How do Photovoltaics work?

We can easily explain how the Photovoltaic effect produces a flow of electrons. In short, electrons are excited by particles of light and find the attached electrical circuit the easiest path to travel from one side of the cell to the other. Envision a piece of metal such as the side panel of a car. As it sits in the sun the metal warms. This warming is caused by the exciting of electrons, bouncing back and forth creating friction and therefore heat. The solar cell merely takes a percentage of these electrons and directs them to flow in a path. This flow of electrons is, by definition, electricity.

Photovoltaic modules (solar panels) convert sunlight into electricity. Wire conducts the electricity to batteries where it is stored until needed. On the way to the batteries, the electrical current passes through a controller (regulator) which will shut off the flow when the batteries become full.

For some appliances, electricity can be used directly from the batteries. This is "direct current" and it powers "DC" appliances such as car headlights, flashlights, portable radios, etc. To run most appliances found in the home, however, we need to use "alternating current" or "AC", the type which is found in wall sockets. This we can produce utilizing an inverter which transforms DC electricity from the batteries into Ac. The inverter's AC output powers the circuit breaker box and the common outlets in your home.

Are photovoltaics cost effective?

Yes, PV is cost effective in the right location. By this we mean where the extension of utility lines are a major factor. We use the figure of one-third of a mile as a rule of thumb for cost effectiveness, yet rates vary substantially from site to site. This third-of-a-mile figure is only a rule of thumb. If you haven't already, get a quote from your local power company.

If you are on utility power at present - PV is not a cost effective move. Utility power is much cheaper than PV power. Why? Because we have not yet begun to pay for the externalities of fossil fuel and nuclear generating plants. When this country begins to pay for the sulfur emissions which cause acid rain, global warming and nuclear waste disposal, to name a few, we will see power costs increase. With this in mind we need to ask and answer the question again. We believe, over the working life of a PV system, it can very well be a cost effective move. It all depends on the real price increases of utility power, 2, 5, 10 and more years from today.

Next - System Planning

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