September 11, 2015

By William Pentland

SolarCity, a rooftop-solar company based in Sunnyvale, California, has agreed to sell power from a 12 megawatt (MW) solar photovoltaic (PV) installation on the Hawaiian island of Kauai at night.

Credit: SolarCity

No, the sun does not shine in the evening -- not even in Hawaii.

The secret behind the solar-at-night scheme is a giant battery linked to SolarCity's recently completed 12 MW solar farm on Kauai. To clarify, the battery has yet to be built. But, assuming SolarCity gets all of the necessary permits and approvals, the proposed 52 MW battery installation would become one of the first utility-scale energy storage systems in the United States to provide the utility with electricity whenever it needs it.

On the island of Kauai, it turns out the utility needs the power in the evening hours between 5 p.m. and 10 p.m., when local demand surges and the sun retreats. Currently, the Kauai Island Utility Co-operative uses solar to meet as much as 95% of daytime demand on the island.

On Wednesday, the Kauai Island Utility Cooperative said it had signed a 20-year Power Purchase Agreement with SolarCity for the solar and battery storage system, which is designed to supply power to the grid in the evening, when demand is the highest.

Assuming SolarCity can secure the necessary permits and approvals to install the mega-storage system, the 52-megawatt-hour battery system will provide the utility cooperative with dispatchable solar energy, meaning that the utility can count on electricity being available when it's needed, even after sundown.

"KIUC has been investigating energy storage options for more than two years and price has always been the biggest challenge," said David Bissell, the President of the island utility cooperative. "This is a breakthrough project on technology and on price that enables us to move solar energy to the peak demand hours in the evening and reduce the amount of fossil fuel we're using."

Under the terms of the 20-year contract, the Kauai Island Utility Cooperative will pay SolarCity 14.5 cents per kilowatt-hour, a lower rate than the current cost of conventional generation.

For more:
- see this background article

© 2015 FierceMarkets, a division of Questex, LLC. All rights reserved.

http://www.fierceenergy.com/story/secret-behind-hawaiis-solar-night-scheme/2015-09-11