Types of solar panels are the following: monocrystalline, polycrystalline, amorphous and gallium arsenide plates. Monocrystalline Si panels can convert the 1000 W / m2 of solar radiation to 140W of electricity on the surface of the plate 1 m2. Those solar panels seem the most useful out of all of them. Polycrystalline SI panels can reach 130W of power for the same surface and solar radiation,those also seem to be cheaper by about 8%. Economical efficiency must also be taken into account, the production of polycrystalline panel is economically more efficient than the production of monocrystalline panels. Amorphous Si panels can convert the 1000 W / m2 of solar radiation in the 50W of power to the surface of cells of 1 m2 at a price approximately 17% lower compared to the monocrystalline plates which makes them the cheapest option, but you should also take into account the low efficiency of these panels . Amorphous panels don’t have wider application, but are commonly used in watches and pocket computers. There are also essential gallium arsenide plates that are used in space applications, butat very high prices, they also have the highest efficiency of 30%. The market of photovoltaic cells has so far had only a growth, which will certainly continue in the coming years. By 2009, the world has installed close to 23GW of photovoltaic systems in which Europe has the largest percentage with 16GW installed and covers 70% of all installed systems, followed by Japan with 2,6GW, USA with 1,6GW and rest of the world