Development of polishing technology using heat for aluminum structure (Mirror-like machining for high reflectance solar concentrator)

Abstract

Recently, solar power generation is widely prevalent in the world because it is expected as a renewable energy which doesn't discharge CO₂ emission during generating electricity and saving natural resource. Therefore, solar power generation is requiring for high efficient and low cost to spread out further and protect the earth from global warming. High efficient generation becomes possible by focusing sunlight on an electric generating device, i.e. solar cell. Although aluminum is suitable for a concentrator, which is used for concentrating sunlight, mirror-like processing is very difficult because it has large and spherical surface. It is very important to obtain mirror-like surface for high efficient generation. Therefore, the polishing technology for aluminum was developed and evaluated. As a trial study, workpiece didn't have large spherical surface, but small and flat surface in this paper. Firstly, the polishing tool which attached polishing cloth consisting of splittable fiber was developed. Optimum polishing cloth for polishing of aluminum was investigated by trial and error approach. Influence of surface roughness on viscosity of slurry was also researched. Fine surface roughness was obtained by heating workpiece with optimum polishing condition. Finally, reflectance of polished surface was measured and industrial effectiveness was evaluated. It is concluded from the results that (1) the developed polishing technology was effective for processing the mirror-like surface of aluminum,(2) polished surface by using optimum processing condition has 83.8 % specular reflectance,(3) the solar power generation using polished aluminum has higher efficiency than conventional solar power generation on numerical simulation.