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Researchers from the National University of Singapore are giving shadows a new meaning by way of harnessing common but often overlooked optical effect to generate electricity. This new concept opens new approaches in generating electricity in an eco-friendly way, using indoor lighting to power electronics.

Swee Ching Tan, a materials scientist at the National University of Singapore, said that "We can harvest energy anywhere on Earth, not just open spaces."

Together with his team, Tan created a novel device called a shadow-effect energy generator (SEG) that makes use of the contrast between lit and shadowed areas to generate electricity. The contrast in illumination can produce electric current as it induces a voltage difference between the shadowed and illuminated sections.

Shadows are often taken for granted, their presence in typical photovoltaic or optoelectronic applications where a steady source of light used to power devices degrades the performances of the device, Science News reported.

'Shadow-effect' Generates Electricity

Tan and his team placed a super-thin coating of gold in silicon, a typical solar cell material that when light shines on it energizes its electrons. When part of the device lies in shadow, the shadow-effect energy generator produces an electric current.

The activated electrons jump from the silicon to the gold. Tam's team reports that with part of the device shaded, the voltage of the illuminated metal increases in relation to the dark area and electrons in the generator flow from high to low voltage. It then creates a current that can power a gadget once it is sent to an external circuit.

The team was able to run an electronic watch in low light using eight generators. Moreover, the devices can also serve as sensors. For instance, a remote-controlled car passes by, and the shadow fell on a generator which generates electricity to light up an LED.

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Moving Towards Lower Cost of the SEG

The researchers took four months to conceptualize, develop and perfect the performance of SEG. On its second phase, the NUS will try using other materials in creating the device to reduce the cost of the device.

They are looking at developing self-powered sensors with a variety of functionalities. These include a wearable version of the SEG which is attached to clothing to harness energy during normal everyday life. Moreover, they are also trying to develop low-cost SEG panels for efficient harvesting of energy from indoor lighting.

More energy will be generated, the higher the contrast between light and dark. Tam and his team are now working on to boost the performance of the device by borrowing strategies from solar cells for gathering light. The greater light these generators provide, allow them to exploit shadows better.

Someday, this device will produce energy in the shadowy parts in the solar array, between skyscrapers or even indoors. This proves that anything can be useful, even shadows, Tam says.

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