The cold side of the engine must be kept very cold, to efficiently remove heat from the working fluid during the contraction portion of the engine's cycle. The device used to accomplish this task is referred to as the Chiller.
In the past, chillers used relatively low efficiency heat exchangers, often just the surface of the cold cylinder itself, to reject cycle waste heat to the surrounding atmospheric air. This was very inefficient and results in the cold side of the engine running at a temperature that is many degrees above that of the ambient.
Our chiller uses a specially designed phase change cooling system to produce temperatures more than 50 degrees below zero (Fahrenheit). This coolant is then run through our heat exchanger (described elsewhere) to reduce the temperature of the engine's working fluid to this same cold temperature. This adds more than 150 degrees F to the temperature differential of the engine, without any need to make the hot side any hotter.
The energy used to produce this cooling effect is recovered from the coolant, and is returned to the heat input side of the engine. This allows us to run the chiller with an extremely low net power input. The final result is a very significant increase in the efficiency of the engine.