• University of Surrey researchers create flexible energy harvesters
• Based on a new model of Triboelectric Nanogenerators (TANGs)
• Static energy created by users can power wearables
• Team hopes commercial products could be ready in a few years

The University of Surrey is home to the world-leading 5G Innovation Centre, but that’s not its only interest in comms technology. Researchers have today announced that they have developed wearable ways to “be your own battery”, allowing people to act as their own power source by wearing smart shirts and shoes that harvest and store electricity.

This isn’t the first attempt at creating alternative power sources for portable devices, and we’ve seen several ideas that feature everything from mini turbines to skin contacts and sweat collectors. To date, none have progressed to the production line.

What the scientists at Surrey have done is create wearable power sources known as Triboelectric Nanogenerators (TENGs), which are energy harvesting devices that convert the movements of materials that produce static charge into usable electricity.

When someone wears a TENG while walking or running, it harvests the mechanical energy from the movement and converts it into electricity. This can then be stored in batteries or supercapacitors, and used to charge mobile phones or power medical devices and wearables.

The research group has created a new model of the original TENG concept, which was originally invented by Professor Zhong Lin Wang at Georgia Tech in the US. The researchers’ new model has improved sensors and energy generating devices which can be made into wearable applications, such as sewn into a T-shirt like a patch, or attached inside a pair of shoes.

The university says that TENGs could also be useful in developing countries, especially in remote locations where the main grid cannot reach, to power equipment such as radios, wireless communication devices, and medical equipment. Subsequently TENGs could also provide the household power requirements using large scale TENG networks.

“TENGs provide the wearer with a self-powered system so they can generate their own power for their energy needs, just with everyday movements, in a cost-effective way,” said University of Surrey PhD student Ishara Dharmasena, lead scientist in the project. “We’re very pleased that our research has laid a platform for developing highly efficient TENGs.”

TENGs could also be used in a sensor pad on a pavement that would light streetlamps by the energy created when stepped on by pedestrians, or placed inside a car tyre which would connect to the vehicle’s battery to create electricity.

“Wearable TENGs can be made from natural fabrics, such as cotton or wool, so the idea is carbon-friendly and a “renewable” technology, and could be used for years,” said Professor Ravi Silva, director of the Advanced Technology Institute (ATI) at the University of Surrey. “We’re looking forward to creating systems to generate power that have the advantages of being portable, autonomous and self-powered.”

Previous models were restricted to known simple geometries and used a parallel plate capacitor model, so practical use was very limited. The new model is generic and can be modified to a wide range of geometries and surface topographies – such as fabrics. The team is hopefully that its version of TENGs will be available in shops within the next few years – and looking ahead a bit further, they could also be used to harness wind and wave energy to help provide grid power for industrial and household use.

A new study conducted at the ATI uncovered many new features by producing a new theoretical model of the devices, supported by experimental observations. The study focused on the behaviour of the electric fields in the TENGs which allowed the researchers, for the first time, to accurately predict the output behaviour of contact-mode TENGs. This subsequently enabled precise design and efficient construction of TENG energy harvesters suitable for different applications. For the technical-minded, there’s plenty more over at the Royal Society of Chemistry.