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Register a new userNetwork of thermoelectric nanogenerators for low power energy harvesting
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We report the design, elaboration and measurements of an innovative planar thermoelectric (TE) devices made of a large array of small mechanically suspended nanogenerators (nanoTEG). The miniaturized TE generators based on SiN membranes are arranged in series and/or in parallel depending on the expected final resistance adapted to the one of the load. The microstructuration allows, at the same time, a high thermal insulation of the membrane from the silicon frame and high thermal coupling to its environment (surrounding air, radiations). We show a ratio of 60% between the measured effective temperature of the membrane, (and hence of the TE junctions), and the available temperature of the heat source (air). The thermal gradient generated across the TE junction reaches a value as high as 60 kelvin per mm. Energy harvesting with this planar TE module is demonstrated through the collected voltage on the TE junctions when a temperature gradient is applied, showing a harvested power on the order of 0.3 $mu$Watt for a 1 cm 2 chip for an effective temperature gradient of 10 K. The optimization of nanoTEGs performances will increase the power harvested significantly and permit to send a signal by a regular communication protocol and feed basic functions like temperature measurement or airflow sensing.
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We introduce herein the advanced application of low pressure plasma procedures for the development of piezo and triboelectric mode I hybrid nanogenerators. Thus, plasma assisted deposition and functionalization methods are presented as key enabling technologies for the nanoscale design of ZnO polycrystalline shells, the formation of conducting metallic cores in core@shell nanowires, and for the solventless surface modification of polymeric coatings and matrixes. We show how the perfluorinated chains grafting of PDMS provides a reliable approach to increase the hydrophobicity and surface charges at the same time that keeping the PDMS mechanical properties. In this way, we produce efficient Ag/ZnO convoluted piezoelectric nanogenerators supported on flexible substrates and embedded in PDMS compatible with a contact separation triboelectric architecture. Factors like crystal-line texture, ZnO thickness, nanowires aspect ratio, and surface chemical modification of the PDMS are explored to optimize the power output of the nanogenerators aimed for harvesting from low-frequency vibrations. Just by manual trigger-ing, the hybrid device can charge a microcapacitor to switch on an array of color LEDs. Outstandingly, this simple three-layer architecture allows for harvesting vibration energy in a wide bandwidth, thus, we show the performance characteristics for frequencies between 1 Hz to 50 Hz and demonstrate the successful activation of the system up to ca. 800 Hz
Wearable thermoelectric devices show promises to generate electricity in a ubiquitous, unintermittent and noiseless way for on-body applications. Three-dimensional thermoelectric textiles (TETs) outperform other types in smart textiles owing to their out-of-plane thermoelectric generation and good structural conformability with fabrics. Yet, there has been lack of efficient strategies in scalable manufacture of TETs for sustainably powering electronics. Here, we fabricate organic spacer fabric shaped TETs by knitting carbon nanotube yarn based segmented thermoelectric yarn in large scale. Combing finite element analysis with experimental evaluation, we elucidate that the fabric structure significantly influences the power generation. The optimally designed TET with good wearability and stability shows high output power density of 51.5 mW/m2 and high specific power of 173.3 uW/(g.K) at delta T= 47.5 K. The promising on-body applications of the TET in directly and continuously powering electronics for healthcare and environmental monitoring is fully demonstrated. This work will broaden the research vision and provide new routines for developing high-performance and large-scale TETs toward practical applications.
Optical properties of core-shell-shell Au@SiO2@Au nanostructures and their solar energy harvesting applications are theoretically investigated using Mie theory and heat transfer equations. The theoretical analysis associated with size-dependent modification of the bulk gold dielectric function agrees well with previous experimental results. We use the appropriate absorption cross-section to determine the solar energy absorption efficiency of the nano-heterostructures, which is strongly structure-dependent, and to predict the time-dependent temperature increase of the nanoshell solution under simulated solar irradiation. Comparisons to prior temperature measurements and theoretical evaluation of the solar power conversion efficiency are discussed to provide new insights into underlying mechanisms. Our approach would accelerate materials and structure testing in solar energy harvesting.
Energy harvesting from sun and outer space using thermoradiative devices (TRD), despite being promising renewable energy sources, are limited only to daytime and nighttime period, respectively. A system with 24-hour continuous energy generation remains an open question thus far. Here, we propose a TRD-based power generator that harvests solar energy via concentrated solar irradiation during daytime and via thermal infrared emission towards the outer space at nighttime, thus achieving the much sought-after 24-hour electrical power generation. We develop a rigorous thermodynamical model to investigate the performance characteristics, parametric optimum design, and the role of various energy loss mechanisms. Our model predicts that the TRD-based system yields a peak efficiency of 12.6% at daytime and a maximum power density of 10.8 Wm$^{-2}$ at nighttime, thus significantly outperforming the state-of-art record-setting thermoelectric generator. These findings reveal the potential of TRD towards 24-hour electricity generation and future renewable energy technology.
This work demonstrates preliminary results on energy harvesting from a linearly stable flutter-type system with circulatory friction forces. Harmonic external forcing is applied to study the energy flow in the steady sliding configuration. In certain parameter ranges negative excitation work is observed where the external forcing allows to pull part of the friction energy out of the system and thus makes energy harvesting possible. Studies reveal that this behavior is largely independent of the flutter point and thus that it is primarily controlled by the excitation. Contrary to existing energy harvesting approaches for such systems, this approach uses external forcing in the linearly stable regime of the oscillator which allows to control vibrations and harvest energy on demand.
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