The Feasibility of Powering an Attic Fan with a Stirling Engine

Interest in stirling engines has increased since existing thermal gradients can be carbon neutral. Our goal is to produce sufficient electricity to run a fan under the constraint of a 20 ºC temperature difference on either side of ceiling drywall in an attic. A small commercial low-temperature gamma type Stirling engine was placed in a model attic with the intent to generate electricity. The first iteration attempted to conduct thermal energy from a heated shingle via copper tubing to the engine’s top plate but was not successful. The second utilized a heated attic chamber and generated a representative temperature differential across the engine’s surfaces. The next hurdle was to transfer the mechanical energy of the Stirling engine flywheel to an electrical generator. Several custom flanges and pulley wheels were designed and printed. Direct frictional contact proved problematic owing to out-of-roundness of the printed wheels. Currently, the engine’s flywheel is being augmented with fenders such that a friction drive belt can allow the transfer using modest tension. We hope that this design is adequate to consistently generate a measurable amount of electricity.