The presentation „Design and Construction of Offshore Wind Farms” by Witold Skrzypiński was given during 'Crash Course on Offshore Wind Energy' which was held on 26 October 2012 in Gdańsk. The event was organized by two partners of the SB OFF.E.R (South Baltic Offshore Wind Energy Regions) Project part-financed by the EU (European Regional Development Fund): POMCERT from Poland and DTU Wind Energy from Denmark. All presentations given during this event are: Introduction to offshore wind energy in Poland, Andrzej Tonderski, POMCERT Offshore wind power meteorology, Alfredo Peña, DTU Wind Energy Technology status, outlook and economics, Peggy Friis, DTU Wind Energy Design and construction of OWF, Witold Skrzypiński, DTU Wind Energy Environmental impact assessment, Peggy Friis, DTU Wind Energy Legal aspects and outlook for Poland. Grid connection, Mariusz Witoński, PTMEW All of them are available on SlideShare.

1. October 26, 2012 – GDAŃSK - CRASH COURSE on OFFSHORE WIND ENERGY
CRASH COURSE
on
OFFSHORE
WIND ENERGY

2. The presentation „Design and Construction of Offshore
Wind Farms” by Witold Skrzypiński was given during
'Crash Course on Offshore Wind Energy'
which was held on 26 October 2012 in Gdańsk.
The event was organized by two partners of the SB OFF.E.R
(South Baltic Offshore Wind Energy Regions) Project
part-financed by the EU (European Regional Development Fund):
POMCERT from Poland and DTU Wind Energy from Denmark.

3. Design and Construction
of Offshore Wind Farms
Witold Skrzypiński
DTU Wind Energy (Risø)
wisk@dtu.dk
Offshore wind crash course 26 October 2012
South Baltic Offshore Energy Regions Project
DTU Wind Energy, Technical University of Denmark

4. Outline
•Design standards and requirements
•Wind turbine classes (taking into consideration wind)
•Wind turbine layout within a farm
•Foundations
o Factors to consider
o Water depth levels
o Types
•High-altitude wind-energy
o Skysails
o Makani Wind Power
4 DTU Wind Energy, Technical University of Denmark 26 Oct 2012

5. What to consider when designing
wind turbines?
Standards!
(a set of rules or principles
that is used as a basis for
judgement)
DTU Wind Energy, Technical University of Denmark

6. Standards
International Electrotechnical Commission (IEC)
IEC 61400
Class of IEC international standards regarding wind turbines
IEC 61400-1
General design requirements for wind turbines
IEC 61400-2
Design requirements for small wind turbines
IEC 61400-3
Design requirements for offshore wind turbines
IEC 61400-3-2
Design requirements for floating offshore wind turbines
DTU Wind Energy, Technical University of Denmark

7. EIC 61400-1 Examples of design requirements
Fatigue – progressive structural damage that occurs ECD – extreme coherent gust with direction change
when a material is subjected to cyclic loading EWS – extreme wind shear
NTM – normal turbulence model EOG – extreme operating gust
ETM – extreme turbulence model

8. EIC 61400-1 Examples of design requirements
Fatigue – progressive structural damage that occurs EWM – extreme wind speed model
when a material is subjected to cyclic loading NWP – normal wind profile model
NTM – normal turbulence model EDC – extreme wind direction change
EOG – extreme operating gust

9. EIC 61400-1 Examples of design requirements
NTM – normal turbulence model EWM – extreme wind speed model
•Around 400 computations to cover design situations 1.1-7.1

10. Design load examples
EIC 61400-3 DLC specify conditions for:
o Wind
o Waves
 Ex. Severe wave height
o Wind and wave directionality
 Ex. Unidirectinal or multiderectinal
o Sea currents
o Water level
o Ice
 Ex. Horizontal load from moving ice floe

11. How are all these computations
carried out?
by BEM Codes
Blade Element Momentum method
Glauert method
HAWC2
DTU Wind Energy, Technical University of Denmark

12. Let’s see some results:
(a) Shaft-main-bearing tilt moment (b) Shaft-main-bearing side moment
20 20
Max
M [kNm]
M [kNm]
Mean
0 0 Min
x
y
Std
-20 -20
0 10 20 30 0 10 20 30
V [m/s] V [m/s]
w ind w ind
(c) Shaft-main-bearing torsional moment (d) Blade-root out-of-plane moment
10 20
M [kNm]
M [kNm]
0 0
z
x
-10 -20
0 10 20 30 0 10 20 30
V [m/s] V [m/s]
w ind w ind
(e) Blade-root in-plane moment (f) Blade-root torsional moment
10 0.2
[kNm]
[kNm]
DTU Wind Energy, Technical University of Denmark
0 0

13. Let’s see some results:
• Postprocessing of the results may include:
o Extrapolation of extreme events
• 50-year recurrence period
• Ex. resulting load in a range twice as large as the
maximum in a 10-min simulation
o Fatigue analysis
• 20-year lifetime
• Wind turbine parts most prone to damage:
o Tower bottom
o Shaft at main bearing
o Blade root
DTU Wind Energy, Technical University of Denmark

14. What to consider when buying
wind turbines?
Choosing
right turbine
... Taking into consideration wind
characteristics of a given location
DTU Wind Energy, Technical University of Denmark

15. Wind turbine classes
Wind turbine classes determine which turbine is
suitable for normal wind conditions of a particular site
DTU Wind Energy, Technical University of Denmark

16. Wind turbine layout within a farm
• Relatively new subject of research
• Until now, most important factors were:
o Aestetics
o Power production
• Incl. losses due to wake of other turbines
• Middelgrunden offshore Danish wind farm
o Close to the coast of Copenhagen
o 20 Bonus B80 2MW wind turbines
o 76 m rotor diameter
o 64 m hub height
DTU Wind Energy, Technical University of Denmark

17. Wind turbine layout within a farm
DTU Wind Energy, Technical University of Denmark

18. Wind turbine layout within a farm
P.-E. Rethore et al: TOPFARM:
Multi-fidelity Optimization of
Wind Farms
DTU Wind Energy, Technical University of Denmark

19. Wind turbine layout within a farm
• Currently an effort is taken to
include more factors in the
optimization procedure:
o Cost of electrical grid
o Foundations costs
o Fatigue loads
• Optimization is a computationaly
demanding process.
• Effort is taken to perform it as
efficiently as possible
P.-E. Rethore et al: TOPFARM:
Multi-fidelity Optimization of
Wind Farms
DTU Wind Energy, Technical University of Denmark

20. Foundations – factors to consider
• Water depth
o Length of the free-standing column
• Wave load
o More load and bending moment than from the turbine
itself!
• Ground conditions
o Bearing capacity of the sea bed
• Turbine-induced frequencies
o Consider combined wave and turbine load
DTU Wind Energy, Technical University of Denmark

21. Foundations – water depth
NREL
DTU Wind Energy, Technical University of Denmark

22. Foundations – different types
• Monopile
o 4-8 m diameter steel tube
o Driven into the seabed using a
hydraulic hammer
o Stands upright because of the friction
of the seabed on its sides
o Hard to semihard seabed conditions
o Water depth up to approximately 25 m
http://offshorewind.net
DTU Wind Energy, Technical University of Denmark

23. Foundations – different types
• Gravity Base
o Heavy displacement structure
o Usually made of concrete
o Stands on the seabed
o 15-25 m diameter base
o Semihard to uniform seabed
o Shallower water depths
o Filled with stones or other ballast
o Weight from 1500 to 4500 tons
o Seabed must be prepared by dredging
and backfilling material http://offshorewind.net
DTU Wind Energy, Technical University of Denmark

24. Foundations – different types
• Tripod
o Single steel tube above the water
surface
o Under water – three-legged
foundation
o Each leg ends in a pile sleeve
o From each pile sleeve an anchor pile
is driven into the seabed
o Great stability
o Reliable at depths up to 50 m
o Expensive to produce, takes long to
install http://offshorewind.net
DTU Wind Energy, Technical University of Denmark

25. Foundations – different types
• Jacket
o Lattice-type structure
o Low weight
o Large water depths
o Pile sleeves and anchor piles
o As expensive as a tripod
o Expensive ice protection
Deepwater Wind
DTU Wind Energy, Technical University of Denmark

26. Foundations – illustrations
Photo: Aarsleff Bilfinger Berger Joint Venture
A2SEA
DTU Wind Energy, Technical University of Denmark BIS

27. Foundations – illustrations
Kurt Thomsen: “Offshore Wind: A Comprehensive Guide to Successful Offshore Wind Farm Installation ”
OWEC
DTU Wind Energy, Technical University of Denmark

28. Offshore of tomorrow – HAWE?
• High-altitude wind-energy
• Flying tethered objects that use mechanical systems
to extract energy from wind
• Kites, gliders and other prototypes
• 200 m to 20 km above the Earth
• Deep water up to 700 m
• 22 firms develop systems worldwide
• GL Garrad Hassan says that the resource at high-
altitude is “very promising”
• No commercial HAWE wind farm yet
DTU Wind Energy, Technical University of Denmark

29. Offshore of tomorrow – HAWE?
SkySails
SkySails
DTU Wind Energy, Technical University of Denmark

30. Offshore of tomorrow – HAWE?
Makanipower
Makanipower
DTU Wind Energy, Technical University of Denmark

31. Offshore of tomorrow– HAWE?
Makanipower
http://www.makanipower
.com/category/flights/
DTU Wind Energy, Technical University of Denmark

32. Sources:
• Kurt Thomsen: “Offshore Wind: A Comprehensive Guide to
Successful Offshore Wind Farm Installation”
• John Twidell, Gaetano Gaudiosi: “Offshore Wind Power”
• Martin O. L. Hansen: “Aerodynamics of Wind Turbines”
• http://offshorewind.net
• http://www.bluehgroup.com
• http://recharge.com
• http://www.makanipower.com
• http://wikipedia.org
Deepwater Wind
DTU Wind Energy, Technical University of Denmark

33. Thank you for your attention.
DTU Wind Energy, Technical University of Denmark