Simulation of photovoltaic-thermal (PV-T) solar assisted heat pump  (SAHP) systems for building thermal demands
Creators: name: Kasturi, Pranay
name: Torio, Herena
Publisher: name: Zenodo
Year: 2024

description: Heat pumps are becoming increasingly acknowledged as a pivotal technology in the effort to reduce carbon emissions from heating and coupling the heat pumps with renewable energy sources will be critical in their decarbonization. In this context, the use of photovoltaic thermal (PV-T) collectors to assist the heat pumps is expanding, due to the ability of such collectors to generate both electrical and thermal energy that can be exploited by the heat pump. The main objective of this study is to simulate the combined operation of PV-T and heat pump systems in meeting the building thermal demands, in order to evaluate the potential benefits that can be achieved with the said combined operation.

In order to achieve this objective, firstly, the basis for the simulations is established, in terms of the appropriate system configuration and system size for the thermal demands in consideration. Then the models required for the simulations -the heat pump model, the PV-T collector model, the hot water tank model, and the controller model- are developed. The developed detailed heat pump model is then functionally validated against an existing simplified heat pump model, establishing its higher suitability to the study, particularly at low temperature lift conditions that result from the combined operation of the PV-T and heat pump systems. The validated heat pump model is then used to perform the system simulations for a baseline scenario, without the PV-T system and with only the heat pump operating to supply the demands. Finally, the systems simulations are performed for the different configurations of the PV-T system, with 2,4,6,8,10 and 12 panels connected in series. 

The comparison of the results from the simulations with the different configurations of the PV- T system shows that an increase in the number of panels in series leads to higher heating capacities and average COP of the heat pump, due to the higher source air temperatures achieved, leading to a reduction in the total electrical energy consumed by the system, and the share of the grid electrical energy used. However, the relative improvement in the performance of the system obtained by adding more panels in series, reduces, as the number of panels increase. Therefore, the configuration of the PV-T system with 4 panels in series, with an increase in the average COP of 6.61% and a decrease in the total electrical energy consumed of 6.17%, as compared to the baseline scenario, is found to be optimal for the building thermal demands in consideration. For the PV-T system configuration with 4 panels in series, an additional simulation is performed with an advanced control strategy aimed at increasing its operation during the daytime when the heat pump can benefit from the simultaneous operation with the PV-T system. When compared to the previous results of the same configuration with a regular control strategy, the average COP of the heat pump decreases by 1.9% and the total electrical energy consumed increases by 1.7%. However, due to the increase in daytime operation, when the PV-T system and the heat pump operate together, the self-consumption of the electrical energy of the PV-T system increases by 19% and the grid electrical energy used decreases by 5.5%. While only the technical comparison of the system performance has been done in this study, the comparison could be extended in further works to include economic and sustainability criteria to gain key insights into the practical implementation of such systems.