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This paper presents the pilot model tests on the ‘Green Water Concept’ for wave energy conversion. These tests also included the initial modelling of an electric and hydraulic Power Take Off (PTO). The accurate modelling of a PTO is an important aspect in testing of wave energy conversion concepts numerically and in a wave tank: at the moment that energy is converted into electricity in the PTO, the hydrodynamic behaviour of the structure is changing. The present tests confirmed the high motions and large amount of green water of the Green Water Concept as predicted in previous simulations. The application of a real PTO gave important insight in the possibilities and challenges of PTO modelling at model scale. For the present concept a mean Power (at full scale) close to 1MW was generated in a regular wave of H = 3.0m for the maximum possible setting in the chosen test set-up. This setting was limited by the chosen mechanical and electronic motor set-up in this pilot test series, not the actual maximum of the Green Water Concept itself. Considering the test results, it is clear that the potential of the system is significantly larger.

To increase workability and safety in tough environmental conditions, and to create a more economical alternative for jack-up barges, Barge-Master has developed a wave compensating platform for marine and offshore installation barges. To minimize the motions of the crane positioned on top of it, the platform is driven by three hydraulic actuators that compensate for the roll, pitch and heave motions of the barge. To quantify the performance of the platform for different environmental conditions and crane configurations MARIN performed both wave basin model tests and time-domain simulations on the platform. In this paper, the experimental setup is first described and the model test results are presented. Then, the theoretical formulation of the time-domain aNySIM model is described and the numerical results are reported. It is shown that the model tests and time-domain results are in good agreement. The results indicate that the barge motions can be compensated by the platform for more than 90% in 1.2m high sea states. However, it is also shown that the instrumentation, data acquisition and controller system need to be fast and tuned to achieve this optimal compensation.