Energy Independence

This year we’ve not had any major power cuts, but if I just add a little electric generator to this Stirling engine, we should be able to withstand anything nature throws at us…

This engine has one piston and one displacer and uses thermodynamic expansion and contraction of the air inside to keep it working. The air near the bottom hot plate warms up and expands, pushing the piston out and rotating the flywheel. This in turn pushes a foam block inside the engine down via a second arm on the flywheel, moving the air up to the cold top plate. This plate cools and contracts the air, and sucks the piston back in, which keeps the wheel rotating further to continually restart the heating and cooling cycle as long as there is sufficient temperature differential between the two plates.

A Stirling engine is a closed-system, invented in 1816 by Robert Stirling, so there’s no need to refill (unlike with a steam engine, where the evaporated water has to be constantly replaced). Even more amazing, you can reverse the operation: instead of putting in a heat source, you can turn the flywheel. The compression and expansion of the air inside cools one of the plates, and warms the other one, and if you turn the wheel in the other direction, the hot-cold also reverses. This principle is used in space to cool scientific sensors, allowing telescopes to look deep into the universe.

Unlike those satellite and space experiments I normally design, I built this little engine with bits and pieces lying around the workshop, without calculations, sketches or design dimensions. And so I was just a little amazed that it actually started rotating when I added the tealight heat source!