AsianScientist (Oct. 3, 2017) – In a study published in the journal Nano Energy, researchers in Korea describe a wearable energy harvesting system capable of generating electricity simply by being attached to clothes, windows and the outer walls of buildings.
Energy harvesting is a diverse field encompassing many technologies that capture small amounts of energy that would otherwise be lost as heat, light, sound, vibration or movement. Thermoelectric generator (TEGs) refer to devices that convert waste heat energy, such as solar energy, geothermal energy and body heat into additional electrical power.
There has been great interest in the study of wearable TEGs that make use of the temperature difference between the body heat and the surrounding environment to produce electricity. However, the minute difference in temperature, ranging from just one to four degrees Celsius, is one of the main drawbacks of wearable TEG techniques, hindering their further commercialization.
In this study, a team of researchers led by Professor Kyoung Jin Choi in the School of Materials Science and Engineering at the Ulsan National Institute of Science and Technology (UNIST) has solved this low temperature difference by introducing a local solar absorber on a polymide substrate.
The solar absorber was a composite of titanium (Ti), magnesium (Mg) and fluorine (F) arranged as a five-period Ti/MgF2 superlattice. The structure and thickness of each layer was designed for optimal absorption of sunlight. They also included flexible bismuth (Bi)- and tellurium (Te)-based thermoelectric legs on the polymide substrate by dispenser printing with a special ink.
They reported that the wearable solar thermoelectric generator (W-STEG) comprising 10 pairs of thermoelectric legs had an open-circuit voltage of 55.15 mV and an output power of 4.44 μW when exposed to sunlight. Moreover, the temperature difference produced by this W-STEG also went as high as 20.9 degrees Celsius, which is the largest temperature difference of all wearable TEGs reported to date.
“Through this study, we have secured a ten-fold increase in temperature difference compared to conventional wearable solar thermoelectric generators,” said Ms. Yeon Soo Jung of the Graduate School of Materials Science and Engineering at UNIST. “Since the output of a TEG is proportional to the square root of the temperature difference, one can significantly increase the output with the help of this technology.”
“Our new W-STEG is expected to be useful in various applications, such as in self-powered wearable electronic devices,” said Choi. “It will also serve as a catalyst to improve the wearable electronic technology market in the future.”
The article can be found at: Jung et al. (2017) Wearable Solar Thermoelectric Generator Driven by Unprecedentedly High Temperature Difference.
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Source: Ulsan National Institute of Science and Technology.
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