Testing the next generation floating wind turbines

Floating solar farms are widely seen as a promising addition to the offshore energy mix. By placing photovoltaic systems on water, developers can unlock vast new areas for energy generation while benefiting from natural cooling effects that improve panel efficiency. 

However, the drive for efficiency comes with tradeoffs. Designers aim to maximise the number of solar panels, while minimising the amount of structural material required. This leads to lighter, more flexible platforms—structures that can be particularly sensitive to environmental forces, especially wind. 

From recent projects, MARIN has learned that the effect of wind and waves cannot be considered separately from each other but must be tested together to capture the true dynamic response. The BlueLabs testing facility will provide valuable new insights into these interesting but complex physics.

Important next step in testing renewables

As well as providing support to the offshore industry in design verification and innovation, the new test facility is expected to play an important role in the validation of multi-fidelity simulation methods that are being used in the innovation, design and optimisation of renewable energy systems. 

With bigger wind generation systems, future renewable projects such as large-scale FOWT systems and floating solar farms can be tested in combined environmental conditions, i.e. in multi-directional waves, currents and high-quality wind. As such these developments are an important next step in laboratory testing to provide reliable advice and first-class data to the offshore renewable industry.

Along with the wind generation system, MARIN developed a new stock wind turbine model to mimic a 22MW turbine at scale 1:47.5, which results in a 6m rotor scale diameter. Additionally, a wireless measurement system was developed (see Report magazine 141/wireless-setup). 

As renewable energy systems are relatively lightweight, the use of electrical measurement cables should be avoided as much as possible to prevent these cables influencing the platform motions. Therefore, the models can be equipped with small transducer units consisting of a battery and wireless data transfer to avoid the use of these measurement cables.
Furthermore, to be able to measure the motions of floating solar farms and floating infrastructure consisting of multiple objects spread out over a large space, a new optical measurement system is being developed.

Large-scale floating solar farms and next generation turbines

Within this test facility, large-scale, lightweight floating solar energy farms and the next generation of floating wind turbines of 20MW+ can be tested in combined wind, waves and current conditions. For this purpose, a new modular wind generation system was developed alongside a wireless measurement system, an optical motion tracking system, and a dedicated stock model for these 20MW+ wind turbines.

The wind generation system consists of modular wind tunnel units including a fan, contraction nozzle, honeycombs and flow conditioners to generate a wind field of high homogeneity and low turbulence. Due to its modular units, the system can be built up to generate a 18m x 3.4m wind field to test large-scale floating solar energy farms and floating offshore infrastructure. Alternatively, the wind field generation system can be transformed to a 9m x 6.8m setup to be able to test 20MW+ floating wind turbines at scale 1:40-50, instead of 1:70-80 in the original setup. The fans that generate the wind can be individually controlled such that time-dependent wind spectra can be generated, as well as a variation of the wind velocity over height to mimic the atmospheric boundary layer observed offshore.

As part of the Scalewind Joint Industry Project, BlueLabs was used for the first time to test a semisubmersible floating offshore wind turbine (FOWT). This milestone marks a significant step towards advancing the design and validation of nextgeneration floating wind technology.

To meet ever-increasing renewable energy demands, floating offshore wind turbines and floating solar energy farms are increasing in size. As a result, the complex demands on controlled laboratory tests move beyond the current state-of-the-art wave basin facilities. To support this trend, MARIN developed an advanced test laboratory to upgrade its existing Offshore Basin.