LIHUE >> Kauai’s electric utility plans to use an irrigation system dating to sugar plantation days to help store solar power for use at night.

Officials say the project will provide about one-quarter of Kauai’s energy needs and allow the Kauai Island Utility Cooperative to obtain 80% of its power from renewable sources by 2025, The Garden Island newspaper reported.

The utility routinely meets 100% of the island’s daylight energy demands using renewable resources. But battery limitations and lack of sunlight currently force the cooperative to rely on fossil fuels during early-morning and night hours.

The West Kauai Energy Project would divert water from four streams along the Kokee Ditch Irrigation System near Kekaha and Waimea. It would restore existing reservoirs and build new pipelines and gate structures.

Two reservoirs at different elevations would be connected by a penstock, or pipe. A solar-powered plant would pump water up the penstock during the daytime. Water would then flow down the penstock to generate energy at night and in the early morning.

“When cranking at full capacity, it will have enough power to energize 18,000 homes on our island,” said Beth Tokioka, the utility’s communications manager. “On the environmental side, it would be reducing our fossil fuel usage by 8 million gallons a year and reducing our greenhouse gas emissions by 80,000 tons of C02 per year.”

Utility officials and engineers explained these details at a recent “talk story” session about the project.

Resident Kaua Mata asked what would happen if Waimea River levels were to drop in the future.

Tokioka said the state Commission on Water Resource Management decides how much water the utility may divert from streams and the utility would abide by these decisions.

The project site is on lands owned and managed by the state Department of Land and Natural Resources, the state Department of Hawaiian Homelands and the state Agribusiness Development Corporation.