Concise Report : Wind Turbine Electric Power System (Siemens)
Selim Tezgel
1. Executive Summary
Wind turbines are a growing source of clean and renewable energy. Siemens is a
manufacturer of wind turbines for on and off shore applications. They have developed a number
of improvements for manufacturing and implementation of wind turbines. These technological
improvements build off of the core electrical and control systems that wind turbines utilize to
generate power. In this report the background and history of wind turbines will be presented,
followed by learning concepts that a mechatronics student should understand, and concluded
with the details on how wind turbines operate and some recent innovations.
2. Keywords
Renewable energy, wind turbine, wind power, generator, turbine conditioning monitoring,
integral blades, direct drive, hywind
3. Introduction
Figure 1 – Wind turbine farm [1]
Wind power is the conversion of wind energy into a useful form of energy like electricity
using wind turbines. Wind power, an alternative to fossil fuels, is a renewable source of energy
that produces no greenhouse gas emissions. It is widely used in European countries, in the
United States, and Asia. Today, 83 countries around the world are using wind power to supply
up to 20 % of their electricity demand. Siemens Wind Power is one of the biggest wind turbine
manufacturers and was established in 1980. Siemens has a great history in offering solutions to
onshore, coastal, and offshore sites worldwide. In 1980, the company first began in Denmark as
Danregn, which was first an irrigation systems manufacturer that went into the wind turbine
industry. The first wind turbines that were manufactured were 10 meter rotor diameters and
generated about 20 to 30 kW. In 1981, the company separated its wind turbine section into
Danregn Vindkraft A/S. At the same time, the company produced a 55 kW wind turbine with a
15 meter blade diameter. Between 1982 and 1987, they started to trade with the USA to build a
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wind farm. In 1983, the company decided to change its name to Bonus Energy to provide
convenience with North American market. In 1991, the first offshore wind farm in the world was
installed in Denmark. In 2005, Bonus designed its own blades. In 2004, Bonus A/S was sold to
Siemens. In 2008, the company started to develop direct drive wind turbines, that is, using a
permanent magnet generator instead of the gearbox and alternator. Since 2010 several new
onshore and offshore projects have been put into use from the offices in Hamburg and Bremen.
In May 2011, the first commercial offshore wind farm called Baltic 1 was installed in the
German Baltic Sea using 21 Siemens wind turbines each capable of producing 23 MW with a 93
meter rotor diameter. [2], [3], [4]
Figure 2 - Recent Projects [5]
4. Mechatronic Learning Concepts
Wind turbines are helping provide clean alternative energy in windy locations around the
world. Siemens is one of the many manufacturers of wind turbines and provides solutions for on
and off shore applications. A mechatronics student interested in wind turbines should be familiar
with basic fluid mechanics along with the following types of systems: mechanical, electrical, and
control.
Wind turbines harvest energy from the wind, which is a fluid, thus in order to understand
where the energy is coming from basic principles of fluid mechanics must be understood. The
primary concept to be familiar with is how the interaction between the wind and blade cause
rotation.
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Figure 3 - Diagram detailing the interaction between the wind and blade. [7]
The blades of a wind turbine have an airfoil shape and figure 3 illustrates how lift is generated
when a fluid flows across an airfoil. The resulting rotation provides the driving force for the
mechanical system inside the turbine.
The mechanical, electrical, and control systems are housed inside the nacelle of the wind
turbine. The internal components of a wind turbine are not overly complicated and a schematic
illustrating them is shown in figure 4.
Figure 4 - Graphic of the internal components of a wind turbine. [7]
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The rotation from the blades drives a shaft connected to a gear box which drives a
generator. The generator then transmits the power to where it needs to go. The interested
mechatronics student should have an understanding of the kinematics of gears because gear
trains and ratios play a significant role in a wind turbine’s electric power system. In addition, a
mechatronics student should also have an understanding of electrical motors and power
generation. Wind turbines that can adjust their direction utilize electric motors to rotate the rotor
into the oncoming wind and generators are used to produce power for an electrical grid. The last
type of system that a mechatronics student should be familiar with is the control systems that are
used to increase efficiency. Various instruments and sensors are used to monitor wind
conditions. The controllers then use this data to adjust the pitch of the blades or the direction that
the rotor faces to allow for more energy to be extracted from the wind. [7] The controllers also
use the feedback to maintain safe operating conditions and create more consistent output. [6]
Siemens has also implemented their own variations and improvements on some of the
above systems. Some of these technologies include lightning protection, “High Wind Ride
Through” control, and Turbine Load Control 2.0. These technologies are incorporated into the
electrical and control systems of the wind turbines [6]. The same fundamental understandings
apply to these technologies though, so as long as a mechatronics student is familiar with
electrical power and feedback control systems there should not be any difficulty understanding
the operation.
5. Operational Issues
a. Basic Operation
A wind turbine operates by converting the energy from the wind into electricity that is
put onto the grid. Figure 5 shows a high level diagram of how a wind turbine performs this task.
The wind blows past the turbine blades and causes them to rotate. The turbine blades are
attached to the rotor which spins the shaft internally in the nacelle. The shaft is connected to a
gearbox. The gearbox translates the low-speed motion of the turbines (around 30-60 rpm) to a
higher speed (about 1,000-1,800 rpm) that drives the generator. The generator converts this
rotational motion into 60Hz AC electricity which is put onto the power grid. [8] This energy
conversion technology can be seen in figure 6.
Wind
Turbine
Blades
Rotor
Gearbox
Generator
Power to
the grid
Figure 5 – High level diagram of wind turbine operation
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Shaft
Figure 6 – Schematic of the energy conversion technology [5]
Siemens has produced different types of turbines that are designed for different
operations. The “Stall Technology” is used for turbines that can produce 600kW or less power
and contain a single speed shaft with a fixed blade. The “CombiStall Technology” is used for
1.0-2.3MW of power with a single speed shaft and variable pitch. The variable pitch is limited to
low speed pitch adjustments and is used to control the output of the turbine. Also, this design has
frequency regulation capabilities. The “Variable Speed/Pitch Technology” is for 2.3MW and
higher power outputs. It has a full frequency converter with rapid response capabilities. It uses a
variable speed shaft on its gearbox and variable pitch capabilities. Some possibilities for
additional capabilities on this type of turbine include “low voltage ride through”, “ramp rate
control” and additional frequency regulation.
b. Innovations
In recent years, Siemens has made several technological innovations to their wind
turbines. Some of these innovations include turbine condition monitoring, integral blades, direct
drive, and hywind.
1) Turbine Condition Monitoring
Turbine condition monitoring is a flexible online system that is used to discover
abnormal operating conditions by monitoring the external and internal events of the wind
turbine. It has been able to reduce service costs because operators are able to optimize the
planning of service work on the turbines based on the information they receive from the
monitoring system. This also helps with reducing down-time for service. This system can help to
make preventative repairs before the turbines actually fail.
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Figure 7 - Conditioning Monitoring Online System [5]
2) Integral Blades
Siemens Wind Power patented a new production method for creating blades. Each blade
is manufactured in a single piece from fiberglass reinforced epoxy resin. The mold is constructed
in the shape of the blade’s state-of-the-art aerodynamic design. There is only one mold used for
each type of turbine which cuts down on manufacturing costs, space, and manpower for
construction. It is impossible to detect any glue joints between spars and shells for this single
operation method and therefore there are no weak points in the blade that would normally be
exposed to damaging environmental conditions. It offers high strength and noise performance.
[9], [10]
Figure 8 - Integral Blades [9]
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3) Direct Drive
Direct Drive generators reduce the generator losses by placing permanent magnet
between the rotor and the generator without a gearbox. This increases the efficiency and
reliability of the turbines while simplifying the assembly of the generator. Increased efficiency is
achieved with the magnetic rotor assembly by reducing losses due to friction in the bearings
normally found in gearboxes as well as losses in the gears themselves. The assembly is simple in
that it is a modular assembly that can be put together in segments. This also helps with
transportation and delivery of this particular part. [5], [11]
Figure 8 - Direct Drive Generator [5]
Figure 9 – Direct Drive Generator [11]
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4) Hywind
The Hywind is the first floating off-shore installation in the world. This technology is
ideal for greater water depths between 120-700 m deep because they do not require to be
mounted on the seabed and therefore can be used in off-shore wind farms that are not limited to
shallower waters. This type of wind turbine has a more advanced control system to be able to
compensate for the special operating conditions that these floating devices can encounter. The
turbine can actually dampen out some of the motions induced by the waves they encounter and
the control system takes advantage of this phenomenon. [12]
Figure 9 - Hywind Off-shore [13]
6. Summary
Siemens has made major innovations in the wind power industry. Wind turbines have
become more efficient and better able to produce the power that our society needs while being
environmentally conscious. Even though other power sources such as nuclear power, coal, gas,
and others have much greater power generation capabilities, the increasing innovations in the
renewable energy industry can help increase the efficiency of these devices and help them
become more prevalent in our society.
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REFERENCES
[1] "Offshore Wind Turbines." Siemens.com. Siemens, 5 Dec. 2012. Web. 10 Mar. 2013.
http://www.siemens.co.uk/en/news_press/pictures/offshore_wind_turbines_2.htm
[2] "Siemens Wind Power." Wikipedia. Wikimedia Foundation, 03 Jan. 2013. Web. 02 Mar.
2013.
[3] "Homepage - WIND ENERGY MARKET." Homepage - WIND ENERGY MARKET. N.p.,
n.d. Web. 02 Mar. 2013.
[4] "Wind Power." Wikipedia. Wikimedia Foundation, 03 Feb. 2013. Web. 02 Mar. 2013.
[5] "TR08 Tue 1030 1200 Nelson Robert Siemens Wind Power Technical Developments Pdf
Free Ebook Download from Www.treia.org." EbookBrowse.com. N.p., n.d. Web. 02 Mar. 2013.
[6] "Siemens Wind Power - Proven Technology." Wind Turbines. Siemens, n.d. Web. 09 Mar.
2013. <http://www.energy.siemens.com/hq/en/renewable-energy/wind-power/wind-turbines/>.
[7] Zumbrunnen, David A. "Renewable Energy Sources." Lecture.
[8] "The Inside of a Wind Turbine." Wind Program:. U.S. Department of Energy, n.d. Web. 10
Mar. 2013. <http://www1.eere.energy.gov/wind/inside_a_wind_turbine.html>.
[9] "Power from the White Giant." Press Pictures. Siemens.com/press, 10 Jan. 2008. Web. 10
Mar. 2013. <http://www.siemens.com/press/en/presspicture/?press=/en/presspicture/picturesphotonews/2008/pn200801/pn200801-03.htm>.
[10] "IntegralBlade." Siemens AG Energy Sector, 2012. Web. 10 Mar.
<http://www.energy.siemens.com/hq/pool/hq/power-generation/renewables/windpower/Integral_Blades_brochure.pdf>.
2013.
[11] "Siemens Industry Presents New Gearless Direct Drive Wind Generator." Press Releases.
Industry Sector / Drive Technologies Division, 19 Sept. 2012. Web. 10 Mar. 2013.
<http://www.siemens.com/press/en/pressrelease/?press=/en/pressrelease/2012/industry/drivetechnologies/idt2012094045.htm>.
[12] "Hywind: Siemens and StatoilHydro Install First Floating Wind Turbine." Press Releases.
Energy Sector / Renewable Energy Division, 10 June 2009. Web. 10 Mar. 2013.
<http://www.siemens.com/press/en/pressrelease/?press=/en/pressrelease/2009/renewable_energy
/ere200906064.htm>.
[13] Stiesdal, Henrik. "Hywind: The World’s First Floating MW-scale Wind Turbine." Wind
Directions (2009): 52-53. Www.ewea.org. 2009. Web. 10 Mar. 2013.
<http://www.ewea.org/fileadmin/ewea_documents/documents/publications/WD/2009_december/
Science_corner_-_December_2009.pdf>.
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