Performance evaluation of solar direct drive refrigerators and freezers using numerical analysis and experimental investigation

This study presents the performance of Solar Direct Drive (SDD) refrigerators and freezers with integrated Thermal Energy Storage (TES) used for food preservation. Laboratory experiments conducted on two prototype units each with 200 Liter storage volume were compared against simulation results obtained from a developed dynamic model. The model was validated following deterministic and probabilistic approaches where the temperatures of the Phase Change Material (PCM), cabinet air, and stored product as well as the compressor energy exhibited excellent agreement. With empty cabinets, experimental results showed that the TES maintained the refrigerator and freezer setpoint temperature for about seven and four days, respectively. Simulations were performed to map the performance of both units under different climate conditions based on the stabilization time required to fully charge the storage and the holdover time during which the product setpoint temperature is sustained without solar energy. Results indicated that the stabilization time can vary between 48 h for the refrigerator and 50−217 h for the freezer, while the holdover time ranged between 62−180 h in all cases. The findings suggest that the main economic driver for SDD refrigerators and freezers is the reduction of food losses that would otherwise be wasted, in addition to the reduction of refrigeration-related greenhouse gas emissions.