Freezer Energy Efforts
CU Green Labs is a resource for CU Boulder on laboratory freezer topics. Labs often reach out regarding freezer failures, sharing opportunities, purchase suggestions for energy-efficient units and other issues. During times of crisis, we provide labs with -20 ⁰C mobile freezers or help them line up space in other freezers in their department while they deal with the critical freezer problem.
By facilitating freezer solutions, we can connect labs to freezer-sharing opportunities and provide monetary incentives from Facilities Management toward energy-efficient units. Laboratories can save research dollars, and the university also saves money. These efforts help CU Boulder work toward university sustainability goals for energy conservation. The incentives CU Green Labs offers are made available by Facilities Management and can apply to other equipment types beyond freezers, such as biosafety cabinets, incubators and vacuum pumps.
-70 ⁰C Efforts
Half of the ultra-low temperature (ULT) freezers on the CU Boulder campus are at -70 ⁰C (~75 of ~150 freezers). We hope to continue to encouraging laboratories to switch their freezers to -70 ⁰C where it makes sense for their samples.
Benefits of raising your ULT freezer temp from -80 ⁰C to -70 ⁰C
- Extend the life of your ULT freezer! Increasing the temperature of your freezer means the compressor does not have to work as hard. Since the compressor works less, there is a reduced risk of compressor failure.
- Energy savings, based on metering data from ULT freezers at two temperatures, it is easy to see the energy-saving impact of raising your unit’s temperature to -70 ⁰C.
- 21.8 kWh/day (at -83 ⁰C) to 14.6 kWh/day (at -70 ⁰C) on a very old upright Forma Scientific Bio Freezer, Mod. 8326, for a total of 7.2 kWh/day saved.
- 12.2 kWh/day (at -80 ⁰C) to 9.2 kWh/day (at -70 ⁰C) on a more energy efficient upright New Brunswick Eppendorf HEF U570 Freezer for a total of 3 kWh/day saved.
- 16.1 kWh/day (at -80 ⁰C) to 14.1 kWh/day (-70 ⁰C) on a chest freezer VWR Model #5459 (Thermo Forma) for a total of 2 kWh/day saved.
What kinds of samples can safely be stored at -70 ⁰C?
Scientists at CU Boulder, UC Davis, and several other campuses have contributed to a database of cold sample storage practices to demonstrate sample types that are being stored at -70 ⁰C. Please note that this database is not science-based data on appropriate temperatures for samples, though these temperatures have been successful for various labs for years.
Did you know that before any ULT freezers could be manufactured to reach -80 ⁰C, ULT freezers were only able to reach -70 ⁰C? To best of our knowledge, the switch from -70 ⁰C to -80 ⁰C was a result of marketing by manufacturers to sell ULT freezers rather than a demonstrated scientific need for -80 ⁰C for samples stored in ULT freezers.
At the International Institute for Sustainable Laboratories (I2SL) conference in September 2013, a presentation by the CDC included the fact that they raised 60 of their ULT freezers to -70 ⁰C from -80 ⁰C on one of their campuses as part of the freezer challenge.
The University of Edinburgh in the UK is currently conducting a study to scientifically address the question of what temperatures are most appropriate for certain sample types. They hope to store their samples at either -60 ⁰C, -70 ⁰C, or -80 ⁰C for a minimum of five years and then test their viability. This is an exciting study, and we look forward to learning about the results in a few years!
Additional Resources for Energy Savings at -70 ⁰C
Advocates for energy efficiency in laboratories have suggested that increasing ULT freezer temperature from -80°C to -70°C can reduce energy usage while maintaining performance. This study corroborated that view, finding that such a temperature change reduces energy consumption by an average of 37% for both standard-efficiency and energy-efficient ULT freezers without any discernable effect on temperature stability.
A representative from Thermo Fisher Scientific mentioned to Allison Paradise at My Green Lab that they have unpublished data supporting the fact that it takes 1 to 1.5 hours less time for an empty ULT freezer at -70 ⁰C to warm up to -50 ⁰C than if the freezer’s set point had been at -80 ⁰C. The representative reported that on average the warm up time went from about 300 minutes to about 235 minutes when you changed the setpoint from -80 ⁰C to -70 ⁰C. For a full freezer, the warm up difference between a freezer set at -80 ⁰C and one set at -70 ⁰C is only 30-40 minutes.
At the University of Copenhagen, freezers were evaluated on the basis of Total Cost of Ownership with focus on energy consumption. Four different models were tested at both -70 C and -80 C under controlled conditions at an external certified laboratory. Results of the tests include 20-22% lower energy consumption at -70C for new ULT freezers and inner temperature being more reliable at -70C than -80C. Additionally, upright freezers are in average 22% more efficient by volume than chest freezers, and large freezers are in average 13% more efficient by volume than small freezers.