There are three main types of solar panel available today and, surprising, there is a lot of discussion about which technology is best. The main difference between the technology is the type of solar cell they use, manufactured from different types of silicon crsytal. Silicon crystals are checmically 'grown', much like the cyrstal growing kits that children play with. The three different types are: monocrystalline, polycrystalline and amporphous silicon.
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Monocrystalline Solar Panels
Monocrystalline solar panels are the most expensive and most efficient solar panels as they are able to convert the greatest percentage of the Sun's energy into electricity (up to 21.5%). The silicon crystals are grown in one single direction so that they all line up in the same way, which also makes them the most difficult and expensive to manufacture. Due to their very high efficicency, the best monocrystalline panels are generally 25-30% smaller than other panels so you can produce more energy from any given amount of space. In addition, monocrystalline panels work much better in overcast conditions and can even work when covered by an inch of snow. Another benefit is that they are less affected by temperature changes than other panels; all solar panels produce less electricity when they get very hot (i.e. over 50°C), but monocrystalline panels lose much less of their efficiency.
Sometimes called 'multi-crystalline', these solar panels are often less expensive and the technology has been on the market for a long time. The silicon in the solar cells is grown in many different directions, so are cheaper to produce. Unfortunately, this results in a solar panel that is less efficient that their monocrystalline cousins. Even the best polycrystalline panels are limited to 16.5% efficiency or less, so they are about 25-30% larger than monocrystalline ones. They are also more susceptible to the effects of the weather and often need external temperature compensation, although the most expensive polycrystalline panels are often fitted with an 'extra' solar cell to make up for temperature related losses. Manufacturers of polycrystalline solar panels often rely on innovative 'packaging', making their panels unique to specific applications.
Amorphous silicon solar cells were initially designed to be a very low cost alternative; they are not really 'crystal' based, but rather the silicon is depsotited in a very thin layer onto a base material. In the past, this base was metal or glass, but nowadays companies usually use a flexible polymer, so that the finished solar panel is also flexible. Whilst they are the least efficient type of solar panels on the market, manufacturing developments have lead to a number of unique products which can be walked on or even rolled up and put in a rucksack.
Example of an amorphous solar panel: Flexcell Sunpack 7W Rollable Solar Panel
