(Solar Cell: The solar or "PV" cell is the component responsible for converting light to electricity. Some materials (e.g., silicon is the most common) produce a photovoltaic effect, whereby sunlight frees electrons striking the silicon material. The freed electrons cannot return to the positively charged sites ("holes") without flowing through an external circuit, thus generating current. Solar cells are designed to absorb as much light as possible and are interconnected in series and parallel electrical connections to produce desired voltages and currents.
PV Module: A PV module is composed of interconnected solar cells that are encapsulated between a glass cover and weatherproof backing. The modules are typically framed in aluminum frames suitable for mounting.
PV Array: PV modules are connected in series and parallel to form an array of modules, thus increasing total available power output to the needed voltage and current for a particular application.
Peak Watt (Wp): PV modules are rated by their total power output, or peak Watts. A peak Watt is the amount of power output a PV module produces at Standard Test Conditions (STC) of a module operating temperature of 25°C in full noontime sunshine (irradiance) of 1,000 Watts per square meter.
A thin silicon cell, four inches across, can produce more than one watt of direct current (DC) electrical power in full sun. Individual solar cells can be connected in series and parallel to obtain desired voltages and currents. These groups of cells are packaged into standard modules that protect the cells from the environment while providing useful voltages and currents. PV modules are extremely reliable since they are solid state and there are no moving parts. Silicon PV cells manufactured today can provide over thirty years of useful service life. Solar Power Limited provided warranties of up to 25 years on their PV product (at 80 percent of original power rating). A 50 Wp PV module in direct sunlight operating at 25°C will generate 50 Watts per hour (referred to as a Watt-hour[Wh]).
(PV systems are made up of a variety of components, which aside from the modules, may include power conditioning units, batteries, trackers, and inverters, depending on the application. PV systems are modular by nature, thus systems can be expanded as more power is needed and components are easily repaired or replaced.