Could solar-powered headphones be the next must-have?

If you’re the type of person who’s forever forgetting to charge your wireless headphones, help may finally be at hand.

It comes as the first commercially available solar-powered headphones are now on sale. Models from Swedish firm Urbanista and German sports giant Adidas have solar panels built into the headbands.

Anyway, the flexible panels are made by another Swedish company, Exeger, which has spent the past decade working on making them light, thin and strong enough to get the job done.

Exeger boss Giovanni Fili says it’s both a matter of comfort and, more importantly, doing the right thing in terms of environmental protection.

“Charging – everybody hates it,” he says. “But every time you don’t charge [using mains electricity] it’s a good thing for the world.

“The new generation of young people expects to be offered the tools to do good [for the environment]and that’s what we offer.”

Exeger’s solar panels are called Powerfoyle, and they are only 2 mm thick. The technology is based on strips of titanium dioxide covered with natural color. In very simple terms, paint absorbs photons from light, which are then converted into electrons.

While only about half as efficient as standard silicon-based solar panels of the same size, titanium dioxide panels, in addition to being significantly thinner, are much cheaper and easier to manufacture.

The solar-powered headphones still have a built-in battery that can provide up to 80 hours of playback. That’s what Powerfoyle tape charges. Mr Fili says that currently the technology can generate an hour’s worth of power “from just 20 minutes of English or Swedish summer sun”.

However, the panels can also generate power from artificial light, such as interior lighting, so the idea is to always charge the headphones unless it’s in the dead of night. And the headphones still have a power outlet if you need backup power after heavy use.

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Mr Fili adds that solar panels are unlikely to be added to mobile phones any time soon, as many of us keep our phones in our pockets and therefore have no access to light. Instead, he envisions the panels being placed on people’s clothes and bags, and phones being charged from them.

The Finnish company Planno already produces fabrics that have built-in solar panels.

The company is led by Elina Ilén, who is also a professor in the Department of Textile and Paper Engineering at the Polytechnic University of Catalonia and a leading expert in wearable textile electronics.

Instead of making clothes that can charge your cell phone, the company is focusing on washable clothes with built-in solar-powered sensors. They can track various aspects of the user’s health, such as heart rate, temperature, posture, sleep quality and body fat levels.

“Although these solar cells produce enough energy to power wearable devices, placing a solar cell behind a textile will never have the same energy collection efficiency as a solar cell in direct sunlight,” says Ms. Ilén.

“Thickness, density, structure, color and finishing treatments of the textile will have an impact on the amount of energy harvesting potential.”

She adds: “Textile-based wearables are one of the best solutions for continuous health monitoring because product acceptance is easier to achieve. Patients already wear clothing, this technology can be hidden under fabric to ensure comfort and discretion.”

At Loughborough University, researchers are taking a different approach to energy-generating fabrics. Instead of using solar cells, they collect static electricity generated when a person moves and convert it into usable energy.

The technology is based on tiny energy converters called triboelectric nanogenerators (tengs). They are made from fibers such as cotton, polyester and nylon, which are covered with a polymer coating that attracts static. These flexible, stretchy and washable thongs can then be woven or knitted into the fabric of garments.

“Our group is investigating how we can use common textile materials and textile fabrication techniques to produce efficient tengas for wearable applications,” says project leader Ishara Dharmasena.

“The goal is to produce energy-generating textiles like T-shirts, bottom layers and pants that are very similar to our regular clothes, but capable of generating electricity or acting as sensors to measure body movement.”

Dr Dharmasena, a research fellow at the Royal Academy of Engineering and lecturer at Loughborough, adds that in the future tengs could be used in combination with solar panels to create hybrid energy-generating clothing.

Denise Wilson, author of the book Wearable Solar Systems, hopes that the market for solar-powered clothing will expand significantly in the coming years.

“I think we could benefit from more imagination when it comes to marketing wearable solar packs,” says Prof. Wilson, from the Department of Electrical and Computer Engineering at the University of Washington.

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“We have not yet fully utilized what they have to offer us in the global community.”

She adds that the biggest area for growth is likely to be clothing that can charge cell phones and other portable electronic devices. “For the average consumer, that can mean being able to charge on the go.”

But she adds that for such clothing to find widespread popularity, solar panel systems will need to last at least a year without significant loss of efficiency.