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What is
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he household refrigerator, sitting in the
corner of virtually every U.S. kitchen, has been
essentially the same for almost 100 years; air-
conditioning, based on the
same technology, almost 75 years.
But with the traditional vapor-
compression model reaching its limits
for advancement in efficiency, cooling
still eats up as much as one quarter of
U.S. daily energy consumption.
So, what if refrigeration systems
could be even better? What is the
future of cool?
Ames Laboratory, together with
the larger scientific community, believes it could be
magnetic cooling, a refrigeration system which exploits
the magnetocaloric effect—a temperature change of a
material caused by exposing it to a changing magnetic
field. Scientists have been attempting for years to push this
promising energy-efficient alternative over the gap between
fundamental research and applied technology.
This April, Ames Laboratory Chief Research Officer
Duane Johnson and scientist Vitalij Pecharsky helped
organize and participated in a workshop, Advancing
Materials for Efficient Cooling 2015, hosted by the
Maryland Nanocenter at the University of Maryland.
There, Pecharsky said, academia, national laboratory
scientists, and representatives from industry met to discuss
the current limitations of all three types of solid state
cooling based on one of three so-called caloric effects
—electrocaloric, elastocaloric, and magnetocalorics,
Pecharsky’s area of research interest.
“The first big question is whether this technology is still
worth pursuing, and the overwhelming sentiment is ‘yes,’ ”
said Pecharsky of the workshop. “The potential gains in
energy efficiency are too significant to ignore.”
Almost 20 years ago, Ames Laboratory scientists Karl A.
Gschneidner, Jr. and Pecharsky announced groundbreaking
progress in magnetic refrigeration—they discovered a
gadolinium alloy that allowed magnetocaloric cooling to
occur at room temperature, and a prototype refrigeration
system was built in partnership with Astronautics
Corporation of America Ltd.
Since then, research at Ames Laboratory and globally
has progressed, and there are occasionally demonstration
models put forth by industry, but there is still no currently
known commercially available product that uses a magnetic
cooling system.
“ ‘What needs to happen next?’ is one of the questions the
workshop was held to answer,” Pecharsky said.
“Everyone agrees we need better materials, it’s as simple
as that,” he said. “We have only a few families of materials
that have a reasonable magnetocaloric effect. Almost 20
years ago we called it giant—a giant magnetocaloric effect.
Now we know that it was just reasonable, even though at
that time it was just about the strongest known. We could
make a device with these reasonable materials, but in order
for them to become commercially successful, we will need
stronger effects that can be triggered by smaller fields.”
“We’re not quite there on the science side yet,” Duane
Johnson concurred. “We not only need to have a material
with these caloric cooling properties, but ones that are
controllable within a range of temperatures for which various
forms of cooling systems are used. That’s going to be key to
getting manufacturers interested.”
Even with a superior magnetic material, it’s a big leap for
manufacturers to make.
“For the consumer, the look and function of a magnetic
refrigerator wouldn’t change,” said Pecharsky. “But for
the manufacturer this is a radical departure, replacing
a compression unit with an entirely different system.
Current refrigeration technology is highly refined, relatively
inexpensive to build, and cost-effective to operate. Until
science can provide them and their consumers with a big
advantage, it won’t be financially viable for them to retool
production.”
That big advantage is a potential 20 to 30 percent
reduction in the energy cost of refrigeration.
“That’s roughly equivalent to the U.S. import of oil every
day, energy-consumption wise,” said Johnson. “The potential
economic and societal impact is enormous, if you think
about all the ways in which we use cooling technology.”
Pecharsky said the improvement in materials wouldn’t
need to be a large one to push the technology over to a
successful commercialization.
“If we could incrementally improve the magnetocaloric
effect using inexpensive and readily available elements, it
wouldn’t even begin to push the theoretical performance
limits of these materials and would still easily be the
more efficient technology,” said Pecharsky. “Scientifically
speaking, I am confident we can get there.”
That is where Ames Laboratory’s strength, basic energy
sciences, comes in, Johnson said.
“Materials design is a task best served by basic energy
research, and we have the history and expertise right here.
That’s where Ames Laboratory has a great opportunity:
for some forward-thinking basic energy sciences research
to come together with applied sciences and partner with
industry to bring a significant improvement to a technology
that nearly everyone uses.”
T
What is
B Y L A U R A M I L L S A P S
the
futureof cool?
The potential economic and societal impact
is enormous, if you think about all the ways
in which we use cooling technology.
Karl
Gschneidner
Vitalij
Pecharsky
Duane
Johnson
Science community discusses the state of magnetic cooling technology