Photovoltaic Systems

'Net' is the difference between what you give and what you take. All of our electricity is metered. State-enacted net metering laws require utilities to allow a customer to put renewable energy onto the electrical grid. Excess power from the home system produces a credit (turns the meter backward), while power consumed by the home produces a debit (turns the meter forward). The difference between the two is the net. At month's end, the utility bills for the amount of power used or credits the customer for power supplied. Utilities generally give full credit for power produced on a monthly basis, but should you become a net power producer on a yearly basis, the utility will generally buy that power from you at a wholesale rate. In Wyoming and in all of its surrounding states except Utah, power companies are required to accept net-metered customers.

View the Wyoming net metering statute »

Crystalline silicon solar cells are the prevalent type in use today. These include single crystalline and polycrystalline cells, which are either grown or cast from molten silicon and later sliced into cells. These wafers are then treated, wired and assembled into modules, which are covered with a protective, tempered glass surface. Single crystal silicon cells have the highest average efficiency for converting solar energy into useful electricity. Polycrystalline silicon cells, though a bit less efficient, are generally less expensive since they are easier to manufacture.

Thin film or amorphous silicon cells can be cheaper to produce than crystalline silicon cells but are not as efficient. These solar cells are produced by depositing a number of thin layers, including silicon, onto a substrate such as glass or metal. This thin, flexible material can be encapsulated in tough plastic and produced as shingles, to readily permit building-integrated photovoltaic systems. Solar roofing materials allow PV to be used in some circumstances where glass covered solar panels would not be permitted or would be impractical. Solar shingles and roofing material tend to be a bit more expensive than crystalline solar modules per quantity of power produced. They also require about two times as much roof area. However, where space is ample and aesthetics are important, this technology is a perfect fit.

A measure of how much sun reaches the area in which your solar collector sits, this measurement is a multiple of the amount of sun received during a perfect midday hour. Typical values range from 3 to 7 peak hours per day.

Insolation is a measurement of sun intensity generally given as watts per meter squared. Insolation values change through the day as the sun’s rays encounter varying amounts of atmosphere before reaching a specific location. Insolation is the actual measurement that is converted to the layman’s average “sun hours per day.” This is also affected by the percentage tilt and orientation of the collector panels. When designing our systems, we factor in the exact orientation and tilt of the array necessary for your specific application. We often use data collected by the National Renewable Energy Laboratory (NREL) or the Renewable Resource Data Center at http://rredc.nrel.gov.