The WWF has been oversimplistic in its argument that no further gas-fired power stations are needed (Report, 14 May). The forecast increase in annual renewable electricity production is only just sufficient to balance the closure of coal-fired electricity generation and the fall in nuclear generation resulting from the retirement of many of our nuclear power stations (most of which are already working beyond their design lives). However, this does not mean more no more gas generation capacity is needed. Electricity demand varies, and renewables are intermittent. There has to be enough capacity to meet demand at all times.

While pump storage systems and batteries are able to store enough energy to cope with short-term variations in demand and the availability of renewable generation, it would not be environmentally friendly, efficient or cost-effective to use such systems to store energy from summer to winter, or even to store enough to survive a long midwinter period of high pressure over the North Sea.

We may not need to use more gas over the year, but with reduced nuclear output and no coal, the peak demand for gas-fired generation will be larger, meaning we will need more plant.

We should not view electricity generation in isolation. We need to reduce carbon dioxide emissions from heating and transport too. Using excess electricity to generate hydrogen, injecting it into the gas grid (or into hydrogen vehicle fuel tanks), and then using an equivalent amount of gas to generate electricity when in short supply, is a viable method of long- or short-term energy storage. The extra gas generation capacity needed for that is cheaper than battery storage.

Steve Bolter

Gestingthorpe, Essex

• Your article (Hydrogen is solution to excess electricity puzzle, say engineers, 9 May) based on a recent report by the Institution of Mechanical Engineers about heat from hydrogen, makes me wonder whether the IMechE are in the pocket of the gas industry. The best electrolyser conversion efficiency I’ve ever come across is about 0.76. If that produces hydrogen from electricity and it’s burned in a boiler with a gross “efficiency” of 0.9, that’s 0.68 units of heat per unit of electricity supplied. Oh, and there’s no hydrogen infrastructure yet. Is there an alternative? Yes – the best lithium-ion batteries have a round trip “efficiency” of 0.89. If that’s fed to a heat pump with an eminently achievable coefficient of performance of 3, that’s 2.67 units of heat per unit of electricity supplied – almost four times as much as can be gained from the hydrogen option. And the infrastructure for that already exists.

Professor Chris Underwood

Northumbria University

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