From Andrew Gigiel
Steve Orchard illustrates the inefficiencies of storing excess wind power as compressed air (15 November, p 31).
Compressed air isn’t the best option for storing energy unless one has a proper use for the huge quantities of very cold air that will be available when the bottled air is released.
Combining wind-powered air compression with a gas-fired power turbine is a much better bet, thermodynamically. Gas turbines require air to be heavily compressed before it is mixed with fuel and burned, a process that requires a lot of energy.
Having “pre-compressed” air on tap makes it possible to operate a gas turbine generator set at remarkably high efficiency.
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These compressorless gas turbines needn’t consume fossil fuel. They could burn biogas, or liquid biofuels.
Admittedly, compressing air does produce a significant amount of heat, as Orchard says. However, that heat needn’t go to waste either: manufacturing plants or district heating systems could certainly exploit it.
Moorlynch, Somerset, UK
