Piezoelectric energy harvester operating in flowing water

Abstract

An energy harvesting system is presented that converts energy out of flowing media, like water or wind. Without the need for any rotating part the harvester converts the energy out of the bending of a piezoelectric cantilever. A bluff body, which the cantilever is attached to, causes vortices and therefore pressure differences above and beneath the cantilever. Thus the cantilever oscillates and generates an alternating voltage. A first macroscopic model proofed this working concept for air and water. Measurements showed good coupling between flow velocity and power generation. Furthermore a self synchronization of different cantilevers could be observed in water. A second model of the harvester was build with improved distribution of piezoelectric layers. To store and distribute the generated energy of the harvester, it was combined with a low power circuit that was developed, too. Therefore, a complete autonomous system that is able to supply a load and the necessary electric circuit with power is presented.

Sensitivity analysis for piezoelectric energy harvester and bluff body design toward underwater pipeline monitoring

“…The electrical power relation is shown in Eq. (6) which depends upon frequency of beam and electrical energy output [21].…”

Flow energy piezoelectric bimorph nozzle harvester

“…There are a variety of potential methods to couple the flow energy to the structure with the transduction mechanism located away from the flow. Several types of flow induced energy harvester methods were considered in this study; one is a hydraulic pressure based method [18,24], a second is a bluff body based method [12,13,14,15,16], yet another is based on leakage-flow instabilites which induce large displacements in the bimorph tip when fluid flows past a narrow passage [25]. For example, when the flow is passing through the nozzle, the pressure fluctuation forces the bimorph to move alternately up and down, creating internal stresses and producing electricity.…”

“…In addition, they can operate with limited strain and in non rotating systems which offers the potential to produce long life harvesting systems due to limited wear, and piezoelectric materials with large piezoelectric activity and with Curie temperatures in the 300 o C range are commercially available so the potential to operate at higher temperatures is also an advantage. A variety of studies have looked at methods to convert flow energy into vibrations including vortex shedding [12,13,14,15,16], flapping motions [17] and hydraulic pressure [18]. This paper presents the results of our experiments on a variety of designs for flow energy harvesters which used nozzles and/or flow cavities along a pipe to produce conditions that excite a vibrating piezoelectric structure.…”

A study of several vortex-induced vibration techniques for piezoelectric wind energy harvesting

“…For example the driving oscillating forces that mechanically strain the piezoelectric cantilevers can be generated in a flowing medium (air or water) by either an obstacle in the flow such as a bluff body or a so called "von Karman's vortex street" 4 . Two different designs were investigated by Pobering et al 4,5 . The first harvester consists of nine, three-dimensionally arranged bimorph piezoelectric cantilevers.…”

“…A total of 18 piezoelectric cantilevers have been arranged in two rows upon each other. The energy harvester was able to supply 2 mW of power at a wind velocity of 8 m/s from the second mode 5 . Akaydin et al have investigated a VIV-based energy harvester with short-length piezoelectric beams kept at the wake of the cylinder with water as the flowing medium 6 .…”