×

Why storing energy in liquid air could be a game-changer

From solar to wind and biomass to geothermal, renewable sources of energy are entering a new era of importance. Within this climate of innovation, efficient energy storage is becoming an increasingly important factor.

"Storage is vital if we are to get the level of renewables that are required for a low carbon future," Stuart Nelmes, engineering director at Highview Power Storage, told CNBC's Sustainable Energy.

U.K. based Highview say they design and develop large scale storage solutions for both utility and distributed power systems. Their process, they say, uses liquid air as a storage medium.

"We start off with the charging," Nelmes explained. "We pull the air in from the atmosphere, we compress that (and) put it through an air purification unit which strips out the moisture," he added. "It also strips out the CO2 and anything that's going to freeze and block the cycle."

An industrial refrigeration process then takes place, Nelmes said, and the gas is compressed. This is then expanded, with the heat taken out. Once made, the liquid air is stored in an extremely cold "vessel", Nelmes added. Their pilot facility holds enough energy to power 2,000 homes for around an hour, he said.

"When we're ready to discharge the energy, we take that low pressure liquid air, we pump it to a high pressure, normally over 100 bar," Nelmes said.

"We're then utilizing the heat that we captured earlier in the process. (We) expand the gas through a turbine, which drives this generator and exports electricity out on to the grid."

While a pilot facility has been in operation over the last few years, the business has plans to expand.

"The vision for the future is very much scaling this technology up to something really, really useful for the grid," Matt Barnett, Highview's business development director, said.

Barnett added that the business was working towards developing a 'gigaplant'. "That's a 1.2 gigawatt hour system, and it would power quite a large town or small city at that scale."

There are environmental benefits too, according to Nelmes. "We're emissions neutral, so it's air in and air out, and there's no hazardous substances involved in the process at all," he said.