Ultra-Low Temperature (ULT) freezers are well known to be high consumers of energy. Holding set temperatures 90°C to 100°C colder than their environment will always require a significant amount of energy. In recent months, the rise in energy costs has further placed emphasis on lab equipment running costs and means by which energy can be conserved.
ULT freezer best practices are often promoted by individual organizations, manufacturers, insurers, and LEAF (the leading lab sustainability certification scheme). Although best practices are widely encouraged, very little quantified data exists outside of changing the set temperature of the ULT freezer from -80°C to -70°C.
By warming up, modern ULT freezer energy consumption will be reduced by 18-34% depending on the model, age, and condition of the unit. However, the energy cost of bad practice has rarely been quantified.
Quantifying bad practise
The impact of bad practice was quantified in a study conducted at the Learning and Research Centre, University of Bristol. The study was jointly commissioned by Scientific Laboratory Supplies Ltd (SLS) and Eppendorf UK. The ULT freezer tested was the Eppendorf F570h.
The laboratory space used was air-conditioned with an ambient temperature of 23°C (+/-1.5°C). This case study used the Logicall Wireless Monitoring system, which utilized energy monitors, temperature probes, and an online platform to record all the data. In each compartment, a UKAS-calibrated PT1000 probe was placed in the center point of each shelf.
Placing the ULT freezer away from other heat sources allows for the efficient cooling of the refrigeration system. One example of what steps not to take is placing two ULT freezers back to back.