Tech UPTechnologyThis device produces electricity using shadows

This device produces electricity using shadows

Shadows are often associated with darkness and even uncertainty. Now, a team of researchers from the National University of Singapore (NUS) have put a positive spin on shadows by demonstrating a way to harness this common optical effect to generate electricity.

Scientists from the NUS Department of Materials Science and Engineering, as well as the NUS Department of Physics, created a device called a Shadow Effect Power Generator (SEG), which uses the contrast in lighting between illuminated and shaded areas to generate electricity. Their work has been published in the journal Energy & Environmental Science .

“Shadows are ubiquitous. In conventional photovoltaic or optoelectronic applications where a constant light source is used to power devices, the presence of shadows is undesirable, as it degrades the performance of the devices. In this work, we capitalize on the lighting contrast caused by shadows as an indirect source of energy. Contrast in lighting induces a voltage difference between shaded and illuminated sections, resulting in an electric current, “explained Tan Swee Ching, leader of the work.


Shadows and light, united to produce energy

According to experts, energy could be harvested from anywhere on Earth, not just in open spaces, as the new device exploits the contrast between bright spots and shadow to create a current that can power small electronic devices , no matter where .

The device was created by placing a super-thin layer of gold on silicon, a typical material for solar cells . Like a solar cell, the light that shines on the silicon energizes its electrons. With the gold coating, the shadow effect power generator produces an electric current when part of the device is in the shadow. The excited electrons jump from silicon to gold. By having part of the device in shadow, the voltage of the illuminated metal increases relative to the dark area and the electrons in the generator flow from high to low voltage. Then sending it through an external circuit creates a current that can power a device, the authors explain.

The SEG system, which can be manufactured at a lower cost compared to commercial silicon solar cells, is comprised of a set of SEG cells arranged in a transparent, flexible plastic film. Each cell itself is a thin film of gold deposited on a silicon wafer. Tests and experiments were conducted using the SEG to measure its performance in two areas: electricity generation and use as a self-powered proximity sensor.

Not only is SEG cheaper to manufacture compared to commercial silicon solar cells, it is also twice as efficient. The energy harvested from the SEG in the presence of shadows created under indoor lighting conditions was high enough to power a digital clock. Additionally, the team also demonstrated that the SEG can serve as a self-powered sensor for monitoring moving objects. When an object passes through the SEG, it projects an intermittent shadow on the device that activates the sensor (an LED, for example) to record the presence and movement of the object.

The greater the contrast between light and dark, the more energy the generator provides. Hence, the team is working to increase the performance of the device. Increasing the light that these generators absorb would allow them to better exploit shadows.

“Many people think that shadows are useless,” says Tan. But ” anything can be useful, even shadows .”

It is clear that this novel power generation concept could open up new approaches to generating green energy indoors and in low light for powering electronic devices.


Referencia: Qian Zhang, Qijie Liang, Dilip Krishna Nandakumar, Sai Kishore Ravi, Hao Qu, Lakshmi Suresh, Xueping Zhang, Yaoxin Zhang, Lin Yang, Andrew Thye Shen Wee, Swee Ching Tan. Energy harvesting from shadow-effect. Energy & Environmental Science, 2020; DOI: 10.1039/D0EE00825G

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