The Highview Cryo Energy System uses liquefied air or liquid nitrogen (78% of air) which can be stored in large volumes at atmospheric pressure. Liquid nitrogen is a very common commercial product, transported daily from liquefaction plant to customer; or, for larger users, produced on site.
Liquefied air has a high expansion ratio between its liquid state (-196º Celsius) and, more common, gaseous state; expanding about 700 times when regasified. As with a traditional steam engine, a cryogenic engine relies on phase-change (liquid to gas) and expansion within a confined space e.g. engine cylinder or turbine.
Since liquid air boils at -196º Celsius, ambient temperature will superheat it, creating regasification and expansion. An engine can therefore use freely available environmental heat as the heat source.
The energy density of cryogenic fluids, such as liquid nitrogen compares favourably with alternative energy storage fluids such as compressed air. Cryogenic storage also has the advantage over compressed gases in that it can be bulk stored above ground in low pressure tanks.
Liquid air energy storage: supporting the low carbon electrical network
From: Smart Grid 2012, 19 September 2012, London, UK
2012-09-19 00:00:00.0 Power Channel