Next Article in Journal / Special Issue
Comparison of the Experimental and Numerical Results of Modelling a 32-Oscillating Water Column (OWC), V-Shaped Floating Wave Energy Converter
Previous Article in Journal
A Two-Stage Continuous Fermentation System for Conversion of Syngas into Ethanol
Previous Article in Special Issue
Modeling of a Point Absorber for Energy Conversion in Italian Seas
Energies 2013, 6(8), 4001-4044; doi:10.3390/en6084001
Article

Discrete Displacement Hydraulic Power Take-Off System for the Wavestar Wave Energy Converter

1,2,* , 2
 and
2
1 Department of Energy Technology, Aalborg University, Pontoppidanstrade 101, Aalborg DK-9220, Denmark 2 Wavestar, Park Alle 350A, Broendby DK-2605, Denmark
* Author to whom correspondence should be addressed.
Received: 14 May 2013 / Revised: 28 June 2013 / Accepted: 15 July 2013 / Published: 7 August 2013
(This article belongs to the Special Issue Energy from the Ocean - Wave and Tidal Energy)
SciFeed

Abstract

The Wavestar Wave Energy Converter (WEC) is a multiple absorber concept, consisting of 20 hemisphere shaped floats attached to a single platform. The heart of the Wavestar WEC is the Power Take-Off (PTO) system, converting the wave induced motion of the floats into a steady power output to the grid. In the present work, a PTO based on a novel discrete displacement fluid power technology is explored for the Wavestar WEC. Absorption of power from the floats is performed by hydraulic cylinders, supplying power to a common fixed pressure system with accumulators for energy smoothing. The stored pressure energy is converted into electricity at a steady pace by hydraulic motors and generators. The storage, thereby, decouples the complicated process of wave power absorption from power generation. The core for enabling this PTO technology is implementing a near loss-free force control of the energy absorbing cylinders. This is achieved by using special multi-chambered cylinders, where the different chambers may be connected to the available system pressures using fast on/off valves. Resultantly, a Discrete Displacement Cylinder (DDC) is created, allowing near loss free discrete force control. This paper presents a complete PTO system for a 20 float Wavestar based on the DDC. The WEC and PTO is rigorously modeled from incident waves to the electric output to the grid. The resulting model of +600 states is simulated in different irregular seas, showing that power conversion efficiencies above 70% from input power to electrical power is achievable for all relevant sea conditions.
Keywords: wave energy; PTO; Wavestar; hydraulics; WEC wave energy; PTO; Wavestar; hydraulics; WEC
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

Share & Cite This Article

Further Mendeley | CiteULike
Export to BibTeX |
EndNote |
RIS
MDPI and ACS Style

Hansen, R.H.; Kramer, M.M.; Vidal, E. Discrete Displacement Hydraulic Power Take-Off System for the Wavestar Wave Energy Converter. Energies 2013, 6, 4001-4044.

View more citation formats

Related Articles

Article Metrics

For more information on the journal, click here

Comments

[Return to top]
Energies EISSN 1996-1073 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert