Investigation On Optical And Heat Transfer Characteristic Of Dish Solar Concentrate System

Solar energy is a kind of promising alternative energy due to its great amount and widely distribution. In recent years, the developing of the solar energy is mainly focused on Photovoltaic power generation and heat utilization. Concentration technology to ground solar energy of low energy density is regarded as the future tendency for a high energy and economic efficiency. The dish reflector employed in a dish concentrating system can lead to a high geometry concentration ratio and it’s convenient for modular developing and distributed utilization.Dish solar concentrating system can be applied in both Photovoltaic system and driving a heat engine. High efficiency is the basic characteristic of a dish solar system for its point focusing style, which is the key reason for the high efficiency. The receiver, however, bears a very high concentrating energy flux which likely to damage the receiver for a thermal stress. It’s important to know about the energy flux on the wall of the receiver.In this paper, a cooperative method is proposed to solve the current difficult problem in the dish concentrating system. The concentration performance and flux distribution is assessed numerically using the Monte-Carlo ray-tracing method. The flat plate receiver and cylinder receiver are analyzed individually and solar angular diameter is considered in the model. Result shown that flux decrease gradually in the direction of radius with a flat plat receiver which is similar to the bottom of cylinder receiver. From the aperture to the bottom, the radiation flux on the cylinder increase firstly, and then decrease. A flux peak is existed on the cylinder. In all, the radiation flux is ununiformed, especially on the side of the cylinder. In this paper the influences of brim angle and geometry is also analyzed.Applied the result in the optical analysis, the heat transfer characteristic is analyzed. Using Ansys to calculate the temperature field of the cylinder receiver, the result shown that the temperature distribution is also not uniform. Correlated to the radiation flux distribution, two peak temperature regions were existed. One is the center of the bottom of the cylinder receiver. the other is a ring peak on the cylinder. The thermal stress is probably generated in these fields, which must be concerned in the future devise.The high cost associated with the fabrication and installation of parabolic reflectors has been identified as one of the major limits for scaled-up applications of solar dish systems. The applicability of spherical reflectors in solar dish systems that require much lower cost than that of the parabolic reflectors is considered in this paper. The concentration performance of spherical reflectors is assessed numerically. It is shown that the spherical reflectors possess a geometric concentration ratio ranging from500to2000, which is lower than that for the parabolic reflectors as expected but is still sufficient for solar dish/engine and dish/PV applications. The radiation flux distribution with spherical reflector is also analyzed.