A membrane with nanometre-sized pores can capture low levels of heat energy to generate power.
Industrial plants are abundant sources of waste heat, but the relatively small temperature difference between the source (which is usually below 100 °C) and its surroundings makes it hard to exploit. Menachem Elimelech of Yale University in New Haven, Connecticut, and his colleagues used a water-repellant membrane that traps air in its pores and placed it between hot and cold water streams, creating a tiny air gap between the streams. The hot water evaporates on one side of the membrane, passes through the pores and condenses in the cold stream, creating hydraulic pressure that drives a turbine.
With a heat source at a temperature of only 60 °C, the device transferred power densities of up to 3.5 watts per square metre to a 20 °C fluid.
Nature Energy http://dx.doi.org/10.1038/nenergy.2016.90 (2016)