The end is looming for aging power plants in California that use an ecologically detrimental process called “once-through cooling” (OTC) that the State Water Resources Control Board (SWRCB) is requiring to be phased out.
In OTC, power plants draw water from oceans, estuaries, lakes or rivers to cool steam after it has passed through a turbine to create power. But, the process results in the yearly loss of billions of aquatic organisms, including fish larvae and shellfish.
Some power plant owners are choosing to retire facilities rather than spending the money to comply with the SWRCB. Between January 1, 2015 and December 31, 2016, seven power plants units that use OTC were retired, according to a tracking progress report from the California Energy Commission.
In 2007, there were 19 power plants in California that used OTC, including the Diablo Canyon Nuclear Power Plant and the San Onofre Nuclear Generating Station. These two nuclear plants accounted for 55 percent of all OTC water use.
San Onofre shut down permanently in 2013, while Diablo Canyon Nuclear Power Plant is scheduled to be permanently retired in 2025.
The phase out of OTC has been underway since a 2010 SWRCB policy required power plant operators to reduce the harmful effects of OTC by installing evaporative cooling technology that would reduce water intake.
The policy was meant to achieve water quality goals while ensuring electrical grid reliability. It included recommendations made by the California Independent System Operator, the California Public Utilities Commission, and the Energy Commission.
Plants using OTC have to comply with the policy by 2024. The compliance date for the Los Angeles Department of Water and Power, which will affect the plants in the Los Angeles region, was extended to the end of 2029. Implementing the policy before then would create grid reliability issues.
All power plants are expected to comply with the policy by 2030. Renewable energy is expected to make up for the lost energy capacity from retiring plants early.
Photo of Diablo Canyon Nuclear Power Plant courtesy of Pacific Gas and Electric Company