Alternate Power DIY

When doing the research for a article on new green products, I was unaware of many of the different ways to convert the energy of the sun into electrical power. I have written about solar cell or photovoltaic cell systems, so let’s look at another type of solar energy system.

This system is not new; it was originally conceived in 1816 as an industrial rival to the steam engine. It has been largely underutilized for the past century. With the need for renewable energy sources caused by the overuse of the fossil fuels interest has resurged in solar designs, and it is now being designed into many new solar collector systems.

The Stirling engine is a heat engine that is vastly different from the internal combustion engine. It is highly efficient, operates quietly and is great at converting otherwise wasted heat into kinetic energy. Its only drawback is loss of power from internal friction. The gasses (most often air) used inside the engine remain inside and are never expelled. With no exhaust valves like a gasoline or diesel engine and with no explosions from combustion, the engines run very quietly.

The heat source needed to start and maintain the Stirling cycle depends on the temperature difference between the hot and cold chambers. The greater the differential between chambers, the faster the engine will operate. In some cases the difference that occurs when the cold chamber is cooled by wetting it is enough differential to start the engine.

The basic operation of this thermal engine is really quite simple. The engine has two chambers, one hot and one cold. When an external heat source is applied the hot air expands moving a piston and flows to the cold chamber. A flywheel is attached to maintain movement.

The reason the Stirling engine works so well for a solar application is that heat from the sun can easily be concentrated to heat the hot chamber. A parabolic mirror much like that seen with the roof mounted satellite dishes is used to gather and focus the sunlight. With the sunlight focused onto the hot chamber of the engine, the temperature raises and the engine starts running. Connect the output shaft to a generator, and electricity is the product.

With the space age list of available materials, the pistons in the hot chamber are much better designed to handle the high temperatures that would have fried previous generations. The new systems with the right mirror design and decent tracking systems are averaging up to 25 kilowatts of electricity

I will compare the different solar technologies in a later article. For now, I need to lay a foundational understanding of each of the green products used to produce power so a comparison can be made.

Michael

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