Simulations and Model Testing on a Wave Engergy Converter based on Inverse Offshore Engineering

For more than 75 years, the Maritime Research Institute Netherlands (MARIN) has been contributing to the development of safe and economic ships and offshore structures as independent advisor. This is done through model tests, simulations, desk studies, full scale measurements, safety studies and training. With the resulting knowledge of the ocean environment and the hydrodynamics of ships and offshore structures, MARIN sees it as its responsibility to contribute to the development of renewable energy offshore from waves, tides and wind:
Wave energy is a concentrated form of wind energy: the wind transfers energy into the waves over a long fetch. Cruz has estimated that Europe has an average wave power of 50kW per metre width of wave front. Others indicate that worldwide the economically exploitable amount of wave energy is estimated at 2,000 TWh/year, an average power of 200GW over a year. This is equivalent of 200 large power stations.
The challenge is to generate a predictable amount of energy, in a reliable way, at a reasonable cost. These challenges of wave energy are very similar to those of the offshore industry: safe and economic design, production, transportation, installation, maintenance, repair and removal. Besides that, knowledge about reducing motions from offshore hydrodynamics can be used by ‘inverse engineering’ to increase the motions of wave energy converters to maximise the wave energy conversion into useful electrical energy. The present paper focuses on the development of a wave energy converter based on these principles.
But in a similar manner, MARIN knowledge in the field of ship propulsion systems can be used to optimise marine turbines to generate tidal energy. The advantage of tidal energy is that the amount of energy is more predictable than wave energy (but its presence is much more localised). MARIN has developed an extensive palette of computational tools and experimental capabilities that suite the design and evaluation of stateof-the-art propellers. For turbine rotors MARIN has already employed its tools and capabilities with panel and CFD codes for evaluation and design of practical turbine rotors.
Finally, offshore wind energy is much related to normal floating and fixed offshore structures. Installation, removal, maintenance, survivability and vessel traffic safety are topics that link offshore wind energy to MARIN’s broad maritime expertise. The Institute also contributed to the development of windmill installation vessels. This included resistance and propulsion of the special hulls, Dynamic Positioning (DP) of the system at the location and the actual installation procedures by simulations and model tests.