Salt caverns have long been used to store fossil fuels underground—the U.S. government’s Strategic Petroleum Reserve is a well-known example. Now, an innovative project in Utah is being developed to store vast amounts of green hydrogen.
A consortium including Mitsubishi Power Americas, a maker of power-generation equipment, and Magnum Development, a developer of fuel-storage caverns, saw potential in central Utah’s underground salt domes and abundant sun and wind. They launched the Advanced Clean Energy Storage (ACES) project, which will use renewable energy to power electrolyzers that will split water into hydrogen and oxygen. The resulting hydrogen will be stored in two caverns carved out of the massive salt dome that lies below Delta, Utah. Once built, ACES Delta will be the largest green hydrogen storage facility in the world.
Ontario Teachers’ invested in ACES Delta in 2022. The project has received US$500 million in financial support from the U.S. government. It also benefits from having a major utility customer, the Intermountain Power Agency, which supplies electricity to communities across the Western U.S., including six cities in heavily populated Southern California. Alongside the ACES Delta program, the IPA plans to retire its coal-fired power generation units in Delta in 2025 and begin generating electricity from units that can run on a mix of natural gas and hydrogen. Its longer-term goal is to generate power using 100% hydrogen from ACES Delta.
Making hydrogen from renewables is currently more costly than making it from fossil-fuel sources. ACES Delta’s economic advantage lies in storage. The project’s caverns will be able to hold up to 11 million kilograms of clean hydrogen for long periods, at low cost, before it is again used to generate power. Its sheer size stacks up well against lithium-ion batteries, which can cheaply and efficiently store excess renewable power only for shorter periods.
ACES Delta will solve a major obstacle to decarbonizing the western U.S.: seasonality. The region is capable of producing vast amounts of renewable energy in the windy and sunny spring and fall seasons—more than can be stored using batteries. But it strains to satisfy power demand during cloudy winter months and summer heat waves. The ACES Delta project can store hydrogen for such times, when it can be converted back into electricity.