Although Lithium-Ion Batteries are Now the Mainstream Grid-level Energy Storage System

Although lithium-ion batteries are currently the mainstream grid-level energy storage system, they are not suitable for long-term storage and transfer of large amounts of electricity, and are primarily used for auxiliary services such as grid frequency adjustment or emergency power dispatch. It is only with the increasing proportion of renewable energy and the connection of solar and offshore wind power into the grid that more diverse storage systems are needed.
Even though the capacity of battery storage systems is now growing, with plans for up to 1GW of capacity, they are still limited to around 200MW/MWh, and now Canada-based Hydrostor Inc’s advanced compressed air energy storage (A-CAES) may be able to capture the market share of long-term energy storage. 
Hydrostor has also recently announced plans to build two 500MW / 5GWh A-CAES facilities in California.
The compressed air energy storage system compresses air into large underground tanks, either through the grid or through surplus power from renewable sources, and then releases the power through turbines when electricity is needed. The A-CAES system also utilizes the “power of water,” the water pressure of a reservoir or body of water to enhance the compressed air effect. When the storage plant is charged and air is pumped into the ground, the compressed air carries water from below to the surface, where it flows downwards to release the compressed air when the power is discharged and the previously stored and heated air is used to increase efficiency, which in turn drives the turbines to generate electricity.
In terms of the round-trip efficiency, compressed air energy storage systems typically fall in the 40-52% range, but Hydrostor's system is at 60%. Two A-CAES systems can store 10GWh of energy and provide 8-12 hours of energy from a single discharge. Although the energy conversion efficiency is still not as high as 90% of lithium-ion batteries, the A-CAES system has a life expectancy of up to 50 years, and as the number of installations increases, the cost of installation and expansion will be lower than that of lithium-ion batteries in the long term.
Hydrostor is currently building a new power plant in California, scheduled to be completed in Rosamond in 2026, and a second one is expected to be constructed in California, although the exact timing and location has yet to be revealed.

Author Professor Wei-Keng Lin Education｜Ph.D., University of Maryland Occupation｜Professor, National Tsing Hua University  Specialty｜Electronic package heat dissipation, Heat pipe, Loop heat pipes(CPL，LHP，PHP), Energy-saving design, Solar heat storage and cooling, Heat flow system, Cooling of electronic components, Two-phase flow, Heat transfer elements of artificial satellite and high-altitude flying object