A hemispherical static concentrator with double aspheric compensated lens array for continued collecting sunlight

Natural light is an inexhaustible and environmentally friendly energy. The solar energy exposed to the earth everyday is about three thousand times to the global energy consumption. Therefore, it would be a considerably large energy saving if we collect and guide the sunlight for lighting. Currently, there are two types of solar concentrators for collecting sunlight purpose, namely, active and static. The former is more efficient, but needs costly active sun-tracking system for supplement; the latter is cheaper, but is limited for certain time slots. In static systems, a hemispherical concentrator can gather the sunlight with longer time, but the collected flux is not stable and the energy density of optical fiber is lower than the illuminance of sunlight. We, in this paper, propose a hemispherical static concentrator that consists of double aspheric compensated lens array. The double layers of lenses are designed with large tolerance for continued collecting sunlight and the apertures of lenses are larger than optical fiber for increasing the energy density. According to the simulation results, we get uniform distribution of collected flux from 10 a.m. to 4 p.m. that is less than 10% change. Moreover, the energy density of optical fiber is about 50 Lm/cm2in summer when the illuminance of sunlight is about 120,000 Lux.