On the Design and Optimisation of Wind Turbine Electrical Generator Supporting Structures Following an Integrated Approach

Pablo Jaen-Sola | Ph.D., MIET, FHEA | p.sola@napier.ac.uk

Assistant Professor in Mechanical Engineering

​

​

​

​

FEMM Hub Annual Conference

20 November 2024

Evolution of wind power

Evolution of wind power (Source: Bloomberg New Energy Finance)

Wind turbines in extreme weather (Source: US Dept. of Energy)

Offshore investment cost breakdown

Source: Jiale Li, 2014

Where is the electrical generator located?

Courtesy of NREL

Why direct-drive?

1 Hub 2 Main shaft 3 Generator

Courtesy of EWT B.V.

Direct-drive vs. Geared

Higher efficiency

Higher reliability

(less components)

Axially compact

design

Generator becomes

a load path

Difficult to transport and install

Radially larger and heavier generator

Loads at play

(a) Shear loading; (b) Magnetic attraction of the moving and the stationary components of the generator; (c) Gravitational loading; (d) Thermal expansion of the generator structure; (e) Centrifugal loading

How to model a generator structure?

Courtesy of Harakosan Europe

Courtesy of MTorres

Deflection modes

Mode 0 Uniform deflection

Mode 1 Rotor eccentricity

Deflection modes

A rotor deforming into the airgap towards a stator

1.- Look at geometry

1.1.- Numerical approach (finite element)

1.2.- Analytical/Mathematical approach

2.- Look at different materials (Composites)

3.- Look at different manufacturing techniques and the design methods associated

Options for structural optimisation

Numerical approach

(a) Enercon direct drive wind turbine generator stator (b) CAD model in ANSYS (c) Finite element model highlighting deformation

​

Courtesy of Enercon

Numerical approach�

Parameter local sensitivity to mass

Numerical approach

Structural parametric optimization

Detailed view of the optimized rotor conical structure

Rotor structure topology optimization study

Analytical approach for rotor structures

Analytical approach for rotor structures

R²=0.9829

Analytical/Mathematical approach

Magnetic stress vs. Theta for different deflection modes

Composite materials

Rotor composite structure with mosaic pattern fibre layout

• Structure characteristics
• Disc structure: 8 plies of 0.00125m thickness with 5 additional layers of reinforcement
• Cylinder structure: 6 plies of 0.00125m thickness

Composite materials

• Material: Carbon/epoxi

• Loads
• 400,000Pa uniformly distributed along cylinder’s upper surface (looking at element features)
• (Ω=12rpm)
• Currently looking at torque (different fibre orientation for the disc structure is needed)

• Mass reduction (gear ratio 1)

Steel structure: 625.9kg

Composite structure: 505kg

-20% (drivetrain mass)

Generator’s dynamic response

Interference diagram of the system

Other points to be considered

A view of a simulated windfield acting on a wind turbine rotor

A real example of a Low-Speed Shaft torque mismeasurements during operation

Courtesy of Qblade.org

QFEM – Static Blade Design and Analysis Result for Rated Setting

Maximum Normal Forces at Blades vs Blade’s Radius Graph for Combined Settings

Other points to be considered

Full turbine LCA comparison showing energy, GHG emissions, and costs per year

11.1 million litres of water are used during production processes, equivalent to over four Olympic swimming pools.

​

Total financial cost of manufacturing an optimised rotor supporting structure for a 15MW direct driven wind turbine electrical generator is $613,300.

Design for manufacturing (based on AI)

Courtesy of Enercon

Rotor structure manufactured using conventional techniques - casting

Rotor structure designed to be manufactured using unconventional techniques – 3D Printing

Design for manufacturing (3D printing)

Guest Editors

Deadline for Manuscript

submissions : 31 August 2024

Special Issue Information

In this Special Issue, original research articles and reviews are welcome. Research areas may include (but not limited to) the following:

• Reliability centred maintenance;
• O&M and probabilistic modelling;
• Decision analysis;
• Advanced structural modelling and health monitoring;
• Component optimization and redesign options;
• Innovative designs and concepts (e.g., airborne, multirotor, X rotor);
• Use of emerging technologies (e.g., AI, additive manufacturing, digital twins);
• Load alleviation through control engineering and misalignment couplings.

Dr. Pablo Jaen Sola

School of Computing, Engineering and the Built Environment, Edinburgh Napier University, Edinburgh, EH10 5DT, UK

Keywords

• reliability
• O&M
• structural modelling

• design improvements
• optimisation
• innovative concepts

• emerging technologies
• load alleviation
• condition monitoring

Prof. Dr. Erkan Oterkus

Department of Naval Architecture, Ocean and Marine Engineering, University of Strathclyde, G4 0LZ, UK

Any questions?

Courtesy of BWEA