NRG Energy outlines its once-through cooling strategy

NRG Energy (NYSE:NRG) owns six generating facilities subject to California’s once-through cooling (OTC) policy, company officials said in a recent email response to questions from GenerationHub.

Generation planners are lining up compliance strategies for the State Water Resources Control Board’s (SWRCB) policy on once-through cooling. Once-through cooling involves a process where water is pumped from the ocean, estuaries, rivers, or lakes to cool steam turbines and then returned to its source.

“It is NRG’s preference, where feasible,  to replace aging  steam boilers that rely on once-through cooling with new, more efficient, air-cooled peaking and fast-start combined-cycle generation,” according to the March 8 response from NRG representatives David Knox and Jeff Holland.

NRG has been actively pursuing new gas-fueled generation that integrates well with renewable energy sources while reducing the impacts of once-through cooling.

“We are accomplishing this objective at the Contra Costa Generating Station where we will retire the remaining steam boiler Units 5 and 6 (680 MW) in 2013, ahead of the 2017 OTC Policy compliance deadline, and replace those units with the Marsh Landing Generating Station – an approximately 720 MW air cooled peaking plant,” the NRG officials said.

“Also in 2013, we will replace three of the four steam boiler units at El Segundo (Units 1-3 totaling 685 MW) with a 560 MW fast-start, air-cooled combined-cycle plant. Units 1 and 2 have already been removed and Unit 3 (335 MW) will shut down during 2013. Unit 4 (335 MW) will shut down by the December 31, 2015 OTC Policy compliance deadline” the NRG representatives said.

NRG intends to replace the capacity from Units 3 and 4 with additional efficient, fast-start generation to support the Los Angeles Basin power needs.

“We remain committed to replacing the Encina Power Station’s (965 MW) steam boilers with the Carlsbad Energy Center – an approximate 560 MW fast-start air cooled combined-cycle plant ahead of the December 31, 2017 compliance deadline,” NRG said.

“At our Pittsburg Generating Station, we have proposed to retire Unit 7, and retrofit once-through cooled Units 5 and 6 to use the existing Unit 7 closed-cycle cooling system by December 31, 2017,” NRG added.

“For our Mandalay (430 MW) and Ormond Beach (1,500 MW) facilities, we are evaluating engineering solutions to modify the intake of ocean water to significantly reduce entrainment and impingement to achieve compliance with the OTC Policy and enable continued operation of these units beyond their respective compliance dates in the event that this generation is not replaced with new, more efficient generation,” NRG said.

Some of the NRG properties affected by California’s once-through cooling policy (Contra Costa, Marsh Landing, Pittsburg, Mandalay and Ormond Beach) were acquired through the 2012 merger with GenOn.

The once-through cooling rules are in many cases affecting plans for retirement or refurbishment of gas-fired power plants along the California coast, according to a Feb. 28 presentation by the California ISO. Other companies affected by the rules include AES (NYSE: AES), Dynegy (NYSE: DYN), Edison International (NYSE: EIX) and Pacific Gas and Electric. AES, for example, hopes to replace existing generating units at its Redondo Beach complex.

About Wayne Barber 4201 Articles
Wayne Barber, Chief Analyst for the GenerationHub, has been covering power generation, energy and natural resources issues at national publications for more than 20 years. Prior to joining PennWell he was editor of Generation Markets Week at SNL Financial for nine years. He has also worked as a business journalist at both McGraw-Hill and Financial Times Energy. Wayne also worked as a newspaper reporter for several years. During his career has visited nuclear reactors and coal mines as well as coal and natural gas power plants. Wayne can be reached at