A research team from the University of New South Wales has developed an electronic device that converts infrared light – e.g. from the night-time heat given off by buildings – into energy.
Think of it as a solar panel for the dark featuring materials used in night-vision goggles (these are also from Australia).
Currently, a difference of 12.5°C between heat source and ambient temperature can help produce 2.26 microwatts per ㎡.
Room for improvement – but that was also true of the first photovoltaic cells.
And there are other ways of generating energy from heat.