Factors affecting the performance, energy consumption, and carbon footprint for ultra low temperature freezers: case study at the National Institutes of Health

The National Institutes of Health (NIH) recognises an opportunity to significantly reduce the energy consumption and its carbon footprint from plug load equipment can be realised by managing –86°C ultra low temperature (ULT) freezers. Energy meters were installed on ULT freezers operating in actual laboratory conditions to determine how their energy consumption is influenced by various factors. Ambient temperature, freezer condition, age, capacity, and set point temperature were the factors that were examined. Based on the study, ultra low temperature freezers operated efficiently when they are: well maintained, operating in ambient temperatures less than 25°C, less than ten years old, are operating at a set point higher than –80°C, and have an internal capacity greater than 23 ft3. The results of the case study are presented and discussed. Freezer performance was assessed to determine how ambient temperature and the freezer condition influenced the freezer's ability to reach set point temperature. The results of the study indicate a freezer that is not maintained and operating in ambient temperatures above 32°C produce cabinet temperatures 12.5°C warmer than the desired set point temperature.