AES Signs Agreement for Unique Solar-Hydro Facility
May 2021
The AES Corporation (AES) is partnering with the Kaua‘i Island Utility Cooperative (KIUC) on the development, construction, and operation of the electric cooperative’s solar + battery powered pumped hydro storage system, known as the West Kaua‘i Energy Project (WKEP). This project will enable Kaua’i, a Hawaiian island, to be powered 80 percent by renewables and to meet 25 percent of the island’s electricity needs. 

The WKEP will produce renewable energy through hydropower and solar photovoltaic generation and will store and release hydropower, pumped hydropower and battery energy storage to deliver electricity throughout the night. The project will offset the use of 8.5 million gallons of fossil fuels annually. It also will rehabilitate three existing reservoirs spanning from mountain to near sea level in West Kaua’i and supply irrigation water delivery to support diversified agriculture on state-owned lands. 

“This project’s integration of pump storage hydropower with large-scale solar power is unique in the energy industry. Working with AES helps keep this important project moving forward while minimizing risk to our cooperative,” said KIUC’s President and CEO David Bissell. “AES is a trusted partner with the expertise and experience to bring this complex project to successful completion.” 

When operational, the solar panels will utilize 35 megawatts (MW) of electricity to pump water uphill between two reservoirs, for storage of up to 240 megawatt-hours of hydro power for dispatch during the evening peak. The hydro resources will produce up to 24 MW and will be firmed up with 12 hours of reservoir storage, compared to the conventional four- or five-hour storage typical of solar battery facilities. 

This is not the first clean energy project the electricity providers have worked on together. KIUC and AES have completed two solar-plus-storage renewable projects: a 20-MW facility in Lāwa‘i and a 14-MW facility at the Pacific Missile Range Facility. AES has more than 200 MW of solar, solar + storage, and wind resources in operation or under development across Hawai‘i. 

"AES has been a long-time provider of low-cost electricity for Hawai‘i, and we are honored to continue our successful partnership with KIUC to support Kaua‘i and the state in transitioning to 100 percent renewable energy,” said Woody Rubin, AES Clean Energy Chief Development Officer. “We look forward to continuing to work with the Kaua‘i community and stakeholders to develop this project responsibly, and to realize the agricultural, economic, and environmental benefits the project offers.” 

“WKEP will deliver many benefits to KIUC’s members and the community,” Bissell said. “To name just a few, the project will move Kauaʻi beyond 80 percent renewable generation, stabilize and lower electricity rates over time for our members, open up agricultural lands for production, assure adequate streamflow, and increase public access and recreational opportunities associated with the Pu‘u Lua Reservoir.” He added that rehabilitation of the reservoirs also will assist first responders in addressing wildfires. 

The long-duration storage capacity will allow the island to run on 100 percent renewable energy for prolonged periods without sunlight and will provide additional grid stability by balancing variable solar energy with 24/7 hydropower. 

Learn more about AES and KIUC’s clean energy projects on the AES website. EEI’s member companies, including AES, are leading a clean energy transformation. To learn more, visit the Clean Energy section of EEI’s website​.