Generating Electricity: Photovoltaics

Photovoltaics (PV), or solar cells, convert sunlight to electricity directly without boilers, turbines, generators, piping or cooling towers.

They generate power when particles of sunlight (photons) strike certain semiconductor materials such as silicon. As silicon atoms absorb the sunlight, they dislodge the electrons and allow them to move.

The free electrons collect on the specially treated front surface of the cell, causing an imbalance of charge between the front and back surfaces. This charges the surfaces like the terminals on a car battery. A flow of electrons occurs when one end of a wire is attached to the top layer and the other end to the layer underneath.

Technicians connect individual cells into panels to obtain required voltage. A power converter is needed to change the direct current to alternating current.

PV devices have provided energy for spacecraft for many years. They also are used for beacons or floating buoys far from the nearest power lines.

Large-scale use of PV devices for industrial or residential power is currently out of the question because of the very high cost. Recent worldwide research could result in considerably lower cost of PV in the near future.

To generate one kilowatt of electricity when the sun is brightest would require about 100 square feet of PV panels.