Solar-Run Stirling Engine

  • What is the effect of using solar energy instead of a flame burner to run a Stirling engine?

Recommended Items:

  • Stirling engine kit
  • Parabolic mirror to focus light onto the Stirling engine

Concepts used:

  • Mechanical systems, Stirling engine, Heat exchange, Thermal expansion and condensation, Solar energy


Stirling engines convert heat energy to mechanical work. Since all heat transfer takes place through the engine’s walls it is known as an external combustion engine.This is done by gas chemistry and physics. When a gas is in an enclosed area such as a balloon, and the temperature is increased the pressure the gas exerts on the walls of the balloon increases and the balloon expands. If the balloon is cooled, then there is less pressure on the walls and the balloon shrinks. If the balloon were not able to expand and contract, then the heating and cooling would produce changes in pressure inside the balloon that could be used to push a mechanical device (like a piston, for example). Similarly, it is possible to take a fixed amount of gas and change its volume. This will increase and decrease the temperature of the volume of gas. In a Sterling engine the gas never leaves the engine and these properties of changing volume and temperature are applied to make the engine run. Specifically, gas contained in the engine is heated by a heat source causing it to expand and to puch a mechanical piston. As the hot gas expands it flows into the condenser section of the Stirling engine where it cools and decreases its volume. The piston motion, therefore, is controlled by the heating and cooling of the gas.

Stirling engines can be heated using a flame source or using sunlight focused onto the engine by a parabolic mirror. In this experiment, construct a Stirling engine that uses the heat from a parabolic mirror to run. Build the Stirling engine and align the mirror so that it heats the gas portion of the engine. Compare the amount of energy generated using this technique to the amount produced using a fame heater or another heating method.

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