From liquid air to supercapacitors, energy storage is finally poised for a breakthrough

“It doesn’t always rain when you need water, so we have reservoirs - but we don’t have the same system for electricity,” says Jill Cainey, director of the UK’s Electricity Storage Network.

But that may change in 2016, with industry figures predicting a breakthrough year for a technology not only seen as vital to the large-scale rollout of renewable energy, but also offering the prospect of lowering customers’ energy bills.

Big batteries, whose costs are plunging, are leading the way. But a host of other technologies, from existing schemes like splitting water to create hydrogen, compressing air in underground caverns, flywheels and heated gravel pits, to longer term bets like supercapacitors and superconducting magnets, are also jostling for position.

In the UK, the first plant to store electricity by squashing air into a liquid is due to open in March, while the first steps have been taken towards a virtual power station comprised of a network of home batteries.

“We think this will be a breakthrough year,” says John Prendergast at RES, a UK company that has 80MW of lithium-ion battery storage operational across the world and six times more in development, including its first UK project at a solar park near Glastonbury. “All this only works if it reduces costs for consumers and we think it does,” he says.

Energy storage is important for renewable energy not because green power is unpredictable - the sun, wind and tides are far more predictable than the surge that follows the end of a Wimbledon tennis final or the emergency shutdown of a gas-fired power plant. Storage is important because renewable energy is intermittent: strong winds in the early hours do not coincide with the peak demand of evenings. Storage allows electricity to be time-shifted to when it is needed, maximising the benefits of windfarms and solar arrays.

This alone would not be enough to justify the costs of storage, but it brings multiple other advantages. The UK’s National Grid already spends £1bn a year on balancing the grid, switching power on or off to keep the lights on, and stored energy could play a big role. Storage can also be a much cheaper option than big new power stations that might be paid to lie idle for much of the year and only kick in on cold winter evenings. The widely distributed nature of storage also boosts energy security. “It’s a ‘no regrets’ option,” says Prendergast.

The most established form of energy storage is pumping water up mountains, and the UK has four such plants. But available mountains in useful places are now rare and Highview Power Storage is about to fire up an alternative: liquid air.

Its new £8m demonstration plant, at Pilsworth, near Manchester, and funded by the Department of Energy and Climate Change (Decc), is set to start in March. By compressing air 700 times into a cold liquid, it stores power which is released by evaporating the liquid air into a high pressure gas to turn a turbine. The 5MW system will be able to power many thousands of homes for a few hours. Gareth Brett, CEO of Highview, says it is like pumped storage, but can be sited wherever it is needed.

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