A Honokaa power plant that provides about a third of the electrical power for Hawaii island is planning an upgrade.

Hamakua Energy will convert its facility to use 100% renewable fuels. The state has set a goal of 100% renewable energy by 2045, and between a quarter to a third of the electrical power that Ha­ma­kua Energy generates now comes from biodiesel, according to officials of Pacific Current, Hamakua Energy’s parent company.

“Biodiesel is locally available today in modest quantities,” Pacific Current President Scott Valentino said. “We are sourcing all our biodiesel through Pacific Biodiesel, so it’s all locally produced, coming from local feedstocks, waste oils from local restaurants.

“But as renewable fuels become more prevalent, there’s going to be more renewable diesel; there’s going to be more renewable naphtha. We’d be looking at the ability to burn a variety of renewable fuels.”

Both renewable diesel and renewable naphtha “are produced from the same feedstocks” as biodiesel, according to Valentine.

The U.S. Department of Energy said those include soybean oil or canola oil. The fats and oils are processed to be chemically the same as petroleum diesel. Naphtha also is produced from hydrogenated vegetable oils and can be used to produce both diesel and aviation fuels.

“The advantage of naphtha is that it’s cheaper than either diesel or oil,” Valentino said Wednesday.

Marcelino Susas, vice president of strategy and business development for Pacific Current, added: “From a resiliency standpoint, you want multiple fuels.

“We love the idea of biodiesel because it’s local, but in five years, by 2030, there will be other fuels available. And to make sure we’re doing the best for the island, we’re going to want to go with the fuel that’s the most economical option for the grid.”

Hamakua Energy generates 60 megawatts of electricity a day to feed Hawaiian Electric’s Big Island grid.

The project is one of 15 renewable energy projects statewide selected by Hawaiian Electric to further reduce Hawaii’s dependence on imported crude oil for power generation.

Hamakua Energy’s is one of four renewable energy power projects-in-progress on Hawaii island, and the only one in operation using firm renewable generation to produce clean electricity even when the sun is not shining or the wind is not blowing.

The other three are Kaiwiki Solar, a 55-megawatt facility in East Hawaii, and Puako Solar and Keaumuku Solar in West Hawaii, with 60 and 86 megawatts, respectively.

All three are solar plus battery energy-storage systems. Kaiwiki and Puako are projected to go online in 2028, while Keaumuku has an anticipated 2030 completion date.

The upgraded Hamakua Energy plant, which uses two turbines to generate steam and electricity, will continue to occupy a 7-acre footprint.

The upgrade will include a battery energy-storage system capable of providing 30 megawatt-hours to provide backup energy to enhance reliability.

“It’s going to be a stand-alone grid resource,” Valentino said of the battery energy-storage system. “It’s going to be charging from excess energy from the grid. … Hamakua is not a great solar radiant site, but HECO will be able to take any excess solar energy from the grid and charge the battery with that. We’re not going to be charging the battery from our plant. We’re talking about two different resources.”

Susas said that in addition to the battery energy- storage system, the majority of the construction on the already existing plant will be refurbishment of the fuel tanks.

“That will go through environmentally permitting with the right agencies at the right time,” he said. “It will have to go through (state Public Utilities Commission) approval, so we’d expect that to start sometime next year.”

Valentine said the existing power-purchase agreement Hamakua Energy has with HECO runs through December 2030, and the goal to upgrade to 100% renewable fuel will be for the next contract with the power utility, which will start in January 2031.

“So, all of this work would be done in the 2028-29 time frame,” he said.

Valentino and members of the Hamakua Energy team will present an overview of this upgrade project at a community meeting, 4 p.m. Oct. 3 at Cafe Il Mondo, 45-3580 Mamane St. in Honokaa. The community is welcome to attend the free meeting. A separate virtual meeting will be held at 6 p.m. Oct. 8.

Those interested in the meetings are invited to register at hamakuaenergyllc.com, where more information is available.