Wave Energy Technologies in Korea

A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Energy Systems".

Deadline for manuscript submissions: closed (30 September 2021) | Viewed by 15797

Special Issue Editors

Marine Renewable Energy Research Division, Korea Research Institute of Ships and Ocean Engineering, Daejeon 34103, Korea
Interests: wave energy conversion and system design; floating offshore wind energy platform and system design; nonlinear and extreme wave mechanics
Department of Naval Architecture and Ocean Engineering, College of Engineering, Seoul National University, Seoul 08826, Korea
Interests: ship seakeeping and maneuvering; offshore hydrodynamics; marine operation and energy utilization
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Special Issue Information

Dear Colleagues,

The development of wave energy technologies in Korea has shown significant progress in recent years, and prototype devices are being actively tested in Korean coastal waters. Wave energy resources are abundant around the Korean peninsula, and the blue economy—including marine renewables—has become a key strategy for the Korean energy mix, which provides great opportunities for wave energy development in Korea. I would like to invite wave energy experts to share their experience and knowledge on the innovative and advanced technologies for wave energy harvesting. In particular, I encourage Korean researchers to submit laboratory and field research achievements in wave energy systems and their hybrid technologies which have been mainly developed in Korea. However, this call is also open to global experts who have studied relevant technologies applicable and optimized for Korean coastal waters. This Special Issue will greatly promote the development of wave energy in Korea as well as the future collaboration between wave energy researchers.

Dr. Keyyong Hong
Dr. Bo Woo Nam
Guest Editors

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Keywords

  • marine renewable energy
  • wave energy resource
  • wave energy converters (WECs)
  • oscillating water columns (OWCs)
  • point absorber
  • wave overtopping
  • oscillating water surge
  • attenuator
  • power take-off (PTO)
  • power control
  • energy storage
  • hybrid system

Published Papers (7 papers)

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Research

18 pages, 8723 KiB  
Article
Dynamic Response Analysis of a Wavestar-Type Wave Energy Converter Using Augmented Formulation in Korean Nearshore Areas
by Sanghwan Heo and Weoncheol Koo
Processes 2021, 9(10), 1721; https://doi.org/10.3390/pr9101721 - 25 Sep 2021
Cited by 6 | Viewed by 2662
Abstract
Interest in water wave power generation, a promising source of renewable energy, is increasing. Numerous types of wave energy converters (WECs) have been designed to transform wave energy into electricity. In this study, we focus on heaving point absorbers (HPAs) of the Wavestar [...] Read more.
Interest in water wave power generation, a promising source of renewable energy, is increasing. Numerous types of wave energy converters (WECs) have been designed to transform wave energy into electricity. In this study, we focus on heaving point absorbers (HPAs) of the Wavestar type, which consist of multiple floats connected to a bottom-fixed ocean structure by structural arms and hinges. Each float moves up and down due to wave forces and produces electricity using the hydraulic power take-off (PTO) system connected directly to the float. A numerical procedure using the three-dimensional augmented formulation was developed to calculate the rotational motion of the float. The frequency-dependent coefficients were calculated using the hydrodynamic solver WAMIT. The nonlinear Froude–Krylov and hydrostatic forces were considered. For the environmental conditions, the wave data of four nearshore areas in Korea, obtained from the Korea Meteorological Administration (KMA), were used. Under the given environmental conditions, Buan was found to be the most suitable area among the locations selected for installing a Wavestar-type WEC without considering installation and maintenance costs. Full article
(This article belongs to the Special Issue Wave Energy Technologies in Korea)
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19 pages, 6396 KiB  
Article
Advanced Maximum Power Control Algorithm Based on a Hydraulic System for Floating Wave Energy Converters
by Chan Roh, Yoon-Jin Ha, Seungh-Ho Shin, Kyong-Hwan Kim and Ji-Yong Park
Processes 2021, 9(10), 1712; https://doi.org/10.3390/pr9101712 - 24 Sep 2021
Cited by 4 | Viewed by 1488
Abstract
An integrated analysis is required to evaluate the performance of control algorithms used in power take-off (PTO) systems for floating wave energy converters (FWECs). However, research on PTO systems based on the existing hydraulic device has mainly focused on the input power generation [...] Read more.
An integrated analysis is required to evaluate the performance of control algorithms used in power take-off (PTO) systems for floating wave energy converters (FWECs). However, research on PTO systems based on the existing hydraulic device has mainly focused on the input power generation performance rather than on obtaining maximum power through hydraulic device-based electrical load control. The power generation performance is analyzed based on the control variables of the existing torque control algorithm (TCA); however, the amount of power generation for each control variable changes significantly based on the cycle of wave excitation moments. This paper proposes a control algorithm to obtain the maximum power by modeling a hydraulic-device-based integrated FWEC. It also proposes a TCA that can obtain the maximum power regardless of the period of wave excitation moment. The proposed TCA continuously monitors the power generation output and changes the PTO damping coefficient in the direction in which the power generation output can be increased. The proposed TCA increased the output power generation by up to 18% compared to each PTO damping coefficient of the conventional TCA. Thus, the proposed method results in higher power generation regardless of the wave excitation moment cycle and performs better than the existing torque control algorithm. Full article
(This article belongs to the Special Issue Wave Energy Technologies in Korea)
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26 pages, 7368 KiB  
Article
Numerical Study of Non-Linear Dynamic Behavior of an Asymmetric Rotor for Wave Energy Converter in Regular Waves
by Yoon-Jin Ha, Ji-Yong Park and Seung-Ho Shin
Processes 2021, 9(8), 1477; https://0-doi-org.brum.beds.ac.uk/10.3390/pr9081477 - 23 Aug 2021
Cited by 7 | Viewed by 1680
Abstract
This study conducted a numerical investigation on the non-linear motion problems between a Salter duck-type rotor and large waves using CFD simulations. Regular waves of five different wave heights were generated. First, the linear motion of the rotor from the CFD simulation was [...] Read more.
This study conducted a numerical investigation on the non-linear motion problems between a Salter duck-type rotor and large waves using CFD simulations. Regular waves of five different wave heights were generated. First, the linear motion of the rotor from the CFD simulation was verified by comparing it with the existing experimental and frequency domain analysis results. Then, a series of CFD simulations were performed to investigate the non-linear motions of the rotor. In the case of a lower wave height, the CFD simulation results were in good agreement with the experimental and frequency domain analysis results. However, as the wave height increased, the resonance periods were different in each other. In addition, the magnitudes of normalized pitch motions by the wave heights decreased as the wave heights increased. To investigate the aforementioned phenomena, the pitch motion equation was examined using separate CFD simulations. The results showed that changing the restoring moments induced changes in the maximum pitch motions and magnitudes of the normalized pitch motions. In the case of a higher wave height, non-linear phenomena and the changing restoring moments induced non-linear motion. Full article
(This article belongs to the Special Issue Wave Energy Technologies in Korea)
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22 pages, 39332 KiB  
Article
Design and Analysis of a Mooring Buoy for a Floating Arrayed WEC Platform
by Sung Youn Boo and Steffen Allan Shelley
Processes 2021, 9(8), 1390; https://0-doi-org.brum.beds.ac.uk/10.3390/pr9081390 - 10 Aug 2021
Cited by 5 | Viewed by 2974
Abstract
This paper presents the design and analysis of a mooring buoy and its mooring systems to moor a floating platform mounting an arrayed Wave Energy Converters (WECs). The mooring buoy allows the WEC platform to weathervane around the mooring buoy freely by the [...] Read more.
This paper presents the design and analysis of a mooring buoy and its mooring systems to moor a floating platform mounting an arrayed Wave Energy Converters (WECs). The mooring buoy allows the WEC platform to weathervane around the mooring buoy freely by the prevailing environment directions, which enables consistent power generation. The WEC platform is connected to the buoy with synthetic hawsers, while station-keeping of the buoy is maintained with catenary mooring lines of chains tied to the buoy keel. The buoy also accommodates a power cable to transfer the electricity from the WEC platform to the shore. The WEC platform is designed to produce a total of 1.0 MW with multiple WECs installed in an array. Fully coupled time-domain analyses are conducted under the site sea states, including extreme 50 y and survival 100 y conditions. The buoy motions, mooring tensions and other design parameters are evaluated. Strength and fatigue designs of the mooring systems are validated with requirements according to industry standards. Global and local structural designs of the mooring buoy are carried out and confirm the design compliances. Full article
(This article belongs to the Special Issue Wave Energy Technologies in Korea)
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23 pages, 8084 KiB  
Article
Numerical and Experimental Analyses on Motion Responses on Heaving Point Absorbers Connected to Large Semi-Submersibles
by Kyong-Hwan Kim, Sewan Park, Jeong-Rok Kim, Il-Hyoung Cho and Keyyong Hong
Processes 2021, 9(8), 1363; https://0-doi-org.brum.beds.ac.uk/10.3390/pr9081363 - 03 Aug 2021
Cited by 4 | Viewed by 1722
Abstract
This study considers the motion responses of heaving point absorbers (HPAs) connected to large semi-submersibles. To analyze the motion responses for HPAs, a motion response amplitude operator (RAO) of a single HPA connected to a fixed wall was obtained in a two-dimensional wave [...] Read more.
This study considers the motion responses of heaving point absorbers (HPAs) connected to large semi-submersibles. To analyze the motion responses for HPAs, a motion response amplitude operator (RAO) of a single HPA connected to a fixed wall was obtained in a two-dimensional wave flume. A frequency-domain eigenvalue analysis is used to evaluate the motion RAO of a single HPA, and the experimental and numerical results of motion RAO were compared. A model test was conducted to analyze the motions of multiple HPAs connected to a large semi-submersible in a 3D ocean basin. The motion RAOs of the multiple HPAs connected to the large semi-submersible were compared with the motion RAO of the single HPA connected to the fixed wall. Full article
(This article belongs to the Special Issue Wave Energy Technologies in Korea)
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24 pages, 7177 KiB  
Article
Optimal Design of a U-Shaped Oscillating Water Column Device Using an Artificial Neural Network Model
by Arun George, Il-Hyoung Cho and Moo-Hyun Kim
Processes 2021, 9(8), 1338; https://0-doi-org.brum.beds.ac.uk/10.3390/pr9081338 - 30 Jul 2021
Cited by 11 | Viewed by 1932
Abstract
A U-shaped oscillating water column (U-OWC) device has been investigated to enhance power extraction by placing the bottom-mounted vertical barrier in front of a conventional OWC. Then, the optimal design of a U-OWC device has been attempted by using an artificial neural network [...] Read more.
A U-shaped oscillating water column (U-OWC) device has been investigated to enhance power extraction by placing the bottom-mounted vertical barrier in front of a conventional OWC. Then, the optimal design of a U-OWC device has been attempted by using an artificial neural network (ANN) model. First, the analytical model is developed by a matched eigenfunction expansion method (MEEM) based on linear potential theory. Using the developed analytical model, the input and output features for training an ANN model are identified, and then the database containing input and output features is established by a Latin hypercube sampling (LHS) method. With 200 samples, an ANN model is trained with the training data (70%) and validated with the remaining test data (30%). The predictions on output features are made for 4000 random combinations of input features for given significant wave heights and energy periods in irregular waves. From these predictions, the optimal geometric values of a U-OWC are determined by considering both the conversion efficiency and wave force on the barrier. It is found that a well-trained ANN model shows good prediction accuracy and provides the optimal geometric values of a U-OWC suitable for wave conditions at the installation site. Full article
(This article belongs to the Special Issue Wave Energy Technologies in Korea)
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20 pages, 7218 KiB  
Article
Hydrodynamic Analysis of a Multibody Wave Energy Converter in Regular Waves
by Sunny Kumar Poguluri, Dongeun Kim and Yoon Hyeok Bae
Processes 2021, 9(7), 1233; https://0-doi-org.brum.beds.ac.uk/10.3390/pr9071233 - 16 Jul 2021
Cited by 6 | Viewed by 2205
Abstract
A performance assessment of wave power absorption characteristics of isolated and multiple wave energy converter (WEC) rotors was presented in this study for various wave-heading angles and wave frequencies. Numerical hydrodynamic analysis of the WEC was carried out using the three-dimensional linear boundary [...] Read more.
A performance assessment of wave power absorption characteristics of isolated and multiple wave energy converter (WEC) rotors was presented in this study for various wave-heading angles and wave frequencies. Numerical hydrodynamic analysis of the WEC was carried out using the three-dimensional linear boundary element method (BEM) and nonlinear computational fluid dynamics (CFD). Experimental results were used to validate the adopted numerical models. Influence with and without power take-off (PTO) was estimated on both isolated and multiple WEC rotors. Furthermore, to investigate the interaction effect among WECs, a q-factor was used. Incorporation of viscous and PTO damping into the linear BEM solution shows the maximum reduction focused around peak frequency but demonstrated an insignificant effect elsewhere. The q-factor showed both constructive and destructive interactions with the increase of the wave-heading angle and wave frequencies. Further investigation based on the prototype WEC rotor was carried, and calculated results of the linear BEM and the nonlinear CFD were compared. The pitch response and q-factor of the chosen wave frequencies demonstrated satisfactory consistency between the linear BEM and nonlinear CFD results, except for some wave frequencies. Estimated optimal time-averaged power using linear BEM show that the maximum extracted power close to the zero wave-heading angle around the resonance frequency decreases as the wave-heading angle increases. Overall, the linear BEM on the extracted power is overestimated compared with the nonlinear CFD results. Full article
(This article belongs to the Special Issue Wave Energy Technologies in Korea)
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