Page - 101 - in Clean Water Using Solar and Wind - Outside the Power Grid

Solar PV 101 The dominating technology is based on either monocrystalline or polycrystalline silicon (c-Si) technology. Monocrystalline cells are produced by slicing wafers (up to 150 mm diameter and 200 microns thick) from a high-purity single crystal boule. Four sides of the silicon ingots are cut off to make high-purity silicon wafers. As a result, a large part of the original silicon becomes waste, which adds to the production cost. Polycrystalline cells are manufactured by sawing a cast block of silicon first into bars, and then into wafers. The process is simpler than the process to make monocrystalline since less silicon waste is produced. The main trend in crystalline silicon cell manufacturing involves a move toward polycrystalline technology. There is an intense effort to reduce the costs to produce monocrystalline cells, so they might be more competitive with polycrystalline in the future. According to Fraunhofer (2016) silicon-based PV technology accounted for about 94% of the total production in 2016. The share of polycrystalline technology is now about 70% of total production. Thin-film cells are constructed by depositing extremely thin layers of photosensitive materials onto a backing such as glass, stainless steel or plastic. Thin-film manufacturing processes result in lower production costs compared to crystalline technology. The most popular thin-film technology is amorphous (uncrystallised) silicon (a-Si). In amorphous silicon solar cells there is much less silicon used (about 1%) compared to crystalline silicon cells. The cells can be grown in any shape or size and can be produced in an economical way. Amorphous silicon cells have been used for a long time in non-critical outdoor applications and consumer products such as watches and calculators. They are now being adopted by other larger-scale applications. In 2016, the market share of all thin-film technologies amounted to about 6% of total annual production (Fraunhofer, 2016). Mass production costs of thin-film modules are lower than for crystalline silicon modules. They also have a higher heat tolerance. The drawback of the thin-film technology is its lower efficiency, due to the active material used. Commercially interesting materials are cadmium telluride (CdTe) and copper-indium/gallium-diselenide/ disulphide (CIS/CIGS). There are several technologies based on organic cells. This includes dye-sensitised solar cells, antenna cells, molecular organic solar Downloaded from https://iwaponline.com/ebooks/book-pdf/520710/wio9781780409443.pdf by IWA Publishing user