System and Method for Recovering Waste Heat

A method for recovering waste heat from a system, the system including an engine and a heat recovery apparatus, the heat recovery apparatus including a cold cylinder, a first piston disposed in the cold cylinder, a hot cylinder, a second piston disposed in the hot cylinder, and a regenerator, wherein the first piston and the second piston are in fluid communication with one another via the regenerator, the method comprising:

• transferring heat at a first temperature from the engine to the regenerator;
• transferring heat at a second temperature from the engine to the hot cylinder, the second temperature being higher than the first temperature;
• and
• converting the heat at the first temperature and the heat at the second temperature into mechanical energy through motion of the first piston and the second piston.

A propulsion machine comprising:

• an engine for generating primary mechanical energy, wherein the engine produces heat from multiple sources;
• a heat recovery system thermally coupled to the engine, and configured to convert heat from multiple heat sources into recovered mechanical energy, the heat recovery system having a cold cylinder, a hot cylinder, and a regenerator, wherein the cold cylinder and the hot cylinder are in fluid communication with one another via the regenerator, and wherein a first heat source produced by the engine is thermally coupled to the regenerator and a second heat source produced by the engine is thermally coupled to the hot cylinder;
• an energy storage mechanism coupled to the heat recovery system, and configured to store the mechanical energy produced by the heat recovery system;
• and
• a motor coupled to the engine and the energy storage mechanism, wherein the mechanical energy produced by the engine and the mechanical energy stored in the energy storage mechanism are provided to the motor.