Energy storage technology startup Highview Power and project developer Encore Renewable Energy on Dec. 18 announced a 50-MW project planned in northern Vermont with more than eight hours of energy storage, one of several so-called cryogenic energy storage systems under development in the U.S.

London-headquartered Highview has demonstrated its approach in two smaller installations in the U.K., where it is also developing a 50-MW/250-MWh project. Relying on industrial processes adapted from the power and gas sectors, Highview uses off-peak or excess electricity to compress and refrigerate air, store it as a liquid in large tanks and then release as a gas to drive a turbine and generate power.

"You're going to need long-duration storage to handle the volatility of increased renewables," Salvatore Minopoli, vice president of U.S. affiliate Highview Power Storage Inc., said in an interview. "You don't have sun shining all the time or wind blowing all the time."

Highview is one of dozens of energy storage innovators pitching alternatives to lithium-ion batteries. The company's installed project costs are half those of projects using lithium-ion batteries, the executive claimed.

Though lithium ion-based systems have dominated the U.S. market for new energy storage resources in recent years, they have limitations. Minopoli expects demand to pick up for longer-duration resources for "sustained peaking power" that goes beyond the typical four hours offered by the incumbent electrochemical options.

That is a view Highview shares with many competing developers who believe that power grids will increasingly require eight hours of storage or more, including compressed-air energy storage startup Hydrostor Inc., which recently completed an installation in Ontario, and gravity-based system developer Energy Vault SA of Switzerland, which recently raised $110 million.

Highview's project in Vermont, planned to come online in late 2022 or early 2023, could be hybridized with a renewable energy project and use energy produced on-site, Minopoli said. Contract discussions with undisclosed utilities for the system's output are underway, he added.

"This will be the first, largest and longest-duration storage project that is geographically relocatable anywhere," Minopoli said, contrasting the technology with conventional pumped hydroelectric storage. "Vermont wasn't selected because of a specific, isolated need. This technology really makes sense throughout the country right now, especially because of renewables penetration."

Two additional large-scale projects are under active development in the U.S. at undisclosed sites in the Southeast and desert Southwest, he added. The southwestern project, while not in California, is proposed to participate in the California ISO's Energy Imbalance Market. The company is exploring about another dozen projects in the U.S., Minopoli said.