A novel approach to compare building-integrated photovoltaics/thermal air collectors to side-by-side PV modules and solar thermal collectors

Abstract

Building-integrated photovoltaics with thermal energy recovery (BIPV/T) shows great potential for integration into net-zero energy buildings. This technology is still not widely used, however. One of the reasons is that its advantages compared to traditional PV modules and solar thermal collectors are unclear. This study addresses the lack of a methodology on how to perform such comparison. It also presents a case study on how this novel approach can be used to demonstrate the actual energy and economic benefits of BIPV/T air systems compared to side-by-side PV modules and solar thermal collectors for residential applications. In this methodology, the thermal energy produced by both systems is transferred into water using a heat exchanger and the concept of annual equivalent useful thermal energy production is used to combine thermal and electrical energy. To perform the analysis, a detailed model of a BIPV/T system was developed and validated against experimental data. Then, the following systems were modeled in TRNSYS: a BIPV/T air system and side-by-side PV modules and liquid solar thermal collectors (PV+T). A case study was performed by simulating the performance of both systems on a 40m2 south-facing roof located in Montreal, Canada. The total energy produced by both systems was assessed by converting electricity into heat with various conversion factors. For a factor of 2, the BIPV/T system was found to produce 5–29% more equivalent useful thermal energy than the PV+T system for a water temperature at the heat exchanger inlet corresponding to 10°C. Under similar operating conditions and for systems operating all year long, the acceptable cost to recover the heat from the BIPV system in order to break even with the cost of the PV+T system was found to be 7000CAD.