Performance of an omnidirectional piezoelectric wind energy harvester

This paper presents a vortex-induced vibration (VIV)-based piezoelectric energy harvester that performs well for all wind directions, a so-called omnidirectional wind energy harvester. The kinetic energy of this harvester stems from wind-induced vibrations of a circular cylinder mounted on an orthogonal bibeam system, rather than a traditional single beam. Wind tunnel testing results show that compared to the traditional single-beam energy harvester, the proposed harvester substantially enhances the effectiveness, in most cases that the beam is skew to the incoming flow. The reasons for the enhancement are explained in detail by examining the wind-induced displacement response components of the cylinder identified by the image processing technique. For all wind directions, both the maximal output energy and the range of effectively working wind speed of the proposed bibeam wind energy harvester are significantly improved with respect to the single-beam system, indicating excellent performance of the proposed omnidirectional harvester in a natural wind environment

Aerodynamic Shape Optimization of an Arc-Plate-Shaped Bluff Body via Surrogate Modeling for Wind Energy Harvesting

Galloping-based piezoelectric wind energy harvesters (WEHs) are being used to supply renewable electricity for self-powered devices. This paper investigates the performance of a galloping-based piezoelectric WEH, with different arc-plate-shaped bluff bodies to improve harvesting efficiency. The Latin hypercube sampling method was employed to design the experiment. After conducting a series of wind tunnel tests, a Kriging surrogate model was then established, with high accuracy. The results show that the wind energy harvester with an arc angle 0.40π and tail length 1.26D generated the maximum power. The output power of the proposed WEH was doubled by optimizing the aerodynamic shape of the bluff body. The reasons for the improvement are discussed in detail. The force measurement results indicated that a large value of the transverse force coefficient means a large galloping response of the WEH. The aerodynamic optimization of this study can be applied to improve the performance of galloping-based wind energy harvesters

Experimental and numerical aerodynamic analysis of an elevated beachfront house

Elevating coastal houses enables residential communities to reduce the risk of flooding due to tropical cyclones. However, wind-induced damage during such events requires an understanding of the inherent wind forces to improve damage mitigation techniques and assessment of climate-related risk in insurance models. In this study, wind-tunnel experiments and computational fluid dynamics (CFD) simulations are conducted for a typical elevated 1:25 scale beachfront house, possessing a 5:12 pitched gable roof with overhanging eave. An atmospheric boundary layer (ABL) wind field is generated in a low-speed wind-tunnel to replicate conditions experienced during tropical cyclones. Testing is performed for a range of incident wind angles to understand the full aerodynamic consequences of strong winds. Measured pressure coefficient (Cp) distributions are compared with CFD simulations using steady-state and transient Delayed Detached-Eddy Simulation (DDES) within ANSYS Fluent 2021 R1. Net Cp values surrounding the overhanging eave are considered to evaluate the role of this typical geometrical feature. It was found that larger uplift suction occurred at incident wind angles of 45°and above, after which the suction remained stable. The roof panels are subjected to the greatest upward suction, where critical regions occur at the roof ridge. The size of the low-pressure regions is determined by the incident wind angle and ensuing flow separation wherein DDES is found to reproduce additional aerodynamic features arising from unsteady turbulent flow. DDES offers improved predictive capability when mean pressure forces are considered but falls short as an accurate means to efficiently evaluate peak distributions

3D Printing of Porous Nitrogen-Doped Ti3C2 MXene Scaffolds for High-Performance Sodium-Ion Hybrid Capacitors

2020 American Chemical Society. 3D printing technology has stimulated a burgeoning interest to fabricate customized architectures in a facile and scalable manner targeting wide ranged energy storage applications. Nevertheless, 3D-printed hybrid capacitor devices synergizing favorable energy/power density have not yet been explored thus far. Herein, we demonstrate a 3D-printed sodium-ion hybrid capacitor (SIC) based on nitrogen-doped MXene (N-Ti3C2Tx) anode and activated carbon cathode. N-Ti3C2Tx affording a well-defined porous structure and uniform nitrogen doping can be obtained via a sacrificial template method. Thus-formulated ink can be directly printed to form electrode architecture without the request of a conventional current collector. The 3D-printed SICs, with a large areal mass loading up to 15.2 mg cm-2, can harvest an areal energy/power density of 1.18 mWh cm-2/40.15 mW cm-2, outperforming the state-of-the-art 3D-printed energy storage devices. Furthermore, our SIC also achieves a gravimetric energy/power density of 101.6 Wh kg-1/3269 W kg-1. This work demonstrates that the 3D printing technology is versatile enough to construct emerging energy storage systems reconciling high energy and power density

Flexible perovskite solar cell-driven photo-rechargeable lithium-ion capacitor for self-powered wearable strain sensors

Next-generation wearable electronics is expected to be self-powered by conformable energy storage devices that can provide energy output whenever needed. The emerging energy harvesting and storage integrated system in a flexible assembly, in this respect, has offered a promising solution. Nevertheless, daunting challenges pertaining to the insufficient energy density, limited overall efficiency and low output voltage of the prevailing integrated power sources still exist. Herein, we report a flexible perovskite solar cell (PSC)-driven photo-rechargeable lithium-ion capacitor (LIC) that hybridizes energy harvesting and storage for self-powering wearable strain sensors. Such flexible PSC-LIC module manages to deliver an overall efficiency of 8.41% and a high output voltage of 3 V at a discharge current density of 0.1 A g −1 . It could still harvest a remarkable overall efficiency exceeding 6% even at the high current density of 1 A g −1 , outperforming state-of-the-art photo-charging power sources. Accordingly, thus-derived, self-powered strain sensor readily manifests precise and continuous data recording of physiological signals without any external power connections, thereby realizing the synergy of energy harvesting, storage, and utilization within one smart system. This multi-field-coupled, function-integrated platform is anticipated to offer significant benefits toward practical self-powered wearable electronics