For the Backwoods / Backstreet Engineer interested in becoming ‘greener’ self sufficient and possibly going off grid, there are some serious problems with the two common types of combustion engine.
- Steam Engines. It is perfectly possible to build, operate and maintain your own steam engine, and you can power it using wood, (or practically any other combustible material come to that). However, you will soon come up against the problem of the high-pressure boiler, (leave aside how many psi constitute high pressure). Very hard to make, requiring official inspection, and a big bomb waiting to go off.
- Internal Combustion Engines. Basically your car / truck / tractor engine. Doesn’t matter what shape you choose the problem you have is making clean fuel. You can make your fuel from just about any type of vegetable matter, including wood, and you can make either a gas or a liquid. But making methanol from wood is fraught with issues. Gasification of wood is a bit easier, and you can even buy a small-scale gasifier in kit form.
The Stirling Engine solves many of the issues raised by the two more common combustion engines. And, here we get into the realm of the impossible. To a lesser engineer a Stirling Engine looks like a perpetual motion machine because it operates on a closed cycle. For an engineer who properly understands heat a Stirling Engine makes perfect sense. Heat = Energy = Work
The good part is that we probably get to explore our pyromania and build a fire.
The Stirling Engine works because a gas takes up more room when it’s hot than it does when it’s cold. If there isn’t any more room ~ as in a container ~ then the pressure increases. Cool the gas and it will take up less room ~ the pressure drops.
Therefore a the operation of a Stirling engine is exactly like the essence of a woman, she will blow hot and cold, and it’s a man’s job to harness and control her.
To make a Stirling Engine 5 elements are needed:
- A temperature difference. This is the essence of a good heat engine. It’s not raw heat that’s needed, it’s a temperature differential. If you have a source of cold ~ (OK physicists can shut up) ~ you can make a Stirling engine run on sunshine.
- A working fluid. A gas is best, you can use everyday air. For the sake of argument our working fluid is any gas, (NOT Gas as in Petrol).
- An expansion cylinder. This is where the hotter part of the gas gives up work.
- A compression cylinder. This is where the colder part of the gas gives up work.
- The mechanical linkages turning lateral motion into rotary motion.
There are two basic models for the Stirling Engine:
- Alpha ~ two cylinder engine
- Beta ~ one cylinder engine
For me, the two cylinder engine is far, far less complicated to build and operate than the one cylinder engine. That is counter-intuitive, but I told you the Stirling Engine is like a woman, the logic is a little twisted, but it’s there all the same.
The benefits of a Stirling Engine are:
- Low noise.
- Very energy efficient
- Simple in operation
- Very low maintenance
- Very scalable ~ you can make a little one or a huge one
- Can use any combustable crap as a fuel
- Can utilise coldness as a fuel
I could design, draw, fabricate, build, operate and maintain an Alpha type, 2 cylinder Stirling Engine using basic tools and techniques. I probably wouldn’t need a machine shop, but access to one would simplify things.
Do some more internet research and you will find some resources to get you started.
But I would caution you NOT to use a pellet system unless you are allergic to hard work. Pellet systems tie you to going on buying your fuel from the outside. The thing about a Stirling Engine is that it should run on any old wood. To get your free power, you need to get away from the bad idea of buying fuel.
A small Stirling Engine is an ideal power generator for anyone going anywhere near the green / self-sufficiency / off grid lifestyle. And, you probably get to use up a hell of a lot of that wood you just happen to have lying around.