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Energies 2016, 9(9), 742;

Coherence Effects on the Power and Tower Loads of a 7 × 2 MW Multi-Rotor Wind Turbine System

Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580, Japan
Department of Aeronautics and Astronautics, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
Wind Energy Research-Center for Doctoral Training, University of Strathclyde, Royal Collage R336, Glasgow G1 1XW, UK
Author to whom correspondence should be addressed.
Academic Editor: Frede Blaabjerg
Received: 16 June 2016 / Revised: 23 August 2016 / Accepted: 30 August 2016 / Published: 13 September 2016
(This article belongs to the Collection Wind Turbines)
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A multi-rotor system (MRS), in which multiple wind turbines are placed on one tower, is a promising concept for super-large wind turbines at over 10 MW due to the cost and weight advantages. The coherence effects on an MRS were investigated in this study. Although a wide range of coherences were measured so far, a decay constant of C = 12 is recommended in the IEC61400-1 standard. Dynamic simulations were performed for a 14-MW MRS, which consists of seven 2-MW turbines and includes wind models with three different coherences. Although the results show that a larger coherence increases the output power and the collective loads due to tower base fore-aft bending, it reduces the differential loads due to tower-base torque and tower-top nodding. The most significant case is the fatigue damage due to tower base fore-aft bending, which was more than doubled between the decay constants of C = 6 and C = 12. The present results indicate that the coherence should be defined carefully in the design of large-scale MRSs because its effect on them is not straightforward. View Full-Text
Keywords: wind turbine; multi-rotor; load; power; coherence wind turbine; multi-rotor; load; power; coherence

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Yoshida, S.; Goltenbott, U.; Ohya, Y.; Jamieson, P. Coherence Effects on the Power and Tower Loads of a 7 × 2 MW Multi-Rotor Wind Turbine System. Energies 2016, 9, 742.

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