Fabrication and laboratory-based performance testing of a building-integrated photovoltaic-thermal roofing panel

Highlights: • A BIPVT solar panel is designed and fabricated for energy efficient buildings. • A high-speed manufacture method is developed to produce the functionally graded materials. • Laboratory tests demonstrate BIPVT's energy efficiency improvement and innovations. • The PV efficiency is enhanced ∼24% through temperature control of the panel by water flow. • The combined electric and thermal efficiency reaches >75% of solar irradiation. - Abstract: A building integrated photovoltaic-thermal (BIPVT) multifunctional roofing panel has been developed in this study to harvest solar energy in the form of PV electricity as well as heat energy through the collection of warm water. As a key component of the multifunctional building envelope, an aluminum/high-density polyethylene (HDPE) functionally graded material (FGM) panel embedded with aluminum water tubes has been fabricated through the vibration-sedimentation approach. The FGM layer gradually transits material phases from well-conductive side (with aluminum dominated) to another highly insulated side (with HDPE). The heat in the PV cells can be easily transferred into the conductive side of the FGM and then collected by the water flow in the embedded tubes. Therefore, the operational temperature of the PV cells can be significantly lowered down, which recovers the PV efficiency in hot weather. In this way, the developed BIPVT panel is able to efficiently harvest solar energy in the form of both PV electricity and heat. The performance of a prototype BIPVT panel has been evaluated in terms of its thermal efficiency via warm water collection and PV efficiency via the output electricity. The laboratory test results demonstrate that significant energy conversion efficiency improvement can be achieved for both electricity generation and heat collection by the presented BIPVT roofing system. Overall, the performance indicates a very promising prospective of the new BIPVT multifunctional roofing panel.