One of four types tested by NIST researchers, this top-mount refrigerator freezer was outfitted with three thermocouples in each compartment, sampling the temperature every 30 seconds. Credit: NIST |
In
tests of four different types of new refrigerators, National Institute
of Standards and Technology (NIST) researchers found that ice makers
increased rated energy consumption by 12 to 20 percent. About
three-fourths of that additional energy cost is due to the electric
heaters used to release the ice bits from the molds.
With
only one-fourth of the extra energy actually used to cool and freeze
water, “there are substantial opportunities for efficiency improvements
merely by optimizing the operations of the heaters associated with the
ice makers” or by introducing a more efficient alternative technology,
report NIST mechanical engineer David Yashar and guest researcher
Ki-Jung Park.*
Since
refrigerators account for 8% of the total energy consumed by 111
million U.S. households according to the Department of Energy, the
potential savings are significant.
Currently,
ice maker energy consumption is not reflected in federal minimum
efficiency standards for refrigerators or in the voluntary Energy Star
program, which requires energy usage to be significantly lower than the
regulatory limit.
DOE,
which helped to fund the NIST study, has announced that it will
increase the minimum efficiency standard by 25% over the current level,
starting in 2014. DOE also intends to incorporate the energy used by ice
makers into their regulatory test. Because no widely accepted test for
ice makers was available when they announced these intentions, DOE plans
to add 84 kilowatt hours to the energy efficiency rating of every
refrigerator equipped with an ice maker, Yashar explains.
In all units tested, electric heaters used to free ice from molds accounted for about three-quarters of ice-maker energy consumption. Credit: NIST |
Once
a reliable, straightforward test is available, he adds, DOE will
eliminate the “placeholder” energy consumption and use actual ice maker
test results in efficiency ratings.
To
speed progress along this path, Yashar and Park evaluated several
different approaches to measure the energy consumption of ice makers.
Their goal was to identify a method that consistently yielded accurate
results but did not add substantially to the complexity of appliance
energy consumption tests under current regulations.
Yashar
and Park examined four refrigerators, which sampled a variety of ice
maker technologies. Their study used a uniform test setup, consistent
with current regulatory procedures, and measured the energy consumption
of the four units while their ice makers were actively producing ice
and, again, while the ice makers were not operational.
The
results point the way to a standard test methodology that appears
promising for several different ice maker technologies and
configurations. Next steps include sharing their approach with other
laboratories, which also will test ice makers and compare results for
similar units. Also, Yashar says he intends to evaluate the measurement
techniques on other styles of automatic ice makers.
*D.A.
Yashar and K.J. Park, Energy Consumption of Automatic Ice Makers
Installed in Domestic Refrigerators. NIST Technical Note 1697, April
2011.
