Thursday, May 19, 2022

Researchers developed invisible, machine-washable solar cell technology for clothing

The Sun-powered Textiles project looked for ways to seamlessly combine solar cells and textiles. Photo: Anne Kinnunen/Aalto University

The discrete nature of the cells protects them – and makes the clothes more attractive, the physics and design researchers say. Promising applications include work and outdoor clothing, and curtains which react to changes in the amount of light.

Lasting power and efficient recycling

Any solar cell placed under the textile it adheres to has to have a significantly larger surface area than a cell that’s placed on top. A piece of regular fabric eats up roughly 70 percent of a cell’s capacity - with a more porous fabric the percentage is smaller.

Key factors in the ability of textiles to let light through them include the material, transparency and crosscut of the fiber, structure of the threads, thickness and weave of the fabric, colors and the finish. Light colors transmit light better than dark colors, but a pitch-black and completely opaque fabric can also work.

The commercial solar cells used in the study comprised of a single crystal and were made of silicon. They can detect light that is invisible to the naked eye, which is what most sunlight actually is. Infrared is an example of such invisible light.

Hiding the textile eats up some of the solar cell’s power but improves its durability, as it’s better protected from the outside world.

” A cell on the surface also dominates the look of the clothing, turning it into a robot-like piece of armor. A cell on the inside makes the product much more visually palatable and affords the opportunity to visually design the product according to the user's wants and needs,” Ilén says.

Researchers used materials that were made of only a single fiber and could be recycled as efficiently as possible. Electronic components can be removed from the fabric simply by first applying heat and then tearing them off.

” Previously solar cells have been weaved into the textiles as tiny pieces, which is a terrible idea in terms of recycling,” Halme says.

Humidity gauges and self-adjusting curtains

The amount of energy the cells receive depends on their size, quantity and location. The amount of energy that’s needed is mandated by what the use-application is. A crucial aspect is how frequently the application sends data. The most energy-hungry functions include sending information, doing calculations, and projecting on screens. That is why solar cells hidden in textiles won’t be enough to charge a smartphone or a smartwatch but are suitable for things like measuring temperature and humidity.

The research team thinks that work clothing is the most potential application for solar cell textiles right now. They are thicker than regular clothes, so the cells have limited impact on the clothing’s look and feel.

” Curtains are another great way to collect solar energy. They could detect the amount of light and adjust themselves accordingly,” says Ilén.

The aim of the research project was to develop a technical solution for use in many different applications. Halme advises those looking to think up more applications for the solution to consider what added value it can bring:

” Solar cells hidden under textiles are worth considering as energy sources for electrical equipment that, for one reason or another, has to adhere to textiles, look and feel like a fabric, be machine-washable, use as little power as possible, and whose battery is otherwise either too hard or too expensive to charge or replace.”

Elina Palovuori from the Department of Design also took part in the study.

The study was part of the Co-Innovation project funded by Business Finland, with Lindström, Foxa and Haltian as partners.

Source/Credit: Aalto University

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