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Hawaii Develops New Clean Energy Storage

Kaua’i is the Garden Isle of Hawaii, covered in lush greenery, high cliffs, and miles of undeveloped shoreline. Local law prohibits the construction of any buildings over 4 stories to protect the natural beauty of Hawaii’s oldest and greenest island. The natural green beauty and striking cliffs, also make Kaua’i the perfect place to develop the United States’ first pumped storage, clean energy power plant. This technology might be the secret to storing power overnight, or in the case of catastrophic weather conditions. 

Kaua’i is familiar with clean energy, and the local energy co-op, Kaua’i Island Utility Cooperative (KIUC) recently finished developing two large solar plus storage projects in cooperation with AES on the island that generate 34 MW of electricity combined. KIUC and AES’s new partnership will be to develop the nation’s first “solar powered” pumped-storage hydroelectric power plant, the West Kaua’i Energy Project (WKEP). 

The WKEP will move Kaua’i past 80 percent renewable energy generation, and the project alone will provide 240MW or 25 percent of the island’s energy needs. The energy will be released over 12 hours at night and will supplement solar generation. Utility companies are eyeing the technology as an effective way to transition from coal-fired power plants since the clean energy stored can be tapped in as little as 20 seconds. 

So how does it work?

During the day, onsite solar panels will provide the energy to pump water from a lower reservoir, Ma̅na̅, to a reservoir much higher, Puu Opea. At night, when the solar no longer generates power, the team at WKEP will flip the switch, and water will flow downward through hydroelectric turbines generating steady, immediate power. 

KIUC chose this site on Western Kuau’i because it has good bones for hydroelectric power. “It’s all about geography, you need a higher elevation, so we had some existing infrastructure that included some irrigation ditches and some existing reservoirs that were used by a sugar plantation out there,” Brad Rockwell told The Business Download. “We’re not creating all of this infrastructure from scratch, but it is in need of significant rehabilitation.” 

By working with the natural resources of Kaua’i, and transforming the existing infrastructure, the site for the WKIP is the perfect geographic location for the nation’s first pumped hydroelectric storage. Looking forward, more projects like this groundbreaking one in Kaua’i could take shape throughout the US, as Congress recently passed a widely supported, bipartisan led coronavirus relief package that will allocate major investments into research and development efforts for clean energy technologies.

The proposed plan for the WKEP details the flow of water through the proposed Puu Opea Powerhouse and Mana Powerhouse along with the PV array and substation. Photo courtesy of Kuaui Utility Island Cooperative.

Kaua’i faces unique challenges in preparation for the island to become home to the first pumped storage plant. Without natural gas or coal resources, the majority of their traditional power came from oil, so businesses and individuals were at the mercy of fluctuating foreign oil prices. So the people of Kaua’i decided to seek energy independence through renewables. They are already operating on 100 percent renewable energy for about 8 hours a day, according to Rockwell. However most of this energy comes from solar power, so the islanders needed effective energy storage that would last them through the night. “The key is to continue to transition away from oil sources” Rockwell shared. “There has been this outflow of billions of dollars from the state economy and now we can keep that money here by paying for renewable projects that are a fixed price for 20-50 year contract terms. This has benefits to the local economy, but it also has benefits to the electric rate because it stabilizes the rate.”

A recent study by global scientists found that pumped hydro storage had one of the lowest cost-to-kilowatt ratios, $0.053/kWh. Moreover, the study found that the lifespan of the project was over 50 years and the payback period for most projects was only 19 years. KIUC is small and agile enough to make bold moves in the clean energy sector, and their position as a cooperative means that the rate-payers are also the owners. Meaning the people who pay for their electricity are making the decisions, rather than utility shareholders, of where their electricity comes from. “I think our cooperative structure has helped us on this path to success that we’ve enjoyed with developing high penetration renewables,” Rockwell commented. “We can be completely aligned with what the people of Hawaii want, which is lower stable rates.” 

There are other benefits for the residents of the Garden Isle in addition to cheap, stable electricity. “We live in a paradise. We want to have clean air and want to keep it that way, and we want to be green,” Rockwell shared. While the designs for the WKEP aren’t finalized, Rockwell estimates that it will cost roughly $200 million and bring upwards of 200 jobs to the area. KIUC will purchase clean energy at a fixed rate over a significant period of time, meaning with inflation, the rate will actually decrease over time. WKEP will also refurbish an existing structure that costs the state money, meaning KIUC will take on that cost for the state and give the area a purpose generating electricity. 

According to Rockwell, “There are benefits to the state and us taking over that infrastructure, as it removes a huge liability from the state removes an ongoing operating cost from the state.” Finally, the project will benefit the native Hawaiian homelands that the WKEP runs through. “We’ll be bringing irrigation, electricity, and improved roads to a large swath of Native Hawaiian homelands, which will then allow them to start doing some pastoral leases and doing some agriculture operations on the land,” Rockwell shared. As states begin to face the same storage needs as Kaua’i, the mainland may soon be finding the solution in the green tropical mountains of the Garden Isle.


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