Seite - 103 - in Clean Water Using Solar and Wind - Outside the Power Grid

Solar PV 103 Table 8.2 Efficiencies of commercial solar PV modules. Type of Panel Efficiency (Commercial) % Efficiency (Best Lab) % Monocrystalline 17–21 24.4–26.7 Polycrystalline 14–16 19.9–22.3 Thin-film CIGS 14–16 19.2–21.7 Thin-film CdTe 14–16 18.6–21.0 Thin-film a-Si 13.8–15.5* 11–14 Source: Data from Fraunhofer (2015, 2016). *Based on modules with highest efficiency of their class. Research on solar cells is making an impressive improvement to available efficiencies. With a combination of concentrated solar PV and new semiconductor technologies (III–V multijunction concentrator solar cells) the achievable efficiency reached 46% in 2017 (Fraunhofer, 2016). Solar panels have a relatively long lifetime and often have a 25-year performance guarantee. This is of course an unusually long time, so the solar panels are considered to be the most reliable parts of a solar system. There is still, however, a degradation in performance and power output decreases about 1% in the first ten years. Another problem of efficiency loss is caused by what is called mismatch. One would assume that the cells in the sun would deliver their power to the load. Instead the shaded cells may absorb the power and significantly reduce the total efficiency of the module. If a single cell gets no light, then the current in all the series-connected cells will be reduced to the same current level as the shaded cell. So, one poorly performing cell (in the shade) can cause the total power output to be reduced to zero. More seriously, there may be a local heating of the module that will damage some cells. This local heating, however, can be avoided by using protective electronics – so-called bypass diodes – around the cell. Solar panels have a commonly guaranteed lifetime of 25 years. Downloaded from https://iwaponline.com/ebooks/book-pdf/520710/wio9781780409443.pdf by IWA Publishing user