The Moss Landing Power Plant is a natural gas powered electricity generation plant as well as a battery energy storage facility, located in Moss Landing, California, United States, at the midpoint of Monterey Bay. As of 2025, the site's battery storage facility is one of the largest in the world, at 630 MW (power) and 2,500 MWh (energy). The energy storage facility stores excess electricity (usually lower-price solar electricity during the daytime) for later use during periods of higher electricity demand (usually evening hours). The battery energy storage facility at Moss Landing consists of two separate energy storage facilities. The first battery storage facility, known as the Vistra Energy Storage Facility is owned and operated by the Vistra Corp, and the second, known as the Elkhorn Battery Facility is owned and operated by California's PG&E utility company. The Elkhorn Battery Facility utilizes Tesla batteries to meet its energy storage needs. The plant's two large 500′ tall stacks are local landmarks, visible throughout the Monterey Bay Area. Both the power generating plant and one of the battery storage facilities are owned and operated by the Irving, Texas based Vistra Corp. PG&E owns the second battery energy storage facility. The power generation plant currently has a capacity of 1020 MW (net) from its two combined cycle units. It was once the largest power plant in the state of California, with a generation capacity of 2560 MW, before its two large supercritical steam units were retired in 2016.
History In 1949, Pacific Gas & Electric (PG&E) began construction on the Moss Landing Power Plant. Five natural gas and oil powered steam units were built during the 1950s. Commercial generation started in 1950 with a capacity of 613 MW. In 1964, the construction of two additional units began (6 and 7), with two new 500-foot (150 m) stacks. These two units had a capacity of 750 MW each for a total of 1500 MW, with 180 feet (55 m) tall boilers. They employed a newer technology using supercritical steam at 3,600 psi (25 MPa). In 1995, the original five units were retired, and in 1997 PG&E let the permits lapse for these units. As part of the Deregulation of Utilities in California, PG&E sold the plant to Duke Energy (DENA) in 1998. To comply with more restrictive pollution regulations, units 6 and 7 were upgraded in 1998 with a selective catalytic reduction unit and digital control systems. Starting in 2000, the eight 225-foot (69 m) stacks and 19 fuel oil storage tanks were removed, and two new units were built on the former site. The new units 1 and 2 were brought online in 2002. They are combined cycle units, 50% more efficient than the other units, because they use two turbines: first, a pair of 170 MW gas turbines, then a 190 MW steam turbine, for a total of 530 MW each. When completed in 2002, the plant was the largest power plant in California by capacity, at 2560 MW. In 2006, having invested over half a billion dollars in upgraded capacity, efficiency and emission control, Duke Energy sold the plant to LS Power Equity Partners. Dynegy purchased the plant in April 2007 along with other assets of LS partners. In 2015, a transmission tower collapsed at the power plant, causing a major Monterey County area power outage. On December 31, 2016, Dynegy retired supercritical steam units 6 and 7 as they were no longer economically competitive. Dynegy continued to maintain the permit on these units. The facility was being dismantled in 2023. In February 2017 Dynegy announced that it may close Moss Landing, due to market conditions resulting from a glut of wholesale electricity capacity in California making it difficult to operate profitably. By 2018, California had 7,000 MW of surplus generating capacity, but a similar amount (mostly ocean cooled) would be retired by 2021. The glut in electricity capacity is partially a result of policies which guarantee utilities like PG&E (a regulated monopoly) a return on investment for building new power plants, even when they are not needed. Independent power producers like Dynegy, on the other hand, did not have a guaranteed return on their investment. Power production had dropped considerably, reducing taxes paid to Monterey County. On April 9, 2018 Vistra Corp merged with Dynegy Inc, and thus also acquired the Moss Landing Power Plant. Vistra opted not to close the Moss Landing plant, but instead to expand it. In 2021 Vistra began to refer to its Moss Landing power plant facility as the "Vistra Moss Landing Energy Storage Facility".
Connections to the California power grid The plant has power lines that connect it to Path 15, and interconnections like Path 26 and Path 66 that allow power to flow to far-away regions. The plant is also connected to local loads and the San Jose region by transmission lines.
Natural Gas power generation Both the supercritical units and the combined cycle units use once-through cooling. The supercritical units have a cooling requirement of 600,000 US gallons (2,300 m3) per minute, and the combined cycle units a requirement of 250,000 US gallons (950 m3).
Supercritical Steam Units 6 and 7 Units 6 and 7 used supercritical steam. These units were retired at the end of 2016. At the end of their life, units 6 and 7 were typically operated as peaking units when demand for electricity was highest. In 2016, the last year of operation, they only operated approximately 3% of the time. The generation process for units 6 and 7 starts with natural gas injected at one end of the boiler to be burned. Primary water is injected at the other end of the boiler to receive the heat produced. The gas simply comes from a natural gas pipeline, and combustion products go up the stack and into the atmosphere. Water has a much more complicated path, and consists of two distinct systems: coolant water and primary (steam-generating) water. Cooling water is pumped out of the Monterey Bay or the nearby Elkhorn Slough. Then it is purified, used to cool down the water coming from the turbines, and discharged into the ocean. Steam for the turbines is created from the primary water flow, which is preheated before entering the boiler. From the boiler, the superheated steam is directed into a first turbine working at high pressure, then into a low pressure turbine. The turbines drive the generators.
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