made up of a battery of rectangular, square or oval cells known photovoltaic cells. The individual cells behave like battery cells, with all the cells having similar specifications which then determine the overall power rating of the solar panel. Thus the amount of electrical energy that a solar panel can generate depends on the following specifications; The surface area of the individual cells in the panel , The material used for making the cells of the panel (type), The power (which depends on the maximum voltage and current ratings of the panel) The intensity and direction of the sun. The surface area plays a crucial role in the quantity of electricity generated because based on the working principles of the photovoltaic systems, the larger the surface area of the panel which are exposed to the sun, the greater the electrical current flowing in the circuit. The type of photovoltaic cells used to make a solar panel also determines it’s solar to electrical energy conversion efficiency. Hence three common types of photovoltaic cells as shown in figure 1.1 (a), (b), and (c) below are; the mono-crystalline, the polycrystalline, and the amorphous silicon cells. According to the Union of Concerned Scientists (UCSUSA) website, the solar panels made of the mono- 9
crystalline cells produce the highest-efficiency cells—as high as 25 percent in some laboratory tests. However, those made of the polycrystalline cells have a lower efficiency of around 15 percent, while those made of the amorphous photovoltaic cells; have the least efficiency of about 5 percent (Retrieved 2012 Nov). The efficiency as mentioned simply describes the percentage of the solar energy from the sun incident on the panel that is being converted to electricity. Figure 1.1: Types of solar panels designed with different Photovoltaic cells (a) Mono-crystalline silicon panel (b) Polycrystalline silicon panel (c) Amorphous silicon panel 10
Table 1.0: A solar panel power comparison chart by photovoltaic cell type: solar cell (type) Intensity of radiation [1x] Efficienc y [%] Maximum power [W/m 2 ] Fill Factor(F F) Mono-crystalline silicon 5000 22 16.74 0.83 Polycrystalline silicon 5000 9 5.84 0.87 Amorphous silicon 5000 8 10.68 0.63 With date from the article - Comparison of electrical characteristics of silicon solar cells (2012), the table above shows the efficiencies and maximum power of the different types of photovoltaic cells used in designing different solar panels. While figure 1.2 below is a chart that shows the overall difference in the efficiencies of the solar panels based on the type of photovoltaic cells used in the respective designs (Vol. 18, pp. 218) Figure 1.2 : Solar panel efficiency comparison based photovoltaic cell type. System: Figure 1.3: A complete solar to electrical energy conversion system 11
Solar Energy Systems, 2012. Retrieved from Thus in order to harness and store the energy from the sun effectively, the system shown in figure 1.2 above is used. The system comprises a of the solar panels, a combiner, charge controller, battery bank, power inverters, circuit breakers, current/voltage meters and an AC generator in some cases. The solar panels convert the solar energy to direct current (DC)
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- Energy, Photovoltaics, Solar cell