Freezers

One of the biggest users of energy in any lab is the cold storage equipment. This is especially true for the ultra-low temperature freezers (-80 freezers). One ultra-low temperature freezer can consume as much energy as a family home every day so anything that can be done in this area will significantly reduce energy consumption. In order to reduce their energy usage, storage should be optimised, old samples regularly cleared out and freezers defrosted regularly. See below the tips for “good” freezer maintenance.

Freezer Maintenance Guide

Storage or Samples

-          Try to store samples at -70 instead of -80, this can result in 30% less energy required to run your freezer. There is anecdotal evidence to suggest there is little difference to the sample when storing at a 10 degree difference see: minus-70-is-the-new-minus-80_3.pdf (teunbousema.nl) & Energy Efficiency and Considerations for Upgrades - International Laboratory Freezer Challenge, however please ensure you do your own research before changing any standard protocols. Note: if samples are required to be stored at -80 in the study protocol this might be more difficult to work around. However, we encourage lab users to question why this protocol exists and to work towards proving that there is little difference between -80 and -70. Just because something has always been done this way, does not mean it is the optimal way to do something.

-          Storing samples at more appropriate temperatures. Not all samples and reagents need to be stored at -80, for example some DNA samples can be stored in the standard -20 freezers. These freezers consume up to 80% less energy than ULT freezers.

-          Regularly clearing away ‘old’ samples. The definition of old can change department to department, however clearing samples that are no longer in use, and will not be used in the future, is one of the most important steps of sustainable freezer management. Not only does this clear space for new samples, preventing the need for potential additional freezers, it also helps lab users prioritise samples that will actually be used. Samples that are unlabelled or unclearly labelled should also be cleared away as they are not reusable if no one knows what they are and what interventions were given.

-          Following from this, samples should be correctly and clearly labelled and catalogued in an inventory system (for example this can be a specific software such as Ziath or just an excel sheet). This way it is easy to locate samples. This will save time searching for samples, will shorten freezer door opening times thereby increasing equipment and workflow efficiency. This will also show clearly where all the current samples are, so when new samples lab users know exactly where there is space in the freezers.

-          Samples should also be collected and stored with the smallest quantities necessary for your study. Try to maximise the storage within freezers by using racks that fill the whole space, and containers that are organised most efficiently for your study.

Inventory System for Sample Management

-          Following from this, samples should be correctly and clearly labelled and catalogued in an inventory system (for example this can be a specific software such as Ziath or just an excel sheet). This way it is easy to locate samples. This will save time searching for samples, will shorten freezer door opening times thereby increasing equipment and workflow efficiency. This will also show clearly where all the current samples are, so when new samples lab users know exactly where there is space in the freezers.

Cleaning Maintenance of Freezers

 

-          Freezers should be fully defrosted regularly (at least once a year) and kept ice free in between defrosts. After a defrost freezers can run approximately 10% more efficiently than before. It is important to ensure the freezer remains ice free, especially around the seal, as ice can prevent the door from closing correctly causing the freezer to use more energy to stay at a constant temperature. Ice forms as a result of condensation caused when opening the freezer, this decreases the efficiency of the cooling causing the freezer to consume more energy.

-          Regularly cleaning of the fans and coils should be part of regular freezer maintenance. Dust removal from the intake and coils can be done with a hoover. Enabling the freezer to run most efficiently. Another important note about the fans, intake and coils of a freezer; they should not be blocked by having boxes/other equipment stored on top of, next to or leaning against the freezers. When these areas are blocked it causes the freezer to have to work harder, using more energy.

Advanced Freezer Maintenance Guide

-          Sharing your cold storage space with other lab and lab users. This is often overlooked but an incredibly effective way of reducing the operational costs of your lab and saving energy. This could also be the case for back-up/spare freezers i.e., your lab and another both share the additional back-up freezer rather than both having their own. Sharing this between more than one lab can reduce the number of overall freezers needed. This can also help to encourage co-operation between different lab users and potentially help share other sustainable lab ideas.

-          Another option is to avoid freezers altogether and try Room Temperature Sample Storage (RTSS). This is becoming more popular for DNA, RNA and plasmid samples, especially when shipping is required (thus eliminating the need for dry ice), or for collections in the field. This method can be used for reagents and diagnostic kits as well.

Correct freezer management and maintenance is one of the most important aspects of sustainable lab management. See the International Freezer Challenge and think about signing up for your lab.

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