Design of yaw system
Proof of concept for 2 MW wind turbine
Supervisors:
Anders Hvilsted, IHA
Jens Otte, Danish Wind Design
Group members:
08759 Anders Elkjær
08839 Daniel Wittendorff Larsen
08789 Rune Diederichsen Grønkjær
M7AFP1 – Group 15, E11
Company:
Danish Wind Design ApS
ABSTRACT
This report is the product of a bachelor project, and is written as a proof of concept for the
company Danish Wind Design (DWD). Its scope is to design an alternative and improved yaw
system for DWD´s existing 2 MW wind turbine. The system is based on a concept which
involves a yaw ring sliding on friction pads preloaded with springs. The produced friction in the
system is necessary to reduce the dynamics when yawing and to reduce the loads acting on
the yaw drives. The main purpose of the project is to increase the friction produced in the
system, without radically increasing the cost of the system.
A full load report of the existing DWD turbine is examined, to discover extreme load cases
acting on the turbine. The yaw system is designed to withstand these extreme load cases.
Through a brainstorm several yaw system concepts are developed, but only one passes on
to the final dimensioning stage. This concept introduces the yaw drives as an integrated part of
the system, by enabling the use of spring packs on the motor axles, and thereby prevents
interruption of the friction surfaces. The system is fitted with eight yaw drives, as opposed to
the three used in the current solution designed by DWD. Doing so reduces the load on each
tooth on the yaw ring and pinion, which despite the extra motors and gearbox reduces the
overall weight of the construction while increasing its performance. The gearboxes chosen are
smaller due to the quantity, which has proven to be an economically valid solution.
The performance of the designed system has increased the friction produced by
approximately 41.5 %. An economical estimation has evaluated the system to approximately 4
% cheaper than the DWD yaw system. As a conclusion the concept is considered eligible to
proceed to the next step in the design phase.
PROJECT SPECIFICATION
INTRODUCTION
The essential components of a wind turbine are the rotor, nacelle and tower. The rotor
transforms wind into mechanical energy (rotation). The nacelle contains the gearbox,
generator, controls etc. The tower insures clearance of the rotor to the ground and a more
even wind profile. To insure that the rotor axis is aligned with the wind direction, the tower
and nacelle are connected by a yaw system. This system must be able to withstand loads
threatening to rotate the nacelle or tilt it of the tower.
Danish Wind Design (henceforth DWD) has developed a 2 MW wind turbine, entitled
DWD93-2MW-FSIG, which will constitute the basis for this project. This is a prototype wind
turbine design, bought by and erected by a Chinese customer in China.
In the evolution of modern wind turbines, yaw systems have been somewhat neglected,
because of the obvious efficiency profit by optimising the rotor and drive train. The
downgraded status of the yaw system has also caused an underestimation of the design
challenges of a yaw system. Hence, this function is an interesting province to concern, due to
the possibilities of improvements.
DANISH WIND DESIGN
Danish Wind Design began in 2007 as a design house for wind turbines, led by a specialist
team headed by Mr. Jesper Kjær Hansen. DWD is located in Hinnerup, north of Aarhus, and
consists to this day of more than 30 wind turbine specialists. DWD offers a full design concept
of a wind turbine to its customers, who to this day are mainly concentrated in China. The
customers are reached through Beijing ADC Integrated Solutions Co., an Asian agent company
with a broad network within the Chinese wind business. DWD does not manufacture any
turbines, but sells a full design of a turbine, including all the technical documentation and
support for manufacturing, installation, etc.
A design from DWD is based on the following key-terms:
Simplicity:
- An easy and simple design approach to ensure a low cost for manufacturing,
installation and service.
Proven technologies:
- DWD uses their experience to base their design on components, systems and
technologies with a long and proven track record.
Modular design:
- The design of a turbine is split into several sub-modules to increase the efficiency.
Sophisticated design methods:
- All the newest technologies are used in designing a turbine, such as load
calculations, finite element calculations and 3D drawings.
Quality assurance:
- All designs are performed according to the international approved standards for a
wind turbine.
REQUIREMENTS
This project will take origin in the yaw system used in the DWD turbine, with a friction
bearing combined with electric motors fitted with brakes. It will focus on developing and
proving a concept where the scope is to increase the friction produced in the system. This
friction is used to dampen the dynamics of the nacelle during yawing, and to reduce the loads
on the yaw gearboxes and motors.
In defining the project, the following requirements are necessary to complete it
successfully.
1. Yaw systems
- Historical overview of wind turbines with focus on yaw systems.
o Different types of existing design approaches.
- Study of a load report made for the DWD wind turbine, with focus on the yaw
system.
- Demands of yaw systems.
2. Concept development
- Brainstorm on yaw systems based on a friction bearing.
- Evaluation of developed ideas.
- Selection using specified criteria.
3. Implementation of the selected concept to the DWD wind turbine.
- CAD-models and technical drawings, supported by relevant calculations.
- Evaluation of the solution.
o Full specification sheet on the developed system.
o Comparison between the existing DWD system and the new developed
system.
o Economical estimation.