There is only one CAES in the USA and one of only two units worldwide. Do you know where it is and what it is? CAES is characterized by high energy capacity and can have exceedingly long duration times several hours to days. Compressed Air Energy Storage (CAES) has slower response times than other storage technologies like flywheels or batteries and may be more suitable for applications like providing peak capacity. Â CAES deployment is limited by unique geological requirements, which may be avoided in new CAES variations.
CAES is a form of mechanical energy storage that uses electricity to compress and store ambient air for later use. The air has historically been stored in underground caverns such as salt caverns. Current CAES development allows the use of any type of storage below or above ground.
There are three types of CAES systems based on how the heat produced during compression is used and stored: diabatic compressed air energy storage (D-CAES), adiabatic compressed air energy storage (A-CAES), and isothermal CAES. Â
D-CAES is the primary type of CAES currently deployed, project development for D-CAES has been restricted by the unique geologic formations required for gas storage, which must be large and impermeable and have storage capacity ranging from several hours to over 24 hours. Compared to other storage technologies, CAES typically has lower energy capacity costs, as it uses off-the-shelf components from more established technologies like compressors. Given the proper geologic formations, CAES can also have significantly longer durations than most energy storage technologies. The main disadvantage of CAES is that development is constrained by the availability of suitable large underground storage.  Â
As CAES relies on spinning turbines to generate and store electricity, it can also provide system inertia, which is critical to arresting rapid changes in frequency or grid disturbances.
CAES is significantly cheaper than most alternatives. As CAES must switch between compression and expansion phases when charging and discharging, it is also possible that the response time for CAES systems may be slower than other technologies, which may make them less suitable for services that require rapid changes in output.Â
There are two operating commercial CAES plants (both diabatic) worldwide—a 290-MW plant in Huntorf, Germany commissioned in 1978, and a 110-MW plant in McIntosh, Alabama, commissioned in 1991.
Gravity Energy Storage (GES):
GES is a new technology with the potential to provide long-term energy storage similar to CAES or PSH. One could consider PSH as a GES. GES uses the potential energy of bulk mass at a given height to restore energy. This system could potentially be used to provide slower, longer-duration services such as peaking capacity, load following, and energy arbitrage. The GES is not fully developed for commercial use. Â