Solar Panels - PV or Photovoltaic Panels
Photovoltaic cells or panels are only one way of generating electricity from solar energy. They are not the most efficient, but they are the most convient to use on a small to medium scale.
PV cells are made of silicon, similar to that used in computer "chips". While silicon itself is a very abaundant mineral, the manufacture of solar cells (as with computer chips) has to be in a very clean environment. This causes production costs to be high.
A PV cell is constructed from two types of silicon, which when hit by solar energy, produce a voltage difference accross them, and, if connected to an electrical circuit, a current will flow. 
A number of photovoltaic cells will be connected together in an "Module", and usually encapsulated in glass held a frame which can then be mounted as required. The cells in a module will be wired in series or parallel to produce a spacified voltage. What may be refered to as a 12 volt panel may produce around 16 volts in full sun to charge a 12 volt battery.
In most cases, a number of panels (modules) will be connected together to form an "Array". Panels of a similar type may be connected in series to give a higher voltage (two 12 volt panels may be connected in series to produce 24 volts).
Usually a number of panels will be connected in parallel to give an increased current.
Monocrystalline Silicon Cells:
Made using cells saw-cut from a single cylindrical crystal of silicon, they are effectively a slice from a crystal. This is the most efficient of the photovoltaic (PV) technologies. The principle advantage of monocrystalline cells are their high efficiencies, typically around 15%, although the manufacturing process required to produce monocrystalline silicon is complicated, resulting in slightly higher costs than other technologies. In appearance, it will have a smooth texture and you will be able to see the thickness of the slice. They are also rigid and must be mounted in a rigid frame top protect them.
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Polycrystalline or Multicrystalline Silicon Cells:
Made from cells cut from an ingot of melted and recrystallised silicon. In the manufacturing process, molten silicon is cast into ingots of polycrystalline silicon, these ingots are then saw-cut into very thin wafers and assembled into complete cells. Multicrystalline cells are cheaper to produce than monocrystalline ones, due to the simpler manufacturing process. However, they tend to be slightly less efficient, with average efficiencies of around 12%. They have a speckled crystal reflective appearance, and again need to be mounted in a rigid frame. |
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Amorphous Silicon:
Amorphous silicon cells are composed of silicon atoms in a thin homogenous layer rather than a crystal structure. Amorphous silicon absorbs light more effectively than crystalline silicon, so the cells can be thinner. For this reason, amorphous silicon is also known as a "thin film" PV technology. Amorphous silicon can be deposited on a wide range of substrates, both rigid and flexible, which makes it ideal for curved surfaces and "fold-away" modules. Amorphous cells are, however, less efficient than crystalline based cells, with typical efficiencies of around 6%, but they are easier and therefore cheaper to produce. Their low cost makes them ideally suited for many applications where high efficiency is not required and low cost is important. One characteristic of amorphous solar cels is that their power output reduces over time, particularly during the first few months, after which time they are basically stable. The quoted output of an amorphous panel should be that produced after this stabalisation.
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Material
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- Monocrystalline
- Polycrystalline
- Thin-film
- Amorphous
- Polymer
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18%
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13-15%
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10-12%
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5-7%
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5%
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