Renewable Energy From An Old Concept

Posted under solar power by Michael Edwards

In the process of doing research for an article I did on solar green products, I came across the Stirling air engine. The engine was once called a hot air engine because it requires no internal diesel or fuel to run. Let’s take a deeper look at this unique engine that requires no fuel and has recently been adapted for use on solar collector dishes.

The Stirling engine was originally invented and patented as an air engine by Robert Stirling in 1816. It may have been designed as a replacement for the steam engine, because the steam engines used in factories would explode frequently, causing many injuries and fatalities. These days, because of the cost of fuel and the environmental problems with coal, many new designs are incorporating the Stirling engine in solar power 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 fraction. 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.

Operation is simple: the gases are heated by an external source, causing the hot gas to move toward a cold chamber, in the process, a piston is driven and a flywheel rotated. To put it simply, movement is achieved from heat expansion. A few knock-offs of the Stirling engines are small enough to fit in your hand. Others system are designed to drive electrical generators. They are a about the size of a fifty-gallon drum.

The Stirling engine is ideal for use in a solar power generating system. With one of the hottest heat sources available (sunlight), the hot chamber will continue to operate without external fuels as long as there is daylight. This makes it ideal for use as a peaker type power plant when the demands for electricity are at there highest.

With better-designed engines and new types of material, a movable (tracking) parabolic mirror, and a single Stirling engine you can produce 25 kilowatts of electricity.

In a future article about green products I will list the different solar technologies and how they compare to the competition.

Michael

Want more green products check out Michael’s website at Green Products