A numerical investigation of the dynamic responds of Solar Direct Drive Refrigerators under different control strategies

Solar Direct Drive (SDD) refrigerators utilizes power directly from a photovoltaic panel. To ensure cooling when no irradiance is available the cabinet liner is equipped with an ice bank. The SDD technology can therefore provide a means for refrigeration of perishable food goods in places with no or unreliable electrical grids. The efficiency and applicability of SDD refrigerators is however highly affected by the implemented compressor speed control. The compressor control shall seek to run the compressor as fast as possible to maximize the utilization of the available power from the panel. The present work compares to control strategies for speed control in a R-600a SDD refrigerator. The comparison was performed using a validated dynamic model. The simulations were performed under different irradiance conditions to give a fair evaluation of the performance of the control strategy. The results show that the constant voltage control always attains the best performance.