Bohm Stirling Engine Kit

In 1816, Scottish inventor Robert Stirling patented an alternative to the steam engine. His closed-cycle engine runs on pressure created by air moving back and forth between heat exchangers. An external heat source warms one exchanger, causing the air inside it to expand into the cold heat exchanger, pushing a piston. The air then cools and contracts, pulling back the piston, which pushes the air back into the warm heat exchanger, restarting the cycle.