New device generates electricity using shadows

News > World

By STEM Caribbean | Posted on July 8, 2020

A team of researchers at the National University of Singapore have created a device that can harvest energy from shadows. | Image by dima_goroziya from Pixabay

What comes to mind when you think of shadows? Besides being desirable for protection from the sun’s scorching rays, shadows are usually symbolic of darkness and fear. But they may one day be greatly valued considering the recent research done by researchers at the National University of Singapore (NUS). The team created a device that can generate electricity using shadows. The research was published in the scientific journal Energy & Environmental Science in April this year.

The device, which contains gold and is referred to as the shadow-effect energy generator (SEG), uses the illumination contrast between areas with light and areas with shadows to generate electricity. According to the research paper, when placed in a low-intensity shadow, the generator outputted enough energy to power an electronic or digital watch.   

Assistant Professor Tan Swee Ching, who led the research team, explains in a news release that “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.”  

Professor Tan has based his research on solar energy conversion in various organisms using the information to design and improve photovoltaic devices with higher conversion efficiency.   

In this study, he and his team took advantage of the illumination contrast caused by shadows as an indirect source of power. The contrast in illumination induces a voltage difference between shadowed and illuminated areas, resulting in an electric current. These findings are “unprecedented,” as stated by professor Tan, and have allowed for an entirely new field of shadow energy generation.   

During the study, the team found they were able to generate the most power when half of the device was illuminated while the other half was shadowed. This makes the SEG optimal for indoor usage. 

“The shadow-effect energy generators are particularly designed for indoor applications where shadows are persistent and in places where solar cells are deemed inefficient,” noted professor Tan.   

The team also discovered that the SEG has twice the efficiency of traditional silicon solar cells. One of the potential uses of the SEG is to provide reliable power generation for mobile and wearable devices since these devices are used both indoors and outdoors. While commercially available solar cells generate power outdoors, their energy harvesting efficiency drops significantly under indoor conditions with low light intensity and shadows.  

“With its cost-efficiency, simplicity and stability, our SEG offers a promising architecture to generate green energy from ambient conditions to power electronics, and as a part of a smart sensor systems, especially in buildings,” the researchers stated.  

The team plans to experiment with other materials instead of gold in the next phase of the research to lower the cost of the device. 



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