The first large-scale commercial plant was built in Huntorf in Germany and has now been in successful operation for many years.
The reason for the slow progress of CAES is the prohibitive cost of a suitable storage vessel. Large CAES schemes have relied on disused underground caverns to provide a reservoir for the compressed air, but these are not readily available and may not be close to a market for electrical energy.
Also, existing CAES plants are not environmentally “green”. Compression of air into the storage reservoir generally relies on compressor power generated by fossil fuel, and recovery of stored energy uses conventional gas turbines burning fossil fuel.
Even if the compressor power is provided by wind turbines, the plant is predominately fossil fuel-powered.
Fresh opportunities
The prospects for CAES could be about to change. Buoyant supports for offshore wind turbines are of increasing interest.
Floating foundations such as the Statoil Hywind type require a substantial buoyancy volume for hydrodynamic stability and this offers an obvious opportunity for storing energy as compressed air.
Figure 1 (below) shows the dimensions of an articulated buoyant column sized for a 6MW turbine in 80m water depth.
Figure 2 (beneath) shows the buoyant column diameters required to achieve sufficient stability for turbines mounted on such columns as a function of turbine power and water depth.
Figure 3 (bottom) shows the total energy that could be theoretically stored in these columns when filled with compressed air at 10 bar.
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