Something in the air


Just as we get to grips with the new PSA ‘Hybrid Air’ hydraulic brake regeneration system, cryogenic liquid air becomes the subject of a new report. Andrew English takes up the story


short-lived Liquid Air Car Company of Boston, USA, produced a car capable of running on it in 1902. Over a century on, however,


C


Off-peak/ ‘waste’ electricity


Liquefaction plant


(converted to additional power)


Waste heat


cryogenic air could provide an answer to grid power generation storage requirements for renewable sources; be used to improve the efficiency of existing internal combustion engines; and also power a new generation of small urban vehicles, with zero tail- pipe emissions. The headline figures are that liquid air has the potential to


ryogenic gas technology is well known. Nitrogen, a major component of atmospheric air, was first liquefied in 1883 and the


create a £1 billion a year industry, with 22,000 UK jobs in grid energy storage alone.


Into the future “Is this the time of the nitrogen economy?” asked John Leggate, managing partner of Quintal Partners, in his presentation at a recent conference at the Royal Academy of Engineering in London. It was a sentiment echoed by other speakers, but not all of them. “It’s really important not to


overhype this technology,” cautions Professor Neville Jackson, chief technology and innovation officer at Ricardo.


So, what is the technology all


about? Liquid air is simply air cooled to minus 196ºC by an industrial process of compression, expansion and heat removal. It is a blue liquid that is stored in a vacuum flask. One litre of liquid air is the equivalent of 700 litres of atmospheric air and, on release, the liquid boils, expands by 700% and returns harmlessly back to the atmosphere. It’s that expansion that can be used to drive turbines or piston engines, such as the Dearman Engine. It was Peter Dearman, a self-


confessed “garden-shed” engineer, who hit upon the idea of injecting liquid air or nitrogen into the engine’s


Cold store Cold Cold


Liquefied air Tank


Liquefied air


recovery


Power


Peak/security of supply electricity


Co-located generation or industrial processes


30


www.automotivedesign.eu.com


May/June 2013


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