The earth absorbs about 3,850,000 exajoules (EJ) of solar energy every year. One hour would cover the world`s entire energy demand for one year. The potential of solar energy is almost beyond anyone`s imagination. How can we tap into this vast resource? Let`s take a look at how solar panels work.
There are mainly two main types of solar panels:
- Photovoltaic (PV) solar panels – the technology most people think of when they say “solar panels”. These devices convert sunlight into electricity. For the sake of this article, the term “solar panels” will be used to describe photovoltaic panels.
- Solar thermal collectors use the same solar energy that photovoltaic panels do, but they generate heat instead of electrical power.
What exactly is sunlight? The best way of describing light in general is probably this: A collection of tiny elementary particles called photons. These light particles carry a certain amount of energy, which can be converted into electrical energy through the photovoltaic effect in solar cells.
Solar cells generate an electric current when they are exposed to light. Exactly how this happens is a quite complex, and varies between the different types of solar panels.
The basic gist is this:
- Incoming photons are absorbed by semiconducting material (in most cases silicon) on the surface of thesolar cell.
- These photons “knock loose” electrons from atoms in the solar cell. Since electrons carry a negative charge, an electric potential difference has been created.
- The solar cell is built in a way that only allows the electron to move in one direction in order to cancel out the potential.
- Put many of these reactions together and current starts flowing through the material.
Solar cells are building blocks of solar panels. Multiple solar cells that are oriented in the same way makes up what we call solar panels. The electrical power out depends on how many of them are put together. The solar panels you have in your calculator and those NASA use in space are essentially built using the same principles – even though they are on completely opposite sides in the strength spectrum.