How Do Solar Panels Work (simplified)

Almost all energy on this planet comes from the Sun. Oil and gas come from living things that died a very long time ago and those living things all got their energy from the Sun. Even wind currents and the water cycle rely on the Sun to some degree. The Sun puts out more energy that reaches earth than we could ever use. So why is there an energy shortage?

Well theoretically you could power an electric car with a solar panel that charged a battery that powered the engine. In reality however this would be difficult with our current solar cell technology, but there has been research that has indicated that it might be possible in the future. In the laboratory solar cells have shown promise but getting the same results in the real world at a price the average person could afford is still a ways off.

So what is a Solar Cell?: The first thing you need to under stand is why electric current "flows". To simplify this lets take a car battery and you probably know that there is a positive and a negative terminal usually marked by a large + or -. The simple explanation for how the battery works is that at the negative terminal there is a large number of electrons and at the positive end there is big shortage of electrons. In nature things like to balance out, so if you connect these terminals with the car's electrical circuits between them, the electrons will flow from the negative to the positive until there is a balance of electrons, at which point we say the battery is dead. We then use a battery charger to force things out of balance again, so that once again we have "all the electrons back to one side" so that there is a natural tendency for the electrons to flow again. This difference between the + and the - is called difference in potential, and we call this voltage. A fully charged car battery has 12 volts of difference in potential. So in order to get a flow of electricity we need to have some area that has more electrons than another and connect the two areas.

You have probably heard of an "electric eye", This is based on a principal called the photo electric effect. An over simplification of this is that some materials will give off electrons when exposed to the energy of certain light.

Well the solar cell takes this a step further and uses something called the photo voltic effect. Now again an over simplification is if you get a material to give off electrons using the photo electric effect and those electrons are collected by another nearby material, the nearby material would have excess electrons and the material that gave off the electrons would have a lack of electrons. This is just like the battery from earlier. In this way a solar cell becomes like a battery and can generate an electrical flow. If you put a bunch of these cells together you get a solar panel.

Now the problem with this is a term called efficiency, which is basically what do you get out compared with what you put in. In nature you always get less out than what you put in because there is always heat loss, friction, etc... Solar cells are very inefficient. The first solar cell was built by a guy by the name of Charles Fritts in 1883 and it's efficiency was about 1%. This means that you would have to put in 100 units of energy to get one unit of energy produced. The sun's energy is free and that is the only reason anyone ever wasted any time on such a bad return.

Today you can buy solar panels that have efficiency ratings from 3or4% to the mid 20% depending on the type of solar cell used and how they are put together. The greater the efficiency the higher the price. In the labratory efficiency ratings of over 40% have been reported but in general use affordable panels generally run between 8 and 20% and of course some are even less efficient and are very inexpensive and are used as science projects, toys and novilties.

So the days of powering your car with a solar panel is not fully here yet, but it might not be that far away since advances are being made daily in this field. Of course the prototypes might only be affordable to Bill Gates, but the first "cell phones" were the size of a large brick and could only be purchased by the rich and look at those today. Space vehicles are solar powered and perhaps soon yours will be also.