Professional Engineering

The debate on energy storage seems to have morphed into a discussion about the impracticality of storing electricity in industrial quantities. Most electricity is used to generate energy in all sorts of other formats – many of which can be stored a lot more easily than the electricity that needs to be thought of as simply a convenient transmission medium.

A major electricity usage – at peak times and central locations – is the operation of air conditioning. The production of cold energy begs for a storage solution for such cold energy. And one way in which this can be done is through ground freezing.

Ground freezing has been used for years to stabilise ground for mining and tunnelling and the technology is well established – though thermal efficiency has not previously been a priority. Utilising coaxial brine cooling tubes in bored holes large volumes of ground can be cooled to temperatures down to -25ºC to be used in reverse for building cooling as required. Powered by off-peak or surplus wind power energy this can be used to peak-lop daytime power requirements saving on both energy and infrastructure costs.

Energy loss of ground frozen energy is very slow – partly because it is cold and also because the thermal conductivity (the only transmission process left) for frozen ground is very low. So once parked in frozen ground the energy will stay there until needed.

The factors that mitigate against the introduction of ground freezing are mostly financial. Any company that works to develop the process will merely save their competitors the effort. Making money out of developing the process will be difficult as it is established technology that cannot be protected – simply used in a different context.

So there is the challenge. Create a high efficiency ground freezing system. And beat your competitors to selling it.

Good luck.

Pete Yates, London

Next letter: Efficiency debate