Dynamic energy efficiency characteristics analysis of a distributed solar photovoltaic direct-drive solar cold storage

Abstract

A novel method for constructing a distributed solar photovoltaic (PV) direct-drive cold storage system is proposed. In this system, the vapour compression refrigeration cycle (VCRC) is directly driven by a PV array, and ice thermal energy storage is used as the energy storage unit instead of a battery. The dynamic energy efficiency model of the system was established at an extremely small resolution. On this basis, the key factors affecting system performance were studied. Moreover, experiments conducted under different weather conditions verified the accuracy of the model. The results show that, the solar-cold energy conversion efficiency of the system is negatively correlated with the solar radiation intensity at the same evaporation temperature. When the solar radiation intensity reaches the minimum value required to drive the VCRC, the average solar-cold energy conversion efficiency of the system decreases by 2.28%–2.62% as the solar radiation increases by 100 W/m2. The changing trend of the solar-cold energy conversion efficiency of the system with time during sunny weather is similar to that of an upper opening parabola. Under lower radiation conditions, the effect of the evaporation temperature on the solar-cold conversion efficiency weakens. Compared with the experimental results, the average daily deviation of the simulation results is approximately 2.8%–3.2% on clear days and 4.4%–5.1% on cloudy days. The experimental results show that the cold energies during sunny and partly cloudy weather are 128.83 and 122.00 MJ and the average solar-cold energy conversion efficiencies are 0.30 and 0.31, respectively.