Hawaiian Electric’s modeling suggests it can reduce curtailment of renewables by an estimated 69% for the first five years thanks to Kapolei Energy Storage, allowing surplus clean electricity that would otherwise go to waste to get onto the grid.
The utility also requested “black-start capability.” If a disaster, like a cyclone or earthquake, knocks out the grid completely, Hawaiian Electric needs a power source to restart it. The Kapolei batteries are programmed to hold some energy in reserve for that purpose. Plus Power located the project near a substation connected to three other power plants so the battery “can be AAA to jump-start those other plants,” Keefe said.
The combination of all these abilities in one site — capacity, grid services, black start — leads Keefe to call Kapolei “the most advanced battery energy storage facility on the planet.”
Model for a reliable clean-energy grid
The new battery is just the latest dispatch from Hawaii’s long-held spot at the vanguard of the energy transition. This is the state that hit mass rooftop solar adoption first and crafted the first utility-scale solar-battery plant in Kauai (not coincidentally, Plus Power CCO Bob Rudd had a hand in that project during his tenure at Tesla).
But when renewables growth and fossil-plant retirements pass a certain threshold, as they have in Hawaii, simply adding more wind, solar or batteries isn’t sufficient. The clean technologies, which run on digitally controlled inverters, have to start maintaining the grid, not just feeding it.
Plenty of other batteries provide frequency services to other grids, and a few of them are larger than Kapolei. But this is the only large-scale battery that we’ve seen capable of combining the basic peak capacity, frequency response, synthetic inertia and grid-rebooting tasks. That’s because Kapolei plays a more central role in its grid than battery plants do elsewhere.
After years of construction, California’s grid battery fleet surpassed 5,000 megawatts installed last year, but that only equates to 7.6% of the mammoth nameplate capacity of the state’s grid. Kapolei alone constitutes about 17% of Oahu’s peak capacity. Hawaiian Electric needed it to take on more responsibility than batteries elsewhere have ever had to.
Take inertia, which stabilizes grid frequency, as one example. Old plants provide this passively, through the spinning mass of their turbines; inertia didn’t need to be defined and compensated for separately in bygone decades because it was part of the package of running a power plant.
Now, across the country, the grid is moving to a model of maximizing cheap renewables when they are available and burning fuel when renewables aren’t. But the thermal plants need to be spinning to provide inertia — sometimes, on the mainland, renewables get curtailed to keep old coal plants running so they can deliver these grid services, Keefe said. This can be a bad deal for electricity customers, not to mention the climate.
Advanced batteries provide a synthetic version of this inertia through savvy programming of their inverters. This offers a more economic alternative while avoiding unnecessary carbon emissions. They also are faster and more precise — Keefe likened the Kapolei battery to a zippy electric sports car compared to the lumbering diesel bus of old thermal plants. That makes batteries a good technical fit for grids that are becoming increasingly volatile due to the fluctuations of renewable production.
Longer-term, U.S. climate goals require a phaseout of fossil fuels from the electric grid. Hydropower and nuclear plants help deliver valuable grid inertia without carbon emissions, but they aren’t on track to grow.
That’s why this project matters to the clean energy shift everywhere: It’s one of the first real-life examples of how to shift critical grid functions from fossil-fueled plants to clean energy plants. And eventually, the kind of grid services Kapolei has pioneered will have to scale nationwide.
Amazing, nice one