ERCOT Renewable Energy: a reality check

by Energy Meteorologist

A local example of renewable energy penetration in Texas

The Electrical Reliability Council of Texas (ERCOT) operates the Texas electrical grid serving 25 million customers in Texas. ERCOT’s production sources are natural gas (51%), wind (24.8%), coal (13.4%), nuclear (4.9%), solar energy (3.8%) ) and hydroelectric or biomass burning units (1.9%). Electricity demand in the ERCOT area is usually highest in the summer, mainly due to the use of air conditioners in homes and businesses. The ERCOT region’s all-time record peak hour occurred on July 8, 2022, when consumer demand reached 78,204 MW.

This paper describes the prolonged lull of wind and solar power during the period 8/1/22 – 9/12/22. I then describe what it would take for a system with 100% renewable generation plus storage to produce enough electrical power for Texas during such a lull.

For background, read Planning Engineer’s previous articles:

Blame the Texas Blackout

Penetration problem. Part I: Wind and Sun – The more you do it, the harder it gets

Penetration problem. Part II: Will the Inflation Reduction Act cause blackouts?

August 2022 temperatures in Texas are pretty typical – hot (daily highs regularly break 100 .)oF), but not the exception. Texas’ temperatures for the first two weeks of September were slightly colder than usual, with daily maximums being the highest in the 80s due to a wet pattern covering most of the state. What is special during this period is the prolonged lull for both wind and solar power in the ERCOT region.

This graph plots the actual electricity demand (load) for ERCOT for the period 8/1/22 – 9/12/22 against combined wind and solar power generation. During this lull in renewables production, load demand has pushed into the mid-70 GW range and above.

Screenshot 2022-10-30 at 9.25.15am

What would happen to a hypothetical power system to meet such demand with only wind and solar power?

Texas sees wind output drop to 600 MW or less with load demand of 41-43 GW in the early morning hours when solar is zero, so 75 times more wind capacity or a battery crapton. Either way, a large amount of battery storage in ERCOT is required for a 100% wind/solar/hydroelectric grid. 400 – 450MWh batteries will be needed for extended wind coverage around August 22nd and August 30order, and in both events the battery will drain to 5-15% capacity. Come the next day, you need to charge the excess energy so they can be used again the next night. Deepest discharge time (August 30order – September 2ndnd) during this period lasted for 63 hours and required discharge of ~940 MWh while charging only ~75 MWh during that period.

Obviously, large amounts of wind and sun are required to fill that gap. Two scenarios are considered here, using population calculations. Scenario #1: if you increase wind and solar to 8 times your current capacity AND add 900 GWh of battery storage, you should be able to cover that month-long stretch with 100% renewable energy ; this turns out to be much more cost effective than the second scenario. Scenario #2: wind at 4.05 times current capacity and solar at 8.45 times current capacity with 5000 GWh battery storage.

Screenshot 2022-10-30 at 9.42.50am

Yes, this whole scenario is pretty sketchy, but how much will it actually cost? For Scenario #1, 8X current wind construction and 8X current solar construction (364,000 MW) plus 900,000 MWh of battery storage, the cost would be $800 billion + transmission load. This calculation assumes that the charge/discharge level of the battery is 100%; if losses are taken into account, you need 10-15% more battery capacity. Additional transmissions cost between $2 and $5 million per mile. Scenario 2 is much more expensive than Scenario 1.

Scenario costs are based on the following cost assumptions (see References at the end of the post):

  • Wind cost 1.35 million USD/MW
  • Solar cost $1.5 million/MW
  • The battery costs $385,000/MWh

Compare this with the estimated cost of nuclear power of $9 million/MWh, whereby the same amount for renewables ($800 billion) could generate more than 90 GW of nuclear power compared to 230,000 MW of renewable energy. The figure below shows the total amount of renewable electricity present plus nuclear power building (red line). Instead, using that money to generate nuclear power will yield more energy than ERCOT will need over the next few years even if the load grows steadily AND will use <1% of the land's energy. renewable quantity. If you place nuclear power plants in old coal facilities and obsolete gas plants, transmission connections are already in place and costs will decrease as more nuclear capacity is built.

Screenshot 2022-10-30 at 9,52.14am

The recent months long periods have been unusually light for wind and sun BUT that’s what the grid needs to be designed for. Assuming 8xWind and 8xXolar + 900,000 MWH batteries, what would summer look like from a supply point of view with fully charged batteries. Slightly overkill, IMO. Remember this assumes that charging and discharging the battery is 100% efficient, if you use a more realistic estimate you need to increase the battery capacity by 10-15%

Screenshot 2022-10-30 at 10.00.30am

Power generation from solar and wind hardware typically declines at 0.5% per year. Not much at first, but in half of their life it will grow to a BIG number. Load growth also needs to be taken into account, with 82 GW achievable next summer for peak demand. ERCOT has grown on average ~2 – 3% per year.

Since ERCOT is more or less an isolated grid, it is a good example for an economic/academic exercise like this. With so much storage of wind and solar energy for ERCOT, a lot of energy is cut/wasted after the battery is fully charged. This graph shows hypothetical wasted power over the recent August/September period with 8xWind, 8xSolar and 900,000MWh batteries. The grid will waste/lose a total of 37.54 TWh to serve a total load of 63.17 TWh. If you want to ship that power somewhere else, keep in mind that it costs 2 to 5 million dollars every mile for new channels.

Screenshot 2022-10-30 at 10.02.02am

Wind and solar are cheaper to build, but Not when you take into account the excessive construction and storage to fully service the grid. When considering total costs, nuclear power is the cheapest option while also having the lowest overall environmental impact.

Here is a link [ERCOT Load vs Renewables ] into the spreadsheet, you can play with different situations yourself.


Click to go to 20190212% 20PSC%20Item%2005a%20Transmission%20Cost%20Etimation%20Guide%20for%20MTEP%202019_for%20review317692.pdf

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