In a few years, shadow will take the responsibility of supplying electricity to the world. A new device has been discovered which uses the contrast between bright spots and shade to develop a current.
Assistant Professor Tan Swee Ching said, “Shadows are omnipresent, and we often take them for granted. In conventional photovoltaic or optoelectronic applications where a steady source of light is used to power devices, the presence of shadows is undesirable, since it degrades the performance of devices. In this work, we capitalised on the illumination contrast caused by shadows as an indirect source of power. The contrast in illumination induces a voltage difference between the shadowed and illuminated sections, resulting in an electric current. This novel concept of harvesting energy in the presence of shadows is unprecedented.”
Tan and his team developed a device called a shadow-effect energy generator. This is made by placing a superthin coating of gold on silicon which a typical solar cell material. The shadow energy generator develops an electric current when a part of the device lies in shadow. This is similar to the working of a solar cell where light shining on silicon energizes its electrons.
According to Tan and his team, the energized electrons jump from silicon to the gold. With part of the device under the shadow, there is an increase in voltage of the illuminated metal relative to the dark area. Electrons flow from high voltage to low voltage. Sending them through an external circuit produces a current which can power a gadget.
The team used eight generators to power an electronic watch in low light.
The amount of energy produced is dependent on the contrast between light and dark. The team is working on different strategis of solar cells to use it in the device.
“A lot of people think that shadows are useless,” Tan says. “But anything can be useful, even shadows.”
After some years, we may have solar arrays producing electricity indoors.