A galloping energy harvester with flow attachment
14 Mar 2019-Applied Physics Letters (AIP Publishing LLC AIP Publishing)-Vol. 114, Iss: 10, pp 104103
TL;DR: In this article, the galloping energy harvester, a curved blade oriented perpendicular to the flow, is capable of producing self-sustained oscillations at uncharacteristically low wind speeds.
Abstract: Aeroelastic energy harvesters are a promising technology for powering wireless sensors and microelectromechanical systems. In this letter, we present a harvester inspired by the trembling of aspen leaves in barely noticeable winds. The galloping energy harvester, a curved blade oriented perpendicular to the flow, is capable of producing self-sustained oscillations at uncharacteristically low wind speeds. The dynamics of the harvesting system are studied experimentally and compared to a lumped parameter model. Numerical simulations quantitatively describe the experimentally observed dynamic behaviour. Flow visualisation is performed to investigate the patterns generated by the device. Dissimilar to many other galloping harvester designs, the flow is found to be attached at the rear surface of the blade when the blade is close to its zero displacement position, hence acting more closely to aerofoils rather than to conventionally used bluff bodies. Simulations of the device combined with a piezoelectric harvesting mechanism predict higher power output than that of a device with the square prism.
TL;DR: In this article , the state-of-the-art advances on flow-induced vibration energy harvesters in terms of their working principles, categories, enhancement methods, model derivation and calculation methods, influence of interface circuits, and energy harvesting efficiency calculation methods are reviewed.
TL;DR: In this article, a new converter consisting of a circular cylinder on an end-spring is proposed to harness hydrokinetic power from water flow and tides, which is inspired by the trembling of cables with ice attached in barely noticeable winds.
TL;DR: In this paper, a galloping piezoelectric energy harvester with an external super capacitor in addition to the small internal PPE was designed to improve the low-velocity wind energy extracting performance.
TL;DR: In this article, a galloping piezoelectric energy harvester with a V-shaped groove on the windward side was designed and tested in a wind tunnel by gradually changing the angle of two symmetrical sharp angles of the V-groove.
Abstract: A square cylinder with a V-shaped groove on the windward side in the piezoelectric cantilever flow-induced vibration energy harvester (FIVEH) is presented to improve the output power of the energy harvester and reduce the critical velocity of the system, aiming at the self-powered supply of low energy consumption devices in the natural environment with low wind speed. Seven groups of galloping piezoelectric energy harvesters (GPEHs) were designed and tested in a wind tunnel by gradually changing the angle of two symmetrical sharp angles of the V-groove. The GPEH with a sharp angle of 45° was selected as the optimal energy harvester. Its output power was 61% more than the GPEH without the V-shaped groove. The more accurate mathematical model was made by using the sparse identification method to calculate the empirical parameters of fluid based on the experimental data and the theoretical model. The critical velocity of the galloping system was calculated by analyzing the local Hopf bifurcation of the model. The minimum critical velocity was 2.53 m/s smaller than the maximum critical velocity at 4.69 m/s. These results make the GPEH with a V-shaped groove (GPEH-V) more suitable to harvest wind energy efficiently in a low wind speed environment.
TL;DR: In this paper , the structural performance and research status of PWEHs based on different mechanisms, such as a rotating turbine, vortex-induced vibration, flutter, and galloping, are analyzed and summarized.
Abstract: Wireless sensor networks play a very important role in environmental monitoring, structural health monitoring, smart city construction, smart grid, and ecological agriculture. The wireless sensor nodes powered by a battery have a limited service life and need periodic maintenance due to the limitation of battery capacity. Fortunately, the development of environmental energy harvesting technology provides an effective way to eliminate the needs and the replacement of the batteries. Among the environmental stray energy, wind energy is rich, almost endless, widely distributed, and clean. Due to the advantages of simple structure, miniaturization, and high power density, wind energy harvesters using piezoelectric materials (PWEHs) have attracted much attention. By the ways of principal exploration, structure design, and performance optimization, great and steady progress has been made in the research of PWEH. This Review is focused on the review of PWEHs. After introducing the basic principle of PWEHs, the structural performance and research status of PWEHs based on different mechanisms, such as a rotating turbine, vortex-induced vibration, flutter, and galloping, are analyzed and summarized. Finally, the development trend of PWEHs has been prospected.
TL;DR: In this paper, a vibration-based piezoelectric generator has been developed as an enabling technology for wireless sensor networks, where the authors discuss the modeling, design, and optimization of the generator based on a two-layer bending element.
Abstract: Enabling technologies for wireless sensor networks have gained considerable attention in research communities over the past few years. It is highly desirable, even necessary in certain situations, for wireless sensor nodes to be self-powered. With this goal in mind, a vibration based piezoelectric generator has been developed as an enabling technology for wireless sensor networks. The focus of this paper is to discuss the modeling, design, and optimization of a piezoelectric generator based on a two-layer bending element. An analytical model of the generator has been developed and validated. In addition to providing intuitive design insight, the model has been used as the basis for design optimization. Designs of 1 cm3 in size generated using the model have demonstrated a power output of 375 µW from a vibration source of 2.5 m s−2 at 120 Hz. Furthermore, a 1 cm3 generator has been used to power a custom designed 1.9 GHz radio transmitter from the same vibration source.
TL;DR: In this paper, the potential use of transverse galloping in order to obtain energy was explored analytically, and the influence of cross-section geometry and mechanical properties in the energy conversion factor was investigated.
TL;DR: In this article, a comparative study of different tip cross-sections for small scale wind energy harvesting based on galloping phenomenon is presented, and it is recommended that the square section should be used for small wind galloping energy harvesters.
Abstract: This letter presents a comparative study of different tip cross-sections for small scale wind energy harvesting based on galloping phenomenon. A prototype device is fabricated with a piezoelectric cantilever and a tip body with various cross-section profiles (square, rectangle, triangle, and D-shape) and tested in a wind tunnel. Experimental results demonstrate the superiority of the square-sectioned tip for the low cut-in wind speed of 2.5 m/s and the high peak power of 8.4 mW. An analytical model is established and verified by the experimental results. It is recommended that the square section should be used for small wind galloping energy harvesters.
TL;DR: In this article, the authors classified vortex-induced motion phenomena into several groups which include Flutter, Transverse and Torsional Galloping, Buffeting, Vortex-Induced Vibration (VIV), and Fluttering-Autorotation.
Abstract: Vortex-induced motions are generally known as destructive phenomena for engineering structures. Nevertheless, they have a positive effect which is their great potential to extract renewable energy from the fluid flow. The phenomenology of vortex-induced motions has been studied and several energy harvesting technologies based on these motions have been reported, separately through literature. However, a comprehensive study that bonds together the phenomenology and the energy extraction technologies does not exist yet. Now that this area has become well established, classification of the relevant phenomena and technologies has become necessary as well. The present paper has two main objectives; The first objective is to classify the whole vortex-induced motion phenomena into several groups which include Flutter, Transverse and Torsional Galloping, Buffeting, Vortex-Induced Vibration (VIV), and Fluttering-Autorotation. The second objective is to review the literature, with the aim of classifying different technologies of renewable energy harvesting based on vortex-induced motion. Also, the performance characteristics and economical costs of these technologies are benchmarked.