Category Archives: Experiments

Wave power absorption: Experiments in open sea and simulation


M. Eriksson, R. Waters, O.Svensson, J. Isberg, and M. Leijon- Journal of Applied Physics, 2007

Abstract

A full scale prototype of a wave power plant based on a direct drive linear generator driven by a point absorber has been installed at the west coast of Sweden. In this paper, experimentally collected data of energy absorption for different electrical loads are used to verify a model of the wave power plant including the interactions of wave, buoy, generator, and external load circuit. The wave-buoy interaction is modeled with linear potential wavetheory. The generator is modeled as a nonlinear mechanical damping function that is dependent on piston velocity and electric load. The results show good agreement between experiments and simulations. Potential wavetheory is well suited for the modeling of a point absorber in normal operation and for the design of future converters. Moreover, the simulations are fast, which opens up for simulations of wave farms.

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Sea Trials of a Wave Energy Converter in Strangford Lough, Northern Ireland


Vladimir Krivtsov, Ian Bryden, Brian Linfoot, and Robin Wallace – Journal of Shipping and Ocean Engineering, 2013

Abstract

This paper describes a campaign of WEC (wave energy converter) testing and presents a selection of the results related to the measured motions and mooring tensions. A 1:20 physical model has been successfully deployed using a three point mooring installed at sea (Strangford Lough, NI) in 10 m depth. Continue reading

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Multistable chain for ocean wave vibration energy harvesting


R. L. Harne, M. E. Schoemaker, and K. W. Wang – Proc. SPIE Active and Passive Smart Structures and Integrated Systems, March 2014

Abstract

The heaving of ocean waves is a largely untapped, renewable kinetic energy resource. Conversion of this energy into electrical power could integrate with solar technologies to provide for round-the-clock, portable, and mobile energy supplies usable in a wide variety of marine environments. However, the direct drive conversion methodology of grid integrated wave energy converters does not efficiently scale down to smaller, portable architectures. This research develops an alternative power conversion approach to harness the extraordinarily large heaving displacements and long oscillation periods as an excitation source for an extendible vibration energy harvesting chain. Building upon related research findings and engineering insights, the proposed system joins together a series of dynamic cells through bistable interfaces. Continue reading

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Experimental Study of Darrieus-Savonius Water Turbine with Deflector: Effect of Deflector on the Performance


Kaprawi Sahim, Kadafi Ihtisan, Dyos Santoso, and Riman Sipahutar – International Journal of Rotating Machinery, February 2014

Abstract

The reverse force on the returning blade of a water turbine can be reduced by setting a deflector on the returning blade side of a rotor. The deflector configuration can also concentrate the flow which passes through the rotor so that the torque and the power of turbine can be considerably increased. The placing of Savonius in Darrieus rotor is carried out by setting the Savonius bucket in Darrieus rotor at the same axis. The combination of these rotors is also called a Darrieus-Savonius turbine. This rotor can improve torque of turbine. Experiments are conducted in an irrigation canal to find the performance characteristics of presence of deflector and Savonius rotor in Darrieus-Savonius turbine. Results conclude that the single deflector plate placed on returning blade side increases the torque and power coefficient. The presence of Savonius rotor increases the torque at a lower speed, but the power coefficient decreases. The torque and power coefficient characteristics depend on the aspect ratio of Savonius rotor.

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Wave Basin Experiments with Large Wave Energy Converter Arrays to Study Interactions between the Converters and Effects on Other Users in the Sea and the Coastal Area


Vasiliki Stratigaki, Peter Troch, Tim Stallard, David Forehand, Jens Peter Kofoed, Matt Folley, Michel Benoit, Aurélien Babarit and Jens Kirkegaard – Energies, February 2014

Abstract

Experiments have been performed in the Shallow Water Wave Basin of DHI (Hørsholm, Denmark), on large arrays of up to 25 heaving point absorber type Wave Energy Converters (WECs), for a range of geometric layout configurations and wave conditions. WEC response and modifications of the wave field are measured to provide data for understanding WEC array interactions and to evaluate array interaction numerical models. Each WEC consists of a buoy with a diameter of 0.315 m and power take-off (PTO) is modeled by realizing friction based energy dissipation through damping of the WEC’s motion. Continue reading

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Analytical and experimental evaluation of energy storage using work of buoyancy force


Abdul Hai Alami – Journal of Renewable and Sustainable Energy, 2014

Abstract

This paper presents theoretical formulation of, and experiments on a method of energy storage using the work of buoyancy force. The experiments proved that the energy storage using buoyancy force is an effective approach, as the experimental efficiency was found to exceed the theoretical estimation due to material properties of the buoys. The storage of mechanical energy without subsequent conversion into electrical energy has many advantages, including more compact storage setups, higher energy density retrieval, and higher efficiencies. For the current system, the efficiency of energy storage exceeds 37%. This value corresponds to earlier work by the author conducted for a single buoy, extending the prospects and applications of this approach to a better position in non-conventional energy storage applications.

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Power extraction using flow-induced vibration of a circular cylinder placed near another fixed cylinder


Yoshiki Nishi, Yuta Ueno, Masachika Nishio, Luis Antonio Rodrigues Quadrante, and Kentaroh Kokubun – Journal of Sound and Vibration, May 2014

Abstract

We conducted an experiment in a towing tank to investigate the performance of an energy extraction system using the flow-induced vibration of a circular cylinder. This experiment tested three different cases involving the following arrangements of cylinder(s) of identical diameter: the upstream fixed–downstream movable arrangement (case F); the upstream movable–downstream fixed arrangement (case R); and a movable isolated cylinder (case I). In cases F and R, the separation distance (ratio of the distance between the centers of the two cylinders to their diameters) is fixed at 1.30. Measurement results show that while cases F and I generate vortex-induced vibration (VIV) resonance responses, case R yields wake-induced vibration (WIV) at reduced velocity over 9.0, which is significantly larger than that of the VIV response, leading to the induction of higher electronic power in a generator. Accordingly, primary energy conversion efficiency is higher in the case involving WIV.

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Experimental study of the turbulence intensity effects on marine current turbines behaviour – Part I: One single turbine


Paul Mycek, Benoît Gaurier, Grégory Germain, Grégory Pinon, and Elie Rivoalen – Renewable Energy, February 2014

Abstract

The ambient turbulence intensity in the upstream flow plays a decisive role in the behaviour of horizontal axis marine current turbines. Experimental trials, run in the IFREMER flume tank in Boulogne-Sur-Mer (France) for two different turbulence intensity rates, namely 3% and 15%, are presented. They show, for the studied turbine configuration, that while the wake of the turbine is deeply influenced by the ambient turbulence conditions, its mean performances turn out to be slightly modified. The presented conclusions are crucial in the view of implanting second generation turbines arrays. In addition, complete and detailed data sets (wake profiles and performance graphs) are made available to the scientific community in order to encourage further comparisons.

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Experimental study of the turbulence intensity effects on marine current turbines behaviour – Part II: Two interacting turbines


Paul Mycek, Benoît Gaurier, Grégory Germain, Grégory Pinon, and Elie Rivoalen – Renewable Energy, February 2014

Abstract

The future implantation of second generation marine current turbine arrays depends on the understanding of the negative interaction effects that exist between turbines in close proximity. This is especially the case when the turbines are axially aligned one behind another in the flow. In order to highlight these interaction effects, experiments were performed in a flume tank on 3-bladed 1/30th scale prototypes of horizontal axis turbines. Continue reading

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Energy Extraction from Shallow Tidal Flows


Jack William Giles – University of Southampton, PhD Dissertation, December 2013

Abstract

Over the past decade within the renewable energy sector a strong research and development focus has resulted in the growth of an embryonic tidal stream energy industry. Previous assessments of the tidal stream resource appear to have neglected shallow tidal flows. This resource located in water depths of 10-30m is significant because it is generally more accessible for energy extraction than deeper offshore tidal sites and hence a good location for first generation tidal stream arrays or fences. The close proximity to shore may lead to improvements in construction feasibility and economic prospects. The objective of this project is to investigate several aspects concerning the exploitation of shallow tidal flows for energy extraction. Fundamental to this project is the importance of developing research alongside and in conjunction with industrial shallow water
prototype projects. Continue reading

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