Interest In Energy Harvesting Applications Research Articles

Effect of boundary conditions on energy harvesting of a flow-induced snapping sheet at low Reynolds number

Recent studies on the snap-through motion of elastic sheets have attracted intense interest in energy-harvesting applications. However, the effect of boundary conditions (BCs) on energy extraction performance still remains an open question. In this study, we explored the snapping dynamics and energy-harvesting characteristics of the buckled sheet at various conditions using fluid–structure interaction simulations at a Reynolds number Re = 100. It was found that the front boundary condition (BC) dramatically affects the sheet's snapping dynamics, e.g., the pinned or relatively soft front BC triggers the sheet's instability easily and thus boasts the collection of potential energy. In the snap-through oscillation state, a stiffer rear BC results in a larger improvement in the sheet's energy collection compared with a minor effect of front BC. Meanwhile, the enhancement can also be achieved by adjusting the rear rotational spring stiffness up to 1.125 × 10−4, after which it remains nearly constant, as observed in the case of EI* = 0.004. This introduction of an elastic BC with krs* = 1.125 × 10−4 not only efficiently enhances energy extraction but significantly reduces stress concentration and, as a result, greatly prolongs the sheet's fatigue durability, especially for the stiffer sheet with EI* = 0.004. The effect of three other governing parameters, including the length ratio ΔL*, sheet's bending stiffness EI*, and mass ratio m*, on the sheet's energy-harvesting performance were also explored. The result shows that increasing ΔL* and EI* could improve the total energy harvested, primarily by enhancing the elastic potential energy, particularly in the aft half of the sheet. In contrast, increasing m* mainly enhances the kinetic energy collected by the sheet's central portion, thus improving the total energy-extracting performance. This study provides an in-depth insight into the dynamics of a buckled sheet under various BCs, which may offer some guidance on the optimization of relevant energy harvesters.

Effects of electrode placement position and tilt angles of a platform on voltage induced by NaCl electrolyte flowing over graphene wafer

The extraction of energy from water in the natural environment has attracted significant interest in energy-harvesting applications in recent years. This study investigates the effects of the electrode placement position and the tilt angle of a platform on the voltage induced by a flow of aqueous NaCl electrolyte solution over a two-dimensional graphene wafer. It is shown that an orthogonal arrangement of the electrodes relative to the electrolyte flow direction maximizes the induced voltage. Further experiments are performed in which the graphene wafers are positioned such that the electrolyte flows over the short and long sides of the electrodes, respectively. The results show that the higher voltage response is obtained when the electrolyte flows through the long side of the electrodes. Finally, an investigation is performed into the voltage induced for various tilt angles from 20° to 60° of the graphene wafers placed on a platform. The charging and discharging time are revealed from experiments for the first time for various tilt angles. Based on the cases studied, the 45° tilt angle induces the highest voltage. Overall, the results presented in this study provide a useful insight into the optimal electrode placement position and tilt angle of a platform for graphene energy harvesting from aqueous sodium chloride solutions.

Lattice Dynamics and Thermal Conductivity in Cu2Zn1- xCo xSnSe4.

The quaternary compound Cu2ZnSnSe4 (CZTSe), as a typical candidate for both solar cells and thermoelectrics, is of great interest for energy harvesting applications. Materials with a high thermoelectric efficiency have a relatively low thermal conductivity, which is closely related to their chemical bonding and lattice dynamics. Therefore, it is essential to investigate the lattice dynamics of materials to further improve their thermoelectric efficiency. Here we report a lattice dynamic study in a cobalt-substituted CZTSe system using temperature-dependent X-ray absorption fine structure spectroscopy (TXAFS). The lattice contribution to the thermal conductivity is dominant, and its reduction is mainly ascribed to the increment of point defects after cobalt substitution. Furthermore, a lattice dynamic study shows that the Einstein temperature of atomic pairs is reduced after cobalt substitution, revealing that increasing local structure disorder and weakened bonding for each of the atomic pairs are achieved, which gives us a new perspective for understanding the behavior of lattice thermal conductivity.

Hybrid energy harvesting systems, using piezoelectric elements and dielectric polymers

Interest in energy harvesting applications has increased a lot during recent years. This is especially true for systems using electroactive materials like dielectric polymers or piezoelectric materials. Unfortunately, these materials despite multiple advantages, present some important drawbacks. For example, many dielectric polymers demonstrated high energy densities; they are cheap, easy to process and can be easily integrated in many different structures. But at the same time, dielectric polymer generators require an external energy supply which could greatly compromise their autonomy. Piezoelectric systems, on the other hand, are completely autonomous and can be easily miniaturized. However, most common piezoelectric materials present a high rigidity and are brittle by nature and therefore their integration could be difficult. This paper investigates the possibility of using hybrid systems combining piezoelectric elements and dielectric polymers for mechanical energy harvesting applications and it is focused mainly on the problem of electrical energy transfer. Our objective is to show that such systems can be interesting and that it is possible to benefit from the advantages of both materials. For this, different configurations were considered and the problem of their optimization was addressed. The experimental work enabled us to prove the concept and identify the main practical limitations.

Vertically aligned BaTiO3nanowire arrays for energy harvesting

Nano-electromechanical systems (NEMS) developed using piezoelectric nanowires (NWs) have gained immense interest in energy harvesting applications as they are able to convert several different forms of mechanical energy sources into electric power and thereby function as reliable power sources for ultra-low power wireless electronics. In this work, a piezoelectric NEMS vibrational energy harvester is fabricated through the development of a synthesis process for vertically aligned barium titanate (BaTiO3) nanowire (NW) arrays directly on a conductive substrate. These poled ferroelectric NW arrays are characterized through direct vibration excitation and demonstrated to provide efficient harvesting of mechanical vibrational energy producing an average power density of ∼6.27 μW cm−3 from 1g acceleration. In order to substantiate the superior energy harvesting performance of the newly developed BaTiO3 NW arrays, a direct comparison is made with conventional ZnO NW arrays. Here, we clearly report that the ferroelectric BaTiO3 NW NEMS energy harvester has ∼16 times greater power density than the ZnO NW NEMS energy harvester from the same acceleration input.