Liquid Air - Storage Medium for the Green Generation?

One of the major problems of renewables is energy storage. Many renewable sources are variable, particularly wind, but also solar, wave and tidal energy. Up till now there has not been a widespread, convenient method of storing electricity for use when needed. It is possible to use "pumped storage" - unneeded electricity is used to pump water to a high reservoir, then it can cascade down turning turbines when required. However this needs suitable mountain reservoirs so there are only two such power stations in the UK. Hydrogen is another possibility. It has also been suggested that when electric vehicles (EVs) reach a critical mass on the UK's streets, there will be enough plugged in and charging at any time to be a giant storage battery. This may be so, but we are a long way from that point.

The Centre for Low Carbon Futures (CLCF) is a research centre formed by the Universities of Birmingham, Hull, Leeds, Sheffield and York. It is working on using liquid air for storage and power. Early indications suggest that it could be a credible alternative to existing energy storage systems which would better harness renewables to existing systems and deliver energy security. This would be of considerable economic value to UK PLC.

How it works

Excess electricity is used to cool down air, till it is in a cryogenic liquid state. It can then be stored in cylinders - like giant Thermos flasks - till it is needed. Then it can be used to power turbines when electricity is required. The Institute of Mechanical Engineers estimates that this Liquid Air system will have an energy efficiency of up to 70%. For comparison, solar panels are only about 18% efficient, and motor cars around 20%.

The technology was developed by inventor Peter Dearman, in his garage in Hertfordshire, originally to power vehicles. Such was the interest in the system he created that it has undergone a two year trial partly-funded by the Government.

The results have been sufficiently impressive for the The Centre for Low Carbon Futures to programme a day long conference on the potential of this new technology at the Royal Academy of Engineering on 9th May. The conference white paper is published by CLCF and based on contributions from a wide range of energy experts including world-class consultancies such as Arup and Ricardo, the German industrial gases company Messer, and academics from the Universities of Leeds, Birmingham, Strathclyde, Brighton and Imperial College.

Like all technological innovations, this will need to be tested in the real world before we can be certain that it will be practical. However using readily-available air looks to be a better bet than creating volatile hydrogen for energy storage, which is the only real competitor technology at the present time.