abstract
Existing PVT collector models are in general using physical balance and transfer equations, thus they are basing on the design data. Furthermore most of the models are simulating glazed PVT collectors. This paper presents a new model for unglazed liquid cooled PVT collectors that is based on the combination of parameters resulting from conventional thermal and electrical performance measurement data and their characteristic curves, which are obtained in standard test procedures. The thermal performance parameters are taken from a collector test according to EN 12975-2, while for the PV part, the ``effective solar cell model'' has been chosen, which uses results from a test according to EN 60904-1. Hence, only experimental performance parameters from established test methods are required to describe the complete PVT collector performance. In addition to this characteristic curve modelling, a physical approach is implemented for describing the condensation effects. Furthermore, the model takes the internal heat transfer coefficient between PV cells and fluid into account. This coefficient may be derived from the thermal performance parameters. The model has been transferred into the simulation program TRNSYS and tested against shortterm measurements on a test roof and validated against measurements in a 40 m$^2$ PVT collector field over the period of one year. The work presented in this paper has been realized within the project ``Solar heat supply for buildings with unglazed photovoltaic thermal collectors, borehole heat exchangers and heat pumps''.