Page - 102 - in Clean Water Using Solar and Wind - Outside the Power Grid

102 Clean Water Using Solar and Wind: Outside the Power Grid cells and completely polymeric devices. The dye cell is the closest to commercialisation; the other organic cells are still in their development phase. In addition to thin-film and organic solar cells, compounds such as perovskite are being used in developing the next generation of solar PV cells. This is a mineral (CaTiO3) that was discovered in the Ural mountains in Russia in 1839 and is named after the Russian mineralogist Lev Perovski (1792–1856). Efficiencies of perovskite cells have jumped from 3.8% in 2011 to over 20% by 2014. While perovskite solar cell technology is yet to be consolidated for commercial use, cells can be very cheap as they are made from relatively abundant elements such as ammonia, iodine and lead. However, there are severe doubts in terms of environmental safeguarding over the use of lead. Moreover, perovskite cells are unstable and deteriorate significantly when exposed to the environment. The replacement of lead with a more environmentally friendly element and the improvement of stability will be important objectives for researchers in this field. Developing a tandem solar cell with correct matching of the top perovskite and bottom silicon cell is expected to increase the conversion efficiency of the solar cells well beyond 25%, while keeping manufacturing costs low. 8.3.2 Efficiency of PV modules A major concern about photovoltaic technologies is their efficiency, life and performance over time. Commercial PV modules convert around or less than 20% of the solar energy irradiation to electricity. The efficiencies of PV panels also have a temperature coefficient, and generally degrade in rising temperatures. Efficiencies of solar PV modules are typically of the order 14–21%. Table 8.2 shows that monocrystalline panels have the highest efficiency. They also have the longest expected lifetime. Polycrystalline and thin- film solar modules have a lower cost but are less efficient. Therefore, there is a trade-off between production cost and efficiency to find the best choice of panel type. Efficiencies of solar PV modules are of the order 14–21%. Downloaded from https://iwaponline.com/ebooks/book-pdf/520710/wio9781780409443.pdf by IWA Publishing user