SOLAR PANEL

SOLAR PANEL

A solar panel (photovoltaic module or photovoltaic panel) is a packaged interconnected assembly of solar cells, also known as photovoltaic 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.

Because a single solar panel can only produce a limited amount of power, many installations contain several panels. A photovoltaic system typically includes an array of solar panels, an inverter, may contain a battery and interconnection wiring

How Solar Panels Work

Photovoltaic (PV) cells are formed from a wafer of semi-conductor material and although there are now several types in production using different materials, the most common semi-conductor used is silicon.

Pure crystalline silicon is a poor electrical conductor but treat it with tiny quantities of an impurity, either phosphorous  or arsenic (a process called “doping”) and enough electrons of these materials are freed to enable a current to pass through. Electrons are negatively charged so this type of silicon is called N-Type.

Dope silicon with gallium or boron and “holes” are created in the crystalline lattice where a silicon electron has nothing to bond with. These holes can conduct electrical current and the lack of an electron creates a positive charge so this type of silicon is therefore called P-Type. Both types of silicon are modest electrical conductors, hence the name semiconductors.

Put a layer of each kind together in a wafer, such as in a PV cell, and the free electrons in the N side migrate towards the free holes on the P side. This causes a disruption to the electrical neutrality where the holes and electrons mix at the junction of the two layers. Eventually a barrier is formed preventing the electrons from crossing to the P side and an electrical field is formed, separating both sides. This electrical field acts as a diode, allowing electrons to pass from the P side to the N side, but not vice versa.

Expose the cell to light, and the energy from each photon (light particle) hitting the silicon, will liberate an electron and a corresponding hole. If this happens within range of the electric field’s influence, the electrons will be sent to the N side and the holes to the P one, resulting in yet further disruption of electrical neutrality. Apply an external pathway connecting both sides of the silicon wafer and electrons will flow back to their original P side to unite with the holes sent there by the electric field.

This flow of electrons is a current; the electrical field in the cell causes a voltage and the product of these two is power.

Several factors affect the efficiency of a solar cell. Some cells, mainly ones made from a single material, are only efficient in certain light wavelengths. Single material cells can at the very most expect to convert about 25% of the light hitting it to electrical power.