Shadows are the bane of renewable solar energy production.
Solar panels work by absorbing sunlight using photovoltaic cells. The cells, in turn, convert the sun’s energy into DC electricity for use.
As you may have guessed, the conventional photovoltaic cells require a steady source of light to function. That means the presence of shadows can degrade the performance of the cells significantly.
There’s just one small thing; shadows are omnipresent. Simply put, shadows are everywhere, and we can’t escape them.
But what if they could serve as a source of power?
The idea may seem like something from a sci-fi movie. However, the National University of Singapore (NUS) researchers have done just that — they generated electricity from shadows.
The prototype device is called a Shadow Effect Energy Generator (SEG), and it could transform how we generate renewable energy indoors.
Speaking on the project, research team leader Assistant Professor from NUS, Tan Swee Ching said:
“The contrast in illumination induces a voltage difference between the shadow and illuminated sections, resulting in an electric current. This novel concept of harvesting energy in the presence of shadows is unprecedented.”
The researchers described the prototype SEG device in their published paper in Energy & Environmental Science.
Generating Electricity from Shadows Around Us
To create the SEG device, the researchers arranged a series of thin strips of gold films on a silicon wafer. Then, they placed the ensemble on top of a flexible plastic base.
The device’s effectiveness depends on the contrast between shadow and light. Under shifting shadows, the SEG is twice as effective as conventional solar cells under similar conditions.
According to the researchers, passing shadows caused by clouds, waving tree branches, or the sun’s movement can generate 1.2V. That’s enough energy to power a digital watch.
“We also found that the optimum surface area for electricity generation is when half of the SEG cell is illuminated and the other half in shadow,” says physicist Andrew Wee. “This gives enough area for charge generation and collection, respectively.”
However, when the SEG is entirely in the shadow or completely in the light, it’s effectiveness reduces significantly. At this point, it generates a low amount of electricity to nothing at all, according to the NUS team.
Since the materials are readily available, the SEG is relatively cheaper to produce than typical solar cells. But the researchers are now working to reduce the cost further.
They wrote in the published paper:
“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 system, especially in buildings.”
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