Performance analysis of a novel façade-based building integrated photovoltaic-thermal system with phase change material for domestic hot water

Since the current contribution of solar thermal energy to the amount of energy consumed for domestic hot water in buildings worldwide is very low (8.4 %, approximately), the potential of this renewable energy to meet the demand for domestic hot water is quite significant. In this context, this paper presents a new façade-based building integrated photovoltaic-thermal system with phase change material which has been patented recently. It is a modular device for installation on façades and roofs, enabling the production of domestic hot water and electricity using solar energy. The main novelty of the system lies in the use of a photovoltaic glass sheet, which improves the building's aesthetics and facilitates the architectural integration of this type of devices. Thus, a photovoltaic glass is used for the production of electricity, a phase change material for heat storage and a water-phase change material exchanger for the production of domestic hot water. The design and verification stages of the system were developed for a case study under typical usage conditions. Two dimensional numerical models of five different configurations (of the energy harvesting and storage module and two dimensional and three dimensional numerical models of the finned exchanger were carried out to simulate the charge and discharge processes. The most suitable configuration of the system, characterised by a 12 mm vacuum gap and a low emissivity of the absorber, was able to meet the requirements in terms of water flow rate and supply temperature (45 °C) for a shower time of 5 min.