In May 2011 at McLean Hospital, Belmont, Mass., a freezer failed that contained brains provided by Autism Speaks for research con- ducted by the Harvard Brain Tissue Resource
Center. The typically -80 C temperatures
climbed to about 7 C, which damaged over 54
samples. This raised awareness about the value
of keeping samples frozen.
Very low temperatures are needed to store
biological samples for research, such as cell lines.
And ultra-low-temperature (ULT) freezers can
keep samples at temperatures below -80 C.
In the ULT freezer market there’s a continued focus on sample protection. As users store
priceless samples, they need to have ULT freezers that provide them with quick recovery and
uniformity after door openings.
However, for most users, the trend is pointing
to energy efficiency and cost, as ULT freezers
cost as much to operate in a year as an average
Dale, Ill., cascade freezers require larger single or
dual compressors operating together to provide
temperatures below -50 C, which translates into
a higher energy requirement while still maintain-
ing rapid temperature recovery times.
Users of ULT freezers also want products
that will store their samples in the most efficient
manner by maximizing storage and footprint,
leading the industry to be dominated by
upright cascade refrigerant systems. Many of
these ULT freezers are built with larger capac-ities to hold more biological samples, usually
featuring 700 L of storage space that can hold
up to 60,000 1-mL vials.
The issue of dependability
Examples like the McLean Hospital sample
loss are frightening in the world of life science
research, and can cost work hours and money.
And while ULT freezer dependability will always
be an issue, many institutions have freezers on
standby, empty, ready to be loaded with frozen
products in case an existing freezer fails. However, many users still have concerns about freezer
temperature warm up. And in ULT freezers an
unexpected warm up can often lead to reduction of the viability or destruction of the samples or products stored in the freezer, which can
cost up to millions of dollars.
On the frontline of the dependability issue
are alarm and monitoring systems. These are
developed as cloud solutions that users can
check their freezer’s performance through their
smartphones or tablets. Some of these systems
provide exception reports, so if the temperature
rises above -70 C, there would be a notification
sent and a service call implemented. Other ULT
freezers units provide a USB port to provide
data logging capabilities.
The second aspect is in the reliability of the
freezer’s components. The compressors, the
air-handling system that moves the heat out
from the freezer and the motors are constantly
improved by vendors. This is exemplified by the
latest Panasonic ULT freezer, the Twin Guard.
The system, according to LaPorte, utilizes two
independent refrigeration systems so that if
one refrigeration system suffers a mechanical
fail, the second system can maintain ultra-low
temperatures. This freezer utilizes a modified
version of cascade technology called autoscade,
which Panasonic has successfully used in their
ULT freezer design for decades. The technology
allows Panasonic to use only two compressors
to provide two completed refrigeration systems
while providing energy savings comparable to
most ULT freezer technologies available.
The further advantage of the system is it can
use the power of both refrigeration systems to
quickly recover in the event of multiple door
openings or the addition of warm products.
When used for storage without multiple door
openings, both systems alternate back and forth
to maintain ultra-low temperature and provide
However, the irony is while there have been
significant efforts from vendors to build safety
nets around the dependability of ULT freezers,
the task is inherently difficult. All of these bells
and whistles are essentially built into a system
that’s inherently under a great deal of stress.
Cascade vs. Stirling:
The battle of the refrigeration systems
While cascade refrigeration has proven the preferred method of providing reliable low-tem-perature storage, a new ULT freezer developed
by Global Cooling, Athens, Ohio, the Stirling
Ultracold, has made a splash both in dependability and energy efficiency.
Refrigeration is defined as the transfer of
heat energy from a place where it isn’t wanted
to a place where it isn’t objectionable. In the
case of ULT freezers, that means removing heat
energy from the chamber and rejecting it into
the surrounding room or water chiller piping.
“The basic principal in achieving this requires
the refrigerant circulating in the walls of the
freezer to change from a liquid to a gas,” says
LaPorte. “This change of state will absorb heat
energy, as ‘cold’ is simply the absence of heat
energy.” The more refrigerant pumped through
the system and available to change state, the
more heat can be removed.
UxF -86 C freezer
is designed with
the latest refrigeration technologies
to reduce energy
usage by over 20%.
Under close scrutiny for dependability and energy efficiency, laboratory freezers are a staple
in many laboratory environments and offer new improvements.
according to the Univ.
of California, Davis.
So, anything that can
be done to mitigate
the energy use in an
ularly in the pharma,
biotech and private
to the bottom line.
ULT freezers are
high energy consumers relative
to their higher-temperature general freezer
counterparts, which operate around - 10 to -30
C. Although their methods of providing refriger-
ation are similar, according to Joe LaPorte, Direc-
tor of the Product Management Group, Panaso-
nic Healthcare Corp. of North America, Wood