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How do solar panels work?

Posted by Jason Ramsdale on 29 March 2016 at 10:30 am

TED-Ed have uploaded a fantastic video explaining the science behind solar panels as part of a TED lesson on solar by Dr Richard Komp. The video explains how solar panels work, what their limitations are and how they can be improved in the future. Definitely one of the better explanations on how solar panels turn sunlight into electricity that I've seen. They also explain why solar panels are not 100% efficient. If you have a spare 5 minutes I'd recommend checking it out!

Photovoltaic effect

  • Sunlight is composed of photons. These contain energy.
  • When photons hit a solar panel, this energy is transferred to the material that makes up the solar panel.
  • This is called a semiconductor and consists of a lattice of metal atoms.
  • Each of these atoms have associated electrons, which have a negative electrical charge. The nucleus of the atom has a positive electrical charge, so they are balanced.
  • Most of the electrons within this lattice are associated with these atoms and form the bonds that bind them together.
  • However electrons can also be “free” and can flow from one part of the material to another.
  • When the energy from the photon is transferred to a fixed electron it becomes “excited” and jumps out of the lattice to become a free electron.
  • This process is known as the photovoltaic effect.

Potential Difference

  • When the photovoltaic effect takes place the electron leaves behind a “hole” within the lattice.
  • This is a region which has no electron and so has a net positive charge.
  • Other electrons move to fill this space, causing the hole to shift across the lattice until it reaches an edge.
  • The semiconductor is designed so that electrons will preferentially flow in one direction.
  • They end up at the far side of the material to the hole.
  • This creates an electrical potential difference, or voltage between one side of the semiconductor and the other.
  • These sides of the semiconductor are connected to an electrical circuit.
  • This potential difference causes an electrical current to flow through the circuit.
  • This electrical current can be used to do work.
  • The energy of the photon has thus been harnessed and converted into electrical energy.

Image: NASA

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