Design Improvements and Evaluation of the New CCStaR Collector
Abstract
The CCStaR project started in 2006 with the aim to bring to the market a solar collector capable of working in the range of 100'C to 200'C that could, at the same time, be easily integrable into light building roofs. The two principal target markets for the development were industrial process heat applications and double stage solar cooling. For the supply of heat in this range of temperatures mainly two designs are currently used: Parabolic trough and Fresnel collectors. Although both designs can be efficiently used on ground applications as well as in flat roofs, capable of resisting moderate to high loads, neither of them are well suited for the light roofs often found in industrial buildings. Therefore the possibility of using a different approach, based on the concept of the Fixed Mirror Solar Concentrator (FMSC), was explored. The main advantage of this kind of solution is that the largest element of the collector, i.e. the mirror, remains fixed to the building structure thus reducing the wind loads and simplifying the collector integration. The original geometry of the FMSC, tested during the seventies by the General Atomic Company (Russell 1976), as well as curved mirror alternatives, were thoroughly analyzed using ray tracing procedures (Pujol et al. 2006, Martinez et al. 2006). Comparing the different alternatives, both from the point of view of efficiency and from manufacturing considerations, a reflector based on a single parabolic reflector was chosen. It is known that a parabola only has a point focus for normal incidence. Nevertheless, given a high enough f/W ratio (where f is the focus distance and W the aperture width) the dispersion of the radiation can be kept in a reduced area for all of the significant (from the energy point of view) sun angles. Furthermore the path described by the area where the radiation is concentrated is a circular path which can be easily tracked with a rotating arm (figure 1).