FROM an engineering perspective, the realisation of massive energy storage (MES) in the context of future security of "green" grids, does not require "something completely different" as Dr John Cameron seems to suggest (Letters, April 8).

MES, as the science and engineering literature amply attests, is well established technically. Methods range from electric storage (batteries, capacitors, super-capacitors), magnetic storage (superconducting coils), kinetic energy storage (flywheels), gravitational storage (pumped-hydro, artificial lagoons) to compressed air (in massive underground caverns).

Compressed air and gravitational systems furnish the really massive levels of storage capable of providing the kind of back-up power needed to smooth grid fluctuations in a world of intermittent renewables. For example, lagoon storage systems being developed off Copenhagen, and at Jiangsu, in China, will potentially provide respectively 2.3GWh and 598GWh of electrical energy. These levels are certainly large enough to confidently advocate the rapid development of fossil fuel free grid systems.

Unfortunately, within our worldwide corporate-driven. neo-liberal economic structures, the privatising buccaneers of this system, who control much of the investment in developing technology, will see no merit in storage because nothing is produced and hence nothing exists to sell at a profit. Until energy is nationalised and becomes democratically controlled, the growth of storage capacity, which is essential to the evolution of a secure green electricity grid supply, seems very likely to fail and the transition to green power will not, therefore, advance fast enough to address climate change.

Alan J Sangster,

37 Craigmount Terrace, Edinburgh.