When light strikes a solar cell, some of the photons knock electrons free from their orbit around the
atoms of the material. These free electrons (electricity) are then directed to devices to perform work
for us. The typical cell produces about .5 vdc while the current output is directly proportional to the
surface area of the cell.
Individual solar cells are normally electrically connected to each other to form panels called
photovoltaic modules. There are basically three types of modules available to the homeowner. The most
common are the typical roof mounted modules or ground mounted modules. For situations where you do not
want to see the panels, you can get building integrated photovoltaic panels (BIPV). These modules are
designed to take the place of traditional roofing materials and blend into the roof.
These assemblies are then combined to form photovoltaic arrays which combine all of the system's
electrical energy to provide useful power for your home.
This DC power can be used to charge batteries or it can be converted to alternating current (AC power)
through a device called an inverter. This AC power is then used to supply the electricity to the
appliances in the home.
Systems that use batteries are commonly called off-grid systems because they can store energy in the
batteries for the times when the sun is not shining. Other systems use batteries as a backup in case the
utility company cannot provide power. The most common type of system does not use batteries and is
called a grid tie system. **NOTE** A grid tied system, without battery backup, must shut down when power
from the utility company goes out. If you live in an area where power outages are common, you would want
a system with battery backup.