Towards a Standard Testing Methodology for Medium-temperature Solar Collectors with Variable Geometry

Abstract

Solar thermal energy is able to provide a considerable fraction of the medium temperature energy demand and should be more widely used in several specific industry sectors in the range between 100°C and 250°C. For the energy collection within this temperature range, the solar collector designs usually use optical concentration and its increasing capability for the integration in buildings. In the last decades various new designs have been developed specifically for industrial applications (state-of-the-art in IEA SHC Task 33/SolarPACES IV on Solar Heat for Industrial Processes).At the end of 2013, the new revision of the International Standard ISO 9806 for testing methods of solar thermal collectors will be published for its certification worldwide. This new Standard will unite all the former existing American, European and International Standards. However, some solar collector types still do not fit the Standard testing methodology, in particular the process heat collectors and the solar collectors with changing geometry.This paper describes the points defined in the future ISO 9806 Standard specifically for the solar collectors with sun-tracking and concentration testing and which of them should still be improved in order to fit all the medium-temperature collector designs. A study has been performed in order to specify the range of incidence angle values throughout which the changing geometry collectors should be tested according to its location and the peak efficiency, in the case of not testing at normal incidence. Some important notes should be taken into account in future Standard revisions for this particular collector type.