HOW THEY WORK : “How Does Solar Energy Work (Cont’d)”

In our previous edition, we looked at the two methods of solar energy generation, viz, “solar thermal” and “photovoltaic”. The former converts the sun’s energy into heat that can be used for different purposes; the latter converts the sun’s energy into electricity. If you resort to the harnessing of solar energy, you might enjoyed a reduction in your utility bills or even go further and begin supplying the power companies with your excess energy and received payment for that energy. Installing solar panels on homes was a very expensive venture, not any more. There are many DIY (Do it yourself) guides on how to embark on the building of your own panels instead of buying them and having them professionally installed. In countries like Israel, the use of Solar Energy is widespread. These people have developed high capacity power accumulators (batteries) that store solar electricity by day and discharge it into homes by night. In brief, during the summer, everybody with a solar system is literary utilizing Mother Nature for their electricity needs.Let us briefly look at how the Photovoltaic Cells Convert sunlight into electricity. The solar cells that you see on calculators, satellites etc, are photovoltaic cells or modules (modules are simply a group of cells electrically connected and packaged in one frame). Photovoltaics, as the word implies (photo = light, voltaic = electricity), convert sunlight directly into electricity. Once used almost exclusively in space, photovoltaics are used more and more in less exotic ways. They could even power your house. How do these devices work? Photovoltaic (PV) cells are made of silicon semiconductors, which is currently the most widely used element. Basically, when light strikes the cell, a certain portion of it is absorbed within the semiconductor material. This means that the energy of the absorbed light is transferred to the semiconductor. The energy knocks electrons loose, allowing them to flow freely. PV cells also have one or more electric fields that act to force electrons freed by light absorption to flow in a certain direction. This flow of electrons is a current, and by placing metal contacts on the top and bottom of the PV cell, we can draw that current off to use externally. For example, the current can power a calculator. This current, together with the cell’s voltage (which is a result of its built-in electric field or fields), defines the power (or wattage) that the solar cell can produce. Most probably, you might have seen calculators that have solar cells, these calculators never need batteries, and in some cases don’t even have an off button, they work day in day out, endlessly. As long as you have enough light, they seem to work forever, these do not use sunlight but all forms of bright light. There are many applications of solar power, e.g. Emergency road signs, phone call boxes, street lights, or even in parking lots to power lights. There are solar cell arrays on satellites, where they are used to power the electrical systems. You can buy custom designed solar systems or build your own, If you are interested in finding a do it yourself guide to help you begin producing your own electricity, there are very simple guides that shows you step by step how to produce your own solar panels and begin cutting your electricity bills. These guides show you how you can produce these panels for around US$200 or so. Furthermore, you can build your own inverter to convert the power into AC. The initial capital may look big but the bottom line will be amazingly cheap. You may or may not have heard of it, the “solar revolution” for the last 20 years has been going on; the idea that one day we will all use free electricity from the sun. This is a romantic promise. Have you ever imagined that, on a bright, sunny day, the sun shines approximately 1,000 watts of energy per square meter of the planet earth’s surface, in the long run; if we could collect that energy we could easily power our homes and offices nearly for free. Imagine, if you installed a large solar panel on a section of your roof, say 10 square metres, you would be in position to harness up to 10,000Watts, that is 10KVA, this is more than enough power to enable you cook, iron, run your home computer as well as supply your next door neighbour with free power; what if say the whole roof of 64 square metres, that could generate around 64KVA, just enough to run a small neighbourhood. The ball is now in your court! eddie@afrowebs.com