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. Combined Cycle Units 1 and 2 Combustion products drive the gas turbines directly. First, air is drawn from the air intake to the compressor (driven by the turbine axle), then it is burned with natural gas in the combustion chamber. The hot combustion gasses then go through the actual turbine (driving the axle). From a thermodynamic standpoint, this is the standard Brayton cycle. Because the gas turbine does not transfer energy from the combustion process to the turbine via steam, it avoids the cost, energy loss and environmental impact of the primary water cycle. At the output of the gas turbines, some of the remaining energy (heat) in the exhaust gas is recovered through a heat exchanger and transferred to water that feeds a steam turbine, similar to units 6 and 7. On a smaller scale than the supercritical units, units 1 and 2 are also more flexible, with a start-up time of only an hour, against 24 hours for units 6 and 7. Battery storage Utilities in California are required by a 2013 law to provide significant battery storage by 2024. Vistra 500 kV On June 29, 2018, Vistra Energy, which merged with Dynegy on April 9, 2018, announced that it will develop a 300 MW / 1,200 MWh energy storage system to be located at Moss Landing, using the existing turbine building and existing interconnection from units 6 and 7, connecting to the 500 kV grid. Vistra Energy expected the energy storage system to begin commercial operation by the end of 2020, pending receipt of approval from California Public Utilities Commission (CPUC). This would be the largest lithium-ion battery energy storage system in the world. The project began construction in December 2019, and Phase 1 began operating at the end of 2020. It is made of LG JH4 cells in TR1300 racks in two storeys in the old turbine hall. Phase 2 adding a further 100 MW / 400 MWh was completed in August 2021, bringing total capacity to 400 MW / 1,600