Sounds like something from a sci-fi movie, but the recently revealed Shadow-Effect Energy Generator (SEG) is a real prototype device. The fascinating concept can help us transform the way in which renewable energy is generated indoors.
SEG uses the contrast between darkness and light to produce electricity. It consists of a series of thin strips of gold film on a silicon wafer, placed on top of a flexible plastic base.
While shadows are usually a problem for renewable solar power generation, here they are actually utilized to continue generating power. The technology – which is cheaper to produce than a typical solar cell, according to its developers – produces small amounts of power and can be used for e.g. Mobile gadgets.
“Shadows are ubiquitous and we often take them for granted,”
“In this work, we utilized the lighting contrast caused by shadows as an indirect power source. The contrast in lighting induces a voltage difference between the shade and the illuminated sections, resulting in an electric current. This new concept of harvesting energy in the presence of shadows is unprecedented. “
It is this contrast between shadow and light that really makes the SEG device efficient: under changing shadows, the Shadow-Effect Energy Generator is twice as efficient as conventional solar cells under the same conditions, the team discovered.
When SEG is completely in shadow or completely in light (when the voltages across the strips are all the same), it produces a very low amount of electricity or nothing at all.
With passing by shadows – caused by clouds or waving tree branches perhaps, or simply the movement of the sun – the device is capable of generating enough power (1.2V) to run a digital clock, the team demonstrated. This could also be increased in the future.
“We also found that the optimal surface area for electricity generation is when half of the SEG cell is illuminated and the other half in shade, as this provides enough space for charge generation and collection, respectively,” said NUS physicist Andrew Wee.
SEG also acts as a sensor: it can detect shadows passing over it to detect the movement of objects passing. It can for example. Have different applications in connected smart home devices and can even be used to create self-powered sensors.
However, there is still plenty of work to be done – the researchers will now try to reduce the cost of their SEGs, perhaps by replacing the gold film with another material. It can also be customized for portable use further down the line.
In the future, the more ways we have to produce renewable electricity, the more imaginative we can get with our gadgets and the less we have to rely on fossil fuel for energy production. Shadows can now be added to the list of alternative energy sources, along with snowfall and the cold in outer space.
“With its cost-effectiveness, simplicity and stability, our SEG offers a promising architecture to generate green energy from ambient to power electronics, and as part of a smart sensor system, especially in buildings,” the researchers write in their published article.
The research has been published in Energy and environmental science.