Dynamic Modeling and Validation of a Solar Direct Drive Freezer With Integrated Ice Bank

From initial production to final household consumption, almost one-third of the globally produced food is lost or wasted. Among the many causes ascribed to this alarming figure is the lack of proper cold storage and facilities in both off-grid areas where such infrastructure does not exist, and in areas with low security of electricity supply. Solar direct drive (SDD) freezers and/or coolers are a technical compact solution that utilizes solar energy to generate electricity, which drives a compressor within a simple refrigeration cycle. The cabinet is integrated with an ice thermal energy storage (ITES) that is charged when the compressor is working and is discharged when the compressor is idle at night and at times of low irradiance to maintain the desired temperature level. This paper demonstrates a dynamic equation-based object-oriented model used for the analysis of SDD freezers under different operation conditions. The model accounts for all components, including the photovoltaic panel, the cabinet, and the ITES, in addition to all parts of the refrigeration cycle. Experimental tests were conducted using a real prototype of a SDD freezer with a capacity of 200 Liters. It was found that the ITES was able to maintain the air temperature well below -18 °C for more than four days without electricity supply. The validation of the dynamic model showed excellent agreement between measured and simulated ice temperature, cabinet air temperature, and compressor power. The validated model paves the way to perform multiple simulations of different operational scenarios to gain deeper understanding of the system in general and the compressor control algorithm in particular.