Solar Panel Basics

Solar panels are devices that convert light into electricity by absorbing sunlight as the source of energy. They consist of a connected assembly of solar cells that can come in different sizes and electrical specifications, and are able to produce voltage and current. The solar cell is considered the basic building block of all solar panels that starts out from silicon and becomes a semiconductor that acts as both an electrical conductor and insulator when exposed to sunlight. The solar cells are doped during manufacturing, usually by other elements such as boron and phosphorous, to become semiconductors and allow for the flow of electrons. 

We have different types of PV modules and can be referred to as two main types of crystalline modules. These two types of modules include the type with monocrystalline cells and polycrystalline cells. Monocrystalline solar panels are generally more efficient than the polycrystalline solar panels due to the uniform molecular structure within the monocrystalline cell that allows for the movement of a greater amount of electrons when under sunlight since the cells are better lined up and facing the same direction. In contrast, the polycrystalline solar panels have cells with crystal structures of various shapes that face different directions, which ends up somewhat reducing the panel efficiency.

Solar panels are rated at different voltage, current and wattage values. Our panel products come with labels on the backsheet with different electrical specification values from the manufacturer. The two current values that are reported on the solar panel label specs are Isc and Imp. Isc refers to short-circuit current, which is the current value if the positive and negative solar panel wires come into contact with no resistance. These values are reported on the label at standard test conditions (STC). Imp refers to maximum power current, or optimum operating current, which is the current value when the panel is producing the max amount of power and when the solar panel is operating in a system. The two voltage values that are reported on the solar panel specs are Voc and Vmp. Voc refers to open circuit voltage, which is the voltage value when you check the voltage of a panel using a multimeter on the disconnected positive and negative panel wires. Vmp refers to maximum power voltage, or optimum operating voltage, which is the voltage when the solar panel is operating in a system. 

Another important spec value to consider in the solar panel labels is the irradiance value, which is the measure of solar power as the rate of solar energy power onto the area of a solar panel surface. It is usually measured as W/m^2.

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