The Azimuth Project
Compressed air energy storage

Contents

The idea

Compressed air energy storage is a way of storing energy by compressing air when energy is available and extracting energy from the compressed air by letting it expand when energy is required (a bit like a spring). It has been used commercially with gas-fired plants since 1978 to smooth out peaks in demand. It is often advocated as a means of making intermittent sources of energy such as wind power more useful.

The main difficulty is doing it efficiently. Compressing air makes it hot, and it is easy to lose this heat energy, while letting it expand makes it cold, so it needs warming up again. Several technologies mitigate the problem in different ways.

Examples

Existing plants

So far there are only two CAES plants in operation in the world: the 290 MW plant belonging to E.N Kraftwerk in Huntorf, Germany, and 110 MW plant of Alabama Electric Corporation in McIntosh, Alabama, USA, commissioned in 1991. (From Cheung et al, in 2003)

Recent research

Professor Seamus Garvey, of Nottingham University, has a vision for a UK powered completely by renewable energy by 2030. He recently launched his own spin-out company — NIMROD Energy Ltd — which is based on the Integrated Compressed Air Renewable Energy Systems (ICARES) research which he has been developing since early in 2006.

The technology is centred on a simple premise — using giant wind turbines to compress and pump air into huge undersea Energy Bags™ anchored to the seabed — or geological formations where deep water is not available. The high pressure air would be expanded in special turbo-generator sets to provide electricity as required — not just when the wind is blowing.

The scheme involves

one thousand 500m-diameter wind turbines with cable-braced rotors driven by nearly 1,000 tonnes of moveable pistons inside each one, all supported on 3D floating frameworks far offshore. They would store around 100 million cubic metres of compressed air stored deep under water in salt-domes and Energy Bags™ and would feature around 200 million tonnes of material (largely seawater) in floating thermal stores and around 300 expander-generator units each rated at 250 MW.

(From Nottingham university press release)

The Energy Storage and Management Study by the Scottish government said:

The ICARES devices have patent but are at experimental stage. They are modular in construction so as long as suitable storage locations are available, a number of energy bags can be put in place as required. The size is in MW capacity approximately and discharge times are in hours. Barriers will be similar to the tidal devices and are centred on suitable location providing sea depths, grid connection and setting alongside energy generation devices.

References

category: energy