A theoretical analysis of a novel solar-assisted heat pump with an integrated collector storage solar water heater

In this paper, a comprehensive analysis of a novel solar-assisted heat pump system is presented, which incorporates an integrated collector storage solar water heater as the evaporator. Building heating spaces account for a significant portion of total building energy demand, making energy-efficient and renewable-based technologies promising strategies for reducing energy demand. To this end, the proposed system comprises a heat pump coupled with an innovative integrated collector storage solar water heater prototype that exhibits a high vacuum level, enabling the storage of hot water at high temperatures, which is then utilized for supplying heat during the refrigerant evaporation phase. This coupling increases the energy performance of the heat pump while reducing the energy demand in buildings. Furthermore, due to the high thermal inertia of the integrated collector storage solar water heater, the proposed system allows for the development of suitable control strategies for load shifting and peak shaving during cold hours, providing a high level of flexibility. To assess the energy, economic, and environmental performance of the proposed system, a dynamic simulation model is developed and presented. The model is developed in MatLab environment, and it is based on a resistive-capacitive thermal network that enables the dynamic evaluation of the temperature field through the integrated collector storage solar water heater prototype, as well as the water flow rates flowing into the system. Furthermore, a subroutine is also developed to assess the energy performance of heat pumps. This subroutine considers heat transfer phenomena and allows for evaluating the impact of different parameters charactering the system (e.g. geometry, thermophysical properties, refrigerant fluid typology, pressure drops, etc.). To demonstrate the potential of the proposed system and the predicting capability of the dynamic simulation model, a case study is also proposed. Preliminary results show promising energy savings by utilizing the proposed system. The results obtained from this case study are intended to provide insights into the benefits and limitations of the proposed system and the dynamic simulation model, which can be used to optimize and design future solar-assisted heat pump systems with an integrated collector storage solar water heater prototype.