Liquid-air engines take a step forward

Telegraph : Compressed and cryogenically cooled nitrogen, commonly called liquid air, was first used to power a vehicle in 1902. When liquid air is released from its container, it quickly boils and expands by a factor of 700%. The expanding gas can be used to drive a turbine or pistons. However, unless it can be expanded at a constant temperature, the engines that are powered by it are inefficient. Now Peter Dearman has developed an engine that uses a liquid coolant to maintain the temperature of the liquid air. The coolant then circulates through a radiator and can be used to scavenge extra heat from the vehicle cabin. When it returns to ambient temperature, it can be reused in the engine. Ricardo , a UK-based engineering consulting firm that has been working to create a useable version of the Dearman engine, envisions several possible uses in vehicles or electricity generators. Liquid air is not currently produced commercially, but current prices for the electricity needed to produce the liquid air are just a few cents per liter. However, significant challenges, including poor energy density and efficiency and the effect of the low storage temperatures on other engine parts, still need to be overcome before liquid-air engines can become viable alternatives.