Integrated approach to energy harvester mixed technology modelling and performance optimisation

An energy harvester is a system consisting of several components from different physical domains including mechanical, magnetic and electrical as well as the external circuits which regulate and store the generated energy. To design highly efficient energy harvesters, we believe that the various components of the energy harvesters need to be modelled together and in systematic manner using one simulation platform. We propose an accurate HDL model for the energy harvester and demonstrate its accuracy by validating it experimentally and comparing it with recently reported models. It is crucial to consider the various parts of the energy harvester in the context of a complete system, or else the gain at one part may come at the price of efficiency loss else where, rending the energy harvester much less efficient than before. The close mechanical-electrical interaction that takes place in energy harvesters, often lead to significant performance loss when the various parts of the energy harvesters are combined. Therefore, to address the performance loss, we propose an integrated approach to the energy harvester modelling and performance optimisation and demonstrate the effectiveness of employing such an approach by showing that it is possible to improve the performance of vibration-based energy harvester, in terms of the effective energy stored in the super-capacitor, by 33% through optimising the micro-generator mechanical parameters and the voltage booster circuit components

A novel fabrication process for capacitive cantilever structures for smart fabric applications

This paper reports, for the first time, capacitive freestanding cantilever beams fabricated by screen printing sacrificial and structural materials onto a fabric/textile. Unlike traditional weaving process, the device will be screen printed layer by layer with desired pattern onto the fabric substrate. Free standing structures will be fabricated directly onto fabrics rather than other methods such as bonding or embedding. In addition, a low temperature removable sacrificial material capable for the removal conditions on fabrics will also be reported

An Integrated Approach to Energy Harvester Modeling and Performance Optimization

This paper proposes an integrated approach to energy harvester (EH) modeling and performance optimization where the complete mixed physical-domain EH (micro generator, voltage booster, storage element and load) can be modeled and optimized. We show that electrical equivalent models of the micro generator are inadequate for accurate prediction of the voltage booster’s performance. Through the use of hardware description language (HDL) we demonstrate that modeling the micro generator with analytical equations in the mechanical and magnetic domains provide an accurate model which has been validated in practice. Another key feature of the integrated approach is that it facilitates the incorporation of performance enhanced optimization, which as will be demonstrated is necessary due to the mechanicalelectrical interactions of an EH. A case study of a state-of-the-art vibration-based electromagnetic EH has been presented. We show that performance optimization can increase the energy harvesting rate by about 40%

Screen printable flexible BiTe-SbTe based composite thermoelectric materials on textiles for wearable applications

This paper presents the optimization of a bismuth tellurium (Bi1.8Te3.2)-antimony tellurium (Sb2Te3)-based thermoelectric generator (TEG) fabricated by screen-printing technology on flexible polyimide (Kapton) and textile substrates. New formulations of screen printable thermoelectric pastes are presented with optimized composition, curing conditions, and printing parameters. The modifications of the thermoelectric materials enable them to be successfully deposited on flexible textile substrates. The optimized values of resistivity of the BiTe and SbTe thick films on Kapton were 9.97 × 10-3 and 3.57 × 10-3 ? · cm, respectively. The measured figure of merit at room temperature was 0.135 and 0.095 for BiTe and SbTe thick films on Kapton, respectively. The dimension of each printed thermoleg was 20 mm×2 mm×70.5 ?m. For the TEG on Kapton, the printed assembly comprising eight thermocouples was coiled up and generated a voltage of 26.6 mV and a maximum power output of 455.4 nW at a temperature difference of 20 °C. For a printed TEG on textile, the maximum power output reached 2 ?W from the same temperature difference

Flexible screen printed thick film thermoelectric generator with reduced material resistivity

This work presents a flexible thick-film Bismuth Tellurium/Antimony Tellurium (BiTe/SbTe) thermoelectric generator (TEG) with reduced material resistivity fabricated by screen printing technology. Cold isostatic pressing (CIP) was introduced to lower the resistivity of the printed thermoelectric materials. The Seebeck coefficient (α) and the resistivity (ρ) of printed materials were measured as a function of applied pressure. A prototype TEG with 8 thermocouples was fabricated on flexible polyimide substrate. The dimension of a single printed element was 20 mm × 2 mm × 78.4 µm. The coiled-up prototype produced a voltage of 36.4 mV and a maximum power of 40.3 nW from a temperature gradient of 20°C

Integrated approach to energy harvester mixed technology modelling and performance optimisation

An energy harvester is a system consisting of several components from different physical domains including mechanical, magnetic and electrical as well as the external circuits which regulate and store the generated energy. To design highly efficient energy harvesters, we believe that the various components of the energy harvesters need to be modelled together and in systematic manner using one simulation platform. We propose an accurate HDL model for the energy harvester and demonstrate its accuracy by validating it experimentally and comparing it with recently reported models. It is crucial to consider the various parts of the energy harvester in the context of a complete system, or else the gain at one part may come at the price of efficiency loss else where, rending the energy harvester much less efficient than before. The close mechanical-electrical interaction that takes place in energy harvesters, often lead to significant performance loss when the various parts of the energy harvesters are combined. Therefore, to address the performance loss, we propose an integrated approach to the energy harvester modelling and performance optimisation and demonstrate the effectiveness of employing such an approach by showing that it is possible to improve the performance of vibration-based energy harvester, in terms of the effective energy stored in the super-capacitor, by 33% through optimising the micro-generator mechanical parameters and the voltage booster circuit components

Textile manufacturing compatible triboelectric nanogenerator with alternating positive and negative woven structure

This paper reports the novel design of a textile-based triboelectric nanogenerator (TENG) with alternate woven strips of positive and negative triboelectric material operating in freestanding triboelectric-layer mode (woven TENG). It was fabricated using processes that are compatible with standard textile manufacturing, including plain weaving and doctor blading. In contrast to the conventional grating structure TENGs, which can operate only in one moving direction, this new design allows the woven TENG to operate in all planar directions. The implementation of the positive and negative triboelectric material also significantly improves the performance of the woven TENG compared to the conventional all-direction TENGs