Why do we Defrost Freezers if Ice is Insulating?
Last week we challenged the Freezer Challenge community to explain why freezers need to be defrosted if ice is insulating. A huge thanks to all who took the time to reply. You've all received bonus points on the Challenge! Today we're featuring two great responses. Jerry Stewart, lab manager of the Beierle lab at the University of Alabama, Birmingham wrote, "While yes, ice insulates...[t]he ice has a reverse effect in a freezer. Ice insulates around the coils, which must get colder than 0C in order to maintain a temperature below the freezing point of ice. This ice prevents [the] exchange of heat in the freezer with the coils. The compressor has to work harder ... to overcome the ice insulation around the coils... Temperature exchange in the freezer environment is achieved much more efficiently with little, to no ice buildup..." Samantha Clements from the Smith lab at the Scripps Institution of Oceanography at the University of California, San Diego added, "Ice buildup on freezers can inhibit even air flow throughout the freezer, creating an environment with both hot and cold spots which can affect freezer efficiency and also sample integrity. Removing ice ensures continued air flow and even cooling throughout the freezer. " We could not have said it better ourselves! We'd also like to recognize the University of Alabama, Birmingham and the University of California, San Diego's Green Labs Programs, as both of our featured responses came from labs that are Green Lab Certified. Thanks again to Jerry and Samantha for sharing this information! And remember - even if you didn't receive bonus points for answering the question, you're sure to receive Freezer Challenge points for defrosting your freezers.
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The Case for Removing Ice
We are often asked, if ice is insulating, and we want our freezers to stay cold, shouldn't we keep the ice? Shouldn't a frost-and ice-filled freezer use less energy? The answer to this is no. Ice build-up negatively impacts freezer performance and energy consumption. But this week, we're not going to tell you why. We're asking you to tell us why, for bonus points! Write to us at info@mygreenlab.org with your answers. Anyone with the correct answer - in your own words, don't just send us a link to a website please - will receive 3 extra bonus points on the Freezer Challenge score sheet. We will publish the best answers in our next blog post. Stay tuned... Cold Rooms Last week we wrote about sharing freezer/refrigerator space as a great way to reduce costs and save energy. Unlike freezers and refrigerators, cold rooms have long been a shared storage space. They are a great resource when used properly, so this week are exploring the best practices for cold room use. Best Practices for Cold Rooms:
Having a shared resource like a cold room is a great asset to any facility. If you're using a cold room, be sure to implement the best practices above as part of the Freezer Challenge. Although cold rooms aren't addressed specifically, they can be included in the Additional Information section for extra bonus points. The Future of Sharing The culture of cold storage ownership may be coming to an end. CU Boulder has implemented a successful ULT freezer sharing program, UC San Francisco is looking to move many of its samples to an off-site biorepository, and many pharmaceutical and biotech companies have begun to employ both strategies, asking their scientists to share local freezer space for frequently-used samples and to use biorepositories for samples that need to be accessed less frequently. CU Boulder's website details their ULT freezer sharing program, where researchers can rent freezer space for as little as 25 cents/month. Christina Greever, CU Boulder's Green Labs Program Assistant and Outreach Coordinator, says of the program, "Though the Shared ULT Freezer Program takes some time and effort to administer, we [CU Green Labs] feel that the benefits to the campus far outweigh the costs. The program is tackling culture change by encouraging labs to share their most precious equipment". Sharing freezer space not only helps reduce energy consumption, but it also reduces waste as well. By not purchasing new equipment, raw materials are not used to create something new, all of the resources that would have been used to run the equipment are not expended, the valuable space that the equipment would have occupied remains open for some other use, and the lab maximizes its economic resources. In addition, the equipment that is being shared is being used to its fullest potential. Sharing cold storage space should not be an innovative best practice. This Freezer Challenge, help make this a standard practice by opening up your (freezer, refrigerator) door to a colleague. The Most Energy-Efficient Freezer is... A Chest Freezer?! That's right. The most energy-efficient type of freezer is a chest freezer. Why is that?
There are two main reasons why chest freezers are more efficient: 1. When the door is opened on a chest freezer, all the cold air stays at the bottom of the chest and does not escape (because hot air rises). With upright freezers, cold air is more likely to escape from the bottom during door openings. This means that chest freezers that are used frequently stay colder with less effort from the compressor. 2. Chest freezers are often made out of plastic material and not stainless steel. Stainless steel conducts heat and is a less effective insulator. This is why chest freezers will often consume less than half of the energy of an upright freezer even if neither is being opened. Does this mean you should switch to a chest freezer? Not necessarily. There are many good reasons why upright freezers are so popular, ergonomics being one of them. But it does mean that if you have a chest freezer - even if it's a really old chest freezer - it's likely using very little energy compared to a new upright model. If it still works, and you're still using it, hang onto it and show it some love for quietly doing its job as efficiently as possible [it's Valentine's Day, we couldn't resist ;)]. |
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