and wind, can’t catch up without a cheap implementation of backup and infrastructure. The present cost of backup and infrastructure raises the price about 600-700%.

        Further, as a large electric user, I can also tell you that even small disturbances can start safety relays to engage. Domino effect can also happen. That really causes issues for the power company and heavy industry.

      • Market are already forced as we speak, JP. Fossil fuel subsidies are immense. Absolutely free markets only exist in Freedom Fighters’ minds – most if not all successful economies to date have been mixed.

        Failures is what capitalists do best. Ask teh Donald. Applying the same principle to science leads to the idea that we should embrace crappiness.

        There’s very little our desire for engineer-level formal derivation can do about that.

      • From the California RPS (renewable portfolio standard):

        (e) (1) Supplying electricity to California end-use customers that is generated by eligible renewable energy resources is necessary to improve California’s air quality and public health, particularly in disadvantaged communities identified pursuant to Section 39711 of the Health and Safety Code, and the commission shall ensure rates are just and reasonable, and are not significantly affected by the procurement requirements of this article. This electricity may be generated anywhere in the interconnected grid that includes many states, and areas of both Canada and Mexico.

        Look at the size of the area needed for one state that is tending to export pollution by importing electricity. That is just one broad category use. They haven’t added transportation, chemical manufacture, food, industry, and other heavy fossil fuel users. The question is how does one “ensure rates are just and reasonable, and are not significantly affected by the procurement requirements of this article.” This is what engineers call a conflict in specifications. Unless it is simply double speak for the taxpayers are simply a captive entity that has to accept what is mandated.

      • johnfpittman

        Willard, the cost per MW is much more for RE than fossil fuels. Total subsidy comparisons are that wind and solar are about $7X more per installed MW. Considering that utility at best is about 33% of installed MW, then the difference starts at about $21X more support for RE. I don’t know if the costs of coal dumps was included in this comparison. If not, then wind and solar are approximately on the same level with coal and nuclear for this cost, fuel oil and NG become even more economical.

        Willard I have posted before about not believing in that absolutely free markets exist. They don’t and as far as I have researched it is a fact they don’t exist. But a $21X increase indicates the real problem. Add in infrastructure costs, land use inefficiencies, total life cycle costs, and demand it replaces 80% of all fossil fuel use, then the real economic problems become apparent.

        All the economic analysis I have studied to date that indicate RE is even just 2X nuclear fuel have several unsupportable assumptions such nonexistent hardware and software, grid stability by load sharing and shedding, assigning infrastructure costs to the dispatchable units, ignoring the real time data of variance, counter indicative results such as the claimed cost is going down even while the consumer prices increase, and trying to hide the costs as tariffs.

      • Beta Blocker

        johnfpittman, forty years ago, back when I was in college, the futurists of the period were predicting the need for what they called a ‘manpower sink.’ The thinking back then was that as automation of the work we do accelerated and began to affect ever-larger numbers of American workers, whole classes of new industries and new service sectors which might not otherwise be created by the private sector economy would have to be artificially created by government as a means of keeping an expanding population busy.

        California’s renewable portfolio standard (RPS) is just such an effort at creating a manpower sink — one which has been brilliantly concocted, I might add. It puts all of the cost and most all of the responsibility for creating the Manpower Sink which is the California RPS onto private industry, while at the same time insulating the politicians and the renewable energy advocates who wrote the RPS from any and all valid public criticism.

        Without including the word ‘nuclear’ directly in its text, the California RPS indirectly but decisively forecloses the possibility of relying on nuclear power for low carbon energy production. The question is, why?

        The problem with nuclear power is that it can generate massive quantities of energy while employing a relatively small number of people, at least in comparison with the number of people wind and solar can employ. Far more than any real concern about issues with public health and safety, the impact nuclear power has in reducing energy sector employment is the true reason why California’s politicians don’t want anything to do with it.

      • > Add in infrastructure costs, land use inefficiencies, total life cycle costs, and demand it replaces 80% of all fossil fuel use, then the real economic problems become apparent.

        I’m sure they do, JP.

        Stop waving your arms and show me.

      • johnfpittman

        Willard:Waiting for his analysis. Last time I studied this in detail was 4 years ago. Lots have changed, but the fundamental challenges have not changed since the 1980’s.

      • I don’t need to wait, JP. First, because I don’t have a dog in this fight. Second, because as a ninja, I leap over the shoulders of thousands of giants with millions of eyes, e.g.:

        We have completed an analysis using detailed US electricity generation data of the period between 2001 and 2014. On the upside, our analysis reveals that there clearly is momentum towards decarbonization. Several CPP building blocks already are being utilized in the period analyzed – though to different degrees and in different ways across the states. Less efficient coal EGUs are disappearing from the generation portfolios of many states. Across the Eastern states, a main factor explaining the observed decarbonization is dispatching lower-emitting generation units due to the falling prices of natural gas. In select states such as in the Midwest has the use of low-/zero-emitting generation such as wind been noticeably expanded.

        Throughout the CPP, the EPA has emphasized flexibility in allowing states to achieve the emissions targets, and we can see the importance of this through the diversity of factors at work across each of the states. Extreme examples exist such as Oregon, which during the course of a year alternates between virtually nonexistent CO2 emissions from power generation, to nearly half their generation coming from fossil sources. There is no one-size-fits-all solution, and what remains to be seen is how the combination of factors such as the long lifetimes of fossil power plants and associated interests, the seasonality and intermittency of renewable generation, along with possibilities such as a greater than expected deployment of electric vehicles and congestion due to a lack of grid investments may impact the routes through which further decarbonization is achieved.


        What is deemed impossible might already be rolling.

      • Willard: What those eyes did not tell you directly is found in the following quotes:”Several CPP building blocks already are being utilized in the period analyzed – though to different degrees and in different ways across the states.”; “Throughout the CPP, the EPA has emphasized flexibility in allowing states to achieve the emissions targets, and we can see the importance of this through the diversity of factors at work across each of the states. “; “Less efficient coal EGUs are disappearing from the generation portfolios of many states. Across the Eastern states, a main factor explaining the observed decarbonization is dispatching lower-emitting generation units due to the falling prices of natural gas.”; and “what remains to be seen is how the combination of factors such as the long lifetimes of fossil power plants and associated interests, the seasonality and intermittency of renewable generation, along with possibilities such as a greater than expected deployment of electric vehicles and congestion due to a lack of grid investments may impact the routes through which further decarbonization is achieved.”

        The CPP is being stopped presently; States sued and stopped the CPP because the EPA flexibility was not directed at the source as the CAA and CAAA stated was legal. Coal is now being replaced by NG because of cost of coal. What remains to be seen is how we can decarbonize the economy. The first technical problem is that infrastructure and the size of infrastructure depend on energy density and its conveyance. The second technical problem is dependability: the vast majority of energy use are designed for dependability, and many large energy users have to have dependable energy as for example my employment where we use large amounts of electricity and have fossil fuel boilers. The intermittency has been solved, to date, by cost increases, hidden or otherwise.

        That is why I want to see the rest of the analysis before I try to go into more detail.

        As Betablocker and others have pointed out, if costs and application don’t matter how come we don’t have the whole population digging ditches with spoons.

      • > What remains to be seen is how we can decarbonize the economy.

        The work I cited provides evidence that we already are decarbonizing the economy, JP.

        It also argues that we can’t provide a one size fit all decarbonizing function.

        Decarbonizing just makes sense.

        As long as ccoal remains in the ground, I’m open to all kinds of portfolios.

      • I understand your POV. Mine is that we may not be able to afford keeping coal in the ground in the short to medium term. Life-cycle is about 40 years for large dispatchable sources, putting major changes without potential major disruptions at the approximate 60 year mark. It is unlikely to be this long if economic solutions are found.

        For humans, not only do we need to have a conservation of the environment, we need conservation of capital. That is a lot of what engineers do.

        athttps://www.iea.org/publications/insights/insightpublications/Getting_Wind_and_Sun.pdf 2017

        The amount is also important. EIA has some good general information on the phases it has for decarbonization in electricity generation. They match in general my hand waving. EIA shows some improvement since I last studied. Their write-up indicates added expense has decreased or the range for such changes needed has increased. Increased expense per increased penetration of RE still indicated. Limits of RE still indicated.

        Phase I 0 -3% (unchanged) helps system with uneconomical areas or special purpose uses.

        Phase II 3 – 15% (was 4 – 9%) noticeable impact, upgrading operational practices such as grid codes. This limits how useful RE nameplate can be tolerated, and other schemes to reduce impact without relying on large capital improvements.

        Phase III 15 – 25% (was 10 – 17%) Significant challenges, capital investments, flexible dispatchable power plants, load shedding or load sharing still part of mix. Predictive software advised.

        Phase IV 25- 50% (was 18 – 33%) Increased challenges compared to Phase III, system and predictive software needed, larger corridor or more flexible dispatchable sources. Voluntary and involuntary use stoppage. Specific solutions as to region and mix.

      • Thanks for this, JP. Here’s how the executive summary starts:

        Wind and solar PV capacity has grown very rapidly in many countries, thanks to supportive policy, and dramatic falls in technology cost. By the end of 2015, these technologies – collectively referred to as variable renewable energy (VRE) – had reached double-digit shares of annual electricity generation in ten countries. In Denmark their share in electricity generation has risen to around 50%, and was around 20% in Ireland, Spain and Germany, in all cases without compromising the reliability of electricity supply.

        Despite this evidence, discussion of VRE integration is often still marred by misconceptions, myths, and in cases even misinformation. Commonly heard claims include that electricity storage is prerequisite to integrate VRE, and that conventional generators are exposed to very high additional cost as VRE share grows. Such claims can distract decision-makers from the real, though ultimately manageable issues; if unchecked they can bring VRE deployment to a juddering halt.

        I will simply note that there are 141 occurences of “storage” on this page as we speak, 142 with mine.

      • “The full implementation of climate pledges will require the energy sector to invest $13.5 trillion in energy efficiency and low-carbon technologies from 2015 to 2030, representing almost 40% of total energy sector investment. Around $8.3 trillion is needed to improve energy efficiency in the transport, buildings and industry sectors, while much of the remaining investment is to decarbonise the power sector. More than 60% of total investment in power generation capacity is projected to be for renewable capacity, at $4.0 trillion, with one-third of this being for wind power, almost 30% for solar power (mainly solar photovoltaics) and around one-quarter for hydropower. While OECD countries absorb 60% of energy efficiency investment ($5 trillion), non-OECD countries absorb a greater share of the investment in low-carbon technologies ($2.7 trillion).”


        It is about 1% of the global economy per year. The use of oil, gas and coal will continue – and increase – for decades. It results according to the IEA in a 3.7 billion metric ton increase in in CO2 emissions to 2030. Non OECD countries have effectively no commitments – and they would be wise to install the most cost competitive generation in strongly growing economies.

        Carbon intensity increases are inevitable as economies grow. Gas generation will continue to expand, Non OECD countries need to focus on providing a base of generation in gas, coal and nuclear. Wind and solar are utterly useless without a reliable base of dispatchable power. Realities of the moment – decarbonisation or not.

      • > Wind and solar are utterly useless without a reliable base of dispatchable power.

        From JP’s cite:

        Claim 2: VRE deployment imposes a high cost on conventional power plants Another frequently made claim goes as follows: “Fluctuations coming from wind and solar PV put a large burden on traditional dispatchable power plants, obliging them to adjust their output very rapidly. This creates significant technical challenges and sharply increases power system costs.”

        This claim is generally not true for larger power systems where deployment of wind and solar power is just beginning. The reason is the same as for the first claim: at low shares of VRE, variability is dwarfed by that of consumer demand, and consequently not much changes for conventional generation.

        As shares increase however, VRE output variability will begin to influence the generation patterns of other power plants. But in many power systems, experience has shown that power plants are technically capable of more dynamic operation without substantially increasing total power system costs. Using VRE production forecasts and adjusting generation schedules close to real time are low-cost, effective tools to mitigate adverse impacts; and failure to adopt such measures can increase costs for the system as a whole. In contrast, in small island systems, VRE can impact other generators earlier on in deployment, and more significantly, but these smaller systems are not the focus here.


        > Carbon intensity increases are inevitable as economies grow.

        Once upon a time, an engineer at IBM was presented with the first microchip. His reaction, according to the lore, was But what … is it good for?

      • “Since 2009, the G20 has made commitments to rationalize and phase out inefficient fossil fuel subsidies. This could simplify the tax system, produce efficiency gains, reduce trade distortions, and help meet environmental goals. Subsidies have been shown to encourage wasteful consumption, exacerbate energy price volatility, encourage smuggling and undermine the competitiveness of renewables.

        The European Union has a goal of phasing out subsidies for uncompetitive coalmines by 2018. Germany has traditionally subsidised hard coal mining. However, Germany has numerous other exemptions from energy taxes that are not deemed inefficient. The main subsidies in the United Kingdom are a partial offsetting of petroleum revenue tax for oil and gas producers and a lower VAT rate for domestic consumers. Sweden has extremely ambitious environmental and climate policies and is in the process of phasing out remaining subsidies to users of fossil fuels. Their experience shows that loss of competiveness and carbon leakage can both be mitigated by gradual change. In all cases, economic effects are marginal.

        Energy services are often heavily subsidized in developing countries so that the costs of (often imported) energy be affordable to their citizens. Subsidies are targeted at the poor but frequently miss their goal entirely, benefiting the middle and upper classes most. Moreover, they are a heavy burden on the public purse. Although the global case for subsidy elimination is clear, it can be less so for developing countries. The wealthiest 20% benefit most from subsidies, while the poorest 20% would be hardest hit by reform.

        Overall the total benefits are at least $600b-$750b per year, plus non-quantifiable benefits from health improvements and emission reductions. The costs are mainly administrative, as well as distributional impacts to the poorest, but these can be mitigated through appropriate revenue recycling. Benefit-cost ratios are likely to be greater than 15 with proper revenue recycling.”

        Poor wee willie – we are preempting all his policies with economic rationalism.

        To add to the my penultimate comment on this thread.

        “There is evidence that each additional 1% improvement in energy efficiency increases GDP growth rates by 0.1%. If there were a 1% improvement in EE, combined GDP for OECD countries in 2030 would be $612 billion (1.78%) larger than projected. For a 2% improvement, it would reach 20% above the projected baseline by 2030.

        The IEA estimated in 2006 a need for $3.2 trillion worldwide to double the rate of energy efficiency improvement, offset by the avoidance of $3 trillion in new supply investments. A global 2.5% efficiency improvement would save 97 EJ and return energy consumption to 2004 levels by 2030. At the industrial level, investments of $360 billion in energy efficient technology will be needed and lifetime savings in energy costs are estimated to be more than $900 billion.” op.cit.

      • Chief wins again:

        Our analysis by economists Isabel Galiana and Amy Sopinka shows that phasing out subsidies for fossil fuels would be a phenomenal target. It will slash waste, reduce inequality, and cut CO2 emissions. The economists estimate that every dollar spent (you still need to help the most vulnerable to energy access) will create benefits for society and the environment of more than $15. The billions of dollars that governments could save from phasing out fossil fuel subsidies could be spent on providing better health, education and nutrition, which could benefit hundreds of millions of people.

        Now is the time to cut fossil fuel subsidies. Thanks to plummeting oil prices, it is easier to reduce the subsidies needed to guarantee regulated consumer prices, taking off public pressure against such reforms. Egypt, for example, paid 30 per cent less in subsidies than originally forecast due to cheap oil. It is encouraging that Egypt, India, Indonesia and Malaysia have recently announced to restructure their state budgets and to phase out energy subsidies.


      • Fossil fuel subsidies are a myth in the conventional sense of what defines a subsidy; ironically what is defined as a subsidy for fossil fuels the Left would mostly have a tantrum if forced to get rid of them:


      • Also, how was the $450 billion figure gerrymandered for subsidy every year for coal? All the coal producers combined in the U.S. only generated $28 billion revenue in 2016. I’m sure it’s “the costs of carbon” fuzzy math that assumes the worst possible attributes and not accounting for any positive attributes.

      • What’s included in the $88 billion global subsidy?

      • Any state owned properties in that math? Links, links — your mantra.

      • Links beat JAQing off, Mop, more so when it’s obvious you don’t even read them. Here’s another:


        Source: http://www.worldenergyoutlook.org/resources/energysubsidies/fossilfuelsubsidydatabase/

        When you’ll show me your Kung Fu, we’ll see if you deserve anything more than linkies.

      • “This claim is generally not true for larger power systems where deployment of wind and solar power is just beginning. The reason is the same as for the first claim: at low shares of VRE, variability is dwarfed by that of consumer demand, and consequently not much changes for conventional generation.”

        Not sure what poor wee willies point is here – but that’s commonly the case.

        In much of the world grids are in their radically undeveloped – and you do need a substantial contribution from dispatchable generation before even small amounts of connected solar and wind are feasible. And this IEA report I quoted extensively just yesterday. Wind and solar are feasible – if they are cost competitive – with incremental increase. But you do need some sort of infrastructure to penetrate. If you have no dispatchable power – or no cost effective storage – there is no point in grid connected wind and solar.

        Poor wee willies can’t take yes for an answer on sudsidies. Subsidies in the G20 are disappearing – most direct subsidies are in the developing world – which the document I linked to discusses. Yes – subsidies bad wee willie.

        Direct fossil fuel subsidies (for oil and gas mostly) in the US are about $4B. It is oan area that can give some budget relief. That leaves $384 for health and climate costs. Instead of letting people get sick and die. Much more sensible to reduce particulate, sulphur and mercury emissions from coal generation. If they cant then so be it – let the dinosaurs die out.

      • > A brief look at your last link does you no favors

        The last link is to World Energy Outlook. The one you cite is from the Tax Foundation, a Freedom Fighters think tank. Your response clearly shows you did not look.

        That other countries subsidize more fossil fuel doesn’t imply anything regarding USA’s subsidies. In fact, you should be able to see that they’re quite similar with the % of the GDP the world gives away to the fossil fuel industry.

        How that think tank drowned these subsidies behind “but taxes” was quite something. Comparing annual rates with cumulative sum was also neat. It also invokes Keynesian rationale, which I’m sure Freedom Fighters around the world celebrate each day.

        That govs give contradictory reasons to keep these subsidies reinforces the argument that we should cut them more than anything.

        If you prefer words:

        This paper estimates fossil fuel subsidies and the economic and environmental benefits from reforming them, focusing mostly on a broad notion of subsidies arising when consumer prices are below supply costs plus environmental costs and general consumption taxes.

        Estimated subsidies are $4.9 trillion worldwide in 2013 and $5.3 trillion in 2015 (6.5% of global GDP in both years). Undercharging for global warming accounts for 22% of the subsidy in 2013, air pollution 46%, broader vehicle externalities 13%, supply costs 11%, and general consumer taxes 8%. China was the biggest subsidizer in 2013 ($1.8 trillion), followed by the United States ($0.6 trillion), and Russia, the European Union, and India (each with about $0.3 trillion). Eliminating subsidies would have reduced global carbon emissions in 2013 by 21% and fossil fuel air pollution deaths 55%, while raising revenue of 4%, and social welfare by 2.2%, of global GDP.


        Thanks for playing.

      • Whatever, a previous link, regardless, it’s your link attempting to support your evidence for massive subsidies.

        The strategic petroleum reserve, farm fuel, and low income heating make up half of U.S. subsidies, you can review the Forbes link for the litany. Around $4 billion. Go ahead and lobby for cutting them if you think it’s the right thing. Global subsidies are not quantifiable, so many of the oil and gas producing nations are state owned. Your infographics are gerrymandered fuzzy math, the stuff of politics.

        “Thanks for playing” requires more than putting your foot on home base, you have to go around the bases. Anyone can throw down a home plate, the paper you cite is throwing down the home plate and stepping on it. There’s no accounting for the benefits fossil fuels have provided and backing those out of the costs. It’s not like one could have invented the solar panel before fire. Despite fires carbon footprint, it has saved infinitely more people than the solar panel has saved lives. Can you put a dollar amount to the benefits fire has provided since the caveman? There’s no reasonable, believable accounting for dropping all fossil fuels and going straight to alternatives other than the global costs would be unimaginable, unthinkable.

      • > it’s your link attempting to support your evidence for massive subsidies.

        You must be new here. It was rather a link to see if you were paying attention. You were not.

        Look. As much as it’d be easy to wipe the floor with your “but benefits”, dear Mop, the post was a good one, and good posts need to be positively reinforced. That fossil fuels benefited mankind is irrelevant to the fact that the industry is massively subsidized:

        Sustainable development proponents and “government downsizers” (also known as libertarians) condemn FFS for different reasons. From a sustainable development perspective, the concerns include that FFS benefit the rich more than the poor, and encourage the use of dirty fuels, creating pollution and undermining human health. Acting as a negative carbon tax, they distort the playing field for energy efficiency and renewables. Further, they create zombie energy, i.e. production from fields that would be economically unviable without government support. They lock in fossil fuel dependency and tie up scarce resources that countries could otherwise reallocate for sustainable development.


        Freedom Fighters should hang on to this low-hanging fruit,and you, dear Mop, should let that point stand.

        But please, do continue.

      • “Undercharging for global warming accounts for 22% of the subsidy in 2013, air pollution 46%, broader vehicle externalities 13%, supply costs 11%, and general consumer taxes 8%. ”

        “The WTO, in the Agreement on Subsidies and Countervailing Measures, states the accepted international definition of a subsidy as a financial contribution by a government that confers a benefit.

        A subsidy exists where

        government provides a direct or indirect transfer of funds,
        revenue is forgone or not collected,
        government provides goods or services or purchases goods, or
        government provides income or price support.*

        The fossil fuel subsidy in the US is $4/yr. The rest is externalities and several questions arise. Quantifying the impacts on climate and health for a start – what the sources of pollution are – whether traffic congestion and accidents are even relevant factors – and I don’t even know what is meant by supply cost. It seems something utterly different to the economics definition,

        But the fundamental point to be considered is the difference between the value of fossil fuels to us and the cost. Markets can create commodities that have tremendous value for us at relatively little cost. The internet for example.


        Fossil fuels have powerful positive externalities because the services they provides have such high value for us. This us not to say that we should not address some or all these externalities. Just that dodgy accounts of externalities don’t begin to suggest the most rational responses. The latter is not a problem for poor wee willie.

      • Willard, from what I can see from the information read to this point is that storage becomes necessary when RE is not integrated correctly for one reason or another, such as mismatched peak/demand, hysteresis of the systems, RE penetration that does not meet conveyance criteria, and other problems.

        The report I linked still indicates that as VRE penetration goes up, costs and problems with the system increases. That is also why I want to see the promised analysis.

        Looking backwards, progress has been made. Looking at high attempted VRE penetration: infrastructure cost avoidance, political and economic prejudices about subsidies, capabilities, and other factors are unnecessarily hurting RE. Storage seems to be in this category.

        It may have been polite for them to say: “”Despite this evidence, discussion of VRE integration is often still marred by misconceptions, myths, and in cases even misinformation. Commonly heard claims include that electricity storage is prerequisite to integrate VRE, and that conventional generators are exposed to very high additional cost as VRE share grows. Such claims can distract decision-makers from the real, though ultimately manageable issues; if unchecked they can bring VRE deployment to a juddering halt.”” Did they include the decision makers mismanagement?

        Willard, though I don’t have enough information to be certain, but from what I have read to date indicates that large storage is a political failure, accepting that the capability of RE is as was indicated in the IEA link. Politicians are not accepting what is practical for their systems. Too much, too fast is indicated. However, testing in real systems is necessary for proving and improving. So, Australia is providing good information on what the potential can be, but also how bad magical thinking can be, or just plain old engineering oversights for that matter.

        Many people think being first in has the advantage. In complex systems, it is often the second or third generation that reaps the most benefits from the least costs. One of the reasons, I did not think that USA should be claiming how getting into RE was going to make money. IMO, the standard of living, pay scales, and other economic factors indicate that China should be doing it.

      • > It may have been polite for them to say […]

        It wasn’t really polite, JP, and it occupied a whole section.

        The Australian example will be interesting to follow. The authors also mention that:

        Examples of countries considered to be in Phase Three of VRE
        deployment include Italy, the United Kingdom, Greece, Spain, Portugal and Germany; the VRE
        penetration in these countries ranges from 15% to 25% in annual generation.

        All this is only for electricity generation anyway, and for the bigger energy challenge it’s hard to escape McKay’s conclusion.

      • You’re a trusting soul Willard. I say to you what I say to anyone else who shows blind faith to government or its surrogates, to its power and benevolence, by asking them to elaborate on the winning track record of budget prognostications by the CBO through the decades.

        In the end we want the same things, prosperity for everyone; cheap energy for everyone. We both see alternative energy as the future, and both want to see its continued development. But at what price, when (as in instantly now), we differ. I see most on the Left wearing opaque rose colored glassed, not only seeing what they want to see but what they need to see, it’s indelibly imprinted on their lenses, basically it’s the way a cult imprints on the psyche. Alternative energy needs and climate change science are convoluted, married through politics; politics is the driving force for its own sake. This is where most of the numbers you rely on are sculpted, politics, coercion by numbers is itself “low hanging fruit”. I’ve seen how trusting humans being asked to work from an inner spiritual self for the good of all turns out, and how freedom without coercion works out. I like the latter. Though nothing is perfect, so far freedoms been shown to have the best track record of accomplishments ever seen by humanity.

  23. Wayne Lusvardi, on peak days solar PV can handle the early afternoon peak, but a high load remains around 8-10 pm when solar PV generation is low or zero. You can find it using the grid model filters for first time of day and the hours with the highest loads. There’s no guarantee that wind generation will kick in on any particular day.

    The analysis is based on a grid model fed by real hourly ERCOT data for load and wind generation, with solar PV generation derived from real solar DNI (direct normal irradiance) – all lined up by hour from the years 2010 to 2012. The problem can be picked up from the image https://curryja.files.wordpress.com/2017/05/slide14.png above. The model scales the generation from wind and solar PV to see what levels are required, while leaving the shape of the generation the same.

    At the moment Texas has very little solar (either utility or rooftop), with around 500 MW, compared to 21GW of wind power, so there’s not much scope for ducks or armadillos right now. But there is 13GW of utility solar in the ERCOT interconnection queues, so the situation could change quite fast.

    Compare 500MW of installed solar PV in Texas to 15GW in California of which 5GW is rooftop solar. Since rooftop solar is connected to the low-voltage distribution network it is counted as reducing demand. That produces the duck curve. What is a current concern for California will be a future concern for Texas – the Armadillo curve.

  24. Peter Lang

    [repost on intended thread]

    100% renewable energy is not viable in even the most ideal situations, so what chance anywhere? see video: http://www.dw.com/en/a-tiny-islands-gigantic-green-goals/a-38753320

    • PL, Energy Matters has been following the El Hierro fiaso. They undersized the pumped storage by half. Screwed up system design. Maybe not applicable to ERCOT. Dunno.

  25. ” Thus 10bn square metres are required, which is 10,000 square km, or a grid 100km by 100km. The Panhandle and West Texas has many times this amount of suitable land.”

    You can’t think of putting all of the wind turbines in one small spot, this is well known to generate local loss of power (wake effects and the “vertical kinetic energy” issue, well documented).
    Additionally all historical, state and federal parks areas must be taken off the list of possible sites. Still there would be plenty of space… ’cause Texas is… Texas… :-) .. it’s a really big piece of land, but still there’s a lot less space available than the “nominal” free space.

    Anyway: the killer argument against intermittent renewables is the storage of their surpluses and the need to criss-cross the country with transmission lines linking any possible production area with any other consumption area… ’cause you never know where and when wind is going to blow. PV is more reliable and predictable in this case, but it needs long term storage (storing during the high-surplus months to use back during the low-surplus ones)… and nobody sane of mind will ever put money into battery storage over a 4-6 month period. Only pumped hydro would help, but the potential for pumped hydro in Texas must not be that great… anybody has data on this?

    So, one would be left with the P2G storage option… and as the author has pointed out… the losses are huge, and so are the per-kWh costs.

    • Don’t expect a silver bullet but in theory this should work in Texas too.

      • Jack

        In Devon in the UK We had our first water powered railway in 1890 which is still running to this day


        Brunel also devised a vacuum powered railway locally some 150 years ago that ran for a few years but had to be converted as the rats kept eating the leather seals so the vacuum kept on being compromised.

        There are lots of inventive transport solutions that can be tried out, some will have a local application only, whilst others might be applied more generally


      • Very cool solution and the draft animals were really happy I bet!
        This idea of using gravity to store energy has a major point in it’s favor in that it has zero energy loss while it stores all that kinetic potential. Unlike other schemes which loose energy through evaporation, thermal loss or chemical degradation.

    • robertoko6, P2G losses are large for all the demand which has to be satisfied this way, but this is only 6% of total demand, so it is not a show stopper on its own. I’ll get to work on part 2.

  26. Peter

    Interesting article, thanks. The former chief scientist of the Uk dept of energy calculated that a country the size of Wales would be needed to be stuffed full of solar panels if our power needs in the uk were to be satisfied. In other words he saw renewables as an unrealistic way of meeting a developed country ‘ s energy needs.

    However, time and technology moves on and in today’s papers was a forecast by a respected Stanford professor that petrol cars would be obsolete within 9 years in the US due to a combination of electric vehicles and robot vehicles.


    Seems unlikely to me but the point is that in this and many other scenarios a vast amount of energy will need to be generated in order to power the vehicles.

    I do not know how renewables can supply this need, unless batteries become far more efficient and the amount of land dedicated to renewables increases exponentially.

    What impact this elimination of petrol vehicles will have on co2 emissions I do not know


    • climatereason, UK is very different from Texas. We don’t get a lot of sun here in London so McKay was right about Wales. But we do have excellent offshore wind and plenty of North Sea to put it in!!!

      Offshore wind prices in the ongoing UK auction are now expected to be very significantly cheaper than the new Hinkley Point nuclear station for which the contract price is 9.2p/kWh (11.9 US cents) or 8.9 p/kWh (11.5 cents) if a second is built. As well as offshore wind we need a second independent source of renewable power to go 100% renewables. Solar probably won’t hack it, but wave or tidal might, though it is very early days yet with both these technologies.

      To give you the head up on the latest offshore wind prices, in last month’s North Sea German offshore wind auction DONG (Danish energy firm) bid for no subsidy for a 30 year contract on two offshore wind farms, expecting to make a profit on wholesale German electricity prices alone. On a third wind farm it bid 6 eurocents/kWh (6.6 US cents/kWh).

      A second company EnBW also bid for no subsidy for a bigger offshore area.

      See :


      There are various reasons why these companies could bid no subsidy for those particular areas, which include existing wind farms close by owned by them enabling easy extension of maintenance, installation dates of up to 2025 enabling huge next generation 13-15 MW offshore turbines to be used, and the wind farms only have to cover transmission costs as far as the onshore end of the connecting cable.

      However, the effect is still one of shock, at least for me, as a few years ago offshore wind was priced at over 20 cents/kWh. No-one was expecting it to be that competitive for another 10 years.

      • Peter

        I live in the south west and we have lots of solar farms. They are quite nonsensical in our climate. Two thousand years ago Tacitus described as a damp and misty island! We get 1700 hours of sun a year in this neck of the woods, just about the best in the country. Solar farms take up vast amounts of land and are very inefficient and deliver virtually no power when most needed, in the winter and no power at all of course at night.

        I am against on shore wind farms as they scar some of our finest landscapes. Flying over to Europe recently I was astonished to see the huge number of off shore turbines. I am not against them at all, in the right place. However, having seen a BBc documentary about the huge logistical problems involved in servicing them I do query How they can ever be cost effective but I suppose technology moves on. Personally, I favour wind/ tidal power in our situation as nowhere in the uk is further than 70 miles from the coast


      • > McKay was right about Wales

        I thought McKay was right about everything.

      • From the Dong site:
        Not full scope: Developers were not bidding for the grid connection in the German auction, which means that grid connection is not included in the bid price.

        So actually is IS still subsidised ?

    • On the issue of cars, there are enough numbers for a back-of-the-envelope calculations. E.g. a Nissan Leaf gets 100 miles for 34kWh. If you scale this to 100 million cars doing 10000 miles each per year in the US, that ends up about 10% of the annual national electrical consumption in the US (4 billion MwH), according to my rough estimate, which does need independent checking for sure.

      • Ordvic

        That was the same link I posted above.

        It would be interesting if someone could confirm Jimd rough calculations as to The amount of electricity needed to power say 100 million electric cars.

        That is in addition to what is currently being generated by all methods and does not take into account the short fall as fossil fuel energy is retired.

        Way sort of size area would be needed to accommodate the solar panels required ? How much co2 would be saved?


      • Also from a rough estimate, the CO2 saving would be 0.5 GtCO2 per year, if the power came from carbon-neutral sources, again about 10% of the US total.

      • USA drivers (and presumably cars) do just under 14,000 miles per year, at around 3.5 miles/kWh (though Texans vehicles are lower at around say 3 miles/kWh because Texas is hot and Texans like trucks). That’s 4,000 kWh/year per car. x100 million = 400 TWh or about 10% of the annual USA electricity grid consumption of 4,000 TWh, confirming what JimD says.

      • Peter Davies: “SA drivers (and presumably cars) do just under 14,000 miles per year, at around 3.5 miles/kWh (though Texans vehicles are lower at around say 3 miles/kWh because Texas is hot and Texans like trucks).”

        Sorry to tell you, Californians seem to really like pick-up trucks, they own the most puck-up trucks in the U.S. This brought to you by the U.S. Department of Transportation, Federal Highway Administration. BTW, I couldn’t help but see your “red state” notation in your essay, so you’re saying your article would have been lacking without this particular scientific notation?


      • Peter

        Thanks for your confirmation. Not sure the co2 reduction is worth it as the US has seemed to do well on this front anyway over the last decade.

        I do not know if this 10% additional electricity requirement can be easily met by renewables or not, bearing in mind there is a commensurate decline in fossil fuel energy generation.

        Presumably the recharging could be problematic in as much many people will not have the means to re charge, as their car and an electric point may not coincide.

        Also, I am hoping someone could work out what physical area of land the additional renewables would take up.

        In Texas that may not be a problem, in the uk we simply do not have the spare land, but have lots of off shore area.


      • climatereason, the 0.5 GTCO2 saved is equivalent to the annual emissions of all but about 10 countries (all in Europe except Germany and Russia). Also the replacement with electric vehicles wouldn’t be all at once. Maybe it would take at least 10 years for it to ramp up, and 1% per year would not be so noticeable. Another number is that the US currently emits 2 GtCO2 per year in electric power generation. So even if this number did not reduce, increasing consumption by 10% is 0.2 GtCO2 per year, versus 0.5 GtCO2 per year saved by not burning gasoline. So electric cars are a net benefit to emissions even with the current power generation system.

      • Jimd

        Are there any issues with the material that needs to be mined to create the vehicles and batteries and for their subsequent disposal?

        I seem to remember that 3 or 4 years ago you were keen on sort of energy production. What was it?


      • I don’t know the other relative costs of electric car production.
        My idea, thanks for asking, was home storage, where everyone gets their own batteries and can download the power from the grid to recharge them when available. This avoids the issues of demand not being at the same time as renewable supply, and also safeguards against short-term regional blackouts, such as from downed power lines, because home storage could be up to a few days worth. It is workable with something not too different from current electric car batteries.

      • Jimd

        See, I do listen to you!

        There seems to have been a considerable advance in car batteries in recent years so it may well be possible. It is the charging element I would be more doubtful about. If you have a house with its own own driveway or garage then you could download and charge the battery. However there are numerous properties where the car may be parked some way away , say across a street pavement.

        Also I do not know the physical size of the battery needed in order to store a worthwhile amount of power.

        So this may be a solution for some properties but what percentage of the total housing stock i do not know.


      • Yes, I visualize about three house batteries: one in use, one recharging and one spare. For apartment buildings perhaps a shared basement battery room. Also a maintenance service would come around and swap in and out batteries on a regular basis, perhaps every few months to a year. Might not need to take a lot of space, perhaps something like a closet, or a part of a garage ceiling or below its floor.

    • Tonyb It would take a WWII effort to change the infrastructure to handle this change in 8 years. So who is going to finance the change in such a short time? Further problems is that the range does not match the vacation habits of the USA where large fractions go much more than 200 miles for vacations and have scheduled the time on the road for gasoline. A ten times increase for downtime for the numbers of vacationers on the road would be a tremendous cost. If it is so cheap, where will the profit model come from?

    • Looks like there may have been some recent developments regarding solid state batteries (glass electrolyte). Talk is of >3x power density, high/low temperature operation, rapid charging (minutes for a car), and thousands of cycles without capacity loss. Might be on the consumer market within 5 years. If so, I wouldn’t bet against EV’s.

      • johnfpittman

        Not to be pessimistic, but share my experience. Not only are these claims almost universally exaggerated, but most don’t even make it to the market. The ones that do almost always have some assumption that means real performance is substantially off, often as much as an order of magnitude. One area where it is good to have places like Australia, and California is that once the units are put to the test, then real data can be had that engineers can design with. Been waiting 32 years and still see much of the same hype and unsupportable assumptions.

      • Your skepticism is most likely well founded. This specific paper has its expert critics, so my expectations are managed as well. There should be ongoing attempts to replicate the results, so we should know soon.

  27. Well that’s Texas what about the rest of the world?

  28. Thermal Energy Partners is Texas firm doing some very interesting things with micro grids utilizing geothermal. They’ve been in operation since 2010; but their potential is intriguing:

    TEP Geothermal MicroGrid (TGM) Benefits
    The benefits that extend to utilities, facility partners and the community at large include lowering greenhouse gas (GHG) emissions and lowering stress on the transmission and distribution system. In many respects, TEP’s Geothermal MicroGrid (TGM) is a smaller version of the traditional power grid consisting of power generation, distribution, and controls such as voltage regulation and switch gears. However, unlike power grids, TEP’s Geothermal MicroGrid provids closer proximity between power generation and power use, resulting in efficiency increases and transmission reductions. TEP’s Geothermal MicroGrid also integrates with existing renewable energy sources such as solar, wind power, small hydro, waste-to-energy, and combined heat and power (CHP) systems.

    The TEP Geothermal MicroGrids (TGM) performs dynamic control over energy sources, enabling autonomous and automatic self-healing operations. During normal or peak usage, or at times of the primary power grid failure, TEP’s Geothermal MicroGrid can operate independently of the larger grid and isolate it’s generation nodes and power loads from disturbance without affecting the larger grid’s integrity. Microgrids interoperate with existing power systems, information systems, and network infrastructure, and are capable of feeding power back to the larger grid during times of grid failure or power outages.

    Our facilities design and construction projects include renewable energy initiatives to help meet the facility energy security goals. For example, TEP can construct onsite geothermal power ranging from 10, 50 or 100+ MW of power generation depending upon the needs of the facilities that constitute an Energy Independent District.


  29. Thx for a well written article. The problem I see as an electrical engineer with 50+ yrs of experience is that the 1% -3% of the time actual conditions of high wind sub-freezing condition winter/spring are going to destroy the model results. Average conditions/peaks/off-peaks are not the issue. Its what the extremes will entail. I’ve lived in Texas… you don’t have to tell me what extremes there are. Texas is the definition of extremes.

    • Rich Van Slooten, the model uses actuals data for 3 years. If extreme Texas conditions occurred during the period 2010 to 2012 then the effects of them will already be present in the load, wind and solar irradiance data used in the model.

      I agree that 3 years of real data is not enough to pick up very occasional conditions. It would be better to use more years, but the spreadsheet is already 20MB and getting slow.

      However, the key thing is that the peak load is correct because the required capacities to meet the load are dependent on that, and this is obtained from more recent ERCOT figures. Other conditions could well result in the renewable methane storage running out when it shouldn’t, but in such extreme circumstance that can be fixed by refilling it with natural (fossil fuel) methane gas of which Texas has plenty thanks to fracking.

      • 2011 was an exceptional year for stress testing ERCOT.
        February 2, 2011 Grid Emergency
        “ERCOT reported that severe weather led to the loss of 50 generation units amounting to 7,000 MW of capacity on Wednesday morning. From news accounts it looks like a few large coal plants failed after water pipes burst. Some natural gas generators found insufficient fuel supplies due to heavy demand for natural gas. Other natural gas generators found their access to fuel curtailed by state rules that give priorities to other customer classes when supplies run short. In addition, a larger than usual amount of generation was off-line for scheduled maintenance – one estimate put this quantity at about 12,000 MW.”

        Then the summer from hell!
        August 03, 2011
        ERCOT breaks peak demand record third time (Update)
        Record power use expected again Thursday; Conservation needed 3-7 p.m. For the third consecutive day, the Electric Reliability Council of Texas, Inc. (ERCOT), system operator for the state’s bulk transmission grid, set a new electricity demand record — 68,305* megawatts (MW) today between 4 and 5 p.m.

        That peak demand record lasted till 2015.
        All-Time Peak Records*
        69,877 MW — Aug. 10, 2015
        68,912 MW — Aug. 6, 2015
        68,459 MW — Aug. 5, 2015
        68,305 MW — Aug. 3, 2011
        67,929 MW — Aug. 2, 2011

      • jacksmith4tx, please see the image above from the grid model for the 2nd Feb 2011 which you say was an extreme day. I’ve hidden a few detail columns giving generation by location etc. (and to do this you have to unprotect the sheet).

        The hourly load is scaled by year so was originally 49.2 to 56.3 GW that day, but becomes 51.1 to 58.5 GW for an annual peak of 71 GW. That’s relatively flat as things go.

        Scaled actual wind (capacity 75 GW) is more or less what you would expect with a bit of a lull at midday. Solar (capacity 80 GW) is interesting as there must be a lot of cloud over a couple of the four 10km x 10km squares with DNI data supplied by SolarAnywhere around midday.

        The net is that there would have been a renewable deficit (pink column N) in the early hours of the morning until solar kicked in, then the unusual deficit at midday for a couple of hours, despite solar, then a surplus until dusk.

        As luck would have it the 300 GW of batteries would have been just over half charged at midnight coming in, so would have coped with the stuff going on until the sun went down. Then they would have been rapidly depleted and gas turbine back up generation would have had to kick in at 8 pm. The peak deficit after the contribution of tier 1 batteries (column T) was just under 30 GW. So with the 40 GW of gas back up to 10GW of it could have been down with burst pipes or unable to obtain fuel and demand would still have been satisfied at all times.

        The day does raise the issue of whether the tier 2 renewable gas produced by electrolysis etc. using surplus electricity is going to be stored in dedicated stores for the grid, or together with natural gas and maybe then subject to state rules on how it is allocated in an emergency.

        The new peaks that year are more a matter of ERCOT getting their forecasting and planning correct (which they normally do) so are less interesting from a grid model perspective.

    • Yes – that was my first idea.

      “Unlike common random series like those observed, for example, in games of chance, hydrologic (and other geophysical) time series have some structure, that is, consecutive values of hydrologic time series depend on each other. A special kind of dependence observed on large timescales was discovered by Hurst half a century ago and has been known by several names such as long-range dependence, long-term persistence, or simply the Hurst phenomenon. Since then, it has been verified that this behavior is almost omnipresent in several processes in nature (e.g., hydrology), technology (e.g., computer networks), and society (e.g., economics). The consequences of this behavior are very significant because it increases dramatically the uncertainty of the related processes. However, even today its importance and its consequences are not widely understood or are ignored, its nature is regarded as difficult to understand, and its reproduction in hydrologic simulation is considered a hard task or not necessary. This article shows that the Hurst phenomenon can have an easy explanation and easy stochastic representation and that simple algorithms can generate time series exhibiting long-term persistence.” http://onlinelibrary.wiley.com/doi/10.1002/047147844X.sw434/abstract

      It happens with hydrology, wind fields and clouds. Climate is stationary over very long time frames (millennia) with shifts between regimes with changing means and variance at all scales. The question of natural extremes is not simple to resolve. With 100% renewables there is a hard limit on resource availability – and if demand exceeds that by even 6% the system runs dry and depends on suitable climatic conditions to start generating again.

      There is an analogous system.


      Climate determines the amount of rain that falls. We may get for instance hundreds of years of high rainfall and a hundred years of drought. You generally try to get as big a storage as possible – because cities inevitably grow. Even then reserves frequently get worryingly thin. We then start rationing.

      If we have been prudent – efficiency is maximised. Stormwater and sewage effluent are recycled. People are encouraged to use water efficient appliances and to sprinkle gardens at night – or not at all. If we are smart we have a desalination capacity to supply some demand continuously and conserve storages.

      With 100% wind and solar you would need the worst day and month resource and sufficient storage to meet demand with some prudent reserve. What happens if we get gloomy skies or the doldrums for weeks? Peter seem to be suggesting additional gas backup on top. The economics are looking fairly shaky – but I suspect that’s a pre-ordained conclusion. A bit of a straw man possibly?

      • Curious George

        “Random” processes where today’s values depend on yesterday’s values are described by a red noise, not a white noise.

  30. Fun reading.


    I couldn’t get past the first paragraph of this John Cook screed.

    “There is a consensus of evidence that human activity is causing all of recent global warming. Not some of it. Not even most of it. All of it.”

    (How does evidence vote?)

  31. Breakthroughs are always just around the corner.

    Here’s a range extender for an EV – 65kW linear generator with 60% efficiency and 18 moving parts.


    Team it with ceramic Ultracapacitors?


    “Right now, electric car batteries are acid-based, toxic, environmentally-unfriendly and heavy with a limited life span. Moreover, charging stations remain scarce. Our UltraCapacitor will significantly reduce the long hours currently required to recharge electric cars. It can endure millions of charging cycles, is fully recyclable and contains no environmentally harmful elements. It paves the way for zero-emission transportation worldwide.”

    Krstic has already proved that his ceramic battery can contain much more electricity in a smaller size than current chemical based batteries. This is due to a multi-layered capacitator design, containing a ceramic di-electric non-conductor. What happens is a number of these capacitators are daisy-chained together to form a small, lightweight green battery. Using this technology, the release of electricity is not limited by chemical reaction rates, so electric cars can recharge in minutes as opposed to hours.

    Furthermore, production of this next-generation battery will be cheaper and cleaner, making electric vehicles more affordable in future.

    The company is currently developing a prototype that is anticipated to weigh less than 20kg (the Tesla Model S 70kWh battery package weighs 535kg) and deliver five consecutive hours of driving. ”

    Some EV’s are supercool.


    If the capacitors were cheap enough – would we need gas generator backup?

    • RE, wrote about FPLG in my post on vehicle decarbonization last year. You pictue a more evolved version of the Israeli one. Is real, and is a solution for Volt type vehicles.
      The pictured ultracapacitor wont work, period. If it has as advertised a ceramic dialectric, it is just a big ordinary MLCC (multilayer ceramic capacitor, about an $8 billion industry). A failed company named EEStor even had two completely bogus issued patents on this idea, and raised millions in Canada. Futzed around for almost a decade. Complete bust. The whole idea violates some very basic capacitor physics. The problem is that high dielectric constant ceramics like CMBT only have those values at low voltages, while energy stored is a function of voltage squared. The tradeoff is known in the mlcc capacitor industry as VCC. Google takes you to standard mlcc info on vcc. EEStor, its fatally flawed physics, and its patent fr*** is an example in my ebook The Arts of Truth.
      Real ultracapacitors aka supercapacitors aka EDLC rely on Helmholtz layer physics, and so must have a liquid or polymer gel electrolyte. Even with the ~50% improvements brought by my patented Nanocarbons, they cannot replace batteries; an order of magnitude too little energy density.
      I remain much less hopeful about energy storage. The only possibility that might make sense is the Fisker Nanotech approach, although there is little info yet. Wrote that up also in the vehicle decarbonization post.

    • It is a linear generator – an idea that , There is a German version I know. Toyota has been working on one for a few years.

      The ultracapitor has an impeccable pedigree.

      The ground-breaking research programme was conducted by researchers at the University of Surrey’s Department of Chemistry where the project was initiated by Dr Donald Highgate of Augmented Optics Ltd. The research team was co-led by the principal investigators Dr Ian Hamerton and Dr Brendan Howlin. Dr Hamerton continues to collaborate on the project in his new post at the University of Bristol, where the electrochemical testing to trial the research findings was carried out by fellow University of Bristol academic – David Fermin, Professor of Electrochemistry in the School of Chemistry.

      Dr Ian Hamerton, Reader in Polymers and Composite Materials from the Department of Aerospace Engineering at the University of Bristol, said: “While this research has potentially opened the route to very high density supercapacitors, these *polymers have many other possible uses in which tough, flexible conducting materials are desirable, including bioelectronics, sensors, wearable electronics, and advanced optics. We believe that this is an extremely exciting and potentially game changing development.”

      • … an idea that is far from new….

      • “Storage-related challenges are important to the widespread adoption of hybrid electric vehicles (HEVs) and electric vehicles (EVs). EVs are propelled by an electric motor that, in turn, is powered by a rechargeable battery. The state of the art Li-ion battery can store considerable power but it charges and recharges slowly, limiting the range that an EV can travel. Supercapacitors, on the other hand, can charge and discharge rapidly but store 10 times less energy than a li-ion battery. Increasing the charge storage in supercapacitors (“supercaps”) at competitive cost, while retaining the charge-discharge rate would be disruptive, enabling their use in a variety of storage applications including EV’s.” https://arpa-e.energy.gov/sites/default/files/documents/files/Fastcap%20-%20Open%202009%20External%20Project%20Impact%20Sheet_FINAL.pdf

        Super and ultra capacitors are the same thing. The energy density that the device can store is proportional to the electrode surface area. Aligned carbon nanotubes allow 3 tines the energy density of a carbon electrode. Organic polymers do this at the molecular level.

        “Supercapacitor electrodes and devices that utilise conducting polymers are envisaged to bridge the gap between existing carbon-based supercapacitors and batteries to form units of intermediate specific energy. This review looks at the major conducting polymer materials, namely, polyaniline, polypyrrole, polythiophene and derivatives of polythiophene, as well as composites of these materials with carbon nanotubes and inorganic battery materials. Various treatments of the conducting polymer materials to improve their properties are considered and comparisons are made with other supercapacitor materials such as carbon and with inorganic battery materials. Conducting polymers are pseudo-capacitive materials, which means that the bulk of the material undergoes a fast redox reaction to provide the capacitive response and they exhibit superior specific energies to the carbon-based supercapacitors (double-layer capacitors). In general conducting polymers are more conductive than the inorganic battery materials and consequently have greater power capability. On the downside, conducting polymers swell and contract substantially on charge and discharge, respectively. Consequently, cycle-life is poor compared with carbon-based supercapacitors which generally only charge via adsorption and desorption of ions (giving typically a few thousand cycles for conducting polymers compared with >500 000 cycles for carbon-based devices).” http://www.sciencedirect.com/science/article/pii/S0378775310010712

        “The technology was adapted from the principles used to make soft contact lenses, which Dr Donald Highgate (of Augmented Optics, and an alumnus of the University of Surrey) developed following his postgraduate studies at Surrey 40 years ago.” http://www.bristol.ac.uk/news/2016/december/super-capacitors.html

        So have they cracked conducting polymer chemistry?

    • There appears to be a goodly amount of techno-hype and gobbledygook on his website:


      ‘By developing a very high capacitance dielectric, it will be possible to store larger amount of charge at lower voltages (all the way to 220V) thus making it easier to charge and possibly eliminating the need for specially constructed charging stations. In comparison with Tesla’s battery, which requires a charging time of 12 hours, Ultra-Cap’s units will be fully charged in only 4 minutes. These results can lead to a total reduction of cost of around 30% per kilometer. ‘

      This really doesn’t sound right at all. Tesla batteries will charge in ca. 30 mins to 80% on a 128kW charging station. 4 minutes would need 1MW for the same charge – some 220V outlet!

  32. I just read something I wrote a while ago – and it reminded what’s at stake in discussions about energy.

    “Climate change can’t be solved on the backs of the world’s poorest people,” said Daniel Sarewitz, coauthor and director of ASU’s Consortium for Science, Policy, and Outcomes. “The key to solving for both climate and poverty is helping nations build innovative energy systems that can deliver cheap, clean, and reliable power.” https://thebreakthrough.org/index.php/programs/energy-and-climate/our-high-energy-planet

    There’s not a huge future for oil, gas and coal – but what future there is needs to unfold according to fundamental economic principles. Prices will rise with demand and scarcity. Fracked gas has decades before it basically just stops flowing. Fossil oil production has peaked and will decline. Coal has 60 years reserves at current use. Innovation will drive technology – and markets will freely and rapidly adapt – with higher productivity – to changing technology.

    But over decades at least the use of gas, oil and coal will continue to expand – strongly in the developing world. That’s as it should be. Non-OECD energy growth must occur with the cheapest and safest sources – if we are to grow economies globally and alleviate dire problems in food security, health, education, social services, environment and human rights more generally.

    The 21st century is when it all begins – and there is little beyond the grasp of the technological monkey.

    • “Innovation will drive technology – and markets will freely and rapidly adapt – with higher productivity – to changing technology.” With all due respect the changing technology could very well be more efficient and effective extraction techniques.

      “Fracked gas has decades before it basically just stops flowing. Fossil oil production has peaked and will decline.” The fracturing technique is being applied to oil production now in the Permian Basin and production and resource assessments continue to increase (https://www.eia.gov/todayinenergy/detail.php?id=30952). In the Eastern US the Marcellus shale has received most of the attention but the deeper Utica shale is relatively untouched. I imagine there are other currently untapped resources worldwide waiting for their own fracturing revolution so I do not agree that there is no future for oil, gas, and coal.

      My point is that when the total cost is calculated the future is still fossil until such time a breakthrough is made to solve the inherent problem of intermittent and diffuse renewable energy. Even if a technological breakthrough is made for nuclear power it has to overcome public misgivings.

    • I am advocating that coal, gas and oil be exploited just as fast as we possibly can. We are pumping gas as fast as we can and loading it on ships. I say we because I have worked on the export terminal on Curtis Island and in the gas fields,
      But between the rock of exponentially increasing demand and the hard place of declining reserves and deeper and more expensive resources – there is a crunch coming. With fracked gas it will be fast.

      Nuclear – btw – is not all that difficult. There have 20 fast neutron reactors built in the past 60 years – with 400 years of operational experience between them. General Atomics have fully costed this version – the only full costing I am aware of – and it is competitive with gas at $6-$7/MMBTU.


      The unmoderated core burns at high temperature allowing the containment vessel to be shrunk dramatically while improving thermal efficiency. It is an unmoderated core design – that is sealed and is passively safe. It has a small footprint and is helium cooled – no water. The rest is just stock standard, highly efficient engineering. Best of all – it can burn any fuel including nuclear waste, plutonium and thorium. It has a closed fuel cycle. It burns most of the energy in fuel – as opposed to 1/2% in light water reactors. After every burn cycle – it is designed to burn for 30 years without human intervention – some 3% as fission products are removed for permanent storage. The rest goes into the next burn cycle with extra fertile material.
      Fission products decay to background levels of the original fuel within 300 years.



  33. so what happens after a couple of days of cloud with no wind? batteries will run down and then you are dead in the water without anywhere near enough capacity. better start eating everything in the freezer before it spoils, only no power for cooking. no power for electric car. back to the stone age, cooking over a wood fire as long as the trees last. only no trees in texas. have to cook using cow chips.

    • ferdberple, you are not thinking big enough!!! You get weeks, not days of cloud and no wind, but fortunately it doesn’t happen very frequently. This is where the 14,000 TWh of tier 2 renewable gas storage comes in. It stores the fuel to run the back-up gas turbines when renewables and 7.5 hours of average load of battery storage cannot cope. Details in the article above.

      • A lot less effort (and invention) would be using Thorium molten salt (or such) generated electricity. Grid concept remains the same with improvements in grid operation more understandable and predicable. I think wind and solar is unwise. Thorium reactors also provide reduction of the current nuclear waste product from Uranium. Its win-win and Thorium reaction can’t melt down.

      • The calculated cost of power-to-gas ist about 0.5€/kWh. Plus storage tanks investment.

        Compared to 0.02 €/kwh for coal/lignite. Why shoud we do that?

      • naturbaumeister, the guy who wrote the mixed renewable gas paper reckons with the 70% efficiency he can get the cost down to 3 cents / kWh. I’m not saying I believe him or that it is low risk to develop a new techniques, but his figure is much higher than yours!

        You’ll have to wait for part 2 to see what the figure for renewable methane is….

  34. 100% renewable includes gasoline. One must add to the future 100% grid-demand that of what gasoline produces today (reduced per efficiency between engines and motors and transportation). This works out to about 35-40% increase in the Texas (or national) grid.

    Regardless of energy-grid type, people still need jobs so that cost will not change. The same with EV production.

    • Albert Hopfer. A link to the 35-40% increase calculation would be appreciated.


      Jim D calculates a move to EV’s for private vehicles to add 10% to the USA grid annual figures, and underneath that I get the same answer using a different method.


      It may be possible to electrify USA freight (and passenger) train transport economically with batteries, because trains are very efficient in energy use. Air travel and long-distance cargo trucks are not so straightforward and are likely to require production of chemical fuel. It’s an interesting topic.

      • Hi, Peter.
        US based 2016

        1-gallon of gasoline = 33.4 Kilo-Watt-Hrs.
        gasoline end-use = 143.4 B Gallons
        generated electricity =4,100 B Kilo-Watt-Hrs. (end use is 3.853 but using raw output here)

        US autos run between 25% and 50% efficiency. Using 25%.

        A note here: The loss is heat, some of that heat (gas auto) is used to warm occupants and defog windows in cold weather. EV’s will have to use charge to run electric heaters.

        EV motors at rated load run 75% efficient, US manufacturing rating to prolong motor life and expense
        Charging large format batteries efficient 90-85% (depending on temperature and rate of charge)
        using 88% against 75% = 66% efficiency EV batteries.

        Note here: EV’s lose mileage big time in cold weather, shorter distance per charge, more charge needed.

        EV motor (savings) versus Gas Engine = 66 – 25 = 41%

        Consumed gasoline x gasoline energy minus (EV efficiency versus Gas) = additional Watt-Hrs. from grid.

        1.434 x 10^11 x 3.34 x 10^4 = 4.8 x 10 ^ 15 = 4,800 B Kilo-WattHrs less 41% equals
        4,800 x .59 = 2,832 B Kilo-Watt-Hrs. additional needed for electrifying EVs

        4,100 + 2,832 = 6,932 B Kilo-Watt-Hrs. or 40.8% more electricity needed to charge EV’s from US grid.
        Diesel = more yet.
        * calculation results vary dependent on amount of sleep.

  35. Peter: I’m skeptical that those running a grid can count on the batteries in electric vehicles to provide a reserve. In Texas, that reserve is most needed in the late afternoon (when solar is dropping and wind is the only renewable available. That is also the time when making cars are being used for commuting. Every weather forecaster on every local TV station (and over the internet) will be warning citizens about nights when winds are forecast to be light and electricity from wind may not suffice to fully charge everyone’s EV overnight. (Or it will be rationed by high price.) Unless there is a large financial incentive to connect your car to the grid on such afternoons (an incentive that needs to be added to the cost of renewable power), IMO batteries in car will not provide a reserve when the grid needs it most.

    Budischak et al (2013) analyzed how renewable power might meet 30%, 90% or 99.9% of power needs hour-by-hour in the PJM region with 99.9% reliability. For high penetrance of renewables, they proposed massive overbuilding of mostly wind turbines, so demand could be met with output that was 10% of nameplate capacity – which results in “spilling” about 2/3rds of the wind power. This is because the cost of storage or transmission to distant locations is too high. You didn’t include transmission costs and the role bottlenecks played in the California Power Crisis. (The nameplate capacity of fossil fuel plants on current grids is about double average demand, but those plants are turned off when not needed and no money is being spent on fuel. We are under the illusion that we will be able to make good use of all wind and solar power, no matter when or where it is produced.


    • franktoo, indeed the success of V2G is dependent on human behaviour and that is notoriously difficult to forecast. But V2G trails are starting right now in some places – I must find out how to volunteer for the Nissan UK one. So by the time the big EV switch happens (my estimate is 2025) we will know whether V2G really can provide all the required grid storage or not.

      In part 2 of the article V2G will probably provide only the low estimate for tier 1 battery storage. The high estimate is for the grid to purchase 300 GWh of its own batteries.

      Transmission upgrade costs will be included in part 2. Transmission is just not in the grid model because there’s an easy assumption that a full 80 GW of transmission from CREZ areas is required (to match the solar capacity), even though the peak load for the scenario is only 71 GW.

      PJM probably doesn’t have both excellent wind and solar but Texas indisputably does. Just because an old model of PJM had to use the old estimates of storage prices doesn’t mean the current estimates show the same thing! Many things have changed in the last few years. Texas scenario 3 has only about 27% overgeneration from renewables (not 500%) to cope with storage losses and inevitable surplus.

      If you look at the grid model or the summary of scenario 3 in the article above you will see that there is indeed some surplus renewable generation that just is not used, at least for grid purposes, because it is only available occasionally and it is not worth investing grid money. Someone might find a use for it however, as it will be virtually free but very sporadic.

      • Peter: Thank for the reply. You are correct, Budischak found that solar didn’t play a major role in the most cost effective scenarios, presumably due to the weaker and more irregular sunshine.

        Budishack did one thing no other previous papers had done (nor have you, as far as I can tell). The took 35,000 hours (4 years) of real demand data combined it with real weather data for the same days. Then they looked at all possible combinations of generation sites and storage capacity that would meet that demand for all but 35 h (99.9% reliability) in those 4 years. Then they identified the lowest cost solutions. Nothing was averaged – historical periods of calm and/or high demand were met (or failed to be met) from current production or available stored power for the full 4 years. It is worth studying for that reason. I don’t think much is badly out of date, but ll of their costs assumptions are fully detailed and you can substitute the numbers you prefer.

      • franktoo, it sounds like there are distinct similarities between the PJM exercise and the Texas grid model.

        The PJM exercise took 35,000 hours (4 years) of real demand data. The Texas grid model has 26,420 hours (3 years) of real demand data, combined with the real wind power generation data for those same hours and the solar irradiation data for four (10km x 10km squares) for those same hours. That’s why the spreadsheet is over 20 MB.

        The Texas grid model also does not average anything (except on the reporting rows). It also meets historical periods of calm and/or high demand from current production or available stored power for the full 3 years.

        Why don’t you have a play with the grid model spreadsheet, which will enable you to understand specifically how it works? You never know, you might actually have some fun with tweaking the scenarios too!

        The cost data in part 2 won’t be used specifically to optimize the solution – mainly because there will be a range of uncertainty in each cost and the optimization would depend on knowing costs more accurately. But the resulting total cost should be in the right ballpark.

        There are some simplifications in the Texas grid model – only three years, only four solar locations, some slight inaccuracies in the way it handles predicted solar generation, but these are going to result in only slightly different results than you would get from a much more comprehensive model which it would be impossible to make available to ordinary mortals armed with only a spreadsheet (which can be free Libre Office).

  36. Is even 80% by 2050 possible? The total is some 4.08 trillion kW/hr from utility scale generation and 0.02 kWh from household solar. In the scheme of things wind and solar are still relatively minor players. The worst that can be said about wind and solar is that they attract subsidies and makes life difficult – apparently – for a NZ power plant operator.

    There are other renewable energy technologies that are feasible of course – and cost competitive. The mix looked something like this in 2016.

    Natural gas = 33.8%
    Coal = 30.4%
    Nuclear = 19.7%
    Renewables (total) = 14.9%
    Hydropower = 6.5%
    Wind = 5.6%
    Biomass = 1.5%
    Solar = 0.9%
    Geothermal = 0.4%
    Petroleum = 0.6%
    Other gases = 0.3%
    Other nonrenewable sources = 0.3%
    Pumped storage hydroelectricity = -0.2%.

    This is the 2050 mix from the NREL energy futures study. There is a limited scope for expansion of most renewables. It does rely mostly on wind and solar. In the 80% scenario there is 50% support from dispatchable sources.


    The cost increase over a baseline scenario is significant. This would further undermine American competitiveness and be a burden on consumers. A problem for the world as American trade and consumption fuels global growth.


    Texas doesn’t meet it’s own demand in this scenario.


    Global energy consumption will increase by 350% this century. It can’t be done with dinosaur technology. It needs a new energy paradigm.

    Current generation capacity is about 6.5tW. Increasing this to 15tW by 2050 requires building 1000 a year of the 250MWe advanced nuclear plants I keep talking about.

    “But to Smalley, there was one key that could unlock the entire puzzle. In the 21st century what the world needs most, he said, is abundant, low-cost, clean energy-a resource that can raise living standards, desalinate seawater (for crop irrigation and human health), increase food production, restore the environment, and promote global peace, health, and cooperation.”

  37. The problem is that cloudy, windless days are happening. Sometimes for weeks. Especially in winter.

    Which means you need nearly full conventional backup.

    This is the case in Germany.

    Here you can look how Renewables have performed in Germany. You can type in any span of time and you will get a graph.
    (Click at “Auswählten Zeitraum darstellen”)


    Storage is simply not yet available and will be very expensive.

    • Naturbaumeister, your assumption is wrong! The grid model shows you need only 30 GW of conventional backup for a grid peaking at 71 GW based on 2010 to 2012 data and perfect forecasting. However, I’ve added 10 GW to that for real-world forecasting and the limited number of years in the model to give 40 GW of back-up which is the average ERCOT load.

      Peak load days are caused by air conditioning and area always very sunny, so solar generation can always be relied on to reduce the daytime peak, but not the evening peak (8-9 pm). So you can always subtract around 8 GW from the peak load for that.

      Then you have 300 GWh of storage, so on cloudy still days you can start all backup generation before you need it and store a few hours of electricity then use batteries alongside back-up generation to get through the peak hours.

      In addition there may be industrial customers willing to be paid large sums on the very infrequent occasion when they are asked to reduce their load considerably, and that may be much cheaper than having gas turbine plant sitting idle most of the time just for peak days. That’s not included in the model.

      That’s why you need to use a grid model rather than rely on intuition – to let you explore solutions to situations such as these. At the moment it is fed with real data on what happened, but you could equally well check out scenarios where you stitch together a series of peak days or whatever, to confirm you can cater for the load combinations which might occur.

      • You say that “Peak load days are caused by air conditioning” but that ignores the fact that there is a winter peak too which is caused by shorter days and colder temperatures. When I started at a NYS Upstate utility 35 years ago the annual peak was in the winter but had changed by the earlier 90’s. Needless to say solar for winter peaks is not nearly as viable as for summer peaks.
        Advocates for less natural gas use in the RGGI region are now arguing that air-source hear pumps are a solution. That, in my opinion, is lunacy because air source heat pumps are inefficient in below freezing temperatures simply because there is less energy in the air to extract. The “solution” is radiant heat which sucks electricity. This will contribute to the inevitable need for subsidies for fossil backup for fewer but increasingly more critical peak hours when you really need the power to prevent freezing in the dark or frying in the heat.

      • Rogercaiazza, the article is about Texas, not about New York. The solution for New York would be different.

        The Texas grid model data includes both summer peaks and winter peaks. Filtering on the grid model spreadsheet, combined with setting the wind generation total to zero shows that solar PV generation covers 8GW of the peak day load. So we know that in the three years of data that either any winter peak is 8GW lower than the summer peak, or that solar PV also covers any winter peak days in the data.

        The spreadsheet data is available if you wish to investigate Texas winter peaks.

  38. Another problem: We are just talking about electricity. Primary energy comsumption is about five-fold in Germany.

    Wind is covering only 2.1%, Solar 1% of Primary energy consumption in Germany.

  39. Peter Davies, thank you for the essay. I look forward to the sequel.

  40. A very interersting article and analysis, but there are a few issues:

    Storage: It would not be practical in any real world sense to build a 300 Terrawatt hour battery storage system. To get an idea of the scale of the problem, let’s use the lead acid battery in your car as an example. For a medium sized car, this might have a rating of 100 amp/hours, or approx 1200 watt hours capacity. That is, 1200 watts for 1 hour, though this would be much less in in practice, being affected by age, load profile and temperature. Weight approx 25Kgms, or ~50lbs.

    Now scale that up to 300 Terrawatt hours and we have:

    300E12 / 1.2E3 = 250E9, or 250 billion batteries at, say, $50 each.

    Weight: 2.79 billion tons

    Ok, a simplistic analysis, but just to illustrate the scale involved.

    Correct me if the sums are wrong. I choose lead acid as it’s the easiest to visualise and also the lowest cost. You could use Lithium tech, as per Tesla energy wall, but that would have more complex issues and is far more expensive.

    Such a system would provide only an hour’s worth of storage and there are other issues as well, such as cost, toxic manufacturing and disposal processes, a typical 5 year battery life under charge / discharge cycled conditions and the infrastructure needed to support and maintain. such a system.

    I’ve been experimenting with backup energy systems for the house and lab here on and off for decades and there really are no easy or low cost answers to the problem. I’m also suspicious about the claimed capacity factors for wind and solar. Though Texas may have more wind and sunshine, here in the UK at least, government reports and actual measured capacity factors, solar or wind, over a year, are never better than 5-10% of nameplate rating…


    • Mostly they have been talking about 300 GWh, not 300 TWh, and also your conversion to tonnes was off. For electric vehicle batteries the storage is about 10 kg/kWh, and there are already some with less than this. This gives 3 million tonnes. At a little greater than the density of water this would be a cubic volume probably about 100 meters on a side.

  41. Right, I should proof read before posting, but even correcting the error, it’s still 250 million batteries. Likewise for the weight, which was based on a lead acid battery model, the cheapest engineering solution.

    Electric vehicles use Lithium, a much more expensive technology and not so stable. I’m not sure I would want one of Tesla’s power wall solutions in my home, but perhaps outside well away from the house. All that made down to a price energy density in a home is a real fire risk…

  42. The solar capacity factors assumed here seem inflated beyond the data:

  43. Rogers Andrews post and my article on Texas make some very different assumptions.

    Roger is posting about the USA as a whole, the data is only for installations generating in the period ending in 2016 and he assumes a considerable proportion of rooftop and distribute solar and probably there’s an implicit fraction of single axis tracking for utility solar only, with . His data is actual power generated.

    Because the current 500MW of solar PV generation in Texas is in sub-optimum locations (East Texas) there is very considerable scope for improvement in the current number which Roger is analysing.

    My projection is for 2030 solar PV and is based on very specific assumptions. It assumes utility solar PV only (no distributed solar PV), with two-axis tracking (adds 5% to the CF), an inverter loading ratio of 1.26 (adds another 5%), with a split of installations in four locations, of which two are excellent locations for solar in the CREZ regions in Texas (adds another few %). The grid model does calculations for all these factors based on solar DNI (direct normal irradiance) which is supplied from NREL via SolarAnywhere.

    The grid model does not explicitly support single axis tracking, though you could easily add it if you wished provided you understand the required spherical geometry factors.. However, provided the same number of GWh was generated per day, by a higher capacity of solar PV generation using single or no axis tracking, then the addition of a little extra storage would enable a very similar result to be obtained as from the current scenario 3. The solar generation would be a little more concentrated into fewer hours, but the storage would enable that to be smoothed out into the evening, albeit with a slightly later morning start time.

    So there’s a small project for someone else to a) validate that the grid model derivation of solar PV generation from DNI is roughly right and b) to implement a second solar PV generation column for each location assuming only single axis tracking instead of dual axis tracking, then to work out approximately how much extra grid battery storage would be required to give the same results as scenario 3 with two-axis tracking currently does.

    Anyone up for it?

  44. The data for Texas in the EIA showed 21.5% capacity. As you note those are actual data, not a hypothetical ideal system. It seems to me that one ought to understand why the actual installations don’t look like the hypothetical ideal in order to decide whether that hypothetical will ever be realistic.

  45. Steve,

    14 large solar PV installations at the end of 2015 totalling 192 MW AC capacity are listed in this ERCOT document – http://www.ercot.com/content/gridinfo/resource/2015/adequacy/cdr/CapacityDemandandReserveReport-December2015.pdf .

    The county is given, which, in conjunction with eyeballing and interpolating the solar irradiance chart in the article shows that these had an average of around 5.1 units of irradiance, whereas West Texas and Panhandle (i.e. CREZ) installations would have an average of around 6.2 units of irradiance.
    This gives an expected uplift to the 21.5% 2015 CF (capacity factor) of x 1.22, resulting in 26.1%. That is the easy bit.

    The second question is how many of the 2015 installations have single-axis tracking (dual axis is unlikely). The Internet says Acacia Unit 1 installation in Presidio county has single-axis tracking, but a search for most (but not all) of the other installations finds no information on tracking capabilities, neither does the NREL OpenPV project record this.

    If none of the remaining installations has even single-axix tracking then a dual-axis tracking CF uplift in CREZ locations of x1.36 would give a CF of 35.5% which is too high. If they all had single-axis tracking then the uplift is x1.11 and the dual-axis tracking CREZ CF would become 29% (both compared with 32.4% from the model). The truth may be somewhere in between.

    In addition to this you have to take into account the differing overconfiguration of the solar panels (less losses), compared with AC grid capacity. The OpenPV NREL database link is https://openpv.nrel.gov/search?state=TX&zipcode= and includes DC capacities. Set the power range size to 1000 to 100,000 and you get a list of records which should include those in the ERCOT document above which has the AC capacities. Ignore those installed after 2015 and then try to match (sometimes 2 : 1) by county and installation year. Sometimes the site or supplier name is present.

    I get ILRs (inverter loading ratios) of 0.82 (X), 1.00 (?), 1.05, 1.07, 1.16, 1.27 and 1.5 (for Barrilla solar in Pecos) with 4 unmatched AC records (25% of capacity). The 0.82 is clearly wrong and the 1.00 is probably not right either – someone has probably copied the AC capacity into the DC capacity field. Only two of the big 4 installations (totalling 125 MW out of 192 MW) have believable matches. These two have an average ILR of 1.14, which makes sense as they are from 2011 and 2013 when solar panels were much more expensive.

    In the grid model a change of ILR from 1.26 down to 1.14 would reduce the solar CF from 32.4% down to 30.6%, a reduction of 1.8%.

    In conclusion, taking into account the available information on Texas solar PV installations present at the end of 2015, the grid model average capacity factor of 32.4% is within a couple of percent of a projection obtained by factoring the 2015 actuals because of changed assumptions. The match will be pretty close if some of the 2015 installations use fixed panels with no tracking.

  46. A new technology may emerge in the US that would substantially reduce the 22.5% in transmission line losses without adding more cost or emissions. This would render solar and wind power obsolescent. Power line losses are a complex matter and vary by state:


  47. Pingback: Can Texas go 100% renewable? | Energy Matters

  48. aporiac1960

    Roger Andrews at Energy Matters has now posted a detailed response to this proposal, here: –


    • aporiac1960, thanks for the heads up.

      Roger Andrews has chosen a different and non-optimal scenario for Texas 100% renewables from the one described in scenario 3 above, so it is not surprising that he has obtained different results. If I feed his assumptions into the grid model (i.e. average renewable generation matches average load) it gives the results he describes (50TWh of total storage needed instead of 14 TWh). This is not the same as scenario 3 above. But it does provide one more test case in which the grid model produces similar results to an independent external calculation, which increases the confidence level in other grid model results.

      Roger Andrews has also misunderstood the way the grid model works – it is an hourly simulation using scaled data from the three years 2010 to 2012, not a probabilistic calculation as he states. Perhaps he wrongly assumed (as others have) that a spreadsheet cannot be used to do such a simulation.

      There’ll be a proper response to Roger Andrews’ points in part 2 of the article. You have to go to a level deeper than his analysis, as scenario 3 in the article above does, to understand why 100% renewables can work in Texas.