Sumitomo Corporation together with Sumitomo Corporation of Americas announced their investment in an innovative battery power storage system which will provide a reliable and stable supply-demand balancing service for the frequency regulation market operated by PJM, the largest regional transmission organization of wholesale electricity in the U.S. Sumitomo acquired an interest in Willey Battery Utility, LLC from Renewable Energy Systems Americas , the U.S. renewable energy developer/constructor, through Perennial Power Holdings, a U.S.-based subsidiary of the Sumitomo Corporation Group. WBU will own this battery energy storage system manufactured by Toshiba Corporation.