Improving the solar panel energy efficiency by cleaning the solar panel was undertaken to study the energy output efficiency for the non-crystalline, monocrystalline, and polycrystalline solar panel with and without the emulated rainfall. The weather in Taiwan is rather humid; the dust in the air is thus easily moistened, adhered to and accumulated on the solar panel, s surface to interfere with the solar panel’s energy efficiency. On-site observations reveals that raindrops were somewhat effective in cleaning the solar panel surface. Hence, a water spraying system was installed above the solar panel and operated once every week to study the effectiveness of cleaning by rainwater. The results are shown in Figure 9.
Without the water spray cleaning system, the polycrystalline solar panel produces 3.7% more energy than the monocrystalline solar panel. Providing the water spray cleaning system, however, causes the solar panels to produce more energy: 17.72% for the polycrystalline solar panel, and 5.38% for the non-crystalline solar panel.
A BIPV building will lower the indoor temperature by 1.8-2.7 °C during summer to save 9.17% to 31.95% of energy in cooling the building. The solar panel used in the BIPV building is made of monocrystalline silicon with a 25° inclination oriented westerly in order to obtain the maximum energy generating efficiency. The variation of ambient temperature may cause the electricity generation to vary by 0.07-4.5%; clear ambient air will assist in elevating the power generation by 3.7% to 29%. The overall experimental results revealed that the order of improved energy efficiency using water spray cleaning is monocrystalline solar panel, noncrystalline solar panel, then polycrystalline solar panel.
The energy output for solar panels before and after cleaning at various ambient temperatures are listed in Tables 1 and 2. The results in each table indicated that the clarity of solar panels affects the efficiency of solar panels made of different materials; dirty solar panels will lower the efficiency of producing electricity by 3.7% (Table 1) to 29.29% (Table 2).
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After cleaning
Table 1. Solar panel energy output for panel before and after cleaning. |
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After cleaning
Table 2. Solar panel surface clarify and temperature before and after cleaning. |
Hence, maintaining a clear solar panel surface by washing with natural raindrops or artificial water spraying system will assist in promoting the energy efficiency of the solar panel. The cleaning will lower the surface temperature of solar panels; but the temperature variation caused by cleaning the solar panel will result in decreasing energy efficiency slightly of only 0.07% (Table 1) to 4.53% (Table 2).
Various factors such as the solar panel’s material, inclination angle, natural cleaning by rainwater and climatic conditions, among many others, may affect the solar panel’s energy efficiency. Additionally, how the solar panel can be integrated with the shell of a building so that the combination will become a reliable source for cheap energy to provide air conditioning for the building is also the ultimate goal of this research.
The research results confirm that installing solar heat shading boards will lower the indoor temperature by 1.8oC to 2.7°C, save about 9.17% to 31.95% of energy consumption. As far as the solar panel’s material is concerned, the monocrystalline panel is better than non-crystalline solar panel, which is better than polycrystalline panel. The order of magnitude for the panel installing angles is 25°>20°>30° with west-orientation being the most favorable for energy production, followed by south-orientation and east-orientation.
Maintaining a clean solar panel surface by washing will reduce the panel surface temperature to lower the energy output by 0.07% to 4.57%; however, this action will improve the energy output by 3.7% to 29%. In summary, installing the shading board will reduce the energy consumption for air conditioning. Raising the energy efficiency of solar panels, and developing new solar panel technology and implementation methods will effectively alleviate the peak power demand, improve the balance of power consumption, and promote the development and reuse of renewable energy sources.
This work was partially supported by CPAMI of R. O.C. The authors wish to thank Professor Chen Jiann-Fuh form NCKU for many helpful suggestions during the course of this work.
Wen-Sheng Ou
Address all correspondence to: wsou@ncut. edu. tw
Department of Landscape Architecture, National Chin-Yi University of Technology, Taichung, Taiwan
