How much can you wash a wearable PV device?

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From pv magazine global

Scientists from Nottingham Trent University have developed a novel and wearable flexible photovoltaic device, which they claim is extremely wash-durable. The solar-powered fabric textile was created by embedding micro crystalline silicon solar cells within the fibers of a textile through very thin copper wires.

In order to obtain what the researchers define as a drapable and soft fabric which is also resistant to machine washing, they decided to maintain the original shear properties and the low bending rigidity of the adopted PV device structure. “Therefore, the rigid PV elements were deployed in a discontinuous fashion within the fabric in yarn form by employing electronic yarn technology,” the research team explained.

The fabric demonstrator

Micro solar cells of 1.5 mm × 3.0 mm × 0.2 mm were soldered in parallel onto two multistrand copper wires and then encapsulated within cylindrical resin micropods. These discrete micropods with diameter of 1.6 mm were covered by a fibrous textile sheath to give them the typical appearance of a wearable PV device. “The textile sheath also allowed the yarn to take any color without significantly altering its optoelectronic performance,” the researchers said.

The fabric demonstrator, with a photoactive area of 44.5 mm × 45.5 mm, was assembled with 200 miniature cells. It has an open circuit voltage of 5.14 V, a maximum power output of 43.4 mW, and a 2.15 mW/cm2 power density. With these characteristics, the PV device is said to be able to provide enough energy to power a mobile phone.

A viable device

The scientists said their analysis has proved the developed fabric textile is viable for wearable applications where the clothing is exposed to different levels of sunlight and undergoes various mechanical deformations during its regular use. Furthermore, they believe that a bypass diode could be included at the end of each cell string to minimize the effects of partial shading.

The durability tests conducted on the solar cell embedded yarn incorporated fabrics have proved that they can maintain their performance even after 15 domestic machine wash cycles, 25 hand wash cycles, and 6000 abrasion cycles. “Research has shown that solar‐E‐yarns can be created in any color, with only a minor effect on their performance,” the paper notes. “The experimental results on power generation performance under various lighting conditions, for wash durability, moisture management behavior, and conformability to three‐dimensional shapes, validate the utility of the solution for regular clothing applications.”

The new device is presented in the study An investigation of a wash‐durable solar energy harvesting textile, published in Progress in Photovoltaics.