A novel Kinetic Energy Harvester (KEH) has been developed for powering oceanic undrogued drifters. It consists on a double pendulum system capable of transforming the wave oscillations into rotation on a flywheel. This rotation is converted into DC current by an electrical generator and further processed by a power management unit (PMU). The PMU includes a "maximum power point tracking" system to maximize energy production by the generator. An oceanic drifter has also been designed to embed the KEH and a custom-made measurement system to perform real sea tests. It counts on an Inertial Measurement Unit to study the motion of the drifter and an embedded measurement system to estimate the rotation speed of the generator and the power at both the input and output of the PMU. A Wi-Fi connection is also included for data transfer at short distances. The generator was firstly characterized at the laboratory; the drifter was then placed on a linear shaker to assess its performance. Finally, the drifter was deployed in a controlled sea area with average values of wave height and frequency of 1.43 m and 0.29 Hz, respectively. In these conditions, the drifter showed horizontal and vertical oscillations with peak-to-peak accelerations of 0.8 g and power spectra centered around 1.5 Hz and 1 Hz, respectively. As a result, the KEH generated a mean output power of 0.18 mW, with peaks of 2.5 mW.

The study of the effects of climate change on the marine environment requires the existence of sufficiently long time series of key parameters. The study of these series allows both to characterize the range of variability in each particular region and to detect trends or changes that could be attributed to anthropogenic causes. For this reason, networks of permanent cabled observation systems are being deployed in the ocean. This paper presents a balance of a decade of activity at the OBSEA cabled observatory, as an example of ocean monitoring success and drawbacks. It is not the objective of this article to analyze the scientific and technical aspects already presented by the authors in different publications (Table 4). We will evaluate the overall experience by retracing the different steps of infrastructure deployment and maintenance, focusing on routines for in situ control, damages experienced, breakdowns and administrative constraints by local administrations. We will conclude by providing a set of guidelines to improve cabled observatories scientific outreach, societal projection, and economic efficiency. As a result of this work, a 10-years dataset has been published in Pangaea that is available for the community. INDEX TERMS Cabled observatories, multidisciplinary observation, coastal ocean monitoring, underwater imaging, european multidisciplinary seafloor and water column observatory (EMSO), JERICO-RI.

A Kinetic Energy Harvester (KEH) device under design for drifter applications has been tested at real sea conditions in a controlled area. The KEH consists on a pendulum system capable to transform the oscillations of the waves into rotation which will be converted into electrical energy thanks to a dc micro generator. The KEH has been placed inside a drifter. First, the motion of the drifter was obtained through an embedded Inertial Measurement Unit, showing natural pendulum frequency of 1.5 Hz. Simulations with OrcaFlex validate the experimental results. Then, the rotation speed of the micro generator was measured. Results show a prevalence of speed of 1400 rpm, which should lead to a potential power output of 2 mW.

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.

The fractional open circuit voltage (FOCV) method is extensively used in low-power energy harvesting (EH) sources to extract maximum power. For fast-varying EH sources a fast sampling rate is required. This work theoretically analyzes the influence of the sampling time and period on the harvested power of sinusoidal EH sources. In addition, the circuit limitations to achieve a fast sampling rate are presented and circuits to deal with them proposed and implemented. Furthermore, one of the circuits is based on a novel pseudo-FOCV method and achieves the fastest sampling rate. Experimental tests are performed with a 2 Hz, 1 V to 3 V sinusoidal source having an output resistance of 127 Ω, and the results are shown to agree with theoretical predictions. It is shown that 1) the harvested power increases with the sampling rate when the sampling time is negligible (sampling 15 times faster than the source frequency extracts around 99 % of the maximum), and 2) for fixed sampling times there is an optimum sampling rate where the harvested power is maximum. The first result is generic and valid for methods other than the FOCV. Tests were also performed with a small-scale wave energy converter placed in a linear shaker emulating a sea environment. Harvested power increases by 25 % with respect using a commercial FOCV unit with a low sampling rate.