When it comes to converting to renewable energy, the biggest success story in the islands is on Kaua‘i. Less than a decade ago, about five percent of the Garden Island’s energy came from renewable sources. Now it’s more than eight times that figure. But the island is also making progress on another important issue: how to make use of solar energy when the sun isn’t shining. HPR contributing reporter Scott Giarman has more from Kaua‘i.

The Kaua‘i Island Utility Cooperative estimates that on a regular basis, more than 40-percent of the island’s electricity now comes from renewable sources.

On sunny days, renewables can account for up to 97% of Kaua‘i’s needs. Some is from hydro-electric and biomass, but as much as 80 percent comes from the sun.

At night, or when it’s cloudy, the Utility Cooperative depends upon its growing network of batteries. One project – contracted jointly to photovoltaic panel manufacturer Solar City and state-of-the-art battery developer Tesla – resulted in the nation’s first utility-scale photovoltaic system with batteries capable of providing 13mWh at night. By 2018, KIUC plans another 20mWh battery power system, this one managed by global sustainable energy giant AES, to come on line. When completed, the utility cooperative says these systems will be capable of providing energy to a third of the island.

A fixed-price power purchase agreement with Solar City / Tesla and AES is lower than what KIUC pays to generate its own power. That means customers can expect their bills to decrease as these projects come on line. Such power purchase agreements have contributed to in 18% drop in consumer costs since 2008.

A pumped-hydro plant is under consideration for Kauai’s West Side that would contribute another 12mWh of nighttime energy. This system involves using photovoltaic energy to pump water vertically into a reservoir for storage when the sun is shining. At night, the water would be released to drive a hydroelectric turbine, generating electricity. Effectively, a battery.