Faculty Publications
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Item Performance of a hybrid TLP floating wind turbine combined with arrays of heaving point absorbers(Elsevier Ltd, 2023) Rony, J.S.; Karmakar, D.In the present study, the hydrodynamic performance of circular and concentric arrangements of cone-cylinder-type heaving point absorbers around a Submerged Tension-Leg Platform (STLP) is analysed using the numerical model in the frequency domain based on the potential flow theory. The presence of the Wave Energy Converters (WECs) around the STLP floating wind turbine platform affects the hydrodynamic performance of the hybrid floating platform. So to illustrate the effects of WECs on the platform, the ratio of hydrodynamic coefficients for a single WEC system to that for a hybrid system is analysed. An array of heaving point absorbers is placed in circular and concentric patterns to understand the performance of heaving point absorbers in the absorption of wave energy. The cone-cylinder type heaving point absorber is selected for the present study as they yield more power as compared to other shaped point absorbers. The study compares the wave power absorption of each point absorber around the platform for irregular wave conditions of the North Sea. The effect of incoming waves is illustrated by analysing four different wave heading angles. To quantify the performance of the WECs in an array, the q-factor and coefficient of variation are studied for each array at different sea states. The study suggested the best possible arrangement pattern for wave power absorption and power uniformity among the floaters in the array. The study performed will be helpful in the design and analysis of the possible arrangement of point absorbers around the floating wind turbine platform for wave power absorption. © 2023 Elsevier LtdItem Laboratory-Scale Airborne Wind Energy Conversion Emulator Using OPAL-RT Real-Time Simulator(Multidisciplinary Digital Publishing Institute (MDPI), 2023) Kumar, P.; Kashyap, Y.; Castelino, R.V.; Karthikeyan, A.; Sharma K, M.; Karmakar, D.; Kosmopoulos, P.Airborne wind energy systems (AWES) are more efficient than traditional wind turbines because they can capture higher wind speeds at higher altitudes using connected kite generators. Securing a real wind turbine or a site with favorable wind conditions is not always an assured opportunity for conducting research. Hence, the Research and Development of the Laboratory Scale Airborne Wind Energy Conversion System (LAWECS) require a better understanding of airborne wind turbine dynamics and emulation. Therefore, an airborne wind turbine emulation system was designed, implemented, simulated, and experimentally tested with ground data for the real time simulation. The speed and torque of a permanent magnet synchronous motor (PMSM) connected to a kite are regulated to maximize wind energy harvesting. A field-oriented control technique is then used to control the PMSM’s torque, while a three-phase power inverter is utilized to drive the PMSM with PI controllers in a closed loop. The proposed framework was tested, and the emulated airborne wind energy conversion system results were proven experimentally for different wind speeds and generator loads. Further, the LAWECS emulator simulated a 2 kW, 20 kW, and 60 kW designed with a projected kite area of 5, 25, and 70 square meters, respectively. This system was simulated using the Matlab/Simulink software and tested with the experimental data. Furthermore, the evaluation of the proposed framework is validated using a real-time hardware-in-the-loop environment, which uses the FPGA-based OPAL-RT Simulator. © 2023 by the authors.Item Dynamic analysis of frustum TLP-type wind turbine multi-purpose floating platform(Taylor and Francis Ltd., 2024) Rony, J.S.; Karmakar, D.The coupled dynamic analysis of a hexagon-shaped Frustum Tension-leg platform (FTLP) combined with wave energy converters (WECs) supporting a 5-MW wind turbine is performed to analyse the dynamic responses of the hybrid system. The responses of the FTLP are investigated using the time-domain numerical simulation for the operational sea-states of the wind turbine. The FTLP is integrated with an array of point absorber-type WECs in a circular pattern to analyse the influence of the WECs on the dynamic responses of the floating platform. The aero-servo-hydro-elastic simulation tool FAST and hydrodynamic simulation tool WAMIT is used to study the rigid body motions of the system. The study observes higher rigid body motions in the surge, sway and yaw directions for the hybrid system. Further, the investigation is performed for the forces and moments developed at the base of the wind turbine and the tension developed on mooring cables to understand the integrity and stability of the hybrid platform. © 2023 Informa UK Limited, trading as Taylor & Francis Group.Item Hydrodynamic response analysis of a hybrid TLP and heaving-buoy wave energy converter with PTO damping(Elsevier Ltd, 2024) Rony, J.S.; Karmakar, D.In the present study, the numerical investigation is performed to analyse the hydrodynamic performance of circular and concentric arrangements of cone-cylinder-type heaving point absorber wave energy converter (WEC) around a Frustum Tension-Leg Platform (FTLP) based on potential flow theory. The responses of the single FTLP and the FTLP-WEC hybrid system are analysed for the rated wind speed of a 5 MW wind turbine to observe the influence of the WECs on wind power absorption of wind turbines supported on FTLP. The presence of the FTLP floating wind turbine platform and other WECs affects the hydrodynamic coefficients of the WEC. The influence of the hybrid system on the hydrodynamic coefficients is analysed on determining the ratio of the hydrodynamic coefficients for a single WEC system to those for a hybrid system. Further, the study analyses the instantaneous wave power absorption for the WECs arranged around the FTLP in a circular and concentric pattern. The hydraulic power take-off for the hybrid system with two different control strategies is then discussed to improve the wave power absorption of the WECs. The study observed higher wave power absorption of the WECs with the influence of the PTO system. The mean interaction factor and the capture width ratio of the hybrid system are further studied to understand the influence of array arrangement for the WECs. The hybrid system is noted to have favourable dynamic responses for different environmental factors and contributes positively in increasing power output. © 2024 Elsevier LtdItem 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.