Wednesday, June 17, 2009

Photovoltaic Solar Energy

By Walter Hull

Photovoltaic panels are used to convert solar energy directly into DC electricity. Currently they are the most common device we have for this purpose. The electricity, once created, can be used immediately or stored in a battery for future use.

How photovoltaic panels convert solar energy is a subject of advanced physics. In simple terms we can say they take advantage of new age materials and a phenomenon called the photoelectric effect. Solar energy on the atomic level displaces electrons, which in turn creates the flow of electricity.

Historically photovoltaic panels were limited to space age technologies. They are used in satellites and the space stations where they reliably and continuously convert solar energy. As an added bonus, the Sun's radiation is at least 50% more powerful once we break into Outer Space.

In more modern times, photovoltaics are used in residential homes and locations far away from the Electrical Grid. The reason is that the cost of running power transmission cables can quickly exceed the cost of installing a photovoltaic power array. If you are greater than mile from the Electrical Grid, then it is probably a good idea to investigate solar energy. The greater this distance, then the easier it becomes to make that decision.

When considering solar energy, one must first establish that they have proper amounts of solar radiation. There are two types of radiation we must think about. The first type is beam radiation, which are the direct rays of the Sun we receive on a clear blue day. Beam radiation can be quite powerful, and is also the primary radiation source for equipment in Outer Space.

The second type of radiation we have is called diffuse radiation. As the name implies, this radiation is scattered in all directions. It is the primary source of radiation on a cloudy day, or when one is sitting in the shade. Diffuse radiation is not as powerful, and therefore one should not plan on running a photovoltaic system with diffuse radiation alone.

To utilize photovoltaic panels one should be in a location with a good amount of Sun. There are quite a few States in the Western U.S. that fit this criterion. The more beam radiation a location receives the better, as this can easily double the total amount of solar energy.

Photovoltaic panels come in a variety of sizes, voltages, and constructions. They can be wired in series or parallel to meet your system's needs. 12 volt and 24 volt configurations are common, while 48 volts and greater are used for heavy duty installations. Most photovoltaics in production are about 12% efficient. This may not seem like much, but keep in mind that the cost of solar energy is zero, and they will have typical service lives of 25 years.

Converting solar energy with photovoltaics can be a costly investment. If properly sized and selected, however, this investment will pay itself over time. Anywhere from 5 to 10 years payback is a possibility. New types of panels are under development and may be released into the solar energy market in years to come. Some of these panels are geared to lower cost, while others are geared toward increased efficiency.

Using photovoltaics to convert solar energy can be a complicated decision. One must consider the cost of local Utility's rate of electricity, and know the solar energy data for their location. In some cases, as with distant properties and transmission cables, the decision can be easy. But in most cases, an investigation of the payback period will be necessary to know if one is making a cost effective decision. In times of uncertainty and surging fuel costs, the simple piece of mind of energy independent technologies may be well worth the effort.

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