The Flow of Electricity

The Flow of Electricity
When the electrons leave their position, holes are formed. When many electrons, each carrying a negative charge, travel toward the front surface of the cell, the resulting imbalance of charge between the cell's front and back surfaces creates a voltage potential like the negative and positive terminals of a battery. When the two surfaces are connected through an external load, such as an appliance, electricity flows.

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.

need a 1/2 symbol in the second sentence in paragraph above.
Weather Affects Photovoltaics
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. Further research is being conducted to raise this efficiency to 20%.

Commercial Applications of Photovoltaic Systems
The success of PV in outer space first generated commercial applications for this technology. The simplest photovoltaic systems power many of the small calculators and wrist watches used every day. More complicated systems provide electricity to pump water, power communications equipment, and even provide electricity to our homes.

Some advantages of photovoltaic systems are:

Conversion from sunlight to electricity is direct, so that bulky mechanical generator systems are unnecessary.
PV arrays can be installed quickly and in any size.
The environmental impact is minimal, requiring no water for system cooling and generating no by-products.
Photovoltaic cells, like batteries, generate direct current (DC), which is generally used for small loads (electronic equipment). When DC from photovoltaic cells is used for commercial applications or sold to electric utilities using the electric grid, it must be converted to alternating current (AC) using inverters, solid state devices that convert DC power to AC.

History of the Photovoltaic Cell
The photovoltaic cell was invented in 1954 by Bell Telephone researchers examining the sensitivity of a properly prepared silicon wafer to sunlight. Beginning in the late 1950s, photovoltaic cells were used to power U.S. space satellites.

Historically, PV has been used at remote sites to provide electricity. In the future, PV arrays may be located at sites that are also connected to the electric grid to enhance the reliability of the distribution system.