scholarly journals Numerical prediction of the natural frequency of an Oscillating Water Column operating under resonant conditions

2016 ◽  
Vol 7 (3) ◽  
pp. 100-107 ◽  
Author(s):  
Marco Torresi ◽  
Filippo Scarpetta ◽  
Giuseppina Martina ◽  
Pasquale F Filianoti ◽  
Sergio M Camporeale
Keyword(s):  
Water Column ◽  
Natural Frequency ◽  
Wave Energy ◽  
Scale Model ◽  
Oscillating Water Column ◽  
Sea State ◽  
Submerged Breakwater ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations ◽  
Mass Spring

Among the different technologies developed in order to harness wave energy, the Oscillating Water Column devices are the most accredited for an actual diffusion. Recently, Boccotti has patented the REWEC1 (REsonant sea Wave Energy Converter solution 1), a submerged breakwater that performs an active coast protection, embedding an Oscillating Water Column device, which is capable of operating under resonant conditions with that sea state, which gives the highest yearly energy contribution. The REWEC1 dynamic behavior can be approximated by means of a mass-spring-damper system. According to this approximation, a criterion for evaluating the oscillating natural frequency of the REWEC1 has been derived. This criterion has been validated against both experimental results and computational fluid dynamics simulations, performed on a REWEC1 laboratory-scale model. The numerical simulations have shown a good agreement between measurements and predictions.

Scale and Configuration Effects of an Airchamber on PTO of Oscillating Water Column Type Wave Energy Converters

2021 ◽  
Author(s):  
Tomoki Ikoma ◽  
Shota Hirai ◽  
Yasuhiro Aida ◽  
Koichi Masuda
Keyword(s):  
Water Column ◽  
Wave Energy ◽  
Water Surface ◽  
Air Pressure ◽  
Scale Model ◽  
Linear Potential ◽  
Oscillating Water Column ◽  
Wave Energy Converters ◽  
Air Chamber ◽  
Energy Converters

Abstract Wave energy converters (WECs) have been extensively researched. The behaviour of the oscillating water column (OWC) in OWC WECs is extremely complex due to the interaction of waves, air, and turbines. Several problems must be overcome before such WECs can be put to practical use. One problem is that the effect of the difference in scale between a small-scale experimental model and a full-scale model is unclear. In this study, several OWC models with different scales and geometries were used in forced oscillation tests. The wave tank was 7.0 m wide, 24.0 m long, and 1.0 m deep. In the static water experiment, we measured the air pressure and water surface fluctuations in an air chamber. For the experiments, models with a box shape with an open bottom, a manifold shape with an open bottom, and a box shape with a front opening, respectively, were fabricated. Furthermore, 1/1, 1/2, and 1/4 scale models were fabricated for each shape to investigate the effects of scale and shape on the air chamber characteristics. Numerical calculations were carried out by applying linear potential theory and the results were compared with the experimental values. The results confirmed that the air chamber shape and scale affect the air pressure fluctuation and water surface fluctuation inside the OWC system.

Effect of Oscillating Water Column Chamber Inclination on the Performance of a Savonius Rotor

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Deepak D. Prasad ◽  
M. Rafiuddin Ahmed ◽  
Young-Ho Lee
Keyword(s):  
Water Column ◽  
Wave Energy ◽  
Hollow Structure ◽  
Flow Characteristics ◽  
Wave Crest ◽  
Oscillating Water Column ◽  
Sea State ◽  
Wave Condition ◽  
Improved Performance ◽  
Incident Waves

Abstract The power potential in the waves that hit all the coasts worldwide has been estimated to be of the order of 1 TW. Each wave crest transmits 10–50 kW/m of energy, which is 15–20 times higher than wind or solar energies. The availability of wave energy is 90% compared to 30% for wind and solar energies. The oscillating water column (OWC), which is the most investigated wave energy converter consists of a partially submerged hollow structure positioned either vertically or inclined. The bidirectional airflow above the water column drives a turbine. The conventional OWCs experience flow separation at the sharp corners of the chamber. To address this issue, researchers have proposed inclining the chamber at an angle with respect to the incident waves to improve the flow characteristics. In the present work, the effect of OWC inclination on rotor performance is studied using the computational fluid dynamics (CFD) code ansys-cfx. The results highlight that the 55 deg inclined OWC showed improved performance compared to the conventional OWC and modified OWC (optimized in a previous work). The maximum power for the inclined OWC was 13% higher than that for the rotor in the modified OWC and 28% than that in the conventional OWC at mean wave condition. The 55 deg inclined OWC recorded peak rotor power of 23.2 kW with an efficiency of 27.6% at the mean sea state. The peak power and efficiency at maximum sea state were 26.5 kW and 21.5%, respectively.

Effect of Oscillating Water Column Chamber Inclination on the Performance of a Savonius Rotor

2018 ◽  
Author(s):  
Deepak D. Prasad ◽  
Mohammed Rafiuddin Ahmed ◽  
Young-Ho Lee
Keyword(s):  
Water Column ◽  
Wave Energy ◽  
Hollow Structure ◽  
Flow Characteristics ◽  
Wave Crest ◽  
Oscillating Water Column ◽  
Sea State ◽  
Wave Condition ◽  
Improved Performance ◽  
Incident Waves

The global power potential of the waves that hit all the coasts worldwide has been estimated to be in the order of 1 TW. On an average, each wave crest transmits 10–50 kW/m of energy and this corresponds to 15 to 20 times more energy per meter than wind or solar energies. Wave energy is environmentally friendly and is the most consistent of all the intermittent sources. While wind, solar and wave are all intermittent, wave is the most consistent. Availability of waves is 90% compared to 30% for wind and solar energy. The oscillating water column (OWC) is the most investigated wave energy converter (WEC). OWC is a partially submerged hollow structure positioned, either vertically or at an angle. The bidirectional flow of air above the water column is used to drive a turbine. Majority of the OWC devices have chambers which are perpendicular to the incident waves. These conventional OWCs suffer severely from flow separation that occurs at the sharp corners of the chamber. In order to address this issue, researchers have proposed inclining the chamber at an angle with respect to the incident waves. This improves the flow characteristics. In addition to this, the flow in the chamber which ultimately decides the turbine performance, also increases. In the present study, the effect of OWC inclination on rotor performance was numerically studied using commercial computational fluid dynamics (CFD) code ANSYS CFX. The results highlight that the 55° inclined OWC showed improved performance when compared to the conventional OWC and current OWC. The maximum power for the inclined OWC was 13% higher than that recorded for the rotor in the current OWC and 28% than that recorded in the conventional OWC at mean wave condition. The 55° inclined OWC recorded peak rotor power of 23.2 kW which corresponded to an efficiency of 27.6% at the mean sea state. The peak power and efficiency at maximum sea state was 26.5 kW and 21.5% respectively. Higher oscillation was observed in the 55° inclined OWC. The combination of increased flow rate and energy in the flow lead to better performance of the 55° inclined OWC.

scholarly journals Effect of wall inclination on the dynamic behaviour of an oscillating water column system

2020 ◽  
Vol 307 ◽  
pp. 01021
Author(s):  
Abdelhamid El Barakaz ◽  
Abdellatif El Marjani ◽  
Hamid Mounir
Keyword(s):  
Water Column ◽  
Natural Frequency ◽  
Wave Energy ◽  
Maximum Efficiency ◽  
Oscillating Water Column ◽  
Wave Energy Converters ◽  
Column System ◽  
Resonance Domain ◽  
Pneumatic Chamber ◽  
Chamber Model

The Oscillating Water Column device (OWC) is one of the most used Wave Energy Converters (WECs) for wave energy harvesting. It consists essentially of two parts: the pneumatic chamber made of concrete and the bidirectional turbine linked to a generator group for energy production. In this study we are interested in the water motion oscillation inside the chamber resulting from the water level perturbation. This process is characterized by its own natural frequency and global damping. The vertical OWC chamber model is limited by the number of parameters defining the natural frequency and the global damping. The objective of this paper is to improve the performances obtained for the vertical OWC by considering an OWC with inclined sidewalls. For maximum efficiency, the device must operate in the resonance domain where the damping is low and the frequency of incoming waves matches with the natural frequency of the OWC. This will theoretically amplify the pneumatic energy to be converted to a mechanical one in the turbine.

scholarly journals Effective Method for Evaluating Airflow Rate of Oscillating-Water-Column Pilot Plants

Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 1884
Author(s):  
Sewan Park ◽  
Kilwon Kim ◽  
Jeong-Hwan Oh ◽  
Chang-Hyuk Lim ◽  
Ji-Yong Park ◽  
...  
Keyword(s):  
Water Column ◽  
Pilot Plant ◽  
Interpolation Method ◽  
Airflow Rate ◽  
Oscillating Water Column ◽  
Impulse Turbine ◽  
Irregular Wave ◽  
Wave States ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

In this study, a method for effectively estimating the airflow rate of the turbine of an oscillating water column (OWC) pilot plant was developed. The validity of the proposed method was verified through computational fluid dynamics simulations. The method was applied to estimate the airflow rate in irregular wave states based on the operation data obtained for the Yongsoo OWC pilot plant installed in the western seas of Jeju Island, South Korea. As an alternative to estimating the airflow rate of the OWC pilot plant, the impulse turbine performance chart-based interpolation method is introduced, and it is shown that the airflow rate time series calculated using the two methods were in good agreement.

Comparative study of offshore spar-buoy oscillating water column dynamic models for captured power estimation

2022 ◽  
pp. 147509022110677
Author(s):  
Seif Bayoumi ◽  
Erkan Oterkus ◽  
Hassan El-Gamal ◽  
Atilla Incecik
Keyword(s):  
Water Column ◽  
Wave Energy ◽  
Dynamic Models ◽  
Numerical Solutions ◽  
Coupling Model ◽  
Scale Model ◽  
Oscillating Water Column ◽  
Financial Assessment ◽  
Energy Technologies ◽  
Reduced Scale

The prompt estimation of power and geometrical aspects enables faster and more accurate financial assessment of wave energy converters to be deployed. This may lead to better commercialisation of wave energy technologies, as they require location-based customisation, unlike the mature wind energy technologies with developed benchmark. The adopted approach provides simple and efficient modelling tool allowing the study of the system from different perspective. The aim of this study is to select the optimum dynamic model to predict the captured power of a spar-buoy Oscillating Water Column (OWC) wave energy converter. Four dynamic models were developed to predict the system dynamics and results were validated experimentally. In-depth investigations on the effect of the mass and damping ratios of the oscillating bodies on the accuracy of the adopted models were performed. Such investigations included the proposed one-way coupling model and three two-degree of freedom models and three reduced-scale models, in addition to analytical and numerical solutions. Pneumatic power was calculated for the reduced-scale model where orifices’ covers simulated the power take-off mechanism damping experimentally. Analysis and comparisons between the adopted models are finally provided.

scholarly journals Numerical Evaluation of the Hydropneumatic Power of the Oscillating Water Column Wave Energy Converter Submitted to Regular and Irregular Waves

2021 ◽  
pp. 32-43
Author(s):  
Augusto Hack da Silva Koch ◽  
Maycon da Silveira Paiva ◽  
Caroline Barbosa Monteiro ◽  
Phelype Haron Oleinik ◽  
Liércio André Isoldi ◽  
...  
Keyword(s):  
Free Surface ◽  
Water Column ◽  
Wave Energy ◽  
Wave Energy Converter ◽  
Irregular Waves ◽  
Oscillating Water Column ◽  
Regular Waves ◽  
Energy Converter ◽  
Sea State ◽  
Electric Generator

The purpose of this study is to computationally analyze the hydropneumatic power available in the air duct of an Oscillating Water Column (OWC) Wave Energy Converter (WEC) device when subject to realistic sea state data (irregular waves) and when submitted to the regular waves representative of this sea state. The OWC WEC is mainly composed of a hydropneumatic chamber and an air duct where a turbine and electric generator are coupled. The chamber is open below the free surface while the duct is open to the atmosphere. The oscillating movement of the water-free surface inside the chamber causes the air to flow, moving the turbine and generating electricity. To execute this study, a bi-dimensional computational model was considered and numerical simulations of wave generation were carried out using ANSYS Fluent, which is a Computational Fluid Dynamics (CFD) software based on the Finite Volume Method (FVM). The Volume of Fluid (VOF) multi-phase model was applied in the treatment of the water-air interaction. To evaluate the average hydropneumatic power available in the duct, the static pressure, velocity, and air mass flow rate were monitored. The results were analyzed, showing that the available power is 250% greater when the device is subject to realistic irregular waves rather than subject to representative regular waves.

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