A modified Wells turbine for wave energy conversion
TL;DR: In this paper, the rotor blade pitch was set asymmetrically at a positive pitch to achieve a higher mean efficiency in a wave cycle and the performance characteristics of a turbine with different blade setting angles in steady flow were found by experimentation.
About: This article is published in Renewable Energy.The article was published on 2003-01-01. It has received 84 citations till now. The article focuses on the topics: Oscillating Water Column & Wells turbine.
Citations
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TL;DR: The aim of event-triggered control is to minimize the control updates, thus providing efficient utilization of resources without compromising the OWC performance, and performance of theET-BSC is better than the ET-SMC in terms of defined indices, control effort, and inter-event execution time.
Abstract: This paper presents event-triggered nonlinear controllers for oscillating water column (OWC) ocean wave energy plant. The study is based on event-triggered backstepping controller (ET-BSC) and event-triggered sliding mode controller (ET-SMC) to control the rotational speed of an OWC turbine coupled to a generator. The designed controllers are capable to avoid the stalling of the Wells turbine so as to maximize its output power. The aim of event-triggered control is to minimize the control updates, thus providing efficient utilization of resources without compromising the OWC performance. In this regard, aperiodic sampling has been applied using an event-triggering rule derived from Lyapunov stability analysis. In order to validate the proposed controllers, simulation results have been performed using a JONSWAP irregular wave model. It is observed that performance of the ET-BSC is better than the ET-SMC in terms of defined indices, control effort, and inter-event execution time.
32 citations
Cites background from "A modified Wells turbine for wave e..."
...The role of controller is to avoid the stalling behavior of Wells turbine [33] by regulating the rotor speed so as to maximize the output power....
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TL;DR: Several pilot plants have been built based on the principle of the Oscillating Water Column (OWC) and the Wells turbine has gained particular attention due to its simplicity and reliability as discussed by the authors.
Abstract: Wave energy is one of the renewable energy sources with the highest potential. Several pilot plants have been built based on the principle of the Oscillating Water Column (OWC). Among the different solutions that have been suggested, the Wells turbine has gained particular attention due to its simplicity and reliability.
32 citations
TL;DR: In this paper, a re-examination of the mechanisms for entropy generation in fluid flow, with a particular emphasis on RANS equations, is presented, and an appropriate methodology for estimating entropy generation is presented.
Abstract: In recent years, a number of authors have studied entropy generation in Wells turbines. This is potentially a very interesting topic, as it can provide important insights into the irreversibilities of the system, as well as a methodology for identifying, and possibly minimizing, the main sources of loss. Unfortunately, the approach used in these studies contains some crude simplifications that lead to a severe underestimation of entropy generation and, more importantly, to misleading conclusions. This paper contains a re-examination of the mechanisms for entropy generation in fluid flow, with a particular emphasis on RANS equations. An appropriate methodology for estimating entropy generation in isolated airfoils and Wells turbines is presented. Results are verified for different flow conditions, and a comparison with theoretical values is presented.
30 citations
TL;DR: In this paper, a 3D CFD model based on Fluent is validated by corresponding experimental data and is used for the numerical simulation of the turbine performance for different setting angles under steady conditions.
29 citations
TL;DR: In this paper, the authors proposed to improve the performance of Wells turbines by optimizing the blade pitch angle, which is implemented using a fully automated optimization algorithm, and achieved an average increase of 4.3% average increase in turbine efficiency.
Abstract: SUMMARY
Wells turbines are among the most practical wave energy converters despite their low aerodynamic efficiency and power produced. It is proposed to improve the performance of Wells turbines by optimizing the blade pitch angle. Optimization is implemented using a fully automated optimization algorithm. Two different airfoil geometries are numerically investigated: the standard NACA 0021 and an airfoil with an optimized profile. Numerical results show that each airfoil has its own optimum blade pitch angle. The present computational fluid dynamics optimization results show that the optimum blade pitch angle for NACA 0021 is +0.3° while that of the airfoil with an optimized profile equals +0.6°.The performance of the investigated airfoils is substantially improved by setting the blades at the optimum blade pitch angle. Both the turbine efficiency and tangential force coefficient are improved, especially at low flow rate and during turbine startup. Up to 4.3% average increase in turbine efficiency is achieved by optimizing the blade pitch angle. A slight improvement of the tangential force coefficient and decrease of the axial force coefficient are also obtained. A tangible increase of the stall-free operating range is also achieved by optimizing the blade pitch angle. Copyright © 2013 John Wiley & Sons, Ltd.
27 citations
Cites methods from "A modified Wells turbine for wave e..."
...[16] for monoplane Wells turbines with NACA 0021 and NACA 0012 airfoil blades....
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...[16] also performed simple calculations and considered the optimum pitch angle for NACA 0021 to be about +10 and +6 during exhalation and inhalation, respectively, and that of NACA 0012 equals +2 with and without guide vanes....
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...[16] for NACA 0012 airfoils at pitch angles g= –4 , –2 , 0 , +2 , and +4 ....
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References
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TL;DR: In this article, the performance of a single plane biplane Wells turbine with or without guide vanes is compared with a wave energy device based on the principle of the oscillating water-air column.
286 citations
TL;DR: In this article, the authors investigated the influence of the turbine aerodynamic design on the overall plant performance, as affected by the turbine peak efficiency and the range of flow rates within which the turbine can operate efficiently.
109 citations
01 Jan 2002
TL;DR: The Mighty Whale is a floating wave power device based on the Oscillating Water Column (OWC) principle, which converts wave energy into electric energy, and produces a relatively calm sea area behind.
Abstract: Mighty Whale is a floating wave power device based on the Oscillating Water Column (OWC) principle. It converts wave energy into electric energy, and produces a relatively calm sea area behind. The open sea tests were begun in September 1998 in Gokasho Bay, Nansei Town, Mie Prefecture. Measurements collected since then include performance data in typhoon seasons. This paper presents the measurements of wave energy absorption, floating body motion, and wave height dissipation. It is expected that these results will be useful in the design of offshore wave power devices in the future.
78 citations
01 Jan 2000
TL;DR: The Mighty Whale as mentioned in this paper was used for open sea tests to investigate the use of wave energy for power generation in Mie Prefecture, Japan, and the results of the tests were summarized in a recent paper.
Abstract: JAMSTEC completed the construction of the prototype device Mighty Whale by May 1998 for open sea tests to investigate practical use of wave energy. Following construction, the prototype was towed to the test location near the mouth of Gokasho Bay in Mie Prefecture. The open sea tests were begun in September 1998, after final positioning and mooring operations were completed. The tests are expected to continue for approximately 2 years. This paper presents an overview of the open sea tests, and summarizes the characteristics of power generation based on the results so far.
59 citations
Journal Article•
TL;DR: In this paper, the performance of the impulse turbine with fixed guide vanes was compared with that of the Wells turbine with a fixed guide vane, and it was shown that the running and starting characteristics of the latter were superior to those of the former under irregular wave conditions.
Abstract: The objective of this paper is to clarify the performance of impulse turbine with fixed guide vanes and to compare it with that of Wells turbine with guide vanes. As a result, a suitable choice of the design factors for the impulse turbine was shown for the inlet angle of rotor blade and the shape of guide vane. Furthermore, it was found that the running and starting characteristics of the impulse turbine were superior to those of the Wells turbine under irregular wave condition.
56 citations