Browsing by Author "Sebastian, B."

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Coupled dynamic analysis of semi-submersible floating wind turbine integrated with oscillating water column WEC
(Springer Science and Business Media Deutschland GmbH, 2024) Sebastian, B.; Karmakar, D.; Rao, M.
The present study envisages to investigate the coupled dynamic behaviour of three configurations of a hybrid wind-wave energy system integrating Oscillating Water Column (OWC) wave energy converters to DeepCwind semi-submersible supporting an NREL (National Renewable Energy Laboratory) 5 MW wind turbine. DeepCwind semi-submersible is a platform designed specifically for the purpose of supporting floating offshore wind turbines and the stability of the platform has been well confirmed by scaled-down experiments and numerical studies. The numerical simulation for the present study is performed using the aero-hydro-servo-elastic tool OpenFAST. The dynamic responses of the hybrid platforms are determined for different operational and parked wind speed conditions of the wind turbine in irregular waves. The motion responses, tower base forces and moments, mooring tensions and power absorption of the hybrid configurations have been characterized. Furthermore, the effect of coupling between the semi-submersible platform and the OWCs is studied by comparing the results of the combined platforms with that of the uncoupled wind energy platform. The coupled dynamic analysis in the time domain shows that increasing the number of OWC helps to reduce the motion responses in heave and pitch. The capture width ratio of the system is observed to be highest for hybrid configuration with a single OWC device. The present study will be helpful in the design and analysis of hybrid floating wave-wind energy platform. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2024.
Dynamic analysis of a semi-submersible offshore floating wind turbine combined with wave energy converters
(Taylor and Francis Ltd., 2025) Sebastian, B.; Karmakar, D.; Rao, M.
Hybrid wind–wave energy systems harness both offshore wind and wave energy resources using a shared floating platform, reducing capital and operational costs through common infrastructure. The present study numerically investigates the dynamic performance and power absorption of three hybrid concepts combining the DeepCwind Semi-submersible Platform (SSP) with (i) Oscillating Water Columns (OWC), (ii) Torus Wave Energy Converter (WEC), and (iii) Flap-type WEC. Frequency-domain analyses using WAMIT and time-domain simulations using OpenFAST are performed to assess platform motions, tower base moments, mooring tensions, and WEC power output for different sea states. The integration of WECs significantly improves the hydrodynamic behaviour of the DeepCwind SSP. Flap-type WECs demonstrate the best dynamic performance, reducing heave and pitch by up to 68% and 58%, and mooring tension by 54%. The OWC system achieves the highest power absorption and a 55% capture width ratio, but increases surge and pitch motions by 6% and 27%, respectively, on introducing additional loads on the system. © 2025 Informa UK Limited, trading as Taylor & Francis Group.
Dynamic analysis of a TLP-type floating wind turbine combined with OWC wave energy converter
(Springer Nature, 2025) Sebastian, B.; Joju, A.; Karmakar, D.
The present study examines the dynamic effects of integrating oscillating water column wave energy converters on the offset columns of a tension leg floating wind turbine platform in an asymmetric and symmetric configuration. Two configurations are considered, featuring two and four oscillating water columns combined with the tension leg platform supporting a 5 MW wind turbine. The hydrodynamic analysis of the combined wind-wave energy system uses a linear diffraction-radiation tool to compute hydrodynamic coefficients and wave excitation forces in the frequency domain. The coupled dynamic responses of the hybrid platforms are evaluated in the time domain under various irregular sea states, using an aero-hydro-servo-elastic simulation tool. The performance of the hybrid systems is compared with a baseline floating wind turbine platform to quantify changes in dynamic responses. Power absorption of the oscillating water columns is computed using a linear power take-off system. The findings indicate that adding oscillating water columns leads to a slight increase in the heave and pitch motions of the platform. The system with a diagonally placed two-oscillating water column configuration demonstrates higher efficiency, achieving a maximum capture width ratio of 57%. This study provides valuable insights into the feasibility of hybrid offshore renewable energy concepts. It supports the design and implementation of integrated wind-wave systems to deliver clean and sustainable energy. © The Author(s), under exclusive licence to Sociedade Brasileira de Engenharia Naval 2025.
Dynamic behaviour and power performance of a Septon semisubmersible floating wind turbine integrated with wave energy converters
(Nature Research, 2025) Sebastian, B.; Karmakar, D.; Rao, M.
The development of renewable energy sources is inevitable to create a sustainable society for the future. Hybrid wind and wave energy systems are highly regarded as a solution to reduce the cost of energy from offshore wind and waves. The manuscript presents a novel semi-submersible floating wind platform referred to as Septon which is designed with the intention of hosting a multitude of wave energy devices in addition to a wind turbine. Three different wave energy converters (WEC) namely oscillating water column, Torus and point absorber along with their combinations with the Septon platform are considered in the study to understand the dynamic behaviour and power absorption of standalone and integrated configuration. Seven different configurations of the hybrid system are considered for the analysis. Coupled dynamic analysis is performed using an aero-hydro-servo-elastic tool based on boundary element method to analyze the responses of the hybrid platforms under realistic sea states. The motion responses, tower base moments, mooring tensions and power absorption of the hybrid systems are analyzed and compared with the Septon floating wind platform to quantify the effect of various combination of WECs around the wind turbine platform. The numerical results shows that different combinations have a significant impact on the dynamic responses of the platform. The study identifies the hybrid system combining OWC and Torus with the proposed Septon platform as the concept with maximum efficiency in power absorption. © The Author(s) 2025.
Dynamic performance of Torus wave energy converter combined with offshore wind turbine semi-submersible platform
(CRC Press, 2024) Sebastian, B.; Karmakar, D.; Guedes Soares, C.
This article investigates the effect of incorporating a heaving wave energy converter (WEC), namely Torus on DeepCwind Semi-submersible platform (SSP) supporting a 5MW wind turbine. The hydrodynamic performance of the hybrid torus-SSP is studied using linear diffraction/radiation code WAMIT. The coupled dynamic analysis of the platform is carried out in the OpenFAST tool which takes the hydrodynamic parameters from WAMIT as input. The motion responses of the hybrid system are obtained in time domain for different irregular sea states. Statistics of motion of hybrid system is computed and compared with the initial platform to quantify the variation. The power absorption of the WEC is computed using a stand-alone MATLAB code. The maximum power is found to be absorbed at the resonance period of the semi-submersible platform. The results indicate that incorporating Torus does not cause a considerable change in the platform dynamics while rendering higher power output to the overall system. © 2024 selection and editorial matter, Carlos Guedes Soares and Tiago A. Santos; individual chapters, the contributors.
Parametric study on the effect of mooring configurations on the dynamic responses of the Septon semi-submersible 5 MW floating wind turbine
(Springer Science and Business Media Deutschland GmbH, 2025) Sebastian, B.; Karmakar, D.; Rao, M.
Offshore floating wind turbines (FWTs) offer a promising solution for harnessing wind energy in deep waters, where fixed-bottom turbines become impractical. Over the past decade, consistent advancements in technology have significantly reduced the levelized cost of energy, making large-scale deployment of FWTs increasingly feasible. The key factors influencing both cost and performance include the design and optimization of the substructure, mooring system, and power grid. The mooring system plays a pivotal role in ensuring platform stability and minimizing excessive motions that could impact the energy production efficiency and structural integrity of the FWT. The present study investigates the effects of different mooring configurations on the dynamic response of a novel semi-submersible wind turbine platform. This study analyzes two distinct mooring arrangements, spread mooring and cross-mooring, to determine the optimal configuration. The numerical investigation takes into account multiple parametric variations, including spread angle, cross angle, mooring line diameter, and line length, assessing their effects on platform motions and mooring line tensions. Numerical simulations are performed using an aero-hydro-servo-elastic simulation, which considers the coupled interactions of wind, waves, and structural components under various irregular sea states. This study reveals that the choice of mooring configuration significantly affects both platform stability and mooring line loads. A spread mooring system with a 30–60° divergence angle is identified as the optimal configuration for minimizing platform motions while keeping mooring tensions within safe operational limits. Conversely, cross-mooring configurations tend to exhibit higher tensions, particularly at larger cross angles. The cross-moorings require a minimum of 15–35 m additional mooring length compared to spread moorings for line tension to be within safe limits. The findings from the present study offer valuable insights into the optimal design of mooring systems for floating wind turbines, contributing to enhanced performance and reliability in deep water offshore wind farms. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2025.