a team of researchers at the king abdullah university of science and technology (kaust) in thuwal, saudi arabia have created a new method for enhancing the power generation properties of thermoelectric generators (teg) by making them stretchable, which maximizes the temperature gradient.
kaust researchers have expanded on the standard thermoelectric generators. (wikimedia commons)
when one side of a thermoelectric material, such as bismuth telluride, is hot but the other is cold then the material spontaneously generates an electric voltage. the greater the distance between the hot and cold sides (the temperature gradient), then the more is generated.
according to an article republished on phys.org, kaust researchers wanted to move past the current standard of solid block of thermoelectric materials and envisioned stretchable teg that could achieve higher power outputs.
“[the] team made the flexible tegs by coating bismuth telluride or antimony telluride onto a helically shaped flexible paper or polymer substrate,” the article explained. “this helical architecture is what allowed the teg to flex and stretch in any direction while maintaining its mechanical integrity.”
the best results came from a simple spiral made from a paper substrate, which had a lower thermal conductivity than polymer, which generated twice as much power when stretched than when laid flat.
there are many applications being considered for thermoelectric generators including wearables, energy storage, and even using teg in ships and automobiles that have some parts of the vehicle in sun and others cooler and in shade or underwater.
this research showed that it is not just the thermoelectric properties of the materials but also the architecture of the teg that can create higher levels of power.
the research was recently published in nano energy. the abstract stated:
“to achieve higher power output from a thermoelectric generator (teg), one needs to maintain a larger temperature difference between hot and cold end. in that regard, a stretchable teg can be interesting to adaptively control the temperature difference.
“here we show, the development of simple yet versatile and highly stretchable thermoelectric generators (tegs), by combining well-known inorganic thermoelectric materials bismuth telluride and antimony telluride (bi2te3 and sb2te3) with organic substrates (off-stoichiometry thiol-enes polymer platform – oste, polyimide or paper) and novel helical architecture (double-arm spiral/helix) to achieve over 100% stretchability.
“first, an oste-based teg design demonstrates higher open circuit voltage generation at 100% strain than at rest, although it exhibits high internal resistance and a relatively complex fabrication process. the second, simpler teg design, achieves a significant resistance reduction and two different structural substrates (pi and paper) are compared. the paper-based teg generates 17 nw (δt=75 °c) at 60% strain, which represents more than twice the power generation while at rest (zero strain). on the other hand, polyimide produces more conductive te films and higher power (~35 nw at δt=75 °c) but due to its higher thermal conductivity, power does not increase at stretch.
“in conclusion, highly stretchable tegs can lead to higher temperature gradients (thus higher power generation), given that thermal conductivity of the structural material is low enough. furthermore, either horizontal or vertical displacement can be achieved with double-arm helical architecture, hence allowing to extend the device to any nearby and mobile heat sink for continuous, effectively higher power generation.”
in other thermal news, kaust recently hosted a research conference that examined new combustion concepts in a continuation of the university’s research into new and cleaner combustion technology from plasma-assisted to electrically-assisted to advanced engine design.
the conference featured speakers from around the world on the mechanisms behind energy conversion, the fundamental chemistry of combustion, re-examining older concepts with new knowledge, technology advances, and managing current challenges.
“this conference was a bit of an experiment in that we brought together two communities that don’t ordinarily have much overlap. i think it was remarkably successful in generating conversations and potential collaborations,” william roberts, director of the kaust clean combustion research center, said in his closing remarks to the conference.
|