Dynamic simulation and experimental study of a variable speed photovoltaic DC refrigerator

A variable speed photovoltaic direct-current (DC) refrigerator (VSPVDR) system is proposed in this paper. In the VSPVDR system, the photovoltaic (PV) cells are directly connected to the compressor without batteries and inverter, and the DC compressor speed changes with the radiation intensity. In the paper, a dynamic model is presented to simulate the behavior of the VSPVDR, and several prototype experiments are conducted to validate the model. On this basis, the impacts of the compressor speed control strategy, ambient temperature and the radiation intensity have been studied. Compared with the fixed speed mode, the cooling capacity of the variable speed mode increases by 32.76% and the average PV utilization efficiency increases by 45.69%. When ambient temperature increases, the average cooling capacity decreases significantly, but the increase of average power consumption is not obvious, which reveals that the ambient temperature has greater influence on the cooling capacity and has less influence on the power consumption. The radiation intensity has a significant impact on system performance. When the radiation intensity increases, the cooling capacity increases significantly. •A VSPVDR system without batteries and inverter is introduced.•A dynamic model of the system validated by prototype experiments is presented.•The average PV utilization efficiency of variable speed model increases by 45.69%.•The impacts of ambient temperature and radiation intensity have been discussed.