Building Blocks of Solar Part 3

How do Solar Panels work?

Solar, or Photovoltaic, Panels work by converting light energy from the sun, or photons, into electricity through the “Photovotaic effect.”  Interestingly, a French physicist built the first ever photovoltaic cell at 19 years old, in 1839.  The first practical photovoltaic cell was demonstrated by Bell Laboratories in 1954 and early on they were primarily used in space.

A Solar Panel is a collection of solar cells that are made up of semiconductors.  Semiconductors absorb the photons–through a process I wont describe in detail–and cause electrons to be excited and break free to be converted into usable DC electricity.  Solar cells are arrangements of silicon “sandwiches” where one layer is activated with boron and the other activated with phosphorus.  This helps the charge to be created and directs the free electrons to the wiring that leads to your charge controller.  

The key to remember here is that its the light energy that is converted to usable electricity, so when siting a group of solar panels, also known as an array, you should do an insolation analysis, which is a fancy phrase for looking at whether or not you are going to have full sun hitting the panels or if there will be shadows cast from structures or vegetation.  A part of this analysis will also be determining how much full sun you get in your area and using that information to determine how many panels you need to charge your battery bank.

This post is about “how do solar panels work” but now that you have a basic understanding, How do solar panels workhere are a few things to remember that can reduce to the amount of energy your panels can produce:  dust/pollen/leaves, temperature, and wire resistance.  If you let your panels get dirty or accumulate leaves or snow, it should be quite obvious that the light cannot reach the covered up cells, which will logically result in less energy production.  When your panels heat up, they also become less efficient.  Remember above when I discussed the electron becoming excited and breaking free?  Well the hotter the cell gets, the less potential there is between the different electrons because the ones that are at rest are already a little “excited” because they are hot.  As a matter of fact when sunlight shines in through your window and heats the air in your house, this is specifically due to excited particles, and its no different with a solar panel.  We will discuss wire sizing in more detail in another post, but remember that current is measured in amps, and wire resistance simply means that smaller wires cannot handle high amps.  This is why we use ideas such as stepping up voltage the reduce the number of amps required to move the same amount of energy.   Amps x Volts always equals Watts so increasing one number always decreases the other.


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