Ceramics in Energy

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Flexible glass-fabric thermoelectric generator converts body heat to electric energy A team from the Korea Advanced Institute of Science and Technology (KAIST) has developed an “extremely light and flexible” glass-fabric-based thermoelectric (TE) generator that moves with the human body and harnesses heat while doing so. According to a KAIST press release, the technique employed by the team, headed by electrical A new flexible thermoelectric generator uses body heat to power wearable electronic devices. engineering professor Byung Jin Cho, “minimizes thermal energy loss but maximizes power output.” Unlike previous TE generators that used polymers, Cho’s concept has a self-sustaining structure sans the usual ceramic and alumina substrates that siphon off thermal energy. By employing in energy a technique similar to screenprinting, the researchers printed “synthesized liquidlike pastes of n-type (Bi2Te3) and p-type (Sb2Te3) TE materials” onto a glass fabric. “For our case, the glass fabric itself serves as the upper and lower substrates of a TE generator, keeping the inorganic TE materials in between,” says Cho. “This is quite a revolutionary approach to design a generator. In so doing, we were able to significantly reduce the weight of our generator (~0.13 g/cm2), which is an essential element for wearable electronics.” When worn as part of a wristband device, KAIST’s small generator— which measures just 10 cm by 10 cm— can produce ~40 mW of electricity based on skin temperature. “Our technology presents an easy and simple way of fabricating an extremely flexible, light, and highperformance TE generator. We expect that this technology will find further applications in scale-up systems such as automobiles, factories, aircrafts, and vessels where we see abundant thermal energy being wasted,” adds Cho. Their findings, “Wearable thermoelectric generator fabricated on glass fabric” (DOI: 10.1039/ C4EE00242C), are published in Energy & Environmental Science. n Advanced ceramic materials may provide hydrogen storage for fuel cells New research on advanced ceramics from the University of California, San Diego may offer a solution to the need for more effective solutions for hydrogen fuel storage. Most fuel cells use hydrogen as fuel. But hydrogen has low energy content by volume, so a substantial volume of hydrogen is needed for a portable fuel cell. Hydrogen also diffuses easily through many materials and is the culprit responsible for hydrogen embrittlement of common engineering alloys, including steels, aluminum alloys, and other nonferrous alloys. According to the United States Department of Energy’s Office of Energy Efficiency & Renewable Energy, an automotive hydrogen fuel cell using current tank storage capabilities would require a hydrogen tank bigger than a standard car trunk to travel just 300 miles. These limitations make current technologies impractical for long-term solutions. In addition to storage as compressed gas or as liquid in a tank, hydrogen also can be bound to advanced materials for storage. ACerS member Olivia Graeve has helped develop a new ceramic advanced material for just that purpose. Graeve and a team of scientists synthesized compounds of calcium hexaboride, and strontium and barium hexaboride. They demonstrated that combustion synthesis is a simple, lowcost production technique for making the new compounds. For combustion, they used a 750°F box furnace to heat boron with metal nitrates and organic fuels, which, when ignited, generates heat for the reaction. “It’s a very simple, nice process,” Graeve says in a UCSD press release. The team used the process to synthesize cages of boron molecules containceramics Credit: KAIST Scanning electron micrograph of hexaboride structures, at 5 μm (left) and 500 nm (right), that may provide a viable hydrogen storage solution. Credit: UCSD 16 www.ceramics.org | American Ceramic Society Bulletin, Vol. 93, No. 5


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