Sunlight slowly damages solar panels; researchers think they have found a natural shield - a red onion

Solar panels are built to capture sunlight, but constant exposure to ultraviolet (UV) rays slowly damages the protective materials that keep them working efficiently. This natural aging process reduces power output year after year and increases the long-term cost of solar electricity. As the United States continues to expand its renewable energy capacity, improving solar panel durability has become just as important as improving efficiency.

For years, scientists have searched for better ways to protect solar panels from the same sunlight they are designed to capture. While sunshine generates clean electricity, its ultraviolet (UV) rays also slowly damage the materials inside solar panels. Over time, that means lower efficiency, shorter lifespans, and higher costs for homeowners, businesses, and the renewable energy industry.

Now, researchers have found an unlikely ally in a common kitchen ingredient: the red onion. Scientists from Finland have developed a biodegradable protective film made from nanocellulose colored with extract from red onion skins. In laboratory tests simulating years of sunlight exposure, the natural coating blocked 99.9% of harmful UV radiation while outperforming conventional petroleum-based plastic films.


The discovery comes at an important time. The United States now has more than 270 gigawatts of installed solar capacity, with millions of homes relying on rooftop solar and utility-scale projects supplying a growing share of the nation's electricity. Yet sunlight-driven degradation continues to reduce power output every year, costing the industry billions of dollars over the lifetime of solar installations.

If this natural UV shield proves effective in commercial applications, it could help extend the life of next-generation solar panels, reduce plastic waste, improve renewable energy performance, and give new purpose to one of the world's most overlooked agricultural byproducts—red onion skins.

Why do solar panels still need plastic components?

Many Americans think solar panels are entirely "green," but every panel contains materials that help protect it from years of exposure to sunlight, rain, heat, and changing weather.

One important part is a UV-protective layer. Solar cells are designed to capture visible and near-infrared light because those wavelengths generate electricity efficiently. Ultraviolet (UV) light, however, can slowly damage sensitive layers inside the panel.

To prevent that damage, manufacturers typically use petroleum-based plastic films such as polyvinyl fluoride (PVF) and polyethylene terephthalate (PET). These materials have been trusted for decades because they are durable and can withstand harsh outdoor conditions for 25 years or longer.

While these plastics perform well, they are still derived from fossil fuels, which is why scientists continue looking for cleaner alternatives.

What did scientists discover about red onion skins?

The new research comes from scientists at the University of Turku, Aalto University, and Wageningen University & Research, who explored whether natural materials could replace traditional UV-filtering plastics in certain solar applications.

Their attention turned to an everyday kitchen leftover: the outer skin of red onions.These onion skins contain naturally occurring pigments that absorb harmful ultraviolet light while allowing most visible light to pass through. That combination makes them surprisingly effective as a natural UV filter.

Instead of using newly manufactured petroleum plastics, researchers extracted these pigments and tested them as protective coatings for solar-related technologies. The results showed the onion-based material blocked damaging UV radiation while still transmitting the wavelengths needed for solar devices to operate effectively.

Could onion skins replace the solar panels on your home?

Probably not—and that's one of the biggest misconceptions surrounding the study. The research is not about making better rooftop solar panels or boosting electricity production.

Today's residential and commercial solar panels are engineered to survive decades of intense sunlight, freezing temperatures, heavy rain, hail, humidity, and wind. Petroleum-based protective films have proven they can last throughout that long service life.

Natural biodegradable materials generally break down much faster, making them unsuitable for solar installations expected to operate for 25 to 30 years. Researchers say onion-based filters are instead better suited for technologies designed to have much shorter lifespans.

Where could this onion technology actually be used?

Rather than replacing panels on American rooftops, the biodegradable material could prove valuable in a growing range of small solar-powered electronics.

Scientists believe future applications could include:

• Environmental monitoring sensors
• Agricultural field sensors
• Smart farming equipment
• Disposable scientific instruments
• Internet of Things (IoT) devices
• Temporary outdoor monitoring systems

Many of these products operate for only months or a few years before being replaced. Using biodegradable materials could significantly reduce electronic waste compared with traditional plastic components.

As industries continue deploying billions of connected sensors worldwide, reducing the environmental impact of these small devices has become an increasingly important goal.

Why is this research important for the future of clean energy?

The study highlights a broader shift in renewable energy research. Scientists are no longer focused only on generating cleaner electricity—they're also examining every material used throughout a product's life cycle.

Agricultural waste has become an attractive area of research because it is abundant, renewable, and often discarded after food production. Red onion skins are generated in large quantities by food processors and commercial kitchens every year. Instead of ending up as waste, they could eventually become a useful raw material for biodegradable electronics.

Researchers hope innovations like these will help reduce dependence on fossil-fuel-derived plastics while creating more sustainable manufacturing practices.

Although the technology remains in the experimental stage, it reflects the growing interest in developing a circular economy where waste materials are transformed into valuable products.