A numerical evaluation of adaptive on-off cooling strategies for energy savings during long-term storage of apples

The main energy costs of long-term apple storage are associated with cooling. Reducing these costs without compromising product quality may be possible with minor room temperature increases. This paper presents a transient CFD model to evaluate automatic on-off cooling control based on different temperature differentials (0.4, 0.5 and 0.7 °C around a setpoint). Effects on temperature uniformity, quality changes and energy consumption during long-term storage of apples were calculated. A model for apple firmness change kinetics was coupled to the CFD model and applied to calculate changes in quality uniformity in a coolstore affected by spatiotemporal fluctuations in temperature. Large temperature fluctuations were observed near the outer edges of the stack and were more pronounced with a higher cooling differential. Using a small cooling differential around the setpoint temperature showed a better overall performance in terms of energy consumption and final product quality.