Friday 31 October, 2014

Turning air into liquid to store energy

Published On: Tue, Oct 2nd, 2012 | Energy Science | By ANI

Turning air into liquid could be a potential solution to one of the great challenges in engineering – how to store energy.

According to The Institution of Mechanical Engineers, “wrong-time” electricity generated by wind farms at night can be used to chill air to a cryogenic state at a distant location. Later this liquid air can be warmed to drive a turbine, when demand increases.

It said that liquid air could compete with batteries and hydrogen to store excess energy generated from renewables.

Engineers say the process to produce “right-time” electricity can achieve an efficiency of up to 70 percent.

IMechE is holding a conference to discuss new ideas on how using “cryo-power” can benefit the low-carbon economy.

The technology was originally developed by Peter Dearman, a garage inventor in Hertfordshire, to power vehicles.

A new firm, Highview Power Storage, was created to transfer Dearman’s technology to a system that can store energy to be used on the power grid.

The process, part-funded by the government, has now been trialled for two years at the back of a power station in Slough, Buckinghamshire.

More than hot air the results have attracted the admiration of IMechE officials.

I get half a dozen people a week trying to persuade me they have a brilliant invention, head of energy Tim Fox told BBC News.

IMechE said the simplicity and elegance of the Highview process is appealing, especially as it addresses not just the problem of storage but also the separate problem of waste industrial heat.

The process follows a number of stages: First the Wrong-time electricity is used to take in air, remove the CO2 and water vapour (these would freeze otherwise).

In doing so the remaining air, mostly nitrogen, is chilled to -190C (-310F) and turns to liquid (changing the state of the air from gas to liquid is what stores the energy).

Then the liquid air is held in a giant vacuum flask until it is needed. When demand for power rises, the liquid is warmed to ambient temperature. As it vaporizes, it drives a turbine to produce electricity – no combustion is involved.

IMechE says this process is only 25 percent efficient but it is massively improved by co-siting the cryo-generator next to an industrial plant or power station producing low-grade heat that is currently vented and being realised into the atmosphere.

Highview believes that, produced at scale, their kits could be up to 70 percent efficient, and IMechE agrees this figure is realistic.

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