Huge battery has replaced Hawaii’s last coal plant



“The battery directly replaces the latter two: It matches the coal plant’s maximum power output (or ​“nameplate capacity,” in industry parlance), and it is programmed to deliver the necessary grid services that keep the grid operating in the right parameters.”

The articles mentions the battery’s185 MW replaces the coal plant’s 180 MW. It doesn’t mention for how many hours the battery can replace the coal plant.

A conventional power plant keeps producing electricity as long as you feed it fuel. A large battery is only storage for electricity produced somewhere else.



Just what I was thinking. What charges the battery? If it’s another carbon fueled plant, carbon emissions have not been reduced. If it’s wind or solar, where is the generation plant?



The article says “the last coal plant.” They could have other base load fossil fuel plants, methane, bunker fuel…

The batteries are good to stabilize the grid and as peaker plants, not for base loads. That would need solar panels and/or wind mills.

Does Hawaii use the geothermal heat from the volcanoes? So many options!

The Captain


The Tesla battery storage unit is balancing the power obtained from solar and wind energy. There is so much customer solar that much of the utility-level renewable energy goes wasted. Now the excess renewable energy can be stored for use when needed. This will allow (without any apparent upgrading of the existing grid):

…10% more new utility-scale renewables than previous models had allowed, while providing for the continued rapid growth of individually-owned renewables such as rooftop solar.

According to Hawaiian Electric, the project will save customers money. The Hawaiian Electric filing for KES estimated it will reduce electric bills by an average of $0.28 per month over a 20-year contract life.

Renewable electrification marches on…


Grid stabilization is a critical role and especially necessary with inconstant renewables. At the same time, the batteries did not replace the coal plant.

FWIW, burning oil provided about a order of magnitude more than coal.


I thought Hawaii had so much residential solar power installed they had to limit grid connections. It makes sense to collect the surplus in a big battery to replace a fossil fuel plant.

And what do you bet they don’t have any wave power installations. Much potential for green energy yet to be exploited. They have volcanos. Geothermal?


Surely the “$0.28 per month” is a typo. Who would brag about saving their customers 28 cents per month?

I don’t think it’s the 28 cents per month savings. It’s the fact that Hawaiians are no longer poisoning themselves with coal.

Also this battery installation was built and operated by Pure Power as an investment, so most of the savings are going to the Private Equity investors


Since they are in middle of the ocean, wouldn’t they simply locate coal plants in a place where the prevailing winds move the coal exhaust away from the island(s)?

If most of the profits went to someone other than the investors … then it wouldn’t exist in the first place!

From the perspective of the utility, it’s 28 cents/month, times 12 months, multiplied by however many millions of customers they have. I have noticed how utilities in Michigan apply to the state PUC for a rate increase. The utility asks for several hundred millions in increase. Then the media breaks that down to what it will cost the “average customer”.


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That’s what they did. The coal plant was located, at Barber’s Point.

So that is how much less the utility’s revenues will be. With 300K customers, Hawaiian Electric’s revenues will decrease by about $1 million/year.

For the average customer the saving is trivial.


From the Kapolei website, the energy capacity of the batteries is 565 MWh. At 185 MW discharge rate, the batteries will last 3 hours. So, if the sun goes down at 5 pm, the batteries will be empty by 8 pm. In reality, I don’t think you want to completely discharge those type of batteries, so it will actually be less than 3 hrs.

I wonder if any of the tourists staying in Hawaii’s hotels ever want to use electricity after 8 pm? Suppose the wind is calm?

  • Pete
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Renewables are replacing the coal plant.

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.”

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It is charged by grid power. Hawaii’s grid is about 30% renewable.

The article indicated the coal plant was used for peak power. So roughly speaking, the net emissions should be about 30% than previous. But the a lot of the solar power is curtailed (wasted), so they will be able to capture some of that curtailed energy and use it later.

Big Island has at least one geothermal plant.

Because of the Jones Act, shipping to Hawaii is very expensive, which means coal is very expensive. Although this battery doesn’t save much money, it still saves some money.

I’m certain HECO is aware of this.


Not true. If it’s a very profitable operation (like oil & gas), the Gov’t will tax it to the point it’s just barely feasible. That’s how Norway got rich.


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Well Hawaii can look into long term energy storage like many other states are doing:

Form Energy’s iron-air battery technology — which provides durations of up to 100 hours — would allow the utility to discharge the battery during peaking events, when intermittent resources like wind and solar may not be generating.

Dive Brief:

  • Minnesota regulators on Thursday approved a 10-MW/1,000-MWh iron-air battery system to be built by Form Energy for Xcel Energy’s Minnesota utility, Northern States Power, or NSP.
  • NSP expects the long-duration energy storage pilot project will be operating by the end of 2025 and will be paired with up to 710 MW of solar at the site of a coal-fired power plant that is being retired.
  • The utility expects the project will cost residential customers about 30 cents per month over the project’s 10-year expected life span. The Minnesota Public Utilities Commission imposed a cost cap on the project.

The Form Energy battery system — which discharges and stores electricity by converting iron to rust and back again — is slated to be built near NSP’s 1,879-MW, coal-fired Sherco power plant in Becker, Minnesota, according to the utility’s application at the PUC. The utility plans to retire a 682-MW unit at Sherco this year, a 680-MW unit in 2026 and the final 517-MW unit in 2030.

NSP has permission to build 460 MW of solar at the Sherco site and is seeking approval for an additional 250 MW, with the entire solar facility expected to be operating in 2025.

With the Form Energy battery system, NSP expects to gain experience integrating renewable energy onto the grid, Ian Dobson, lead assistant general counsel at Xcel, told the PUC at its meeting.

NSP also hopes to better understand the value of energy storage systems with dispatching during renewable energy “droughts,” mitigating transmission congestion, providing emergency electricity during power outages and reducing peak power costs, the utility said in its application.

The project will support a more just energy transition by building the project in a community directly affected by the shift away from fossil fuel generation, it said.

NSP expects the battery system will be eligible for a 10% bonus tax credit on top of the 30% investment tax credit for siting the project in an “energy community,” according to the application. It may also qualify for a 10% bonus tax credit under the Inflation Reduction Act from Form Energy’s commitment to meeting domestic content requirements, the utility said.

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The MN battery will be part of the power facilities powering the Twin Cities and surrounding area. The Sherco coal power plant #2 is now closed.

On New Year’s Eve, Xcel Energy shut down one of three units at the Sherburne County Generating Plant in Becker. The company plans to retire Sherco’s remaining coal-fired units in 2026 and 2030. Sherco Unit 2 was built in 1977.Jan 4, 2024


Form Energy’s technology uses a process called reversible rusting, whereby the system discharges by absorbing oxygen and converting iron into rust and charges by using an electrical current to convert the rust into iron.

Other utilities and jurisdictions have also shown interest in the technology

In December, California regulators awarded the company $30 million to build a 5 MW/500 MWh battery storage project at a Pacific Gas & Electric substation, expected to come online by the end of 2025.

New York Gov. Kathy Hochul, D, in August gave Form Energy a $12 million grant to build a 10 MW/1,000 MWh demonstration project in the state, which the company expects will be online in 2026.

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