Engineers and scientists have been developing ways to store unused energy from renewable sources as the world moves from fossil fuels to renewable energy. We’ve seen different types of batteries making their mark, including lithium-ion batteries, pumped hydro, tanks full of molten salt or silicon and more. Now, California has found a way to move past lithium into an even more sustainable battery – compressed air batteries. Compressed air batteries do not require lithium which is expensive and environmentally damaging to dig up. They store energy like solar and wind and are a 24/7 source of clean power for homes and businesses.
In 2021, Hydrostor opened two new compressed air energy storage facilities in California, which provide almost twice the storage capacity. Their facilities use surplus electricity from the grid to run an air compressor. The compressed air is stored in a big underground tank until the energy is needed. When needed, the energy will be released through a turbine to generate electricity that is fed back into the grid. Reheating the air as it is fed into the turbine increases the system’s efficiency.
Hydrosor’s system is optimized for system sizes of over 100 megawatts with 5 hours up to multi-day storage duration. This is longer than the four-hour standard for lithium-ion. Hydrostor projects that it can produce 60% to 65% of the electricity it consumes, which is a larger energy loss than lithium-ion batteries or similar types of storage. Hydrostor says its systems will store up to 10 GWh of energy, providing between eight and 12 hours of energy over a full discharge at close to its maximum rate.
Earlier this year, California’s Central Coast Community Energy (3CE) approved a 25-year contract with Hydrostor to construct a compressed-air energy storage facility, making it the world’s largest compressed-air energy storage project. Two hundred megawatts of energy would help 3CE serve 447 000 customers between Santa Cruz and Santa Barbara with 100% clean and renewable energy by 2030. This project will help California transition off fossil fuels without causing blackouts.
Compared to lithium-ion batteries that degrade and must be replaced every few years, compressed air batteries can store energy for decades without any loss of efficiency. Compressed air batteries are significantly more expensive than lithium-ion, but the battery’s longevity will outweigh the cost.
Hydrosor has figured out a way to capture and reuse the heat generated when the air is compressed, which means no gas needs to be burned. The company also found a way to dig caverns out of rock rather than salt. These projects have been used elsewhere in places with underground salt domes, but they depend partly on natural gas to heat compressed air as it leaves caverns to make it more efficient. Digging caverns out of rock opens up the possibility of compressed air battery storage worldwide.
3CE’s partnership with Hydrosor will allow for California’s renewable energy to be clean and sustainable. These compressed-air batteries will protect the planet and the people of California and will be an example for other states to implement.