Advances in ULT Freezers

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 Advances in ULT Freezers

Scientists can keep samples super cold in greener ways

Keeping samples cold makes up a big part of today’s research scenario. Sometimes, the samples need to be very cold—in most cases as low as −86°—and that’s where ultralow-temperature (ULT) freezers come into play. New features make this possible in more environmentally friendly ways. At the same time, new devices provide features for convenience and sample integrity. In looking for a new ULT freezer, many factors should be considered. From footprint and minimum temperature to sample access and stability, today’s market offers advances worth examining. This article looks at a handful of options.

NuAire Blizzard −85C HC ultralow-temperature freezers include RS ports (shown at top) to provide communication to track the temperature over time. (Image courtesy of NuAire.)

A Minnesota blizzard

NuAire (Plymouth, MN) developed a family of Blizzard −85C HC (hydrocarbon) models. Four of these are uprights and one is a chest. “There are several advantages of NuAire HC freezers compared to previous-generation HFC (hydrofluorocarbon) refrigerant freezers,” says Buckner Richerson, vice president international sales at NuAire (Plymouth, MN), and he gives a thorough list. At the top of his list, Richerson notes, “All five models are also VIP (vacuum-insulated panel), which means each carries a smaller footprint, and that means it takes up less lab space.” Given all of the equipment that labs need today, space really matters. So, it’s great to get advanced ULT capability that takes up less room.

One key of modern ULT freezers is the method of cooling. “HC models use propane, R290, in the high-stage compressor system and ethane, R170, in the low-stage compressor system,” Richerson says. “However, they are not deemed flammable, because the quantity of each gas charge is well below the maximum allowed before the freezer must be labeled flammable.” Energy efficiency is often at the top of the ULT-want list for many scientists, universities, and companies. To keep samples so cold, it used to take much more energy than new freezers use. “NuAire HC models use up to 45% less power than our non-HC models,” Richerson says. “Greater efficiency of the system allows both compressors to cycle off for longer periods of time after reaching setpoint temperature.” These ULTs can also handle a 20% fluctuation up or down in voltage.

How a ULT freezer impacts a lab also matters. Making the inside of a freezer cold, for example, puts off heat. The new ULT freezers from NuAire, though, have what Richerson calls a “lower heat rejection rate.” But, it’s not just heat these devices give off, because they used to be pretty noisy. In fact, some ULTs were so loud that scientists preferred placing them outside of the lab. In NuAire’s new ULT line, however, Richerson points out that the “noise-pollution level has been greatly reduced to 50 decibels.”

Inside a lab or not, all freezers are opened to add or remove samples, and that warms up the freezer. This makes it crucial that a ULT can get back to its intended temperature quickly. “The pull-down time to setpoint temperature is much more efficient and provides better temp uniformity and reliability,” Richerson says of his company’s new line. To keep track of a sample’s environment, NuAire’s new ULT freezers also include a USB data port and R485 communication to track the temperature over time.

A shining star

The Thermo Scientific TSX Series ultralow-temperature freezers earned ENERGY STAR certification. (Image courtesy of Thermo Fisher Scientific.)

When shopping for a home freezer, many people look for a model that meets ENERGY STAR requirements. Thermo Fisher Scientific (Waltham, MA) built its Thermo Scientific TSX Series ultralow freezers to get that “star.” “ENERGY STAR certification is relatively new for ULT freezers,” says Tom White, global product manager at Thermo Fisher Scientific, “and we are quite proud to say that this entire portfolio meets those standards.”

Part of gaining ENERGY STAR certification came from powering the compressors, which use natural hydrocarbon refrigerants, with V-drive adaptive control. “This includes distinct controls that allow a freezer to adapt to different patterns of use,” White says. The compressors run at higher speeds when a ULT is being opened and closed, and at lower speeds when samples aren’t being accessed, such as overnight. “When a scientist comes back in the morning and opens the ULT door, the compressor speeds up for more capacity to ensure proper cooling to get back to temperature as soon as possible,” White says. All of the use and temperature data are stored in an onboard computer for record-keeping, and system diagnostics and can be downloaded.

The energy efficiency can be more than a nice addition—it can be a requirement in some organizations. “Groups in companies—like sustainability departments or officers—are starting to expect that new freezers are very efficient.” As mentioned above, noise matters, too. “The TSX line reduces noise by 20 times compared to previous generations of freezers,” White notes. “It’s approaching the level of a refrigerator in a house.”

With the TSX series, that efficiency also comes in four sizes. White describes those sizes based on the number of 2-inch cryoboxes that can be stored. For the TSX line, users can choose from a ULT freezer that holds 400, 500, 600, or 700 cryoboxes. “This ensures that this line can meet a customer’s needs,” White explains, “because space is money.”

The larger size works best at a biobanking facility. The smaller ones provide options where space is limited or where access to a lab, such as an elevator, limits the size of a ULT that can be installed. Even with a smaller outside, the TSX ULTs fit more inside. “Thin-wall design utilizing advanced vacuum insulated panels maximizes the storage space and minimizes the amount of lab footprint,” White explains. This allows scientists to store more sample with less lab space.

The green side of the TSX ULTs goes beyond the device itself. Thermo Fisher Scientific manufactures these at a Zero Waste to Landfill facility in Asheville, NC. “There are specific bins for specific materials in the facility,” White explains. “Making this work requires a culture, and everyone has to embrace it.”

With samples that need to be super cold, scientists can now also get greener, all while keeping samples safer than ever. It just takes a little shopping around to find the right size ULT that fits a lab, and still keeps data safe for decades.

Mike May is a freelance writer and editor living in Texas. He can be reached at [email protected]

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