Current work is focused on second generation CAES plants with potentially lower costs, higher efficiency and faster construction times. Construction of Compressed Air Energy storage (CAES) project called ADELE started in 2013 in Staßfurt in Sachsen-Anhalt, Germany as part of collaboration between RWE, GE, Zueblin and German Aerospace Centre, with improved operations.
A project is being planned in the US, which uses two CAES systems, one with below ground storage and one with above ground storage. The below ground capacity will be 300 MW for 10 hours and the above ground capacity of 15 MW for 2 hours.
Advanced adiabatic CAES systems extract heat energy from the air before storing to cool the air then reuse this heat to expand the compressed air through turbines to meet demand. This system should have high storage efficiency and zero CO2 emissions, and is being developed through the EU funded project, AA-CAES (Advanced Adiabatic-Compressed Air Energy Storage).
The power needed to drive the compressor maybe reduced by the use of an internal cooler and water atomisation cooling (WAC). Water mist is injected at the compressor inlet and vaporised through the compressor. The heat of vaporisation causes the air temperature to decrease.
Several potential storage sites have been identified in Europe and the US, and China also has a lot of potential for CAES because of the presence of salt mines. Whereas there is limited potential for CAES in Japan because the country has no salt mines.
Sites for CAES must have
- confined space that can store enough compressed air for the intended use;
- access to natural gas transmission for the turbine;
- access to electric transmission.
The storage capacity of the site depends upon the volume of the cavern and pressure used.
Several companies are developing the potential of CAES. For example, General Compression signed an agreement in April 2009 with ConocoPhillips to develop general compressed air energy storage projects. The first project will be a pilot project in Texas. RWE and Gaelectric are also investigating the feasibility of a CAES at a site in Northern Germany and Ireland respectively.