A solar panel is a set of solar photovoltaic modules electrically connected and mounted on a supporting structure. A photovoltaic module is a packaged, connected assembly of solar cells. The solar panel can be used as a component of a larger photovoltaic system to generate and supply electricity in commercial and residential applications. Each module is rated by its DC output power under standard test conditions (STC), and typically ranges from 100 to 320 watts. The efficiency of a module determines the area of a module given the same rated output an 8% efficient 230 watt module will have twice the area of a 16% efficient 230 watt module. A single solar module can produce only a limited amount of power; most installations contain multiple modules. A photovoltaic system typically includes a panel or an array of solar modules, an inverter, and sometimes a battery and/or solar tracker and interconnection wiringPhotovoltaic FeaturesPhotovoltaic technology converts sunlight into electrical energy in a direct way as opposed to the more circuitous approach of solar thermal technologies that capture sunlight to heat a gas or fluid and subsequently use heat engines to generate electricity.The most common PV technology uses solar cells made of semiconductor materials (such as silicon or germanium) dosed with small amounts of impurities (typically metals or metalliods). In simple terms, when sunlight strikes a cell, a certain portion of its energy is absorbed within the semiconductor material. The absorbed energy knocks electrons loose, allowing them to flow freely under the influence of electric fields.Solar cells have inbuilt electric fields that force the freed electrons to flow in a certain direction. Metal contacts on the top and bottom of the PV cell enable the cell to generate a current in an external circuit. This current, together with the cell s voltage (which is a result of its in-built electric fields), defines the power (or wattage) that a solar cell can produce.This direct current can be used to recharge batteries and run direct current devices, or can be converted via inverters into alternating current, the form of electricity most commonly used in homes, offices and industry.The word photovoltaic derives from the Greek word photo meaning light and the modern word Volt or Voltage meaning a unit of electrical potential (named in honor of the Italian physicist Alessandro Volta (1745 1827), who is attributed with inventing the first chemical battery. This is the subject of debate, though, as working batteries may have been used in antiquity).