Published: 5 May 2021, 14:06 By: Containerised battery energy storage systems (BESS). Image: Mitsubishi Power. Mitsubishi Power Americas and Powin Energy have been appointed to retrofit 640MWh of batteries to solar PV plants in California, while a community energy group in the state has just signed a power purchase agreement for a 100MW solar plant with 150MW / 600MWh of storage. Wholesale energy provider Southern Power said in February that it would add a 72MW / 288MWh battery energy storage system (BESS) at Tranquility Solar Facility, a 205MW project in California’s Fresno County, as well as 88MW / 352MWh of battery storage at the 200MW Garland Solar Facility in Kern County.