Wearable Human Motion and Heat Energy Harvesting System with Power Management

A combined human motion and heat energy harvesting system are under investigation. Main parts of the developed human motion energy harvester are flat, spiral-shaped inductors. Voltage pulses in such flat inductors can be induced during the motion of a permanent magnet along its surface. Due to the flat structure, inductors can be completely integrated into the parts of the clothes, and it is not necessary to allocate extra place for movement of the magnet as in usual electromagnetic harvesters. Prototypes of the clothing with integrated proposed electromagnetic human motion energy harvester are created and tested. Voltage of generated impulses is shown to be high enough to be effectively rectified with commercially available diodes and ready to be stored; however, efficiency depends on properties of controlling circuit. In order to increase the sustainability of the energy source and its stability, an option for combining a motion energy harvester with a human body heat energy harvester is also considered. Thermoelectric generator that harvests electricity from waste heat of human body is presented, and generated voltage and power are compared at different activity levels and ambient temperatures. Power generated with thermoelectric generator located on lower leg reached up to 35 mW with peak voltages reaching 2 V at certain conditions. A possible power management set-up and its efficiency are discussed

The role of intermolecular forces in contact electrification on polymer surfaces and triboelectric nanogenerators

This research was supported by the European Regional Development Fund within the project ‘‘Hybrid energy harvesting systems’’ 1.1.1.1./16/A/013.The contact electrification of polymer interfaces provides an energy harvesting function to triboelectric (nano)generators (TEG). The electron transfer between contacted-separated surfaces has been considered as the main electrification mechanism for polymers in TEG. The electron transfer mechanism widely proposed in literature requires a contact between chemically different polymer materials, as well as subsequent increase of the specific contact area, which is commonly accomplished via nanostructuring. Herein, we showed that contact electrification could be controlled by intramolecular forces in the polymer bulk and adhesive forces at the contact interface, and the chemical contact between different polymers was not needed for contact electrification. The results also confirm the breaking of the covalent bond as a mechanism of the contact electrification of polymer insulators.ERDF 1.1.1.1./16/A/013; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Development of Wearable Multiple Source Energy-Harvesting System for Smart Clothing

An energy-independent wearable electronic system is being researched, where the energy required for its operation is obtained from human body movements and heat flow. The system power source consists of an electromagnetic motion energy harvester (mass up to 70 g, peak power reaching 38 mW depending on the intensity of movement), a thermoelectric harvester (mass 112 g, peak power up to 3 mW), power converters and a storage capacitor. The functional part of the system consists of a temperature and humidity sensors and a wireless data transmission module, while the energy-aware power management and the main function control is accomplished by a microcontroller, maintaining a safe input voltage range by adjusting the average consumption of the device. Only off-the-shelf components that provide greater configurability and could utilize a broader harvested voltage range were used. This study demonstrates that using a common energy storage element provides an energy flow stabilization effect that reduces the overall power instability, which can be a limiting factor for a single energy harvester system. The prototype was tested in controlled environment by walking on a treadmill and provided the necessary amount of energy for a sustained system operation even during motion pauses. Electrical energy storage efficiency of the system averaged at 17 %, with a peak efficiency reaching 21 %

Energy Generating Outerwear

This study investigates whether energy harvesting systems can be integrated or placed in/on clothing. The first part of the study includes general information about smart clothing that is already made with integrated energy systems and different types of energy sources to operate energy harvesting systems. During this study a male jacket prototype with an integrated planar structure electrodynamic converter was made. Experiments were done to verify the harvesting system according to system location, components (it was decided to experiment with 2 and 3 coil connections in series) and textile layer thickness. It was concluded that many factors affect the trajectory of permanent magnets and the amount of generated energy

EMF Shielding Effectiveness of Knitted Fabrics of Metallized Threads

The aim of the study is to clarify the EMF shielding effectiveness (SE) of textiles with metallized yarns depending on their combinations and the position of samples with respect to the radiation source. For developing of the samples 3 types of metallized threads were used. Single and double jersey samples were made with manual flat knitting machines (gauges E7 and E10). To measure SE, two methods were used. The samples were placed between the radiation source and the detector and radiated with frequencies of 1.161 GHz and 870 MHz. The average result of SE is 92 % for all knitted fabrics produced in this study

EMF Shielding Effectiveness Depending on Location of Yarns with Metal Filaments in Fabric

Using three types of yarns with metal filaments, textile samples with various arrangements of yarns and mutual combinations were made with an industrial loom. Textile shielding effectiveness (SE) characteristics were measured using a waveguide method and network analyzer with radiated frequency 1.161 GHz to identify metal filament fabrics with the highest SE

Femtosecond X-ray measurement of coherent lattice vibrations near the Lindemann stability limit.

The study of phase-transition dynamics in solids beyond a time-averaged kinetic description requires direct measurement of the changes in the atomic configuration along the physical pathways leading to the new phase. The timescale of interest is in the range 10(-14) to 10(-12) s. Until recently, only optical techniques were capable of providing adequate time resolution, albeit with indirect sensitivity to structural arrangement. Ultrafast laser-induced changes of long-range order have recently been directly established for some materials using time-resolved X-ray diffraction. However, the measurement of the atomic displacements within the unit cell, as well as their relationship with the stability limit of a structural phase, has to date remained obscure. Here we report time-resolved X-ray diffraction measurements of the coherent atomic displacement of the lattice atoms in photoexcited bismuth close to a phase transition. Excitation of large-amplitude coherent optical phonons gives rise to a periodic modulation of the X-ray diffraction efficiency. Stronger excitation corresponding to atomic displacements exceeding 10 per cent of the nearest-neighbour distance-near the Lindemann limit-leads to a subsequent loss of long-range order, which is most probably due to melting of the material