laska’s electric utilities often use diesel as a back-up to generate power. The fuel sits in tanks, always ready, and it can be fired up in a matter of minutes. Yet there may be a better way to store energy when demand is high and supply is low: long-duration energy storage (LDES).

LDES enables utilities to store energy that can be discharged to minimize the frequency and length of power interruptions. While lithium-ion batteries can provide short-term power (4 to 8 hours) and pumped storage hydropower can provide 10-plus hours of energy, those solutions don’t always work in Alaska. Batteries and pumped hydro also have safety and siting issues—including the fact that water—the source for hydropower—freezes in the winter. As a result, utilities are looking for a new way to harness and store energy to be used as needed.

“When something fails because of cold weather, for example, we need enough time to bring up additional generation or to repair items to bring them back online,” explains Travis Million, CEO of Golden Valley Electric Association (GVEA). “In the Lower 48, there are power sources all over the country, so it’s easy to pull from different sources. But Alaska is limited by how much power generation is in each area, which means that one point of failure anywhere on the system is a struggle.”

By having excess energy stored and ready to use, power plants won’t need to use more expensive diesel generation, which Million says could result in saving millions of gallons of fuel a year.

In June 2024, the US Department of Energy’s (DOE) Office of Clean Energy Demonstrations (OCED) awarded $5.5 million to the Pumped Thermal Energy Storage in Alaska Railbelt (POLAR) project. It was one of nine projects selected for the demonstration program.

The POLAR project is a partnership between GVEA and Westinghouse Electric Company, which is further collaborating with technology provider Echogen Power Systems and construction partner ASRC Energy Services–Houston Contracting Company. The companies are devising a plan to design and build a pumped thermal energy storage system that will have a 1,200 MWh capacity and be capable of a minimum continuous output of 50 MW for 24 hours. That would be greater than one day’s output from GVEA’s oil-fired Zehner Power Plant and significantly greater than its current Battery Energy Storage System.

“This project in Alaska will be the first commercial scale demonstration of this technology,” says John Battaglini, vice president of new market development and sales for Americas at Westinghouse, noting that smaller, lab-scale and vendor sited demonstrations have already taken place. “Having the DOE involved in the first phase has helped us get this technology off the ground, and it will also be helpful in follow-up phases as investors looking into the technology and the project see that DOE has done its due diligence.”

Pumped thermal storage charges by heating large reservoirs of specialized concrete elements through the flow of mineral oil. The heat is created by the phase change of ice to water. When needed to discharge, the flow is reversed, and energy is converted back to electricity for the grid.

The project is nearing completion of Phase 1, which includes planning related to budgeting, permitting, procurement, and early development activities. By spring, Battaglini says that the front-end engineering design study will be complete, as well 30 percent of the design, supply chain quotes, and project reconfiguration as needed.

While GVEA’s Healy Power Plant was originally considered to host the POLAR Project, Million says further evaluation showed it was not the best location.

“So much has changed with this administration and with the power generation mix in Alaska,” says Million, noting that Healy’s coal plant will now remain open longer than originally scheduled. “During our next stage of modeling for the greater region, we’ll determine the precise location for this asset.”

He adds that the project team began looking at other sites about six months ago, including a possible site next to GVEA’s power plant in North Pole.

If the project is approved to go forward, the partners will move on to site prep with construction partner ASRC Energy Services–Houston Contracting Company. ASRC Energy has a history of completing large energy projects in Alaska and is deeply familiar with the state’s energy needs and limitations.

“We’re excited to partner with Westinghouse and GVEA to help implement this important technology,” says Liam Zsolt, senior director of innovation and new business development at ASRC Energy Services. “Through our significant operations footprint in the Interior, the ASRC Energy team has a long-standing relationship with GVEA as a client and a supplier, and together we understand the unique challenges of providing affordable, reliable power in the Interior and across the state.”

He adds that Alaska has a unique need for long-duration energy storage. Zsolt says, “The electrical grid in Alaska is aging and delicate, and long-duration energy storage assets help provide resilience and energy security.”

Westinghouse has been exploring the idea of LDES for about eight years, according to Battaglini. While the company originally planned to combine thermal storage with nuclear technology, more opportunities arose as the market has begun utilizing other types of energy generation.

“There are a lot of benefits to LDES,” Battaglini explains. “To begin with, it is very safe; unlike some issues with lithium-ion batteries, there are no safety risks associated with this technology. We can also site this technology anywhere because it is not dependent on water availability, elevation changes, and underground caverns associated with pumped hydro and/or compressed air.”

The footprint is larger than GVEA’s lower capacity massive rack of nickel-cadmium batteries, but it’s smaller than a hydro reservoir. “We can store one gigawatt hour on a five-acre site,” says Battaglini. “Energy density, or the amount of energy that can be stored, is best-in-class.”

LDES also adds value to the energy grid, as it has a flexible architecture that allows utilities to shift large amounts of energy from, say, low-demand nighttime hours to higher demand during the day. Long-duration storage can provide energy for more than eight hours, and it can be scaled up to 200 hours.

“Up to this point, there’s been a gap in the technology between storage options that provide shorter duration power, such as a standard lithium-ion battery that’s good for two to four hours, and extremely long duration solutions, like pumped storage hydropower that can provide weeks or months of energy,” explains Million. “For Golden Valley and other utilities, there’s a sweet spot—longer than four hours, but less than the long, long-term.”

One day’s worth of storage would fit the bill. Million says, “If we can solve this problem, it would help us greatly; we need about 8 to 24 hours of stored energy to use as we make operational changes on the system.”

When the POLAR Project was first proposed, GVEA was looking at adding large renewable energy projects, including wind power, with the idea of storing excess energy. Changes since the project’s inception, including the change and reduction of federal tax credits for renewable energy projects, raised costs.

However, LDES doesn’t care where electricity comes from. “LDES can be used to optimize gas-fired generation, coal-fired generation, and solar and wind power, filling in the gaps as needed and allowing power companies to optimize their assets already in the field,” says Battaglini. “LDES is the glue that holds it all together, especially in a sensitive grid like the one in Alaska where you need high reliability, high-resiliency solutions.”

Because pumped thermal uses abundant, safe, low-cost elements such as water, ice, and concrete, it does not require critical minerals, including lithium. “This technology does not require reliance on foreign entities of concern, which is becoming a very complex issue for other energy storage technologies,” says Battaglini. “It utilizes a high amount of US domestic content.”

Battaglini was hesitant to provide a full cost estimate while the project is in the early stages. To date DOE has provided a $5.5 million grant that includes a 100 percent cost match during the first phase. DOE estimates its total cost share for all phases to be up to $50 million.

“While that will not cover the full size of the project, it’s very substantial; very significant,” says Battaglini. “When we finish modeling and dial in the exact size, I’ll be able to state the full cost.”

According to Battaglini, Westinghouse is commencing regional modeling for other possible stakeholders in Alaska, such as military bases or other utilities along the Railbelt. The company has already introduced pumped thermal LDES to various markets, working with early adopters around the globe and meeting with several prospects in the United States, Canada, Slovakia, South Africa, the United Kingdom, and Ireland.

“Because we can couple LDES with numerous renewable technologies as well as existing coal and gas-fired plants, it’s attracting global interest,” he says.

Westinghouse, GVEA, and their partners anticipate it will take about three years to build this ground-breaking project—weather and short construction seasons permitting—once it commences. Battaglini expects it to come online in roughly 2030.