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Thermoelectric materials near production scale
Researchers at Fraunhofer Institute
for Physical Measurement Techniques
IPM, Freiburg, Germany, show that half-
Heusler compounds—highly suitable ma-
terials for thermoelectric processes—can
be produced significantly more efficiently
and cost-effectively than before. “Half-
Heusler compounds fulfill almost all of
the necessary criteria,” explains project di-
rector Benjamin Balke at the University of
Mainz. “The alloys consist of a wide range
of materials, nickel being one, and are
much more environmentally friendly than
previous materials, possess good thermoelectric properties, and withstand high temper-
atures.” Researchers achieved a ZT value of 1.2, which corresponds to the best published
values for half-Heusler compounds so far, according to the team. It is crucial for indus-
trial applications to attain the efficiency values achieved in the lab during actual mass
production.
Could rainfall power cell phones?
Georgia Tech, Atlanta, researchers are developing a family of power generators that
take advantage of the triboelectric effect to produce small amounts of electricity for
portable devices and sensors. Professor Zhong Lin Wang is using the triboelectric effect to
create surprising amounts of electric power by rubbing or touching two different materi-
als together. He believes the discovery could power mobile devices such as sensors and
smartphones by capturing the otherwise wasted mechanical energy from sources such as
walking, wind currents, vibration, ocean waves, or cars driving by.
“The fact that an electric charge can be produced through triboelectrification is well
known,” Wang explains. “What we have introduced is a gap separation technique that pro-
duces a voltage drop, which leads to a current flow in the external load, allowing the charge
to be used. This generator can convert random mechanical energy from our environment
into electric energy.” Wang and his research team report that a square meter of single-layer
material can now produce as much as 300 W. They have found that the volume power den-
sity reaches more than 400 kW/m3 at an efficiency of more than 50%. For more information:
Zhong Lin Wang, 404/894-8008, , .
Test facility to improve wind turbines
Premature failures of mechanical systems have a significant impact on the cost of wind
turbine operations and the total cost of wind energy. The DOE’s National Renewable En-
ergy Laboratory (NREL), Golden, Colo., added a new 5-MW Dynamometer Test Facility
at its National Wind Technology Center (NWTC). The facility is capable of testing drive-
trains up to 5 MW—large enough to test virtually any land-based turbine—and employs dy-
namically variable loading capabilities that allow researchers to better simulate turbine
field conditions. A dynamometer system replaces the rotor and blades of a wind turbine and
allows researchers to control the turbine drivetrain’s mechanical and electrical systems
while simulating normal and extreme operating conditions.
The facility incorporates a non-torque loading system into
the testing regimen, a hydraulic device that allows for simu-
lation of both the rotational and bending loads that a wind
turbine rotor places on a drivetrain.
A visitor looks at the high-speed driveshaft on the new
dynamometer at the NWTC’s 5-MW Dynamometer Test Facility.
Courtesy of Dennis Schroeder.
ADVANCED MATERIALS & PROCESSES • FEBRUARY 2014 12
ENERGY TRENDS
briefs
U.S. Department of Energy,
Washington, D.C., announced more
than $13 million for five projects to
strengthen domestic solar
manufacturing and speed
commercialization of efficient,
affordable photovoltaic and
concentrating solar power
technologies. As part of the DOE’s
SunShot Initiative, these awards
will help lower the cost of solar
electricity, support a growing solar
workforce, and increase U.S.
competitiveness in the global clean
energy market.
Researchers at The University of
British Columbia, Canada,
discovered a universal electronic
state that controls the behavior of
high-temperature superconducting
copper-oxide ceramics. The work
reveals the universal existence of
so-called “charge density
waves”—static ripples formed by
the self-organization of electrons
in the material’s normal state.
These ripples carry the seeds out
of which superconductivity
emerges. The findings suggest the
existence of a universal charge-
ordering that is common to all
cuprate materials, and uncover its
connection to the emergence of
superconducting behavior. The
work also proves that two
techniques—resonant x-ray
scattering and scanning tunneling
microscopy—can be used to
probe the mysteries of charge
density waves. .
Copper-oxide superconducting
pellet levitating over a magnetic
track. Courtesy of UBC Science.
Individual components of thermoelectric mod-
ules are only a few millimeters in size. They are
cut from specific alloys such as half-Heusler
compounds. Courtesy of Fraunhofer IPM.