Optical Characteristics of Glass Mirror Reflector for off-axis Concentrators: A Ray-Tracing Approach
Abstract
Various solar-concentrators have been widely used to direct the beam solar radiation on to the absorbing surface.. The performance of solar-concentrators depends on the distribution and intensity of the reflected radiation. This research aims at investigating the performance of the easily available and cost-effective glass mirror and aluminum foil reflectors. Simsun target ray-tracing software was employed to model and simulate the interaction of the radiation reflecting materials for the establishment of parameters that allow the design of the most suitable type and geometry. Four samples of tiled glass mirror and aluminum foil were prepared and assembled on an offset type low-tech parabolic dish to carry on the validation by experimental tests. The ray intercept factor from the simulation and experimental investigation studied by laser beam for the mirror samples vary from 56.06% to 51.4% and 51.21% to 45.61% respectively. For aluminum foil the respective results yield 57% and 49.47%. The thermal performance was also investigated by the temperature level of the receiver within 30 minutes and the water boiling test procedures. The temperature level varies from 157.170C to 119.200C for glass mirror samples and yields 146.380C for aluminum foil. The duration obtained from the boiling test resulted in 40 to 69.50 minutes for glass mirror samples and 43.33 minutes for aluminum foil. These results and the reflected image sizes from the experiments indicate that the use of small-sized glass mirror or aluminum foil reflector on the dish best fits the curvature of the parabola and attains the higher optical efficiency.