In electric grid power generators, curtailment is the deliberate reduction in output below what could have been produced in order to balance energy supply and demand or due to transmission constraints.[1][2][3] The definition is not strict, and several types of curtailment exist. "Economic dispatch" (low market price) is the most common.[4]
Curtailment is a loss of potentially useful energy, and may impact power purchase agreements.[5][6] However, utilizing all available energy may require costly methods such as building new power lines or storage, becoming more expensive than letting surplus power go unused.[7][8][9][10]
Examples
After ERCOT built a new transmission line from the Competitive Renewable Energy Zone in West Texas to the central cities in the Texas Interconnection in 2013, curtailment was reduced from 8-16% to near zero.[11]
In 2018, curtailment in the California grid was 460 GWh, or 0.2% of generation.[13] Curtailment has since increased[7][14] to 150-300 GWh/month in spring of 2020 and 2021,[15][16] mainly solar power at noon as part of the duck curve.[17]
In Hawaii, curtailment reached 20% on the island of Maui in Hawaii in the second and third quarters of 2020.[18]
Curtailment in Texas
Monthly curtailment in California
Solar power and curtailment in California, by hour
^Paulos, Bentham (3 April 2017). "Too Much of a Good Thing? An Illustrated Guide to Solar Curtailment on California's Grid". www.greentechmedia.com. Archived from the original on 26 September 2020. CAISO considers three types of curtailment: Economic dispatch, a self-scheduled cut, and exceptional dispatch. These can all happen at the local level, to reduce congestion, or at the system-wide level, to reduce oversupply.
^ abPyper, Julia (9 May 2019). "Electric Ridesharing Benefits the Grid, and EVgo Has the Data to Prove It". www.greentechmedia.com. Archived from the original on 18 October 2020. the cumulative annual load profile by hour of LDV fleets using its fast charging network — with rideshare vehicles currently making up the lion's share on a gigawatt-hour basis — aligns with the cumulative solar curtailment by hour on the CAISO system
