Can Solar Power Go Truly Transparent?

Improving on somewhat opaque solar windows and related ideas, MSU team makes fully clear solar power concentrator

2 min read
Can Solar Power Go Truly Transparent?
Photo: Yimu Zhao

The idea of solar windows has been around for some time now, and a number of different approaches—from spray-on solar cells to just really thin film possibilities—are under investigation. Though these are promising, the underlying issue with many of the ideas is that in order for them to work they need to stop some amount of light from getting through the window. And tinted windows are fine, in some situations, but too much tint turns a window into a wall. But not with a new idea out of Michigan State University, where researchers have created a solar concentrator that, if the efficiency is revved up, would provide truly clear, glass-like generators of solar power.

The team, led by Yimu Zhao of Michigan State's department of chemical engineering and materials science, achieved this by "exploiting the excitonic nature of organic luminescent salts that provide perfectly tuned near-infrared-selective absorption and even deeper near-infrared emission." The organic molecules are tuned to absorb only ultraviolet and those near-infrared wavelengths; they then "glow" at a different infrared wavelength. That second wavelength light is guided by the material to the edge of the plastic substrate and converted to electricity by thin bits of standard photovoltaic cells.

That means that no electricity production is actually done in the middle of the cell. With other "transparent" solar ideas, they are actually marred by tiny wires, or just require tinted or colored glass to absorb any of the usable wavelengths of light. "No one wants to sit behind colored glass," said the senior author of the paper, Richard Lunt, in a press release. "It makes for a very colorful environment, like working in a disco.

We take an approach where we actually make the luminescent active layer transparent." The transparency is assured because the organic molecules only "glow" in infrared, which humans can't see. The result, at least for us: a clear window. Compare that image above to, just for example, New Energy Technologies' spray-on solar window, at left.

The key roadblock, as with most any solar power idea, is efficiency. The Michigan State team has its prototype up to only about one-percent efficiency, far below what might be considered useful. The researchers say they hope to get it up to around 5 percent, and if it proves cheap to mass produce, then that would be plenty for some applications. And obviously, clear solar power does have a lot of applications: the obvious ones are the skyscrapers glimmering in most big cities these days, but Lunt said this could also be applied for smartphones or tablets as a self-charging screen that doesn't affect visual quality.

"Ultimately we want to make solar harvesting surfaces that you do not even know are there," he said. 

Photo: New Energy Technologies

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Smokey the AI

Smart image analysis algorithms, fed by cameras carried by drones and ground vehicles, can help power companies prevent forest fires

7 min read
Smokey the AI

The 2021 Dixie Fire in northern California is suspected of being caused by Pacific Gas & Electric's equipment. The fire is the second-largest in California history.

Robyn Beck/AFP/Getty Images

The 2020 fire season in the United States was the worst in at least 70 years, with some 4 million hectares burned on the west coast alone. These West Coast fires killed at least 37 people, destroyed hundreds of structures, caused nearly US $20 billion in damage, and filled the air with smoke that threatened the health of millions of people. And this was on top of a 2018 fire season that burned more than 700,000 hectares of land in California, and a 2019-to-2020 wildfire season in Australia that torched nearly 18 million hectares.

While some of these fires started from human carelessness—or arson—far too many were sparked and spread by the electrical power infrastructure and power lines. The California Department of Forestry and Fire Protection (Cal Fire) calculates that nearly 100,000 burned hectares of those 2018 California fires were the fault of the electric power infrastructure, including the devastating Camp Fire, which wiped out most of the town of Paradise. And in July of this year, Pacific Gas & Electric indicated that blown fuses on one of its utility poles may have sparked the Dixie Fire, which burned nearly 400,000 hectares.

Until these recent disasters, most people, even those living in vulnerable areas, didn't give much thought to the fire risk from the electrical infrastructure. Power companies trim trees and inspect lines on a regular—if not particularly frequent—basis.

However, the frequency of these inspections has changed little over the years, even though climate change is causing drier and hotter weather conditions that lead up to more intense wildfires. In addition, many key electrical components are beyond their shelf lives, including insulators, transformers, arrestors, and splices that are more than 40 years old. Many transmission towers, most built for a 40-year lifespan, are entering their final decade.

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