Use of finite element models for estimating thermal performance of façade-integrated solar thermal collectors

Research on building-integrated solar thermal collectors is attracting increasingly more interest. Many efforts have been focused at the design level for obtaining specific building-orientated products, but there is a significant lack of standardised methods for evaluating how the efficiency of solar collectors changes when a wall is an integral part of the solar component itself. Generally speaking, experimental tests on integrated components are not easy to realise and are, in any case, expensive in terms of time and money. Physical and numerical methods can be utilised, but at the moment, there is no common approach. The present work addresses a method for the calculation of a building-integrated component performance curve by means of a finite element method model. The main idea is to exploit data measured for a simpler and non-integrated component, which are readily available, for validating and calibrating a more complex model in which the system is coupled with a building element. Simulation assumptions and outputs are designed to comply with the main standards utilised for defining solar collector performance curves. The proposed method proves that it may be a good way to assess the performance curves of building-integrated solar thermal collectors and that it is suitable for reducing test costs. The authors have also highlighted the measures that must be taken for the sample collector to better fit the BIST performance model.