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Solar panels generate electricity by absorbing light to create what is known as a photovoltaic effect.

All of the work is done on the surface of the solar cell when light falls onto it.  Electrons in the silicon (which the cell is made of) absorb energy from rays of light, giving some of them enough energy to jump across the "band gap".  This creates a small electric field and the loose electrons flow from the negative to the positive around the circuit as an electric current.  This current (which is direct current, or DC) travels though the wires into an inverter fitted into your loft (usually) which converts it into alternating current (AC).  AC is the type of electricity which is used in your home.

In order to receive the most direct sunlight, panels should be sloped between a 30 and 45 degree angle and be pointing south, south-east or south-west. You can still generate solar electricity with the panels placed at any angle between 0 and 90 degrees; and you can even position panels facing due east or west, though the output will be lower.

There are a number of types of solar panels:

Polycrystalline 
This is the most common type of panel.  It is made using very pure molten silicon.  In a casting process, the silicon is heated to extremely high temperatures and then cooled within a mold.  Once cool, it sets as an irregular form consisting of a lots of crystals.  Slices of this crystallised form are then put through chemical processes, an anti-reflective layer is added and a conducting grid and electrical contacts are fixed. 

Standard polycrystalline PV cell modules have an efficiency of  around 11-15%. This efficiency refers to the proportion of the solar energy falling on the panel that is converted into electricity.

Monocrystalline
These panels are also made using very pure molten silicon.  However, the process creates single crystals which are cut into hexagon-shaped slices which form the basis of the PV cell.  These slices then undergo similar chemical and fixing processes to the polycrystalline modules.

Monocrystalline panels have efficiencies of around 13-17%, which means that they are more efficient than polycrystalline modules. The manufacturing process takes more time than for polycrystalline panels, which means that the monocrystalline panels are slightly more expensive.  There are most commonly used where space is tight in order to obtain maximum output.

Amorphous
The silicon used to make these cells is non-crystalline.  A thin film of amorphous silicon is deposited as a gas on a flat surface, such as glass.  This undergoes other chemical processes and then a conducting grid and electrical contacts are fixed.  This type of cell can also contain a number of layers, each of which is sensitive to different wavelengths of the light spectrum.

This type of PV cell uses much less raw material and so is considerably cheaper than other types.  However, they only have an efficiency of around 5-7%.

This type of PV cell is not suitable for domestic systems, given the low efficiency, but is often used where there is a large surface area. Semi-transparent models can be integrated into buildings with lots of glass.

Hybrid
Hybrid panels are a combination of monocrystalline panels with a very thin layer of amorphous silicon on top. The output is considerably higher, by as much as 12%, and they perform better at high temperature, but these panels are more expensive.   They are most commonly used in large solar farms.


greentomatoenergy can advise on the most appropriate type of panel for your project and budget.