Analysis of key influencing factors for multi-mode solar heat pump systems

Abstract

To further improve the stability and renewable energy utilization of the compound heat source heat pump system under complex operating conditions, a multi-mode solar heat pump system was proposed and a mathematical model was established in this paper. The accuracy of the model is verified by the experimental data, with the relative error within ±15%. The effects of the number of solar photovoltaic/thermal (PV/T) collectors (area), environmental parameters, and refrigerant flow rate on system performance are discussed separately for different models by the validated model. The results show that (1) PV/T-water source heat pump mode: the number of PV/T collectors in parallel (area) increases to 3 (3.84 m2), and the system performance improves the most, subsequently weakening; (2) PV/T-water and air composite heat pump model: When the refrigerant distribution ratio in the double-pipe heat exchanger 1 is increased from 55% to 95%, the collector's heat collecting capacity, power generation efficiency, and system coefficient of performance (COP) increase by 8.99%, 1.22%, and 6.4%, respectively. Moreover, the increase in solar irradiance can promote more refrigerant flow into the double-pipe heat exchanger 1 and improve heat pump COP more than the effect of increased ambient temperature. The research results can provide an effective reference for further optimization of solar heat pump systems and full utilization of renewable energy.