Development of polishing technology using heat for mirror-like surface of aluminum

Recently, high efficient solar power generation is required because eco-awareness is increasing. High efficient generation becomes possible by focusing sunlight on electric generating element, i.e. CPV (Concentrator photovoltaic). Although the concentrator is used for focusing sunlight, it demands large spherical surface with high solar reflectance, fine accuracy and lightweight. Aluminum is considered as suitable material for concentrator. However, mirror-like processing on large spherical surface is very difficult. Therefore, new polishing technology for aluminum was developed and evaluated in this paper.Main objective is to obtain high solar reflectance by improving surface roughness. As a trial study, workpiece was not large spherical but small and flat. Firstly, the polishing tool which attached polishing cloth was developed.Optimum polishing cloth for tool was investigated by trial and error approach. When workpiece was heated before starting polishing, a number of oxides were adhered to polishing cloth and surface roughness was improved efficiently.Then optimum polishing condition was decided by using design of experiments method. Finally, solar reflectance on polished surface was measured and evaluated. It is concluded from these results that (1) the developed polishing technology was effective for processing the mirror-like surface on the surface of aluminum, (2) 82% solar reflectance was obtained with developed polishing technology by improving surface roughness of workpiece.