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Extreme Biobanking: How to Build and Operate a -80°C Walk-In Freezer

Posted by Sheri Gimigliano, MS on Jun 12, 2014 10:00:00 AM

Opening a door and walking into the equivalent of Antarctica takes preparation. Scientists studying climate can use instruments to measure extremely cold temperatures: NASA documented the lowest temperature on record, -93.2°C, in 2010 from a high ridge on the East Arctic ice sheet, using satellite data. But what if instruments won’t do the job? What if your employees have to work in such an environment?

-80C High Density Storage eBook

Research biospecimens are commonly stored at -80°C, but this usually occurs inside mechanical reach-in freezers that result in minor, transient exposure of workers to the extreme cold. However, if the freezer is the size of a large room, then employees must be specially equipped and protected. How do you protect workers handling research materials in an environment that has to be maintained at a temperature that is typical of winter in Antarctica? The first step is to team with an organization that is already expert in safely managing materials at ultra-low temperatures.

The cost of storing biospecimens at ultra cold temperatures (-80°C) is one of the most significant operational expenditures of a biorepository and affects the long-term sustainability of biobanks. Storage at ultra-low temperatures has relied predominantly on mechanical freezers, which have storage capacities ranging from 25 to 32 ft3, and will hold 23,000 to 47,000 cryovials, depending on their size. While these freezers may work well in smaller facilities where sample collections are limited, some aspects of these freezers can be problematic in the operation of larger, more complex biobanks. For instance:

  • These freezers typically include high stage and low stage compressors with a single condenser that may be susceptible to failure if ambient temperatures rise (ultra-low freezers using a free piston Stirling engine do not have compressors, but these are relatively new and to date few of these freezers are in use at biorepositories or biobanks).
  • Although mechanical ultra-low freezers have become more energy-efficient and offer greater storage capacity for a given footprint, these units still represent a high energy cost.
  • Mechanical freezers have a useful life of from 7 to 15 years, after which they must be replaced and/or compressors rebuilt.
  • The condensers release heat directly into the surrounding space, resulting in a need for excess HVAC capacity, especially in warmer weather, which adds to energy costs.
  • The expelled heat needs a minimum amount of space to efficiently dissipate, or the mechanical freezers will not function properly and may fail. This requirement creates the need for a larger footprint (for better air circulation) and fewer ultra-low units can be installed in a facility, compared with the number of -20°C freezers or refrigerators.

An alternative to stand-alone mechanical freezers is a walk-in freezer. Large, walk-in storage environments allow for space-efficient biospecimen storage in flexible configurations. These units may last a very long time with appropriate preventive maintenance and occasional replacement of the compressors, and can operate over extended years while exhibiting narrow windows of temperature fluctuation (+/- 5°C). Walk-in freezers are cooled by mechanical refrigeration units, but provide an advantageous ratio of storage space per compressor.

Fisher BioServices operates a repository facility for a client with more than 15 million samples, a large proportion of which was initially stored at ultra-low temperatures in more than 80 mechanical freezers. The maintenance and energy cost of these freezers, as well as the cost of replacing the aging units, was rising. In addition, the facility housing these specimens was nearing capacity. Automated ultra-low storage was considered, but the client’s inventory consisted of a variety of vial sizes, and the client questioned the reliability of automated units. At the client’s request, Fisher BioServices assisted in the design and construction of a 2,500 ft3 walk-in, ultra-low (-80°C) freezer that provided high-density, high-energy efficiency storage for approximately 40 percent of the client’s inventory.

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Because the client could identify such a large proportion of inventory that was primarily archival, it was determined that automation/robotics was not cost-effective. However, without robotic components to move samples in and out of the unit, repository staff would on occasion have to enter the unit, and Fisher BioServices, as part of assisting in the design and construction of the unit, also created and implemented a number of processes and designed some specialized equipment and software tools for the safe and efficient management of the specialized storage unit.

Are you looking for alternative ways to reduce savings in energy, maintenance, and replacement costs?

Are you considering designing and constructing an -80ºC walk-in freezer? 

Are you seeking ways to maximize technician time while protecting them from temperature excursion and exposure to ultra-cold temperatures?

We would love to hear from you about your experiences in our comment box below!

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