There are 3 basic types of construction of PV panels. All of those discussed here employ silicon.
Mono Crystalline cells are cut from one crystal of silicon- they are efficiently a slice from a crystal. In appearance, it has a soft surface and you will be able to see the thickness of the slice. These are the most efficient and the priciest to produce.
Polycrystalline (or Multi Crystalline) cells are efficiently a slice cut from a block of silicon, having a large number of crystals. They have a speckled reflective appearance and again you can see the thickness of the slice.
Amorphous cells are manufactured by putting a thin film of amorphous (non crystalline) silicon onto a wide choice of surfaces. These are the least photovoltaic efficiency and lowest priced to manufacture of the three types. Because of the amorphous nature of the thin layer, it is flexible, and if made on a flexible surface, the whole solar panel can be flexible.
Depending on the main idea that a solar cell getting more light energy will produce much more electricity, concentrating photovoltaic solar panels simply include a method (generally using a lens or mirrors) to concentrate more sunlight onto a photovoltaic cell. As fewer cells are then required for the same area of panel (or light capturing area) it may then become economical to use an extremely efficient multi junction cell.
Conceivably, this kind of panel has the following benefits:
- It has a higher overall performance, capturing far more solar energy per meter squared contributing to a smaller area of panels required for a particular output. Resulting effectiveness levels can approach 50%.
- Probably lower cost per watt of output because of lower number of solar cells needed, while the material cost and manufacturing process of the optics (light concentration mechanism) is relatively inexpensive.
- Lower utilization of environmentally unfriendly chemicals involved in the panel production process because of lower number of pv cells.
- Where the focus is such that cooling of the photovoltaic module is needed, a panel may have the capability to output heat at the same time as electricity.
However, there are drawbacks:
- In all but the lower levels of focus, heat must be dissipated from the cells. Cooling is needed as cell efficiency is substantially reduced at higher temperatures, or in extreme situations, cells may be damaged.
- In all but the lesser levels of concentration a tracker system will be required to keep the concentrated light focused on the cells.
- As diffuse light cannot be effectively centered, concentrating PV panels are best suited to areas with a high level of clear sunshine.
Though research has continued on focusing photovoltaic efficiency for many years, they have not made their mark on the industry, and exactly where they have been used, it has been in big scale projects. CPV panels that have been produced have come in “various shapes and sizes” with no obvious design leading the field.
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