by Energy Meteorologist

A local example of the penetration problem for renewable energy in Texas

The Electric Reliability Council of Texas (ERCOT) operates Texas’ electric power grid that serves 25 million customers in Texas.  ERCOT’s sources of generating are natural gas (51%), wind (24.8%), coal (13.4%), nuclear (4.9%), solar (3.8%), and hydroelectric or biomass-fired units (1.9%).  Power demand in the ERCOT region is typically highest in summer, primarily due to air conditioning use in homes and businesses. ERCOT region’s all-time record peak hour occurred on July 8, 2022, when consumer demand hit 78,204 MW.

This article describes an extended lull in wind and solar power during the period 8/1/22 – 9/12/22.  I then describe what it would take in terms of a system with 100% renewable generation plus storage to produce sufficient electric power for Texas during such a lull.

For background, read these previous articles by Planning Engineer:

Assigning blame for blackouts in Texas

The Penetration Problem. Part I:  Wind and Solar – The More You Do, The Harder it Gets

The Penetration Problem. Part II: Will the Inflation Reduction Act Cause a Blackout?

August 2022 temperatures for Texas were fairly typical – hot (daily high temperatures frequently broke 100oF), but not exceptional.  Texas temperatures during the first two weeks of September were slightly cooler than normal, with daily maximums in the high 80’s as a wet pattern enveloped most of the state.  What was exceptional about this period was an extended lull in both wind and solar power in the ERCOT region.

This chart plots the actual electricity demand (load) for ERCOT during the period 8/1/22 – 9/12/22 vs combined wind and solar production of electricity.  During this period of lull in renewable energy production, the demand loads were pushing into the mid and upper 70 GW range.

What would it take for a hypothetical electric power system to meet such a demand solely with wind and solar power?

Texas saw wind generation fall to 600 MW or lower with demand loads of 41-43 GW in the early AM hours when solar was zero, so it’s either 75 times wind capacity or a crapton of batteries. Either way, massive amounts of battery storage are needed in ERCOT for a 100% wind/solar/hydro grid. 400 – 450MWh of batteries would be needed to cover the extended wind lulls around Aug 22nd and Aug 30th, and during both events the batteries would be drained to 5-15% of capacity. Come the next day, you need excess energy to charge them so they can be used again the following night. The deepest discharge period (Aug 30th – Sep 2nd) during this time lasted for 63 hours and required a discharge of ~940 MWh while only charging ~75 MWh over that time period.

Clearly, a massive buildout of wind and solar would be needed to cover that gap.  Two scenarios are considered here, using back-of-the-envelope calculations.  Scenario #1: if you increase wind and solar 8 times current capacity AND add 900 GWh of battery storage, you would have been able to cover that month-long period with 100% renewables; this turns out to be much more cost efficient than the second scenario.  Scenario #2: wind at 4.05 times current capacity and solar at 8.45 times current capacity with 5000 GWh of battery storage.

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

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

Cost of Wind $1.35 Million /MW
Cost of Solar $1.5 Million/MW
Battery cost $385,000/MWh

Compare this with an estimated cost of nuclear power at $9 million /MWh, whereby that same amount of money for renewables ($800 billion) could build over 90 GW of nuclear power vs the 230,000 MW of renewables.   The figure below shows the current renewable generation stack plus the buildout of nuclear power (red line). Using that money to build out nuclear power instead would yield more power than ERCOT would need for the coming few years even with steady load growth AND would use <1% of the land area of the renewables. If you site the nuclear power plants at old coal facilities and outdated gas plants, the transmission interconnection is already there and costs would decrease as more nuclear capacity is built.

The recent month long period was unusually light for wind and solar BUT that is what electricity grids need to be designed for.  Assuming the 8xWind and 8xXolar + 900,000 MWH of batteries, this is what the summer would have looked like from a supply standpoint with batteries fully charged.  A little overkill, IMO.  Remember this assumes the charge and discharge of the batteries is 100% efficient, if you use a more realistic estimate you need to increase the battery storage by 10-15%

Power production from wind and solar hardware typically decays at 0.5% per year. Not much at first, but half way through their lifecycle it adds up to BIG numbers. Load growth as well needs to be taken into account, with 82 GW possible in the coming summer for peak demand. ERCOT has been averaging ~2 – 3% growth per year.

Since ERCOT is more or less an isolated grid, it is a good example for an academic/economic exercise such as this.  With such an overbuild of wind and solar for ERCOT, there would be a great deal of curtailed/wasted power once the batteries were fully charged. This chart shows the hypothetical wasted power for the recent Aug/Sept period with the 8xWind, 8xSolar and 900,000MWh batteries.  The grid would have wasted/lost a total of 37.54 TWh to serve a total load of 63.17 TWh. If you want to transport that power elsewhere, remember it costs $2 to $5 million per mile for new transmission lines.

Wind and solar are cheaper to build, but not when you take into account the overbuild and storage to fully serve the grid.  When total costs are considered, nuclear power is the cheapest option while also having the smallest environmental footprint overall.

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


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



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