Thermo-Economic Optimization of Solar Thermal Devices by Coherent Integration of Technologies

Abstract

Radiation is a form of energy where the angular variable of the direction of its photons has a primary importance, particularly for radiation concentration processes, which are essential tools to reach high temperatures from radiation beams (as the solar ones) with moderate intensities. Solar radiation cannot be used directly to feed thermodynamic cycles, and optical concentration must be applied to that goal. In general, reflection from mirrors is preferred to refraction by lenses in this case, because they have less optical aberrations. Concentration conveys very high temperatures in the receiver. However, the higher the temperature, the lower the efficiency of the solar thermal apparatus. Besides that, economy also suffers quite a lot when going to very high concentration factors, which is one of the main burdens in the development of Solar Thermal Energy. A new configuration of solar radiation concentrator is presented. It includes a salient innovation in the way the mirrors are given the right curvature by mechanical forces. Those mirrors are originally flat and do not need any special thermal treatment for this purpose. The whole device concept has been guided by the principle of thermoeconomic coherence, which requires similar efforts in all degrees of freedom that have strong influence in the performance and cost of the system. The paper shows the decision tree that has oriented the project, following the principle of equilibrium in efforts, which leads to a design window of moderate values in the main variables. The prototype of this new configuration has already been built, and the first stage of research is considered to be finished, because the prototype has shown excellent conditions to include selected (fitting) technologies at a very low cost.