scholarly journals Design Optimisation of a Multi-Mode Wave Energy Converter

2020 ◽  
Author(s):  
Nataliia Y. Sergiienko ◽  
Mehdi Neshat ◽  
Leandro S. P. da Silva ◽  
Brad Alexander ◽  
Markus Wagner
Keyword(s):  
Wave Energy ◽  
Average Power ◽  
Clean Energy ◽  
Wave Energy Converter ◽  
Irregular Waves ◽  
Viscous Drag ◽  
Design Parameters ◽  
Energy Converter ◽  
Design Optimisation ◽  
Anchor System

Abstract A wave energy converter (WEC) similar to the CETO system developed by Carnegie Clean Energy is considered for design optimisation. This WEC is able to absorb power from heave, surge and pitch motion modes, making the optimisation problem nontrivial. The WEC dynamics is simulated using the spectral-domain model taking into account hydrodynamic forces, viscous drag, and power take-off forces. The design parameters for optimisation include the buoy radius, buoy height, tether inclination angles, and control variables (damping and stiffness). The WEC design is optimised for the wave climate at Albany test site in Western Australia considering unidirectional irregular waves. Two objective functions are considered: (i) maximisation of the annual average power output, and (ii) minimisation of the levelised cost of energy (LCoE) for a given sea site. The LCoE calculation is approximated as a ratio of the produced energy to the significant mass of the system that includes the mass of the buoy and anchor system. Six different heuristic optimisation methods are applied in order to evaluate and compare the performance of the best known evolutionary algorithms, a swarm intelligence technique and a numerical optimisation approach. The results demonstrate that if we are interested in maximising energy production without taking into account the cost of manufacturing such a system, the buoy should be built as large as possible (20 m radius and 30 m height). However, if we want the system that produces cheap energy, then the radius of the buoy should be approximately 11–14 m while the height should be as low as possible. These results coincide with the overall design that Carnegie Clean Energy has selected for its CETO 6 multi-moored unit. However, it should be noted that this study is not informed by them, so this can be seen as an independent validation of the design choices.

scholarly journals Experimental Analysis of a Novel Adaptively Counter-Rotating Wave Energy Converter for Powering Drifters

2019 ◽  
Vol 7 (6) ◽  
pp. 171 ◽  
Author(s):  
Guoheng Wu ◽  
Zhongyue Lu ◽  
Zirong Luo ◽  
Jianzhong Shang ◽  
Chongfei Sun ◽  
...  
Keyword(s):  
Wave Energy ◽  
Wave Energy Converter ◽  
Irregular Waves ◽  
Surface Velocity ◽  
Small Scale ◽  
Power Constraint ◽  
Energy Converter ◽  
Wave Tank ◽  
Wide Range ◽  
Rotating Wave

Nowadays, drifters are used for a wide range of applications for researching and exploring the sea. However, the power constraint makes it difficult for their sampling intervals to be smaller, meaning that drifters cannot transmit more accurate measurement data to satellites. Furthermore, due to the power constraint, a modern Surface Velocity Program (SVP) drifter lives an average of 400 days before ceasing transmission. To overcome the power constraint of SVP drifters, this article proposes an adaptively counter-rotating wave energy converter (ACWEC) to supply power for drifters. The ACWEC has the advantages of convenient modular integration, simple conversion process, and minimal affection by the crucial sea environment. This article details the design concept and working principle, and the interaction between the wave energy converter (WEC) and wave is presented based on plane wave theory. To verify the feasibility of the WEC, the research team carried out a series of experiments in a wave tank with regular and irregular waves. Through experiments, it was found that the power and efficiency of the ACWEC are greatly influenced by parameters such as wave height and wave frequency. The maximum output power of the small scale WEC in a wave tank is 6.36 W, which allows drifters to detect ocean data more frequently and continuously.

Modeling and Experiment of a Novel Micro Wave Energy Converter

2017 ◽  
Vol 863 ◽  
pp. 175-182
Author(s):  
Yi Ming Zhu ◽  
Zi Rong Luo ◽  
Zhong Yue Lu ◽  
Jian Zhong Shang
Keyword(s):  
Output Power ◽  
Wave Energy ◽  
Mechanical Energy ◽  
Vertical Motion ◽  
Electrical Energy ◽  
Wave Energy Converter ◽  
Design Parameters ◽  
Energy Converter ◽  
Drive Power ◽  
Continuous Rotation

This paper proposed a novel micro wave energy converter which can convert irregular wave energy into rotating mechanical energy, then into electrical energy. The device consists of an energy absorption part and an energy conversion part. In details, the blades are installed on the absorber circumferentially and averagely, which are capable of converting the vertical motion of the surface body to continuous rotation of the absorber and leading to a great increase in efficiency. A physical prototype was built to test the performance of the novel generator and optimize the design parameters. In the experiment part, a linear motion electric cylinder was used as the drive power to provide the heaving motion for the device. And the experiment platform was built for modeling a marine environment. Also, a data acquisition program was edited in Labview. Thus, the experiment analyzed the influence of amplitude, frequency, blade angle and resistance value to the output power, and then obtained the optimum parameters combination which can maximize the value of the output power. The result will provide reference for the device’s further application.

scholarly journals Using Flexible Blades to Improve the Performance of Novel Small-Scale Counter-Rotating Self-Adaptable Wave Energy Converter for Unmanned Marine Equipment

2019 ◽  
Vol 7 (7) ◽  
pp. 223 ◽  
Author(s):  
Sun ◽  
Shang ◽  
Luo ◽  
Lu ◽  
Wu ◽  
...  
Keyword(s):  
Output Power ◽  
Wave Energy ◽  
Power Supply ◽  
Simulation Analysis ◽  
Average Power ◽  
Wave Energy Converter ◽  
Small Scale ◽  
Energy Converter ◽  
Experimental Conditions ◽  
Blade Thickness

Unmanned marine equipment has been increasingly developed for open seas. The lack of efficient and reliable power supply is currently one of the bottlenecks restricting the practical application of these devices. In order to provide a viable power supply method for unmanned marine equipment, such as sonic buoys and sea robots, we originally propose a novel small-scale flexible blade wave energy converter (WEC) based on self-adaptable counter-rotating operation mechanism. The flexible blade WEC is designed on the basis of the rigid blade WEC with the caging device. This paper identifies the key factors affecting WEC performance through theoretical analysis. According to the numerical simulation analysis, the output mechanical power of the double-layer absorber is 12.8 W, and the hydraulic efficiency is 36.3%. The results of the verification experiment show that the peak power of WEC is 5.8 W and the average power is 3.2 W. The WEC with 65Mn flexible blade under most experimental conditions has the best performance when the blade thickness is 0.10 mm. The study shows that the new generation WEC can effectively overcome the excessive fluctuation of the output power of the previous generation WEC. The output power curve of the novel WEC is relatively smooth, which is conducive to its smooth operation and subsequent utilization and storage of electrical energy.

Latching Control of a Floating Oscillating Water Column Wave Energy Converter in Irregular Waves

2014 ◽  
Author(s):  
João C. C. Henriques ◽  
Juan C. Chong ◽  
António F. O. Falcão ◽  
Rui P. F. Gomes
Keyword(s):  
Water Column ◽  
Wave Energy ◽  
Rotational Speed ◽  
Phase Control ◽  
Wave Energy Converter ◽  
Irregular Waves ◽  
Oscillating Water Column ◽  
Random Waves ◽  
Energy Converter ◽  
Excitation Force

The paper concerns the phase control by latching of a floating oscillating-water-column (OWC) wave energy converter of spar-buoy type in irregular random waves. The device is equipped with a two-position fast-acting valve in series with the turbine. The instantaneous rotational speed of the turbine is controlled through the power electronics according to a power law relating the electromagnetic torque on the generator rotor to the rotational speed, an algorithm whose adequacy had been numerically tested in earlier papers. Two alternative strategies (1 and 2) for the latching/unlatching timings are investigated. Strategy 1 is based on the knowledge of the zero-crossings of the excitation force on the floater-tube set. This is difficult to implement in practice, since the excitation force can neither be measured directly nor predicted. Strategy 2 uses as input easily measurable physical variables: air pressure in the chamber and turbine rotational speed. Both strategies are investigated by numerical simulation based on a time-domain analysis of a spar-buoy OWC equipped with a self-rectifying radial-flow air turbine of biradial type. Air compressibility in the chamber plays an important role and was modelled as isentropic in a fully non-linear way. Numerical results show that significant gains up to about 28% are achievable through strategy 1, as compared with no phase control. Strategy 2, while being much easier to implement in practice, was found to yield more modest gains (up to about 15%).

Design and Hydrodynamic Performance Testing of One-Base Multi-Buoy Floating Sharp Eagle Wave Energy Converter

2015 ◽  
Vol 1092-1093 ◽  
pp. 152-157
Author(s):  
Zhen Peng Wang ◽  
Ya Ge You ◽  
Ya Qun Zhang ◽  
Song Wei Sheng ◽  
Hong Jun Lin
Keyword(s):  
Wave Energy ◽  
High Efficiency ◽  
Performance Testing ◽  
Clean Energy ◽  
Wave Energy Converter ◽  
Hydrodynamic Performance ◽  
Wave Direction ◽  
Energy Converter ◽  
Working Principle ◽  
Period Wave

Research on wave energy extraction has been conducted in many countries to meet the growing demand for clean energy. To find an efficient and economic way to convert wave energy, an one-base multi-buoy offshore floating Sharp Eagle wave energy converter is designed, consisting of four Eagle head absorbing buoys, one semi-submersible barge, one energy conversion system, buoyancy tanks, underwater appendages and other components. The working principle of the device is described in this paper. To test the hydrodynamic performance of device and make an initial evaluation for the design, a model experiment of 1/13.78th scale was carried out. The influence of wave period, wave height, pressure in hydrocylinders and wave direction is tested. All the efficiencies in different conditions are compared with each other, while the high efficiency and stability of device are verified.

Latching Control of an OWC Spar-Buoy Wave Energy Converter in Regular Waves

2012 ◽  
Author(s):  
J. C. C. Henriques ◽  
A. F. O. Falcão ◽  
R. P. F. Gomes ◽  
L. M. C. Gato
Keyword(s):  
Water Column ◽  
Wave Energy ◽  
Phase Control ◽  
Wave Energy Converter ◽  
Irregular Waves ◽  
Wave Direction ◽  
Regular Waves ◽  
Energy Converter ◽  
Chamber Volume ◽  
The Time Domain

The present paper concerns an OWC spar-buoy, possibly the simplest concept for a floating oscillating-water-column (OWC) wave energy converter. It is an axisymmetric device (and so insensitive to wave direction) consisting basically of a (relatively long) submerged vertical tail tube open at both ends, fixed to a floater that moves essentially in heave. The length of the tube determines the resonance frequency of the inner water column. The oscillating motion of the internal free surface relative to the buoy, produced by the incident waves, makes the air flow through a turbine that drives an electrical generator. It is well known that the frequency response of point absorbers like the spar buoy is relatively narrow, which implies that their performance in irregular waves is relatively poor. Phase control has been proposed to improve this situation. The present paper presents a theoretical investigation of phase control by latching of an OWC spar-buoy in which the compressibility of air in the chamber plays an important role (the latching is performed by fast closing and opening an air valve in series with the turbine). In particular such compressibility may remove the constraint of latching threshold having to coincide with an instant of zero relative velocity between the two bodies (in the case under consideration, between the floater and the OWC). The modelling is performed in the time domain for a given device geometry, and includes the numerical optimization of the air turbine rotational speed, chamber volume and latching parameters. Results are obtained for regular waves.

scholarly journals KNSwing—On the Mooring Loads of a Ship-Like Wave Energy Converter

2019 ◽  
Vol 7 (2) ◽  
pp. 29
Author(s):  
Kim Nielsen ◽  
Jonas Thomsen
Keyword(s):  
Numerical Model ◽  
Wave Energy ◽  
Numerical Models ◽  
Breaking Waves ◽  
Wave Energy Converter ◽  
Experimental Results ◽  
Irregular Waves ◽  
Mooring System ◽  
Energy Converter ◽  
The Waves

The critical function of keeping a floating Wave Energy Converter in position is done by a mooring system. Several WECs have been lost due to failed moorings, indicating that extreme loads, reliability and durability are very important aspects. An understanding of the interaction between the WEC’s motion in large waves and the maximum mooring loads can be gained by investigating the system at model scale supported by numerical models. This paper describes the testing of a novel attenuator WEC design called KNSwing. It is shaped like a ship facing the waves with its bow, which results in low mooring loads and small motions in most wave conditions when the structure is longer than the waves. The concept is tested using an experimental model at scale 1:80 in regular and irregular waves, moored using rubber bands to simulate synthetic moorings. The experimental results are compared to numerical simulations done using the OrcaFlex software. The experimental results show that the WEC and the mooring system survives well, even under extreme and breaking waves. The numerical model coefficient concerning the nonlinear drag term for the surge motion is validated using decay tests. The numerical results compare well to the experiments and, thereby, the numerical model can be further used to optimize the mooring system.

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