Converting The Sun's Heat Into Electricity

By Michael Edwards

During the process of researching an article about green products on photovoltaic cell systems (solar panels), I came across another way to convert the sun's light into electricity. So let's take a 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 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.

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 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 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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