Power curtailment is often viewed as a limiting factor of renewable energy, as intermittent cycles of generation can lead to excess electricity on the grid during peak production. Curtailment is the deliberate reduction in output that otherwise could have been produced, and typically occurs when supply exceeds demand.
The California Independent System Operator (CAISO) curtailed 1.5 million MWh of utility-scale solar in 2020, representing 5% of total production, according to the Energy Information Administration (EIA). Solar is by far the most dominant source of energy that undergoes curtailment in the state. EIA said 94% of power curtailments in 2020 involved solar energy.
While curtailment is often viewed as a bad thing, the National Renewable Energy Laboratory (NREL) said based on its research and modeling of the grid of the future, it may be time to reframe our thinking about power curtailment.
“(Curtailment) can happen not just in cases of oversupply but also when there’s a lack of system flexibility, which could mean congested transmission lines, other power plants being unable to reduce their output safely or economically, or other constraints,” said Kerrin Jeromin, NREL correspondent in a video on the subject.
“Think about it like buying a cable package for your TV—or a subscription to any of the streaming services out there. Buying that package knowing you can’t possibly watch all of the thousands of programs available to you isn’t all that different from building more renewable power plants, knowing we won’t always be able to use all the energy they produce. The point is, you have it for the shows you can’t miss, and the package gets you the best value in the end. We’re going to need a lot of wind and solar in a super-high-renewable future. And the best strategy might be to max out our renewable energy “package,” so we have enough power when we really need it, and get comfortable with curtailing some of it sometimes, to maximize its value at other moments.” National Renewable Energy Laboratory
Power curtailment is nothing new, as the grid has always had more power plants than are used. It is essential to reserve backup power for times of peak demand to keep the lights on. Currently, solar energy is serving that role in Texas, where fossil fuels are struggling to meet demand during summer heat peaks.
Curtailment comes with a particularly negative connotation because it represents lost opportunity. But as the cost of grid-scale renewables continues to decline, so does the cost of that lost opportunity.
“Curtailed electricity can be used to help make the grid more flexible and reliable, making these solar and wind systems more valuable in the end. It’s happening today: Xcel Energy can actively curtail wind generation to support reliability in its US power systems. And First Solar’s large-scale PV plant in Chile uses curtailment as a tool to help the grid respond to changing system needs, letting grid operators turn the system’s output up and down as needed,” said Jeromin.
NREL concluded that creating regulations that discourage curtailment could create barriers for renewable energy buildout, thereby limiting the many benefits it can offer.
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