Courtesy of Plus Power

Plus Power Activates 185 MW/565 MWh Battery System In Hawai’i

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Just a few days ago, we did a story about the State of Maine’s plan to begin construction of a 175 MW/350 MWh battery storage system from Plus Power this spring. Until that news arrived on the teletype machine in the communication center at CleanTechnica, we didn’t know very much about Plus Power, but since then, the company has activated an even larger system near Honolulu, Hawaii. It is currently involved in the construction of 60 energy storage projects either already operating or in development across the US and Canada.

According to Plus Power, the Kapolei Energy Storage “is ideally located on roughly eight acres of land in Kapolei on the island of Oahu, where it interconnects at a critical Hawaiian Electric substation. The 185 MW/565 MWh battery storage project provides load shifting and fast-frequency response services to Hawaiian Electric, enhancing grid reliability and accelerating the integration of readily available renewable energy. KES received approval from the Hawai’i Public Utilities Commission in May 2021. The Kapolei Energy Storage facility is now online.”

Plus Power System Replaces Coal Fired Generating Station

“The KES project helps replace the AES coal fired plant that closed on September 1, 2022 and supports the state’s goal of shifting from fossil fuels to 100 percent renewable energy generation by 2045. In a statement, Brandon Keefe, the company’s executive chairman, said:

“This is a landmark milestone in the transition to clean energy. It’s the first time a battery has been used by a major utility to balance the grid, providing fast frequency response, synthetic inertia, and black start. This project is a postcard from the future — batteries will soon be providing these services, at scale, on the mainland.”

The KES installation uses 158 Tesla Megapack 2 XL lithium iron phosphate batteries, each roughly the size of a shipping container. It offers the grid 185 MW of total power capacity and 565 MWh of electricity, acting as an electrical “shock absorber” for the grid. It can begin supplying power in as little as 250 milliseconds if there is a surge in demand for electricity. So-called peaker plants that burn methane gas can take several minutes to come online. Because the need can be great for electricity as soon as possible, those peaker plants are exempt from normal emissions rules when they are activated, which means they pour huge amounts of carbon dioxide and other emissions into the atmosphere during the start up phase.

“KES is an important part of a portfolio of resources that work together to provide reliability and energy security on Oahu’s isolated island grid,” said Jim Alberts, senior vice president and chief operations officer of Hawaiian Electric. “Energy storage technology that responds quickly to constantly changing conditions is an essential tool for us to use to manage the grid and operate it as efficiently as possible.”

Mike Snyder, senior director of Tesla’s Megapack division, added “This is the first time a standalone battery site has provided grid-forming services at this scale. This is a critical application for high renewable penetration grids supplied by 185 MW of Megapack inverters,” said

Solar power from individual consumers has become so abundant that Hawaiian Electric must regularly ‘curtail’ or turn off large volumes of existing utility scale solar and wind in order to keep the electric system in balance. Its modeling found that in its first five years in operation, the KES battery plant will allow the utility to reduce curtailment of renewable energy by 69% and integrate 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.

The battery plant’s specifications include:

  • 135 MW/540 MWH of capacity and energy
  • 50 MW/25 MWH of additional fast frequency response to help keep the electric grid stable
  • “Virtual inertia” to replicate the power-smoothing function of a spinning turbine
  • “Black start” capabilities to support grid recovery in the event of a blackout

The KES plant interconnects near three of Hawaiian Electric’s critical power generation facilities, enabling KES to support the reboot of those power plants in the event of an island-wide emergency, otherwise known as “black start” capability. “No one has used batteries to provide such a diverse range of grid-forming services at this scale before in the world,” Brandon Keefe said.

There are other important benefit to where the Plus Power system is located. Proximity means it has access to existing grid interconnections, which eliminates the need to build expensive transmission lines to allow the battery storage facility to tie into the grid.  The KES batteries will help replace the grid capacity formerly provided by an AES coal power plant less than a mile away, which once produced up to one fifth of the electricity on the island of Oahu. In addition, such areas are already devoted to heavy industry or commercial development, which means NIMBY objections are less likely.

Plus Power Has Its  Eye On The Future Of Energy

Plus Power is a leader in the development and operation of standalone energy storage wherever it is most needed on the power grid. The company operates multiple KES-sized projects, and has a rapidly growing development portfolio of large scale battery systems. It has 10 gigawatts of projects in transmission queues pending in the US and Canada, with over $1.8 billion in project financing in place as of  October 2023. By June, 2024, Plus Power will be operating a total of seven large scale battery energy storage plants across Arizona and Texas with a total capacity of 1325 MW/3500 MWh.

“Plus Power is in the business of solving hard climate problems,” said Brandon Keefe. “Our projects, like KES, help our customers provide affordable, reliable, clean electricity on hot summer afternoons and cold winter nights, while enabling the decarbonization of the electric grid.”

KES Gets Its First Test

On January 8, the Plus Power energy storage system got its first real test, as heavy rains caused two generating stations to go offline unexpectedly, leading to rolling blackouts across the Honolulu area. Local news reports claimed the KES battery was only 50% charged at the time, which limited its ability to offset the loss of generating capacity. Late in the day on January 11, the teletype machine in the basement of CleanTechnica world headquarters sprang into life to bring us a statement from a spokesperson for Plus Power.

“News reports that the new Kapolei Energy Storage project was less than fully charged on Monday evening before the rolling outages are incorrect. KES was at full capacity and then was nearly fully discharged, before the rolling outages commenced.

“In fact, KES provided critical support to the grid, and discharged over 130 MW of its 135 MW capacity commitment to Hawaiian Electric. Plus Power is pleased that KES was operational and fully charged on Monday to help during a challenging storm.”

The Takeaway

Not all of us are electrical engineers. We can’t really explain what synthetic inertia is or why it is important, but Canary Media can. It says,

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, according to Brandon Keefe. 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.

That’s why this is not just another battery storage story.


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Steve Hanley

Steve writes about the interface between technology and sustainability from his home in Florida or anywhere else The Force may lead him. He is proud to be "woke" and doesn't really give a damn why the glass broke. He believes passionately in what Socrates said 3000 years ago: "The secret to change is to focus all of your energy not on fighting the old but on building the new."

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