Research Information System
SCIENCE AND TECHNOLOGY FOR THE BUILT ENVIRONMENT, 2025 (SCI-Expanded)
Today, conventional controllers are commonly used in most refrigerators and freezers. They adjust the compressor speed to maintain the desired air temperature, irrespective of users' usage profiles. In this study, a fuzzy logic-based smart control concept that incorporates occupant door-opening profiles was integrated into a free-standing commercial freezer. The intelligent controller adjusts air temperature setpoint, maximum compressor speed, and defrost periods according to the door opening patterns of users. The selected freezer was tested under two different usage profiles with both fixed-speed and variable-speed compressors. Test results showed that the intelligent controller can achieve more homogeneous pack temperature profiles by precooling before active usage and desynchronizing defrosting events with active usage periods. For the active user profile, the intelligent controller achieved around 7% improved energy efficiency compared to the standard controller for both fixed-speed and variable-speed compressors while keeping the maximum pack temperature at the same level. For inactive usage profile tests, the smart controller decreased the temperature rise of the packages by 0.5 degrees C with fixed-speed and by 1 degrees C for the unit with variable-speed compressor. Additionally, the intelligent controller demonstrated approximately 5% higher energy efficiency than the standard controller for units with fixed-speed and variable-speed compressors.