Keeping cool by twisting and coiling 'twistocaloric' yarns

Scientists have figured out how to induce a cooling effect in materials by a change in yarn or fiber twist, which they call "twistocaloric" cooling. Their "twist fridges" could offer a more energy-efficient and sustainable alternative for use in household refrigerators and air conditioners. A considerable portion of the world's energy budget is spent on cooling, which is largely done using vapor-compression refrigeration technologies. Although the technology is inexpensive and has been highly optimized over more than a century of use, it remains limited in terms of its efficacy and reliance on refrigerants known to be powerful greenhouse gasses. As the global need for cooling increase, so, too, does the need for higher efficiency, lower cost and more sustainable forms of refrigeration. Attractive refrigeration alternatives have included solid state electrocaloric and magnetocaloric materials, which cool in response to electric or magnetic fields, respectively. However, none have demonstrated the performance required for widescale application. By contrast, mechanocaloric materials - solids that undergo cooling through physical deformation - have demonstrated theoretical efficiencies nearly 20% higher than traditional vapor compression technologies. Here, Run Wang and colleagues show the high cooling potential of strands of mechanocaloric materials - like natural rubber, polyethylene fishing line and nickel titanium - when twisted, a phenomenon the authors call twistocaloric cooling. To demonstrate the applicability of the technology, Wang et al. built a twist-based refrigeration device - a "twist fridge" - which was able to cool flowing water by up to 4.7 degrees Celsius in a single cycle, highlighting its high cooling energy.

Credit: 
American Association for the Advancement of Science