They design a device that uses the contrast between bright and shaded areas to generate voltage and generate electricity. It could surpass solar panels in terms of efficiency.

Sunlight has been studied and used to generate energy for over 70 years. What if tomorrow we could also exploit the shadows? Researchers from the National University of Singapore have decided to give this optical effect a new role in harnessing renewable energies.

This research group created a device known as a Shadow Effect Energy Generator (SEG), which uses the contrast between lighted and unlit areas to generate electricity. The research was published in the scientific journal Energy & Environmental Science on April 15, 2020.

Shadows are everywhere. In conventional photovoltaic or optoelectronic applications, its presence is detrimental because it reduces the performance of the devices. In this work, we have exploited the contrast of light and shadow as an indirect source of energy.

Tan Swee Ching, head of the investigation team.

But how is it possible in practice to capture the energy of this effect? Scientists created a SEG prototype consisting of a transparent flexible plastic base and four solar cells, each made of a thin film of gold deposited on a silicon wafer. When the SEG is placed entirely in the sun or shade, it generates little or no electricity. However, when the light only reaches the middle of the body, there is a voltage difference between the lit and unlit sections. This difference, in turn, produces an electric current.

During laboratory testing of the system, the attenuated medium was able to power small devices such as a digital clock (1.2V). Show it twice the efficiency of a photovoltaic module of similar capacity and under the same conditions.

The team also demonstrated that the SEG can act as a self-powered sensor to monitor moving objects. When a shadow passes in front of it, it activates the sensor which records the presence and movement of any object. The team’s next step will be to replace gold with a cheaper material to further reduce the cost of the technology.

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