New device can harvest energy from shadows, produce enough power to run a small watch

Shadows can do a lot more than scare people and help tell time on Earth, as it turns out. A device has now been engineered that can produce power using the difference in energy of a sunlit and shadowed surface area. The device makes use of the contrast between bright spots and shaded ones, producing a tiny current that could power small electronics today. “We can harvest energy anywhere on Earth, not just open spaces,” Swee Ching Tan, a materials scientist at the National University of Singapore, told ScienceNews. [caption id=“attachment_8463321” align=“alignnone” width=“1280”] Shadow effect energy generators could someday be used to produce power from the difference between bright spots and shady ones. Image: Royal Society of Chemistry[/caption] Tan and his team designed and developed the device, which they’re calling a “shadow-effect energy generator”. The device essentially has a layer of gold over a layer of silicon, which is typical of solar cells. Light shining on silicon energizes its electrons, which rush to the gold layer, producing an electric current when part of the device lies in shadow. When only part of the device is shaded, the voltage of the illuminated metal increases relative to the shaded region. This causes the electrons in the generator to flow from high to low voltage. And sending this voltage differential through an external circuit creates a current, which  could power a gadget, as per the team’s  report in Energy & Environmental Science. Apart from its usefulness in generating electricity, the device also worked well as a sensor. When a remote-controlled car passed by it, the car’s shadow fell on a generator, powering an indicator LED. This, in itself, could be a useful application of the device in both ground and space projects.

Using a series of 8 such shadow-effect generators, the team managed to run an electronic watch in low-power mode. The greater the contrast between light and dark, the more energy the generator provided. The team is looking to improve the device’s performance by looking into solar cell technology, particularly the advancements made in their light-gathering capabilities. The more light these generators absorb, the better they can exploit shadows and power other devices. The tiny generators could someday be used in the shadowy spots of solar arrays, between skyscrapers or even indoors, to generate power, per the team’s report. “A lot of people think that shadows are useless,” Tan says. But “anything can be useful – even shadows.”