NEZZY2 Tank test 1:36 scaled model

As proven system validation approach a tank test for a 1:36 Froude scaled model was carried out to investigate on the sea-keeping behavior and to perform an advanced economical feasibility. Based on the great validation results of the nezzy project the twin-rotor configuration is a valid extension of the nezzy capabilities.

In November 2017 a 10 days measurement campaign was carried out at the LiR NOTF Deep Ocean Basin of the University College Cork, Ireland. Starting with unmoored and moored decay tests the hydrostatic characteristic and eigenperiods are investigated. Followed by regular wave tests with and without turbine operation response characteristics are measured to compare the results from irregular wave dynamic testing. RAOs (Response Amplitude Operators) are extracted from irregular wave testing receiving a greater statistical basis. All eigenperiods are outside of usual wave excitation areas allowing nezzy² to show its outstanding performance in word wide operation areas.

Tested survival conditions show that the entire system provides a stable basis in severe weather conditions for the wind turbine system allowing for a mass and cost reduction in the design phase. Even the loads on the mooring system are significantly lower compared to systems with similar power ratings.

Even if the model is shown on different events with turbine blades, during the test two ducted fans and a rotating bar with counter weights is used to represent the physical effects of a wind turbine. In non-operation tests both rotors are parked in horizontal orientation as the full-scale system will do to reduce thrust loading at high wind speeds. As advanced nezzy² feature testing the rotor counter-rotation and non-counter-rotation was tested to confirm the design approach.

Finally the measurement campaign shows a great agreement with load assessments and design approaches. All implemented features allow for a further cost reduction for the full scale unit.