Energy from the Sun

The sun has produced energy for billions of years.  Solar energy is the sun’s rays (solar radiation) that reach the earth. Solar energy is by far the earth’s most available energy source. Solar power is capable of providing many times the total current energy demand. Solar energy is converted to electricity via Photovoltaic (PV) modules. PV modules or “solar cells” change sunlight directly into electricity. Individual PV cells are grouped into panels and arrays of panels that can be used in a wide range of applications ranging from single small cells that charge calculator and watch batteries, to systems that power single homes, to large power plants covering many acres.

Photovoltaic Cells Convert Sunlight into Electricity
A photovoltaic cell, commonly called a solar cell or PV, is the technology used to convert solar energy directly into electrical power. A photovoltaic cell is a non-mechanical device usually made from silicon alloys.

Photons Carry Solar Energy
Sunlight is composed of photons, or particles of solar energy.  These photons contain various amounts of energy corresponding to the different wavelengths of the solar spectrum.
When photons strike a photovoltaic cell, they may be reflected, pass right through, or be absorbed.  Only the absorbed photons provide energy to generate electricity.  When enough sunlight (energy) is absorbed by the material (a semiconductor), electrons are dislodged from the material’s atoms.  Special treatment of the material surface during manufacturing makes the front surface of the cell more receptive to free electrons, so the electrons naturally migrate to the surface.

How Photovoltaic Systems Operate
The photovoltaic cell is the basic building block of a photovoltaic system. Individual cells can vary in size from about 0.5 inches to about 4 inches across.  However, one cell only produces 1 or 2 watts, which isn’t enough power for most applications.

To increase power output, cells are electrically connected into a packaged weather-tight module.  Modules can be further connected to form an array.  The term array refers to the entire generating plant, whether it is made up of one or several thousand modules.  The number of modules connected together in an array depends on the amount of power output needed.

The performance of a photovoltaic array is dependent upon sunlight.  Climate conditions (such as clouds or fog) have a significant effect on the amount of solar energy received by a photovoltaic array and, in turn, its performance.  Most modern modules are about 10% efficient in converting sunlight.