The Dearman Engine Company is developing an engine that runs on what most people would not think of as fuel, liquid air.
Call it a new kind of cold fusion. The pistons get pushed by the pressure of rapidly expanding air in the cylinder. Liquid air is stored at -256 degrees Fahrenheit. The engine pumps liquid air into the cylinder along with what Dearman calls a heat exchange fluid. The liquid air very quickly changes to a gaseous state as it reaches ambient temperature, expanding at the same time. When the exhaust valves open, the only emission is air.