Solar Energy Technology Description

Solar energy uses specially treated semiconductors, typically made from silicon, to absorb energy emitted from the sun. These panels are photovoltaic (PV) and are constructed of two sheets of silicon: the N-layer and the P-Layer. Silicon used in PV cells is modified to work by the deliberate addition of impurities.

The N-layer is composed of silicon atoms that have extra electrons, freely bouncing around inside the silicon material. Silicon in the P-layer has missing electrons, which can be viewed as holes that attract free electrons. An electrical current separates the two sheets.

Process diagram courtesy of Research Institute of Sustainable Energy

When photons emitted by sunlight strike the solar panel, electrons in the panel are knocked loose. In the P-layer, these free electrons cross through the “holes” into the N-layer. This movement of electrons is one-way—electrons in the N-layer cannot cross over into the P-layer. As a result, the N-layer builds an excess of free electrons that can be easily converted into usable electricity.

By attaching a metal wire to the N-layer, the excess electrons have a place to travel. This creates an electrical circuit that eventually ends up back at the P-layer, where free electrons are deposited to be used again. Before returning to the P-layer, electrons routed through the wire can be used to power any type of electrical appliance, or they can be tied into a power grid. Electrical current is maintained as long as the sun is shining and the PV panels are able to absorb photons.

In order to make this current usable, it must be converted from direct current (DC) to an alternating current (AC) using a power inverter. Inverters turn DC power into usable, utility-grade AC power. Standalone PV systems can store excess solar energy in batteries, while grid-tied systems feed into utility lines and can earn PV system owners credit on their energy bill. 

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