Here are some Solar Photo Voltaics facts to try and make it simple to see how they work
Note that Solar panels make no pollution and use no water. This is unlike the main power sources of coal, nuclear, natural gas, diesel generators and other fossil fuel sources. They also make the most power when you use it the most at the Peak Time Of Day. You can also make the power right where you use it, at your home. When you add up the benefits it really great.
FACT A -Solar panels that make electricity are made up of many cells or ribbons . Each small round or square shaped cell is normally about 3 to 4 inches. Some THIN FILM and Ribbon use long strips. They make DC voltage and are connected in series to the other cells in a panel. A typical panels makes 12 volts at about 3-4 amps. The voltage is the potential and the amperage is the amount of flow. The panels are normally rated in watts. Watts = volts times amps. So a 12 volt panels at 4 amps is said to make 48 watts.
Panels are rated under a perfect day at 25 C temperature and full clear sun of 1,000 watts per square meter called STC Standard Test Conditions. See below from wikipedia.
Point (1) So you have to have your solar panels facing directly at the True South along the exact path of the Sun to get close to the full rating. Shade on any one cell (3 inch spot) can stop the power of most panels. So Keep you panels out in an area with no shade. The SUN moves across the sky so that is hard to do. Some use trackers that follow the sun. These cost money and can also fail. The most sun power is from 10 am to 2 PM.
An East or West facing roof can work but gives 10% less total energy. Facing South is always best for total output.
Point (2) Heat at high levels can affect performance. Keep the panel where it has room to allow air to flow and keep cool. A panel flat and tight to a roof can get hot and not work as good. Keep panels 4 to 6 inches off the roof to allow air flow. I like pole mounted panels so they stay cool and I can change the angle to the sun. The sun moves lower in the sky in winter and work up higher and higher to summer. I can adjust that angle in minutes on a pole.
Check your are for the suns path and shade for all times of year. Keep them out in the open with nothing next to them that would shade them.
I found this SITE with some solar facts-They seem honest but do take advertising money.
Module performance are generally rated under Standard Test Conditions (STC) : irradiance of 1,000 W/m², solar spectrum of AM 1.5 and module temperature at 25°C.
Electrical characteristics includes nominal power (PMAX, measured in W), open circuit voltage (VOC), short circuit current (ISC, measured in Amperes), maximum power voltage (VMPP), maximum power current (IMPP) and module efficiency (%).
In kWp, kW is kilowatt and the p means “peak” as peak performance. The “p” however does not show the peak performance, but rather the maximum output according to STC .
Solar panels must withstand heat, cold, rain and hail for many years. Crystalline silicon modules offer for 10 years the 90% of rated power output and 25 years at 80%. 2 million were sold in 2004. 4 million were sold in 2005 and 7 million were sold in 2006. In 2007 8 million were sold.
FACT B- Inverters , Since Solar panels make DC at about 12 volts you have to connect then together to make high voltage. You also have to then change the DC into AC with an intverer. A new design 2009 puts a small Inverter on each panel. Read about enphase solar. Each type of inverter requires different voltages. So you have to figure out the inverter and then how many panels to use for a full system for you home or application. A DC pump could just use DC and be done.
Another possibility is to have some DC light or appliances. Then you could make a system with no inverter. This is possible but you have to try and find a fridge , TV etc that runs on DC. Even lights can run on DC if you get the right type BUT you may want to go back on this page and read the article in AC versus DC between Edison and Westinghouse. It's seems simpler and more efficient to me to buy standard items the entire world uses that are AC.
FACT C- A very important fact is that Solar PV panels make electricity as soon as they are in the light. They are never off. It's DC power but always be careful. This is live electrcity. If you connect a lot of them together to make more than 48 volts it is considered deadly. Many systems today 2009 use 200-600 volts DC , AC power is very dangerous and is normally 120 or 240 volts. DC power can also become dangerous especially at high voltages. BE CAREFUL !