Kauaʻi Island Utility Cooperative (KIUC) has signed a power purchase agreement (PPA) with SolarCity for electricity from the first utility-scale solar array and battery storage system (13 MW / 52 MWh) designed to supply power to the grid in the evening, when demand is highest. The proposed SolarCity project next to KIUC’s Kapaia power plant is believed to be the first utility-scale system in the U.S. to provide dispatchable solar energy, meaning that the utility can count on electricity being available when it’s needed, even hours after the sun goes down.

The 52 MWh battery system will feed up to 13 megawatts of electricity onto the grid to “shave” the amount of conventional power generation needed to meet the evening peak, which lasts from 5 p.m. to 10 p.m. By using the solar energy stored in the battery instead of diesel generators, KIUC will reduce its use of imported fossil fuels and also cut its greenhouse gas emissions.

Lithium-ion Battery