Energy harvesting from ambient vibrations using piezoelectric effect is a promising alternative solution for powering small electronics such as wireless sensors. A conventional piezoelectric energy ...harvester usually consists of a cantilevered beam with a proof mass at its free end. For such a device, the second resonance of the piezoelectric energy harvester is usually ignored because of its high frequency as well as low response level compared to the first resonance. Hence, only the first mode has been frequently exploited for energy harvesting in the reported literature. In this article, a novel compact piezoelectric energy harvester using two vibration modes has been developed. The harvester comprises one main cantilever beam and an inner secondary cantilever beam, each of which is bonded with piezoelectric transducers. By varying the proof masses, the first two resonant frequencies of the harvester can be tuned close enough to achieve useful wide bandwidth. Meanwhile, this compact design efficiently utilizes the cantilever beam by generating significant power output from both the main and secondary beams. An experiment and simulation were carried out to validate the design concept. The results show that the proposed novel piezoelectric energy harvester is more adaptive and functional in practical vibrational circumstances.
One of the critical issues for the conventional TENGs for applications in biomechanical and blue energy harvesting is to develop adaptive, simple-structured, high performance but low-cost TENGs for ...the complex excitation conditions. To solve this problem, we propose an origami-inspired TENG integrated with folded thin film electret, which can be facilely formed from two pieces of liquid crystal polymer (LCP) strips through high degrees of paper folding. It has been proved efficient for harvesting energy from both sinusoidal vibrations and impulse excitations which are universally existed in the ambient environment. Double-side corona discharging process is employed to maximize the charge density generated by the electret thin films. Attributing to the excellent elastic property of self-rebounding spring structures based on the origami design, the flexible TENGs can be readily integrated into smart shoes, floors, watches and clothes for wearable and energy harvesting applications. Triggered by impulse excitation of gentle finger tapping, instantaneous open-circuit voltage and short-circuit current of 1000 V and 110 μA, respectively, have been obtained with a remarkable peak power density of 0.67 mW/cm3 (or 1.2 mW/g). A spherical floating buoy generator integrating multiple origami TENGs is further developed to harvest ocean wave energy at various frequencies and amplitudes as well as in arbitrary directions. The outcomes of this work offer new insights of realizing single structured TENG designs for multifunctional applications.
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•An origami TENG device that is efficient for harvesting energy from both sinusoidal vibrations and impulse excitations.•Double-side corona charging process to maximize the charge density in the thin film electrets.•Integration of the flexible TENGs into wearable and energy harvesting applications.•A floating buoy generator with multiple TENGs to harvest ocean wave energy in complex excitation conditions as demonstration.
Small-scale wind energy can be harvested for wireless sensing applications by exploiting the galloping phenomenon of a bluff body attached to a piezoelectric cantilever. Certain predictive model is ...required to understand the behavior of such a galloping-based piezoelectric energy harvester (GPEH). Conventional analytical and numerical models have simplified the interface circuit as a pure resistor. In practice, the energy generated by the harvester should be rectified before delivery to a real application. In such a case, the formulation of analytical or numerical model becomes cumbersome considering the complex coupling between the structure, fluid, piezoelectric transducer, and practical interface circuit. This paper proposes an equivalent circuit representation approach to predict the performance of GPEHs, capable of incorporating various interface circuits. The mechanical parameters and piezoelectric coupling in the system are represented by standard electronic components and the aerodynamic force by a user-defined component (nonstandard). The entire system is modeled in a circuit simulator for system-level simulation and evaluation. The proposed approach is verified by theoretical solution and experiment. Subsequent parametric study is performed to investigate the influence of standard ac and dc interfaces on the GPEH's behavior, with a focus on the threshold of galloping, power output, and induced electrical damping.
In recent years, several strategies have been proposed to improve the functionality of energy harvesters under broadband vibrations, but they only improve the efficiency of energy harvesting under ...limited conditions. In this work, a comprehensive experimental study is conducted to investigate the use of magnets for improving the functionality of energy harvesters under various vibration scenarios. First, the nonlinearities introduced by magnets are exploited to improve the performance of vibration energy harvesting. Both monostable and bistable configurations are investigated under sinusoidal and random vibrations with various excitation levels. The optimal nonlinear configuration (in terms of distance between magnets) is determined to be near the monostable-to-bistable transition region. Results show that both monostable and bistable nonlinear configurations can significantly outperform the linear harvester near this transition region. Second, for ultra-low-frequency vibration scenarios such as wave heave motions, a frequency up-conversion mechanism using magnets is proposed. By parametric study, the repulsive configuration of magnets is found preferable in the frequency up-conversion technique, which is efficient and insensitive to various wave conditions when the magnets are placed sufficiently close. These findings could serve as useful design guidelines when nonlinearity or frequency up-conversion techniques are employed to improve the functionality of vibration energy harvesters.
► We develop a physically based non-point source pollution model. ► The model simulates long-term runoff, sediment, and pollutant variations. ► Land-use and climate changes affect catchment hydrology ...as evaluated quantitatively. ► Climate variability causes annual runoff decline in the study area from 1980–2005. ► Land-use changes had different effects on runoff, sediment, TN, and TP loads.
Water shortage and water pollution are two major water issues in Northern China. In recent decades, the decrease in inflow and the deterioration of water quality in the Miyun Reservoir have affected the water supply in Beijing. This paper presents a geomorphology-based non-point source pollution (GBNP) model that links the processes of rainfall–runoff, soil erosion, sediment routing, and pollutant transport. On the basis of long-term simulation of the GBNP model, annual runoff presented a decreasing trend from 1980 to 2005. Total nitrogen (TN) and total phosphorus (TP) loads increased from the early 1980s to the mid-1990s, and then decreased after 1999. The decrease in precipitation and increase in air temperature were the dominant factors in runoff decrease. Afforestation, a water–soil conservation practice, positively affected the reduction of non-point source pollution; however, it also caused a reduction of streamflow. A comparison between 1980–1998 and 1999–2005 showed that land-use changes accounted for 39.1% and 23.7% of the decrease in TN and TP, respectively, as well as 6.6% and 9.2% of the decline in streamflow and sediment load, respectively. Although annual sediment, as well as TN and TP loads decreased after 1999, their long-term accumulation in the reservoir continues to diminish water quality.
Obesity is occurring due to continue taken high fat diet; this is the fast-growing problem reaching epidemic proportion globally. Ursolic acid altered the abnormal glucose metabolism in diabetic ...rats. In this experimental protocol, we examine ursolic acid (UA) anti-obesity effect against streptozotocin (STZ) and high-fat diet-induced obesity in rats. Orally administered the ursolic acid (2.5, 5 and 10 mg/kg) dose to the hyperglycemic rats for 8 weeks and estimated the blood glucose level at different time intervals. Biochemical, hepatic, lipid, renal and antioxidant parameters were estimated. Traf-4, Mapk-8, Traf-6 and genes such as Ins-1, ngn-3 and Pdx-1 mRNA expression were estimated using qRT-PCR to scrutinize the molecular mechanism in MAPK downstream JNK cascade and insulin pathway signalling pathways. Ursolic acid significantly (p<0.001) down-regulated the blood glucose level at dose dependent manner. Its also reduced the plasma insulin level, non-essential fatty acid and increased the level of adiponectin as compared to obese control group rats. Ursolic acid treated group rats reduced the level of total cholesterol and triglycerides. Ursolic-acid-treated rats have been shown to decrease oxidative stress in pancreatic tissue by restoring the free radical effect of scavenging, suppress the Traf-6, Mapk-8 and Traf-4 mRNA expression, enhance the expression of Pdx-1, Ins-1 and Ngn-3 and ensure the regeneration of pancreas β cells and therefore pancreas insulin. The current result suggested the anti-obese effect of ursolic acid against high fat diet (HFD) induced obese rats via alteration of insulin and JNK signaling pathway.
Due to the complex aero-electro-mechanical coupling involved in wind energy harvesting systems, power enhancing efforts in the literature are mostly devoted to structural modifications while the ...interface circuit is simplified to a resistive ac load. Yet the ac outputs are not applicable for practical usage. In this paper, we study the dynamics and dc power generation of galloping energy harvester. In particular, the enhancement of wind power extraction using the synchronized switching harvesting on inductor (SSHI) power conditioning circuit is emphasized. Analytical solution of the steady-state mechanical and electrical responses with the SSHI interface is derived explicitly and validated with wind tunnel experiment and circuit simulation. The performance of SSHI interface is compared to that of a standard bridge rectifier interface circuit. It shows that the SSHI interface achieves tremendous power enhancement in a weak-coupling system, and higher wind speeds render more significant power enhancement. Moreover, given the same wind condition and output power requirement, a system connected to the SSHI uses much less piezoelectric material compared to that connected to the standard circuit. With a weak-coupling harvester operating at a wind speed of 7 m/s, the SSHI can harvest up to 143% more wind power than the standard circuit.
Zinc oxide (ZnO) is an environmental-friendly semiconducting, piezoelectric and non-ferroelectric material, and plays an essential role for applications in microelectromechanical systems (MEMS). In ...this work, a fully integrated two-degree-of-freedom (2DOF) MEMS piezoelectric vibration energy harvester (p-VEH) was designed and fabricated using ZnO thin films for converting kinetic energy into electrical energy. The 2DOF energy harvesting system comprises two subsystems: the primary one for energy conversion and the auxiliary one for frequency adjustment. Piezoelectric ZnO thin film was deposited using a radio-frequency magnetron sputtering method onto the primary subsystem for energy conversion from mechanical vibration to electricity. Dynamic performance of the 2DOF resonant system was analyzed and optimized using a lumped parameter model. Two closely located but separated peaks were achieved by precisely adjusting mass ratio and frequency ratio of the resonant systems. The 2DOF MEMS p-VEH chip was fabricated through a combination of laminated surface micromachining process, double-side alignment and bulk micromachining process. When the fabricated prototype was subjected to an excitation acceleration of 0.5 g, two close resonant peaks at 403.8 and 489.9 Hz with comparable voltages of 10 and 15 mV were obtained, respectively.
•Demonstrating a fully integrated MEMS p-VEH with two close and effective peaks•Having a completeness of theoretical approach and experimental validation•Realizing 2DOF multimodal MEMS vibration energy harvester using piezoelectric ZnO thin films
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•The export coefficient model was improved by integrating a grid-based rainfall-runoff module.•It analyzed spatiotemporal characteristics of the non-point source nutrient loads into ...the rivers.•Impacts of the non-point source nutrient loads on the river water quality was discussed.
Accurately quantifying the spatiotemporal nutrient loads from nonpoint sources (NPSs) is still difficult due to the high spatial heterogeneity and temporal variability in rainfall-runoff processes. The export coefficient model (ECM) is a widely used tool to estimate the NPS nutrient load on an annual time scale, but it hardly considers the spatiotemporal distribution of the export coefficient. To address this issue, the ECM is improved by incorporating a grid-based rainfall-runoff module together with land-use data and analysing the spatiotemporal characteristics of the NPS nutrient loads in Yancheng city located in eastern China. Moreover, the effect of NPS nutrient loads on river water quality is assessed using a conceptual model. The results indicate that the improved ECM can simulate reasonable spatiotemporal variation in NPS nutrient loads, and the relative error in the total phosphorus (TP) load is less than 17.14 %. Precipitation has a considerable influence on both the total nitrogen (TN) and TP loads, which varied greatly from 1990 to 2018, with average annual values of 30.57 × 103 tons and 2.44 × 103 tons, respectively. The spatial distributions of the TN and TP loads were greatly affected by land-use patterns, and bodies of water and rural land had relatively high load intensities. Both TN and TP concentrations in the river exceeded the national standard, but TP was significantly reduced in the past 10 years, while TN was still at high level. This study provides a reference for reducing the river pollution in Yancheng city, especially by identifying pollution sources requiring priority control.
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