Optical Analysis of A Sliding-Type Cylindrical Fresnel Lens Concentrating Collector for Agricultural Greenhouse

Abstract

Agricultural greenhouses are commonly built around cities to supply residents with agricultural products or green plants. With an increasing demand for plants’ growing environment, the temperature and illumination inside the greenhouses are counted especially during cold winter. This paper proposes a new construction idea of an energy-saving agricultural greenhouse, by which a solar energy collector is added onto the agricultural greenhouse to improve the energy utilization efficiency. Besides, the solar collector does not occupy extra land resource and merely influence the illumination inside the greenhouse. The design and modeling of solar system are introduced in accordance with the actual parameters of agricultural greenhouse. Then the characteristics of energy collection and inner house’s illumination are elaborated by simulation. It shows that when the inclination incident angle of the sunlight ranges from -38° to 38°, the receiving efficiency of ray in receiver is more than 80%. This implies that the system can work about 5 hours in heat collection. The light environment and the thermal environment are both important. When scattered and direct light are set 40% and 60% of daylight, respectively, the illumination of ground is up to 8.38×105 Lux. The minimum illumination is not less than 4.22×105 Lux. In addition, the illumination of rear wall ranges from 3.05×105 Lux to 7.62×105 Lux. Thus, the light environment in the greenhouse is not influenced and all the indoor activities could be maintained. Finally, local meteorological data are combined with simulated solar collection results to evaluate the economy. It shows that the system could provide about 1887.8 MJ/m2 in six cold months, which approximately equals to 6153.9$ per year.