Researchers at the Leibniz Institute for Photonic Technologies in Jena are developing a self-sufficient energy supply based on textiles. In the future, it will be even easier to supply power to mobile electronic devices worn close to the body, even when no external power supply is available. For this purpose, smart textiles use the emitted human body heat and convert it into electricity. Their additional cooling properties make the novel materials interesting for safety-relevant applications and at the same time ensure increased wearing comfort and enhanced well-being.
Miniaturized electronic devices worn on the body, so-called wearables, check vital functions, count steps or provide information about traffic and weather. In order to continuously supply these technical companions with electricity, researchers at the Leibniz Institute of Photonic Technologies (Leibniz-IPHT), together with a team from ITP GmbH in Weimar and the textile manufacturer E. CIMA in Spain, have developed a material that supplies the required energy independently of external power sources: Modern, intelligent textiles convert body heat into electricity using thermoelectric effects, which can be stored in a battery.
Power supply becomes independent
“Our vision is to use textile materials for energy generation. These smart fabrics can supply mobile devices for consumer electronics or health applications with energy in a flexible, demand-oriented and environmentally friendly manner. Smartwatches or fitness bracelets are worn directly on the body and can thus be supplied with power at any time. Vital parameters, for example, can be continuously measured and monitored,” explains Dr. Jonathan Plentz, head of the Photonic Thin Film Systems research group at Leibniz-IPHT.
People in focus for energy generation
To generate energy, the Jena researchers use thermoelectric generators that convert the body’s own heat into electrical energy (Seebeck effect). For this purpose, thin-film coatings in the form of aluminum-doped zinc oxide (Al:ZnO) are applied to textile fabrics as a thermoelectric functional layer. Using temperature differences between the user’s skin surface and the ambient temperature or industrial waste heat, the researchers were able to measure thermoelectric effects with powers of up to 0.2 μW. The electricity generated could be stored in a battery to meet the energy needs of electronic devices for health or sports. “This makes the energy supply of devices self-sufficient,” says Dr. Gabriele Schmid, project manager at Leibniz-IPHT.
Thermoelectric cooling for more safety and well-being
The smart textiles can do much more: The thermoelectric effect can also be used for cooling by means of electrical energy and thus be used for cooling applications and temperature regulation (Pel-tier effect). Plentz sees a possible area of application in the steel industry, for example: “Workers at blast furnaces are exposed to high levels of heat. Even after a short time, the body temperature rises significantly due to the surrounding heat. Intelligent cooling fabrics integrated into protective clothing can help to better regulate body temperature. In addition, the textile materials are characterized in particular by their air permeability, lightness and flexibility, which not only has a positive effect on thermal management, but also provides additional comfort in challenging working environments.”
In tests, Peltier cooling demonstrated a temperature difference of up to 12 °C, which is unique for textile thermoelectric elements. In the future, not only could process-critical areas in industry be temperature-controlled, but the smart textiles with their cooling properties would also provide even better protection for police and firefighters. Active regulation of body temperature with high textile comfort is also very important in the field of well-being and in the medical environment (for example, to reduce fever). The cooling of transport goods by means of functionalized textiles opens up further fields of application.
The projects were funded by the German Federal Ministry of Economics and Climate Protection (BMWi) as part of the Central Innovation Program for SMEs (ZIM).
G. Schmidl et al: 3D spacer fabrics for thermoelectric textile cooling and energy generation based on aluminum doped zinc oxide. Smart Materials and Structures 29, (2020) 125003, https://doi.org/10.1088/1361-665X/abbdb5
G. Schmidl et al: Aluminum-doped zinc oxide-coated 3D spacer fabrics with electroless plated copper contacts for textile thermoelectric generators. Materials Today Energy 21 (2021) 100811, https://doi.org/10.1016/j.mtener.2021.100811