Many people believe that solar energy will form the backbone of our future energy structure. When the trend towards solar energy started, there were many competing technologies (eg. solar thermal, concentrated solar, and solar photovoltaic). Due to the drop in the price of solar photovoltaic technology (solar panels), it is now the leading candidate for mass adoption. Do you know what a solar panel is and how they work?
What’s a Solar Panel?
The solar cells that you see on calculators and satellites are also called photovoltaic (PV) cells, which convert sunlight directly into electricity. A module is a group of cells connected electrically and packaged into a frame (more commonly known as a solar panel).
How do they work?
Photovoltaic cells are made of special materials called semiconductors such as silicon, which is currently used most commonly. Basically, when light strikes the cell, a certain portion of it is absorbed within the semiconductor material. This means that the energy of the absorbed light is transferred to the semiconductor. The energy knocks electrons loose, allowing them to flow freely.
PV cells also all have one or more electric field that acts to force electrons freed by light absorption to flow in a certain direction. This flow of electrons is a current, and by placing metal contacts on the top and bottom of the PV cell, we can draw that current off for external use, say, to power a calculator. This current, together with the cell’s voltage (which is a result of its built-in electric field or fields), defines the power (or wattage) that the solar cell can produce.
A typical silicon PV cell is composed of a thin wafer consisting of an ultra-thin layer of phosphorus-doped (N-type) silicon on top of a thicker layer of boron-doped (P-type) silicon. An electrical field is created near the top surface of the cell where these two materials are in contact, called the P-N junction. When sunlight strikes the surface of a PV cell, this electrical field provides momentum and direction to light-stimulated electrons, resulting in a flow of current when the solar cell is connected to an electrical load.
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