This Compressed Air Grid ‘Battery’ Is an Energy Storage Game Changer

Pumped hydropower is great. This method might be even better.

• World-record compressed air energy storage is coming to California this decade.
• Using air reduces overhead and materials costs compared with hydrogen storage.
• Compressed air is stored during surplus times and fed back during peak usage.
  

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Two new compressed air storage plants will soon rival the world’s largest non-hydroelectric facilities and hold up to 10 gigawatt hours of energy. But what is advanced compressed air energy storage (A-CAES), exactly, and why is the method about to have a moment?

Compressed air is part of a growingly familiar kind of energy storage: grid-stabilizing batteries. Like Elon Musk’s battery farm in Australia and other energy overflow storage facilities, the goal of a compressed air facility is to take extra energy from times of surplus and feed it back into the grid during peak usage.

Here’s how the A-CAES technology works: Extra energy from the grid runs an air compressor, and the compressed air is stored in the plant. Later, when energy is needed, the compressed air then runs a power-generating turbine. The facility also stores heat from the air to help smooth the turbine process later on.

While the efficiency of similar systems has hovered around 40 to 50 percent, the new system from Hydrostor, a major global leader in building hydroelectric storage, reportedly reaches 60 percent, according to Quartz.

Hydostor will store compressed air in a reservoir that’s partly filled with water to balance out the pressure. The whole system will hold up to 12 hours of energy for the grids where the two plants are planned. (The first plant will be built in Rosamond, California, while the second location is to be determined.)

Why branch out from hydrogen to compressed air? While hydro storage is a great part of the global energy scene, storing massive amounts of water requires a ton of infrastructure that Hydrostor says uses a lot of energy it’s ultimately trying to save. That makes intuitive sense if you think about the relative force of water compared with even heavily pressurized air.

New Atlas elaborates:

“Pumped hydro accounts for around 95 percent of the world’s grid energy storage and gigawatt-capacity plants have been in operation since the 1980s. The problem is that you need a specific type of location and a staggering amount of concrete to build a pumped hydro plant, which works against the goal of reaching net zero. Rotting vegetation trapped in dams also contributes to greenhouse gas emissions. Meanwhile, the biggest mega-batteries built so far are only in the 200 MW/MWh range, though installations bigger than 1 GW are planned.

Recharge reports that companies have built smaller existing CAES facilities over naturally occurring salt caverns. In contrast, Hydrostor will be digging new caverns to use for its larger facilities in California, just as engineers are constructing huge salt caves in Utah to store hydrogen.

The first of Hydrostor’s two plants is set to open in 2026, and the company says its system will last for about 50 years—making it a lot longer-lived than almost any energy storage of its kind. The near future of energy is likely made of a dozen different solutions that are all suited to different environments and situations, so adding compressed air to the portfolio simply makes sense.