CAES is not a simple energy storage system like other batteries. It is a peaking gas turbine power plant that consumes less than 40% of the gas used in conventional gas turbine to produce the same amount of electric output power. This is because, unlike conventional gas turbines that consume about 2/3 of their input fuel to compress air at the time of generation, CAES pre-compresses air using the low cost electricity from the power grid at off-peak times and utilizes that energy later along with some gas fuel to generate electricity as needed. The compressed air is often stored in appropriate underground mines or caverns created inside salt rocks.
The first commercial CAES was a 290 MW unit built in Hundorf, Germany in 1978. The second commercial CAES was a 110 MW unit built in McIntosh, Alabama in 1991. The construction took 30 months and cost $65M (about $591/kW). This unit comes on line within 14 minutes.
The third commercial CAES, the largest ever, is a 2700 MW plant that is planned for construction in Norton, Ohio. This 9-unit plant will compress air to 1500 psi in an existing limestone mine some 2200 feet under ground.
Professor Garvey’s research has proven that by taking offshore wind turbines to a scale never before imagined — 230m diameter is the baby of the family — and considering some radical redesigns, the total amount of structural material per kW of rated power can be slashed, effectively cutting costs by a factor of four or more. He believes it is possible to store energy at costs well below £10,000/MWh — less than 20 per cent of pumped hydro energy, the cheapest competing technology.
Testing of scale-model prototype Energy Bags ™ has already commenced. A research project funded with €310,000 from the EON International Research Initiative has already funded the development of analysis and design tools for the energy bags and will provide further prototype testing in seawater leading to an energy storage product that will be ready for use in energy systems by May 2011.