Design and development of a kinetic energy harvester device for oceanic drifter applications

Abstract

A novel electronic energy harvester (EH) has been developed for oceanic undrogued drifter applications. First, spherical body motion simulation has been performed at sea environment in Orcaflex. Results help to understand the acceleration and forces applied on the drifter where the device will be placed. Second, the design of the EH is presented, consisting on a gyroscope pendulum system capable to transform the oscillations into rotation on a flying wheel. This rotation is converted into a DC current by a micro generator and further processed by a power management unit (PMU). Both, the generator and the PMU are characterized. Preliminary results in a water tank show that an average power of 0.22 mW can be produced. Finally, the feasibility of the proposed harvester is assessed as a backup power of a drifter using SigFox for coastal communications at low tracking rates.

Design and Testing of a Kinetic Energy Harvester Embedded Into an Oceanic Drifter

“…Recently, a first prototype of an inertial KEH device was designed and manufactured [14], which is a mixture of gyroscopic and pendulum systems. It consists of three gyroscopic arms which capture the oscillation induced by waves and transforms it into rotation in a DC generator.…”

“…Fig. 2 the device introduced in [14], the three gyroscopic arms have been replaced by an articulated pendulum arm with a proof mass. This way, the design of the KEH device is simplified and its size is reduced, thus increasing its power density.…”

“…The gear system also increases the rotation velocity with a positive ratio of 35 and, thanks to a one-way gear mechanism, the flying wheel only rotates in one angular direction, at which energy is accumulated. The electrical generator, updated with respect to [14], [15], is a miniature DC motor, which can be modelled as an equivalent Thévenin circuit [18], as shown in the leftmost part of the circuit in Fig. 3, where Rg is the internal equivalent resistance and Voc is the generated electromotive force (EFM) in volts.…”

“…The total gear ratio is 35. The miniature DC motor referred to in [14], [15], used as electrical generator, has been replaced here by the 118391 model from Maxon Motors, presenting a nominal voltage of 12 V and a terminal resistance (Rg) of 114 . Apart from being more rugged and reliable, it provides higher voltage outputs at the same mechanical excitation, letting the PMU to work at higher efficient rates.…”

“…This paper continues and extends two previous works. A first design of a Kinetic Energy Harvester (KEH) system for spherical oceanic drifters was presented in [14], including a preliminary characterization of the electrical generator and the PMU followed by first results of the prototype when located in an anchored buoy placed on a water tank. Later, in [15], an improved version of the KEH device was presented, as well as a first approach of a specially designed oceanic drifter for testing purposes.…”