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How does a solar panel work?

Guide written by:
John, DIYer & IT developer, Brighton

John, DIYer & IT developer, Brighton

59 guides
Solar panels recover the energy from the sun and transform it into electricity. Let's talk photovoltaic cells, atoms, semiconductor materials, electrons, doping and PN junctions, everything you need to know to understand how a solar panels works and manages to transform DC into AC.  
 

Important features

  • Composition
  • Photovoltaic cell
  • Atoms and electrons
  • DC and AC current

Composition of a solar panel





solar panel generates electricity thanks to numerous photovoltaic cells that are mounted in a series and/or in parallel. Each panel produces on average around 0.5 volts (V).


On the surface, a glass pane allows the light to come in, along with the energy it carries. A rigid panel serves as an achor at the very bottom, protecting the entire installation. The whole is secured by a rigid frame that protects the panel from impacts
 

Solar panels are easily recognizable due to the grid-like outline that the cells form on the surface. They are also identifiable due to the panel's composing material, which reflects any shade of blue or gray. A outlet cable, which normally comes out of the frame, transfers a direct current at a constant voltage.

How a solar panel produces electricity: the physics of atoms


Without going into too much detail, let's try to paint you a mental picture of each composing layer of a solar panel. To start off on the right foot, remember that an atom is composed of a nucleus, around which electrons, organized into different layers, are constantly circling. The physical properties of an atom is determined by the number of electrons in the outer layer.


The term physical properties refers to an atom's innate ability to combine with other atoms to form molecules, crystals and eventually ions. By ripping electrons off of these atoms and putting them in motion, you can produce a current.

Photovoltaic cells: semiconductor materials


A photovoltaic cell is made of the same semiconductor materials that are often found in many electronic components. To create these semiconductors, a group of atoms all bearing 4 electrons on their outer layer must be selected. These atoms are referred to as tetravalent atoms and have the ability to be combined in a structure known as a crystal.










The general mode of operation for manufacturing semiconductor materials is to introduce specifically selected impurities into this structure, which is referred to as doping. If our crystal of tetravalent atoms is supplemented with one additional atom, this time carrying three valent electrons, we wind up with an unbalanced charge, with one electron missing. Since an electron is negatively charged, the crystal will have an overall positive charge. This technique is referred to as P doping. On the other hand, if an atom with 5 valent electron is inserted, the crystal will be negatively charged, due to the excess of electrons. This approach, as you have probably guessed, is referred to as N doping


If you align a plate of N-doped material next to a plate of P-doped material, this results in what is referred to as a PN junction
. Where they meet, negative charges on one side and positive charges on the other create an electric field.

How does a photovoltaic cell work?


A solar cell is simply an installation featuring a PN junction, with a metal grid on the top and a conductive collector around the back. Rays of light hit the N-doped semiconductor, where the energy they contain is transferred to electrons. The electrons use this energy to break off from the nucleus' orbit and free themselves. 


The electric field that is generated by the PN junction pushes these electrons towards the metal grid and through the panel's circuit. They exit the circuit through the back collector into the semiconductor where they are again attracted by a grid, re-starting the cycle.

Transformation of AC direct current: the role of the inverter

A solar panel's intensity, voltage and resulting power depends entirely on the number of cells mounted both in series and in parallel. It's output voltage is continuous, which is only suitable for recharging batteries or powering a motorhome if kept in this state. To benefit from this power in your home or re-sell it to an operator, the current needs to run through an inverter, which transforms the DC current into an AC current with 220V and 50Hz.
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Guide written by:

John, DIYer & IT developer, Brighton 59 guides écrits

John, DIYer & IT developer, Brighton

Since I was a child, I was always interested in manual and technical works. Always fascinated by woodworking, I took advantage of my first flat as a playground. On the cards: electricity (of course, safety first!) and some partition walls; but also decorating with the help of the missus, made-to-measure furniture and little tricks to optimise the space, all the while remaining as original as possible. When the little one arrived, I started building bits and pieces for him!

Lacking space, I have not got a permanent workshop and certain tools I dream about but are not part of my collection. Not to worry, I already know a lot about DIY and I have a high-tech profile that I hope will guide you in your decisions!

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