Ray Tracing of a Solar Collector Designed for Uniform Yearly Production

Abstract

One of the problems with solar flat plate collectors for domestic water heating is that they produce more energy in the summer months, when the domestic hot water needs are lower than in winter months. This causes a significant difference between supply and demand and thus overheating during the summer. A method to avoid this problem is to design solar collector fields that offer a 100% of the water needs in the summer, but a small percentage during the winter, which is certainly not ideal.In this work, ray tracing is used to design a solar thermal collector that offers a more uniform production during the year. A novel geometry is chosen where the collector is split in two parts, a curved absorber and a mini parabolic concentrator. The concentrator is designed to concentrate the radiation during the midday hours of winter days and to not doing it in the midday hours of summer days. This increases the energy produced in winter and prevents the installation from overheating.In order to study the hours when this geometry will concentrate the solar radiation, ray tracing is used. As the solar collector has a design that allows the collector to be easily integrated into a facade, the simulations in the most useful architectural integration positions are simulated, those are horizontal positions, but vertical positions or any other position are suitable if the collector is installed on a roof.For each position, the amount of hours where the whole collector is working and the total radiation captured are calculated and compared with the solar radiation captured by an equivalent flat surface, which would corresponds to conventional flat plate collectors.Simulation results shows how for a concentrator designed to work properly in the 5 midday hours during the winter solstice it will not work during the 5 midday hours during the summer solstice, avoiding overheating.