Half a decade ago a scientist, an engineer and a businessman met in a Dublin backyard to conduct an experiment. They heated water in an electric tea maker, then poured it into a bisected segment of pipe. At the bottom of the half-pipe lay a length of wire, and one of the men held a ruler next to it. As the hot water gushed through the pipe, the wire shortened by several centimeters; when they poured cold water over it, it returned to its original length. The trio thought they might be onto something big.
The strange, morphing wire they tested was made of a material called shape memory alloy. Such metals (and some nonmetals) shift into and out of predetermined shapes when subjected to certain temperatures or to pressure or electrical stimuli. Invented 60 years ago, shape memory alloy has been used in fields such as biomedicine and aeronautical engineering. But one of its most stubbornly elusive applications is harvesting energy from hot water. Now those former backyard experimentalists—founders of a company called Exergyn—say they have created an engine that uses morphing wire and hot water left over from industrial processes to generate electricity.
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