Isaac Ansah

Date of Award

January 2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Energy Engineering

First Advisor

Olusegun S. Tomomewo

Second Advisor

Mohsen S. Mosleh

Abstract

Wind energy continues to lead the global transition to renewable power, driven by its minimal environmental impact and high scalability. Offshore wind farms benefit from stronger and consistent wind resources. However, these advantages are tempered by challenges related to installation, maintenance, and drivetrain reliability. Conventional bearings, which support the drivetrain system, are prone to wear related failures due to lubrication breakdown and mechanical fatigue from continuous loading. This study explores the integration of Active Magnetic Bearings as an alternative to conventional bearings in offshore Horizontal Axis Wind Turbines. Using advanced engineering simulation tools, the main driveshaft of a 130 MW wind turbine was remodeled and optimized to facilitate the integration of magnetic bearings. Also, a bench test using scaled wind turbine models was conducted to examine the performance characteristics of both bearing systems. Simulation results show that shaft weight and input current characteristics significantly affect the geometric features and magnetic field properties of the AMB system respectively. The bench test findings indicate that wind turbines using conventional bearings achieve higher power output and efficiency when the shaft mass is increased, due to enhanced rotational inertia and reduced friction effects provided by smaller-sized bearings, particularly when coupled with an optimized blade pitch angle. In contrast, turbines supported by magnetic bearings demonstrated superior performance when the shaft was optimized for reduced weight, highlighting the latter system’s efficiency under low-load conditions. Overall, the results emphasize the performance trade-offs between bearing types and underscore the potential of AMBs in enhancing turbine compactness and efficiency, especially in offshore or spatially constrained environments. While real-time control and scalability remain areas for further development, this study provides a strong foundation for future innovations in magnetic bearing integration for wind energy systems.

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