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Challenges and perspectives in future wind energy technology and the role of system engineering

Flemming Rasmussen, DTU Wind Energy Aeroelastic Design Risø Campus

DTU Wind Energy, Technical University of Denmark

Outline

•Global market status •Historical perspective - evolving of engineering practices,

science and technology •Status and future of wind energy technology and concepts •Wind energy perspectives

Challenge: •Wind energy has the potential to become the backbone of

a future secure global energy supply - or wind energy as “base load”. • It’s all about cost of energy, however, including a future

perspective (not necessarily the cheapest now)


GLOBAL STATUS (early estimate by GWEC)

• ~ 47 GW installed in 2014 • ~ 369 GW installed in total • ~ 3.5 % of global electricity • Wind energy begins to count STATUS DENMARK • 39% from wind in Denmark • 62% in January, 23% in June • Days with more than 100% • Energy Plan: 50% by 2020 • Plan to promote heat pumps,

electric cars….. • Electricity prices varies…

Global market status - 2014

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

0

9,000

18,000

27,000

36,000

45,000

54,000

1983 1990 1995 2000 2005 2010 2013

Cu

mu

lati

ve M

W

MW

per

year

Year

Installed Wind Power in the World- Annual and Cumulative -

Installed MW in year Accu. MW

Source: BTM Consult - A Part of Navigant - March 2014


Global market development 1983 - 2014

4 20 January 2015

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

0

9,000

18,000

27,000

36,000

45,000

54,000

1983 1990 1995 2000 2005 2010 2013

Cum

ulat

ive

MW

MW

per

yea

r

Year

Installed Wind Power in the World- Annual and Cumulative -

Installed MW in year Accu. MW

Source: BTM Consult - A Part of Navigant - March 2014

Exponential growth. The challenge is the bumps. Generate and maintain enough momentum to overcome the bumps by i.e.: - cost of wind energy - financial capacity in industry, - funding of research, - political will, - underpinning science, - knowledge, design tools and standards - perspectives for wind energy, scalable

Bumps


The Test Station for Wind Turbines/Risø 1979 – a variety of concepts

Risø 1979


Employees at The Test Station for Wind Turbines, Risø 1979


System engineering network

7 20 January 2015

• Plans for a complete optimization tool even including manufacturing •Wind turbines developed in a kind of system engineering

context in a network – manufacturers, private persons, interest organizations, research community

- open exchange of knowledge and ideas - setting requirements, airbrakes... - system approval included - concept selection


1980’s turbine concepts

8 20 January 2015

Standard concept Radical technology, Carter Vision


Evolving of engineering practices

• Development of specific simple design tools and rules in the beginning

• Aerodynamic model (BEM) • Extreme design load 300 N/m2

swept area distributed on the three blades in a triangular shape for blade and tower design

• One blade full load, the two others with half load to determine yaw and tilt moments

• Main shaft 1% of rotor diameter • Equally simple rules for fatigue • Similarity rules and upscaling:

• Blade testing • Gradually supplemented by

specific codes

9 20 January 2015



•Break through with the development of aeroelastic simulation tools •Development of standards and certification

10 20 January 2015

Aeroelastic code


System approval, optimising reliability

Root section, 3D rotational effects, deformations

Tip, 3D

-10 0 10 20-0.5

0

0.5

1

1.5

angle of attcak [deg]

Cl,C

d,C

m

0 0.02 0.04-1

0

1

2

Cd

Cl

-0.2 0 0.2 0.4 0.6 0.8 1 1.2

-0.2

-0.1

0

0.1

0.2

r = 0.2

Mid span, 2D, structure

Airfoil data Mode shapes Edgewise vib. Flutter Couplings



•Science, research and development on track - in global interaction. • Progress on research and development, refinement and

coupling of codes. •Change from open to closed environment. Competition in

industry. •New perspectives in System engineering <> Crowd

sourcing, crowd funding also used in 1750’s. •Our goal is cost efficiency and sustainable development.

Not the same as the cheapest right now. •System engineering to help develop new insight and

maintain knowledge. Increase crowd intelligence.

12 20 January 2015


Upscaling and longer blades -evolving of technology

13


Standard three-bladed turbine, DTU 10 MW

14 20 January 2015

>20.000 m2

Thrust

Torque

Airflow at 10 m/s: 250 t/sec


Low induction rotors

• Two rotors designed by simple means and maintaining thrust:

– Radius=89.166m, a=0.333, TSR=8.0, CP=49.5%

– Radius=98.083m, a=0.243, TSR=8.8, CP=46.7%

• Area increase=21%, CP reduction=5,6% • Total power increase at low wind speed=14% • AEP increase ~7%

15

0

2

4

6

8

10

12

0 20 40 60 80 100 120

Ch

ord

[m

]

Radius [m]

10MW rotor with a=0.333

10MW rotor with a=0.243

0

2

4

6

8

10

12

4 9 14

Po

wer

[M

W]

Wind speed [m/s]

a=1/3

a=0.243


Wind turbine concepts

Envision 3.6 MW DeepWind Multi-rotor


Number of blades: 2-bladed/3-bladed

The 2-bladed has: • 50% larger chord • 4% lower efficiency • 15 % larger turbulence load input

(as 2p<3p) • App. 2/3 rotor weight

With teetering hub: • App. 50% rotor weight • Blade load ~ blade load for 3-

bladed • Possibility for larger diameter

• Tower natural frequency has to be

lower (down towards 1p, or lower)

17


Coupled deformations Flap-torsion Flap-camber

18

A Twist–flap Coupled Blade Design to Alleviate Fatigue Loads (on the left with material coupling and on the right with a curved blade (Sandia)

Feather

Combined passive built-in coupling and multi-variable control - an optimum design


Aeroelastic stability

Example: Swept blades

Different section motion gives different damping and load alleviation


Combined blade pitch and trailing edge flap

20

Load reduction • Cyclic pitch: 15% • Flaps: 14% • Combined: 24%


21 20 January 2015

Standstill Vibrations

Emergency Shutdown

Fluid-Structure Interaction Simulations Using CFD


Segmentation of large blades ?

22

Source: Lutz Beyland, Dr. Jochen Birkemeyer, Nordex

Finger joint

Possibility to make sweep and prebend from ”straight sections”


Electro-mechanical conversion

Superconducting direct drive

Pseudo magnetic direct drive Magnomatics

Trend to reduce number of gear stages and use medium- speed multipole PM


Offshore & foundations bottom mounted

24

NREL

Rambøll DONG Energy


Technology perspectives

• Upscaling - 10 MW is within reach. • Aeroelastic tayloring and

distributed control. Future blades will become longer, more coupled and more flexible (in the tip). Possibly made in sections.

• Great perspectives for emerging technologies.

• Getting more complex. • Turbine in the power plant in the

energy system. • Lots og benefits in a more

integrated system approach – and in more integrated turbine and plant design.

• Conversion of new concepts into mainstream is a challenge.


Wind energy perspectives - World electricity generation

26 20 January 2015


0

200

400

600

800

1000

1200

1400

1940 1950 1960 1970 1980 1990 2000 2010 2020 2030

POW

ER [G

W]

YEAR

Nuclear Wind Hydro Wind installed

Accumulated power in the world, 2014 10 % Wind energy-scenario (1998)

Percent of World electricity supply:

Nuclear: 10.9 %, 374 GW installed (2012)

Hydro: 16.5 %, 1025 GW installed (2012)

Wind: 3.5 %, 369 GW installed (2014)


Outlook for wind electricity generation

28 20 January 2015

Integration is the challenge Wind-Hydro-pumped storage part of the solution Example Norway: 30 GW hydro power 2 GW pumped storage 15 GW potential for both Global: Hydro power supply 16.5% with a capacity factor of 1/3 Could supply 50 %, ”if there was enough water”


29

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