Cold Storage: How Low Can You Go?
Despite the “old tech” reputation of cold storage products, customer-driven innovation has been ongoing and steady.
Despite the “old tech” reputation of cold storage products, customer-driven innovation has been ongoing and steady. Alex Esmon, PhD, product manager of cold storage at Thermo Fisher Scientific (Asheville, NC), sees several notable trends.
The first is independent, wireless monitoring in cold chaining and cold storage. “Independent” and “wireless” refer to monitoring systems that are not part of the onboard control and monitoring package. Wireless monitoring provides verification, validation, recordkeeping, and an independent means to confirm temperature status. Once strictly the domain of pharmaceutical and clinical labs, wireless monitoring is “jumping out” into other markets, according to Mr. Esmon. “What’s helped has been improvements in technology and usability over the past few years and the ease of setting up and managing a wireless system.”
“We’re now seeing wireless monitoring in academic labs, where it was considered a luxury,” Esmon says. “Wireless will continue to grow as customers begin to understand, and put a dollar value on, the criticality of their samples.”
Purchasers of cold storage systems increasingly view that equipment as a way to store samples safely and securely with maximum capacity, peace of mind, accessibility, and compatibility with accessories such as wireless monitoring. The trend is driven by sustainability officers, compliance officers, and end users who demand improvements that will provide lower energy cost, greater capacity, and better performance. And, Esmon says, it extends from typical refrigerators and freezers to ultra-low temperature units and cryopreservation.
Cold sample prep?
Esmon’s second observation is the view of refrigeration as a form of sample preparation—usually for cells, bone marrow, and blood that is about to undergo cryopreservation. The operative term for this type of device is “controlled rate freezer.”
Low temperature is not viewed as an independent sample preparation method, but Esmon explains why this view is valid: “Controlled-rate freezers take samples from point A to point B not for long-term storage, but to enable the subsequent process and thereby confer maximum viability at the other end.” Therefore, these devices provide speed, consistency, and uniformity to the freezing step, which is, thermodynamically speaking, chaotic.
For example, if a bone marrow sample is placed directly in the cryopreservation tank, the latent heat of fusion will cause a temporary spike in temperature that will adversely affect the cells’ subsequent viability. A controlled-rate freezer compensates for the heat of fusion that water gives up when it turns to ice. The result is rapid but very linear freezing with minimal loss of viability. “As biobanking grows, the use of controlled-rate freezers for sample prep will grow as well,” Esmon tells Lab Manager.
Innovation within a mature marketplace
Dennis O’Brien, product service manager at The Baker Company (Sanford, ME), notes that vendors continue to innovate with compressor technology—particularly on ultra-low-temperature units. Cascade compressors, which use one compressor to reach an intermediate temperature and a second compressor to reach a set temperature, have been around for a while. One goal of advanced ultra-low designs has been to keep the compressors and motors that pump refrigerant through the system running cool and not overheating. “When they overheat, oils inside the units get hot and eventually cause seizures,” O’Brien says. “It’s directly analogous to an automobile heating system.”
Ultra-low-temperature devices are the most dynamic segment of the cold storage market and a prime area for innovation, according to Jean Fallacara, president and CEO, Z-SC1 Biomedical (Montreal, PQ). While what Fallacara calls “pharmaceutical” refrigerators are improving incrementally through improvements in design, ergonomics, and control, ultra-low devices have been undergoing steady engineering improvement.
Another area of innovation is in compressor gases. The Chinese firm Haier is believed to be testing up to six different gases to achieve low temperature and stability that is unmatched in current ultra-low units. The current “record” for low temperature, achieved by Z-SC1 with a mixture of compressor gases, is about -100ºC.
The performance of ultra-lows is often measured by efficiency, temperature capability, and recovery speed. Individually, these factors need not be deal-killers. Fallacara notes that many samples do not require the theoretical or even the practical low temperatures advertised by manufacturers: “Samples that are typically stored at -86ºC can be safely maintained at -70ºC without deterioration.”
Manufacturers are also experimenting with insulation as a way to achieve higher efficiency and lower operating costs while providing greater capacity. A recent trend has been to improve vacuum insulation panels (VIPs) to reduce the size of cold storage units. Meant to replace bulky foam insulation, VIPs consist of rigid walls filled with a poorly heatconductive material such as glass fiber or aerogels. Z-SC1 has tweaked this idea by injecting a thin layer of foam between panels and creating a vacuum to improve insulation without increasing thickness.
Baker’s Dennis O’Brien advises potential customers to consider capacity, temperature, temperature recovery time, and the cooling unit’s efficiency under their lab’s normal operations. Laboratory design and layout are factors as well. “If you don’t have a room large enough for several freezers, or if the unit is sitting next to a window that receives direct sunlight or is so close to a wall that ventilation is a problem, you might think of purchasing a unit that is not affected by ambient temperature,” he says.
After lab design, site layout, or footprint can affect the suitability of a particular freezer. It is too late to consider this factor once the unit is at the loading dock. Baker sends professionals to potential customers’ labs to perform a site assessment of widths, heights, and angles of passageways and doorways, the presence of equipment that might require moving, and the layout of the proposed location.
O’Brien stresses that while freezers are low maintenance, usage (particularly opening and closing doors) creates a need for low-level care. Door seals and gaskets should be inspected and, if necessary, cleaned every few days to prevent ice buildup. He warns, “If you don’t do this, ice will be the width of a pin one day; then the width of a pencil; and before you know it, the size of a baseball bat, and you will no longer achieve a seal.”
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