A battery system that stores excess energy when it’s plentiful will power an apartment building in Buffalo, New York, when the grid is strained and electricity is costly. The manufacturer and state officials hope it will show that larger batteries can safely operate where people live and work. Buffalo-based battery storage manufacturer Viridi and developer Good Carbon Co. say the lithium-ion battery system is connected to the electric grid for Peace Bridge Place. Viridi says the 3.75 megawatt-hour system can power the building for several days. It's among the largest of these systems in a U.S. residential building.