A coupled numerical framework for hybrid floating offshore wind turbine and oscillating water column wave energy converters

The offshore wind power exploitation has experienced rapid development in recent years and has gradually moved into deeper waters with the floating wind turbine technology getting mature. Due to the strong concurrence of the wind and wave power in offshore sites, the idea of combined utilization of wind and wave power by one integrated device has attracted tremendous interests worldwide and a number of concepts and designs have been proposed. This article describes a novel integrated floating wind-wave generation platform (FWWP) consisting of a DeepCwind semi-submersible floating offshore wind turbine (FOWT) and a point absorber wave energy convertor (PAWEC). Three models including the single PAWEC, single FOWT, and FWWP are considered to investigate the feasibility of the FWWP and its advantages over the single device. Hydrodynamic analyses are first conducted using the potential flow code AQWA with the viscous correction to investigate the hydrodynamic interactions effect of the integrated model. Then, a fully coupled model for the FWWP is established by calling OpenFAST in AQWA using the F2A method. The accuracy of the established coupled model is firstly validated with OpenFAST for analysing the dynamics of the single FOWT. Finally, fully coupled analyses of the FWWP are carried out for both regular and irregular waves in the operational sea-states. The coupled dynamics and wind and wave power generation of the FWWP are compared with those of the single PAWEC and FOWT for both the regular and irregular waves.

https://www.frontiersin.org/articles/10.3389/fenrg.2022.931057/pdf

Fully Coupled Analysis of an Integrated Floating Wind-Wave Power Generation Platform in Operational Sea-States

The urgent demand for energy structural reform and the limitations of single energy development have promoted the combination of wind energy and wave energy. A hybrid energy system means that two or more energy devices share the same foundation. It reduces the levelized cost of energy and improves competitiveness through infrastructure sharing and increased power output. This paper starts with the development of the joint resources of wind and wave energies, then introduces the foundation forms of the hybrid system. It reviews the latest concepts and devices proposed with the integration of wind energy and wave energy, according to the foundation forms, and makes a preliminary assessment of the synergies of the hybrid system. The existing study methods of the hybrid systems are summarized. In view of the challenges faced by the development of hybrid energy systems, several suggestions are put forward accordingly. This paper provides a comprehensive guideline for the future development of the hybrid wind-wave energy converter system.

A state-of-the-art review of the hybrid wind-wave energy converter

Conceptualization and dynamic response of an integrated system with a semi-submersible floating wind turbine and two types of wave energy converters

To increase the utilization of wave and other renewable energy resources, an integrated system consisting of an offshore wind turbine and a wave energy converter (WEC) could be used to harvest the potential energy. In this study, a dimensionless optimization method is developed for shape optimization of a hollow cylindrical WEC, and an optimal shape is obtained using a differential evolution (DE) algorithm. The frequency domain response characteristics of the WEC with different geometric shapes and viscous damping loads are studied. The numerical model of the wind-wave integrated system, which consists of a semisubmersible platform and the WEC, is developed and used. The dynamic responses of the integrated system with and without using the WEC optimum section are compared. The results show that the dimensionless optimization method utilized in this paper is very applicable for hollow cylindrical WECs. A smaller inner radius and larger draft increase the heave RAO amplitude of the WEC significantly. In addition, optimization of the WEC shape and power take-off (PTO) damping coefficient can significantly improve the energy capture of the integrated system, which increases by 32.03%. The research results of this paper provide guidance for achieving the optimum design of offshore wind-wave energy integrated systems and quantify the benefits of using optimum designs in the produced wave energy power. In addition, the proposed dimensionless optimization method is generic and can be widely applied to different types of WECs.

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Dynamic Load Effects and Power Performance of an Integrated Wind–Wave Energy System Utilizing an Optimum Torus Wave Energy Converter

There is a huge energy demand from offshore renewable energy resources. To maximize the use of various renewable energy sources, a combined floating energy system consisting of different types of energy devices is an ideal option to reduce the levelized cost of energy (LCOE) by sharing the infrastructure of the platform and enhancing the power production capacity. This study proposed a combined concept of energy systems by combing a heave-type wave energy converter (WEC) with a semisubmersible floating wind turbine. In order to investigate the power performance and dynamic response of the combined concept, coupled aero-hydro-servo-elastic analysis was carried out using the open-source code F2A, which is based on the coupling of the FAST and AQWA tools by integrating all the possible environmental loadings (e.g., aerodynamic, hydrodynamic). Numerical results obtained by AQWA are used to verify the accuracy of the coupled model in F2A in predicting dynamic responses of the combined system. The main hydrodynamic characteristics of the combined system under typical operational conditions were examined, and the calculated responses (motions, mooring line tension and produced wave power) are discussed. Additionally, the effect of aerodynamic damping on the dynamic response of the combined system was examined and presented. Moreover, a second fully coupled analysis model was developed, and its response predictions were compared with the predictions of the model developed with F2A in order for the differences of the calculated responses resulted by the different modeling techniques to be discussed and explained. Finally, the survivability of the combined concept has been examined for different possible proposed survival modes.

Jinghui Li

Papers

Wind–Wave Coupling Effect on the Dynamic Response of a Combined Wind–Wave Energy Converter