Renewable ENergy Team RENT
Renewable Energy by Sharing Maritime Knowledge
For more than 80 years, MARIN has been contributing to the development of safe and economic ships and offshore structures as independent advisor. 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. A special Renewable ENergy Team (RENT) was started, consisting of specialists covering all aspects of offshore renewable energy systems.

For more information download the RENT brochure.

Model tests for floating wind turbines
After the present generation shallow water fixed wind turbines, floating wind turbines are considered to be the next step in development of offshore wind energy. To ensure safe and economically feasible designs, model tests are often used for validating and optimizing the floater design before construction starts. This is common practice in the oil&gas offshore market. A key point of model testing floating wind turbines is that wind and waves are presented simultaneously in the basin. This makes it possible to correctly study the complex motions and loads of the rotating wind turbine on a moving platform in wind and waves.
In the last years MARIN has been involved in an increasing number of projects for offshore wind industry. For this special type of floaters, new model testing and numerical simulation techniques have been developed. Based on the previous model tests MARIN developed and constructed a generic model scale wind turbine including an active pitch control which permits to test different control strategy systems. This “stock” wind turbine is available for new floating wind turbine projects, reducing the cost of model testing. Next to this a high quality wind generation machine in the MARIN testing facility has been developed to accurately test floating wind turbines.

'Inverse' Wave Energy Concept 'Inverse' Wave Energy Concept
Wave Energy
The challenge for offshore wave energy concepts is to generate a predictable amount of energy, in a reliable way, at a reasonable cost. These challenges are very similar to those of the offshore industry: safe and economic design, production, transportation, installation, maintenance, repair and removal.

Normally knowledge is used to reduce motions; ‘inverse engineering’ can be used to increase the motions of wave energy converters to maximise the wave energy conversion into useful electrical energy. As a pilot project, MARIN initiated the development of the ‘green water concept’ for wave energy conversion. The concept is a combination of existing heave or pitching concepts (making use if the relative motions with respect to the seabed) and overtopping concepts (where the overtopping wave flow is collected in a reservoir and used to generate electricity through a turbine).

An important aspect that should not be overlooked, is the correct modelling of the Power Take Off (PTO) system, whether electrical or hydraulic, and its interaction with the wave energy device. Because the moment that energy is converted into electricity in the PTO, the hydrodynamic behaviour of the structure is changing.

Tidal Current Turbine Tidal Current Turbine
Tidal Energy
MARIN knowledge in the field of ship propulsion systems can also 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).

An extensive palette is available of computational tools and experimental capabilities that suite the design and evaluation of state-of-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.


Floating Wind Turbine Concept (SWAY) Floating Wind Turbine Concept (SWAY)
Offshore Wind Energy
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. MARIN has the capabilities to investigate the wave loads, wind loads, platform motions, mooring response, current loads and Vortex Induced Motions (VIM) of offshore wind turbines.

In addition, MARIN has already been involved in a number of environmental studies for planned offshore wind parks, particularly those examining the impact wind farms have on shipping. For any development of an offshore wind farm an Environmental Impact Analysis is required. This analysis examines the wind park’s impact on fisheries, bird life and on shipping. MARIN performs this type of studies using the safety assessment model SAMSON. This model has been developed and improved during the last 25 years through different studies for the Dutch Ministry of Transport, the European Union and other commercial parties.

Finally, MARIN also contributes to the development of windmill installation vessels. This includes 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. The installation vessels may either be floating, on DP or at anchor, or jacked up to the required elevation by a hydraulic jacking system.



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Simulation Software for Floating Offshore Wind Turbines
A new way of sharing hydrodynamic software

For our hydrodynamic toolbox “aNySim”, MARIN decided to come up with a completely new concept. It allows clients to use the latest version of the validated aNySim program for a specific project with MARIN's dedicated support and advice but without paying full licence fees, named “aNySimpro”: it is the professional aNySim code for your specific project.

MARIN has been developing, using and selling hydrodynamic simulation software for many years. Specialised tools were developed for specific areas: coupled mooring analysis, Dynamic Positioning, multiple-body lifting operations, riser dynamics, offloading operations, etc. Developments in the offshore industry in recent years showed the need for more integrated and flexible tools. Therefore, we decided to develop the new modular ‘aNySim’ code. It brings together the capabilities of the different software packages and has become MARIN’s main hydrodynamic toolbox. Various modules can be coupled to the central N-body time domain simulation module. Such a coupling has been done with the wind turbine design tool of the Dutch Research Institute of Energy (ECN): PHATAS. The coupled computer program aNySIM-PHATAS makes it possible to study a wind turbine on a floating foundation, including all the hydrodynamics, the mooring line dynamics and the aerodynamics and the control algorithm of the rotor.

Until now, aNySim-PHATAS has been benchmarked against the results of other similar software for the OC3 study. aNySim-PHATAS can ideally be used in combination with model tests, so that the tool can be tuned to best represent the OFWT based on physical results. aNySim-PHATAS is not for sale at the exception of this project version. aNySim-PHATAS can only be run by experienced people or with direct support from ECN and MARIN.

Based on these considerations, ECN and MARIN decided to come up with a new way of sharing this hydro-aero-dynamic software. Clients can now use aNySim-PHATAS code for a specific project: aNySIMPHATASpro. Instead of buying or leasing the general program, a project-specific version of the program can now be shared. This allows clients to use the latest version, together with dedicated MARIN support and advice. Instead of buying or leasing a general code, clients pay a project licence fee for the use of the program and for the actual support and training clients expect from ECN and MARIN a that moment.

Contact
To contact one of the RENT specialists for an independent advice or study on a renewable energy concept, please e-mail Rent@marin.nl.

Front row, from left to right; Haite van der Schaaf (electronics, modelling of power take offs), Hans Cozijn (mooring), Erik Jan de Ridder (wind and sailing, RENT team leader), Pieter Aalbers (full-scale measurements), Rien de Meij (installation). Second row, from left to right; Sebastien Gueydon (time-domain simulations), Guilherme Vaz (CFD), Bas Buchner (offshore and wave energy), Gert-Jan Zondervan (propulsors and turbines), Tom van Terwisga (propulsors and turbines), Koos Hoefakker (model testing), Christian Schmittner (waves and seakeeping). Not in picture; Yvonne Koldenhof (safety studies), Joop Helder (wave energy). Front row, from left to right; Haite van der Schaaf (electronics, modelling of power take offs), Hans Cozijn (mooring), Erik Jan de Ridder (wind and sailing, RENT team leader), Pieter Aalbers (full-scale measurements), Rien de Meij (installation). Second row, from left to right; Sebastien Gueydon (time-domain simulations), Guilherme Vaz (CFD), Bas Buchner (offshore and wave energy), Gert-Jan Zondervan (propulsors and turbines), Tom van Terwisga (propulsors and turbines), Koos Hoefakker (model testing), Christian Schmittner (waves and seakeeping). Not in picture; Yvonne Koldenhof (safety studies), Joop Helder (wave energy).
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