Currently, floating offshore wind is experiencing rapid development towards a commercial scale. However, the research to design new control strategies requires numerical models of low computational cost accounting for the most relevant dynamics. In this paper, a reduced linear time-domain model is presented and validated. The model represents the main floating offshore wind turbine dynamics with four planar degrees of freedom: surge, heave, pitch, first tower fore-aft deflection, and rotor speed to account for rotor dynamics. The model relies on multibody and modal theories to develop the equation of motion. Aerodynamic loads are calculated using the wind turbine power performance curves obtained in a preprocessing step. Hydrodynamic loads are precomputed using a panel code solver and the mooring forces are obtained using a look-up table for different system displacements. Without any adjustment, the model accurately predicts the system motions for coupled stochastic wind–wave conditions when it is compared against OpenFAST, with errors below 10% for all the considered load cases. The largest errors occur due to the transient effects during the simulation runtime. The model aims to be used in the early design stages as a dynamic simulation tool in time and frequency domains to validate preliminary designs. Moreover, it could also be used as a control design model due to its simplicity and low modeling order.

Of the cost centres that combine to result in Levelised Cost of Energy (LCOE), O&M costs play a significant part. Several developers have calculated component costs, demonstrating how they can become commercially competitive with other forms of renewable energy. However, there are uncertainties relating to the O&M figures that can only be reduced through lessons learned at sea. This work presents an O&M model calibrated with data from real sea experience of a wave energy device deployed at the Biscay Marine energy Platform (BiMEP): the OPERA O&M Model. Two additional case studies, utilising two other O&M calculation methodologies, are presented for comparison with the OPERA O&M Model. The second case study assumes the inexistence of an O&M model, utilising a Simplified Approach. The third case study applies DTOcean’s (a design tool for ocean energy arrays) O&M module. The results illustrate the potential advantages of utilising real sea data for the calibration and development of an O&M model. The Simplified Approach was observed to overestimate LCOE when compared to the OPERA O&M Model. This work also shows that O&M models can be used for the definition of optimal maintenance plans to assist with OPEX reduction.

The increasing interest in the use of renewable energy technologies is directing attention towards the potential contribution of marine energy technologies, especially ocean wave energy, to world energy demand. While open-sea demonstrations of full-scale devices have been carried out to validate several technologies, the focus now is shifting to optimising the components for efficiency and reliability. The efficiency of the electrical generator plays a crucial role in wave-to-wire numerical models for converting wave energy into usable electricity. It provides essential data that enables the industry to reduce technical risks and uncertainties. Wave-to-wire models typically simplify the generator’s efficiency through assuming a single curve based on the load. This curve is usually provided by the machine manufacturers for the nominal rotational speed. However, the rotational speed varies in the case of air turbines used in OWC devices. Therefore, to accurately estimate decision variables derived from these models, a comprehensive efficiency map is necessary. This map should demonstrate the performance at different rotational speeds and loads, as it directly influences the estimation of key parameters. The main objective of the present work is to improve the generator behaviour of an OWC for different generator operation regimes. For this purpose, a numerical model of the generator’s efficiency will be developed throughout the segregation of losses and validated experimentally. Finally, an optimal control law will be presented to maximise the electrical power output of the wave energy converter, considering the efficiency of both the generator and the turbine.

The aim of this work is to show that a significant increase of the efficiency of a Wave Energy Converter (WEC) can be achieved already at an early design stage, through the choice of a turbine and control regulation, by means of an accurate Wave-to-Wire (W2W) modeling that couples the hydrodynamic response calibrated in a wave flume to a Hardware-In-the-Loop (HIL) test bench with sizes and rates not matching those of the system under development. Information on this procedure is relevant to save time, because the acquisition, the installation, and the setup of a test rig are not quick and easy. Moreover, power electronics and electric machines to emulate turbines and electric generators matching the real systems are not low-cost equipment. The use of HIL is important in the development of WECs also because it allows the carrying out of tests in a controlled environment, and this is again time- and money-saving if compared to tests done on a real system installed at the sea. Furthermore, W2W modeling can be applied to several Power Take-Off (PTO) configurations to experiment different control strategies. The method here proposed, concerning a specific HIL for testing power electronics and control laws for a specific WECs, may have a more general validity.

La instalación en los últimos años de varios parques eólicos offshore flotantes es un paso muy importante de cara a lograr la viabilidad comercial de esta tecnología. Sin embargo, el agresivo entorno marino, caracterizado por fuertes solicitaciones causadas por vientos, olas y corrientes, combinado con el creciente tamaño de las turbinas eólicas y el comportamiento dinámico de sus componentes, plantea serias preocupaciones sobre la viabilidad de la producción de energía y la durabilidad del sistema en un entorno tan agresivo. Un componente crítico dentro de las plataformas eólicas flotantes es el cable dinámico, responsable de transportar a la red de tierra la energía generada en mar. Cualquier fallo en este cable provocaría la caída de la generación, al menos, de la turbina eólica asociada, lo que enfatiza la necesidad de un diseño preciso de estos cables dinámicos durante las fases más tempranas del proyecto de un parque eólico flotante. Sin embargo, la complejidad de la estructura interna de estos cables dinámicos, formadas por diversos cuerpos con diferentes características mecánicas, hace muy difícil el desarrollo de modelos numéricos fiables. Este hecho, unido al restringido acceso a infraestructuras de ensayos o a datos reales necesarios para validar dichos modelos, redunda en la dificultad de obtener diseños precisos y tempranos. TECNALIA dispone de un laboratorio flotante, el HarshLab, fondeado en condiciones offshore en la costa de Vizcaya, en el que va a instalar un cable dinámico en los próximos meses, incorporando en el conector submarino, fabricado por la empresa DITREL, con el que este cable se une a dicho laboratorio, un conjunto de instrumentos de medida con el propósito de monitorizar el comportamiento de dicho cable umbilical. Este trabajo pretende exponer los modelos numéricos que se han empleado para implementar la sensórica apropiada en el conjunto de cable y conector submarino, así como presentar los primeros resultados de esa monitorización y validación de los modelos, si a la fecha del congreso hubiera ya resultados.