Critical Reserve Margins

Critical Reserve Margins

Are reserve margins for the grid a quaint idea from the past? One would think so, given how RTO/ISOs are approaching the question.

Reserve margins are supposed to ensure there will be sufficient generating capacity even if demand suddenly and unexpectedly surges.

This could happen during a heat wave when the use of air-conditioning increases. See, Wind Power Threat http://wind power threat

As mentioned in the last article, ERCOT has seen its reserve margin become dangerously low, at 7.4%. In the past its reserve margin was 13.75%.

But, what is the reserve margin when wind and solar are added to the grid? 

How can they be included as a reserve for use in an emergency when the reserve might not be there? As the last article explained, power from wind might not be available if there are freezing temperatures, or if it’s too hot. Or, when the wind isn’t blowing.

Power might not be available from solar when skies are cloudy for several days.

There have been attempts to use probabilistic analysis to estimate how much of installed wind and solar capacity should be included in the reserve. Though based on probabilities, it’s still only an estimate.

The only certain method would be to exclude wind and solar from any reserve margin.

The accompanying chart shows how much new build will be required in ERCOT’s territory to ensure a safe grid without blackouts. But how much of the new build can be wind or solar while still maintaining a safe grid?

ERCOT has said that the 10% of new build required in 2020 will be from new wind installations. Are they really counting on wind to provide sufficient reserve to bring the reserve back to 13.75%? A reserve that is only 3.5% if the wind doesn’t blow? And what about the following years? How safe will Texans be from blackouts when there is a negative reserve, i.e., shortfall?

The purpose of the reserve margin is to guarantee that electricity will always be available, barring system failures, so that there won’t be blackouts. But, any reserve based on estimates, no matter how scientifically made, can’t make that guarantee.

This is just another way in which wind and solar make our lives less safe.

. . .


4 Replies to “Critical Reserve Margins”

  1. Donn,

    the last two articles along with this one made me think about some of the problems with wind and solar that may not have been considered. What I’m talking about is wind and solar in areas hit with hurricanes and tornadoes. When those events happen, typically the end user of electricity is affected by the loss of structures and the transmission lines to get it there. I don’t recall hearing that power plants have been completely devastated or destroyed from this storms. While the transmission lines and poles/towers will need to be replaced, the power plant will still be serving those not affected.

    Now let’s remove the power plants and replace them with wind and solar serving that community. Throw in a devistating storm, and how quickly will the wind turbines in the fields, and solar panels on roofs be replaced or restored to get the rest of the area serviced with reliable electricity production?

    Questions like this need to be answered before we can say wind and solar are as reliable a source as our natural gas and nuclear plants.

    • Thanks. Great questions and great observations. I do not know of studies that have investigated how well wind turbines and solar plants have withstood hurricane winds.
      The power plants, i.e., coal, nuclear and natural gas, have survived these types of storms and we know from experience that it’s the transmisison and distribution lines that get knocked down.
      I don’t have an answr to your questions, but I’ll be on the look out for relevant information.

      • Thanks. Very interesting. At first blush one would think a rotted pole went first, but there is a lot about wind we don’t know.

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