Wind Turbines: Will they ever become Economically

Feasible?9th Session of MT5009

A/Prof Jeffrey Funk

Srikanth Narasimalu

Division of Engineering and Technology Management

National University of Singapore

For information on other technologies, see http://www.slideshare.net/Funk98/presentations

2 | Presentation to PE forum, 18th Feb2011 N. Srikanth

Session Technology

1 Objectives and overview of course

2 Two types of improvements: 1) Creating materials that better exploit physical phenomena; 2) Geometrical scaling

3 Semiconductors, ICs, electronic systems

4 MEMS and Bio-electronic ICs

5 Lighting and Displays (also roll-to roll printing)

6 Nanotechnology, 3D printing and DNA sequencing

7 Human-computer interfaces

8 Superconductivity, fusion, energy storage

9 Solar cells, wind turbines (also background on energy)

10 Telecommunications and Internet

This is part of the Ninth Session of MT5009

Horizontal Axis Wind Turbines on Land and at Sea

Figure 1. Horizontal Axis Wind Turbine

Large Wind Farms in the Ocean and on Land

Scale of Individual Wind Turbines are Being Increased

meters per second

0.0 1.3 2.7 3.5 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 >12.0

                             

0.0 2.9 6.0 7.8 10.0 11.2 12.3 13.4 14.5 15.7 16.8 17.9 19.0 20.1 >26.8

miles per hour

Wind Speed

Wind Speed for U.S.

Wind Speed is not Constant!Frequency of Wind Speed in a Ranch in Texas

Installed Global Capacity of Wind Power (MW)

Nation 2006 2007 2008 2009 2010 2011 2012

 China 2,599 5,912 12,210 25,104 44,733 62,733 75,564

 U.S. 11,603 16,819 25,170 35,159 40,200 46,919 60,007

 Germany 20,622 22,247 23,903 25,777 27,214 29,060 31,332

 Spain 11,630 15,145 16,740 19,149 20,676 21,674 22,796

 India 6,270 7,850 9,587 10,925 13,064 16,084 18,421

 UK 1,963 2,389 3,288 4,070 5,203 6,540 8,445

 Italy 2,123 2,726 3,537 4,850 5,797 6,747 8,144

 France 1,589 2,477 3,426 4,410 5,660 6,800 7,196

 Canada 1,460 1,846 2,369 3,319 4,008 5,265 6,200

 Portugal 1,716 2,130 2,862 3,535 3,702 4,083 4,525

 Denmark 3,140 3,129 3,164 3,465 3,752 3,871 4,162

Wind Capacity by Country

TWh: Tera Watt Hours

But Wind Contributes Small % of Electricity Generation (1)

The Future of Wind Power

• Will wind power continue to diffuse?• Advantages

• It has lower carbon and other environmental emissions

• Disadvantages• Wind doesn’t blow all the time (actual output about 1/4 of rated output)• Wind is far from large population centers, so high transmission costs• Wind turbines are considered ugly by many people• Sound of wind turbines causes health problems for some people• Wind power is still more expensive than fossil fuels

• But will wind power become cheaper than fossil fuels• Will countries continue to subsidize wind power?• Are wind turbines becoming cheaper on an cost per Watt basis?

14 | Presentation to PE forum, 18th Feb2011 N. Srikanth

Investment costs per kWatt were fallingBut now they are rising in both Denmark (upper) and U.S. (lower)

Source: http://srren.ipcc-wg3.de/report/srren-drafts-and-review/srren-sod-drafts/sod-chapter-07

Outline• Overview of Wind Turbine Costs• Theoretical Output from Wind Turbines (function of diameter squared, wind speed cubed)

• Empirical Data• Power output vs. rotor diameter• Impact of rotor diameter and other factors on rated wind

speed• Cost of wind turbines

• Implications of Analysis• New materials are needed• Are new designs needed?

Wind Farm Investment Costs

Data source: EWEA for a 2MW Turbine.

Main Components in Terms of Costs

Outline• Overview of Wind Turbine Costs• Theoretical Output from Wind Turbines (function of diameter squared, wind speed cubed)

• Empirical Data• Power output vs. rotor diameter• Impact of rotor diameter and other factors on rated wind

speed• Cost of wind turbines

• Implications of Analysis• New materials are needed• Are new designs Needed?

Figure 1. Horizontal Axis Wind Turbine

Three Key Dimensions in Geometric Scaling: 1) rotor diameter; 2) swept area of blades; and 3) hub or tower height

Theoretical Output From Wind Turbine

Turbine power output by Rotor 2 33.229RP D V

P = electric power (energy per second or watts)D = rotor diameter (meters)V = wind speed (meters/second)

• Output from rotor depends on square of rotor diameter; thus cost of electricity from wind turbine might fall as diameter increases, as long as cost of wind turbine rises at a rate less than diameter squared

• Cost of electricity from wind turbine might fall as diameter increases, if larger diameter rotors enable a wind turbine to handle higher wind speeds.

(Equation 1)

Outline• Overview of Wind Turbine Costs• Theoretical Output from Wind Turbines (function of diameter squared, wind speed cubed)

• Empirical Data• Power output vs. rotor diameter• Impact of rotor diameter and other factors on rated wind

speed• Cost of wind turbines

• Implications of Analysis• New materials are needed• Are new designs Needed?

Empirical Data Finds Stronger Relationship

Equation (2)

Data source from Henderson et al.(2003) & manufacturer catalogue.

Reason for Discrepancy

•Equation in previous slide does not contain wind velocity:• which as noted above has large impact on output

• It does not contain wind velocity since the turbines used for the collection of data on power and rotor diameter for Figure 3 • operate under different wind speeds• these wind conditions depend on the respective region• But larger wind turbines can handle higher speeds

•The impact of larger rotor diameter and related factors (e.g., tower height) on wind speed can be investigated in four ways

First, relationship between diameter and maximum rated wind speed

Data source: Hau (2008).

Best fit curve:Rated wind speed (m/sec) = 9.403D0.081

Second, data on efficiency of wind turbines was also collected

• Efficiency is the ratio of annual turbine power output compared to the energy available in the wind

• Less of wind can be harnessed at tips of blades than near center of the rotor

Average wind speed (m/sec)

Maximum Power density achievable

(W/m^2)

Small turbine (<25 meters)

efficiency Large turbine (>25 meters) efficiency

4 75 19% 35%

5 146 20% 37%

6 253 18% 35%

7 401 17% 31%

8 599 15% 26%

9 853 14% 21%

Third, Higher Towers, Higher Speeds

• Wind velocity is often lower near ground due to uneven terrain or buildings

• The factor alpha depends on the condition of the terrain and in particular on the impact of the terrain on wind friction and is usually about 0.32

• Combining equations (4) and (1) leads to equation (5). Since the exponent for the ratio of the two heights is 3α, an α of 0.32 would cause a doubling of the tower height to result in a 94% increase in power output.

refref H

H

V

V

3

refref H

HPP

Equation (4)

Equation (5)

Comparison of Wind resource at different altitudes (Indiana, USA)

Data source: EWEA

Outline• Overview of Wind Turbine Costs• Theoretical Output from Wind Turbines (function of diameter squared, wind speed cubed)

• Empirical Data• Power output vs. rotor diameter• Impact of rotor diameter and other factors on rated wind

speed• Cost of wind turbines

• Implications of Analysis• New materials are needed• Are new designs Needed?

Cost of Wind Turbines

• More than 2/3 the cost of electricity from wind turbine farms comes from capital cost of wind turbine and almost half the capital costs are in tower and blades (Krohn et al, 2009)

• Beginning with tower, WindPACT analysis (Malcom and Hansen, 2006) found R-squared of 0.999

c = cost of steel ($/Kg); H = tower height; D = rotor diameter

• Comparing equations (5) and (6), output from turbine increases faster than costs as height is increased. • For example, if alpha is 0.32 as was shown above and assuming a

constant rotor diameter, • increasing height from 10 meters to 20 meters would cause output to

rise by 94% and costs to rise by 9 percent

Tower cost (in $) = 0.85 (cD2H) – 1414 Equation (6)

Cost of the Rotor

Data source: Hau (2008) and EWEA (2010) .

D>50 meters (Purple): Rotor cost = 96.7D2.3257

D<50 meters (dark blue): Rotor cost = 434.D1.9258

Rotor Cost

Cost of the Rotor

D>50 meters (Purple): Rotor cost = 96.7D2.3257

D<50 meters (dark blue): Rotor cost = 434.D1.9258

Compared with Output

Theoretical Output: 3.229D2V3 (Equation 1)

Empirical Output: 0.1034D2.2538 (Equation 2)

Rotor Cost Per Swept Area of Turbine Blades (1)

• Compare last two slides’ regression equations with theoretical cost curve (equation 1)

D<50 meters: Rotor cost/output = 434.D-0.0742

D>50 meters: Rotor cost/output = 96.7D0.3257

• Compare last two slides’ regression equations with empirical cost curve (equation 2)

D<50 meters: Rotor cost/output = 96.7D-0.2280

D>50 meters: Rotor cost/output = 434.D0.0719

Rotor Cost Per “Swept Area” of Turbine Blades (2)

• Benefits from increasing scale• diameters < 50 meters; Some• diameters > 50 meters; Hard to say, Maybe Not

• “Maybe” because equation (2) does not take into account • the impact of increased tower height or rotor diameter on maximum

rated wind speeds or increased efficiencies.

• Including the increased efficiencies, maximum rated wind speeds, and greater tower heights, which are partly represented by equations (3) and (5) • would provide a further improvements in our understanding of scaling• would probably show some benefits to increases in scale

The previous slides are consistent with other sources(IPCC, Chapter 7)that say investment costs per output are now rising!!

Source: http://srren.ipcc-wg3.de/report/srren-drafts-and-review/srren-sod-drafts/sod-chapter-07

Why? Cost of Blades Rise

• The reason for the change in slopes for < and > than 50 meters is that lighter, thus higher cost materials are needed:• for diameters > 50 meters (carbon fiber-based blades). • than for diameters < 50 meters (aluminum, glass fiber reinforced

composites, and wood/epoxy).

• Early blades can be manufactured with methods borrowed from pleasure boats such as “hand lay up” of fiber-glass reinforced with polyester resin.

• Carbon-based blades require better manufacturing methods such as vacuum bagging process and resin infusion method that have been borrowed from the aerospace industry (Ashwill, 2004)

Outline• Overview of Wind Turbine Costs• Theoretical Output from Wind Turbines (function of diameter squared, wind speed cubed)

• Empirical Data• Power output vs. rotor diameter• Impact of rotor diameter and other factors on rated wind

speed• Cost of wind turbines

• Implications of Analysis• New materials are needed• Are new designs needed?

New Materials are Needed

•Stronger and lighter materials are needed for further increases in scaling• Lighter materials are needed in order to reduce

inertia of large rotors• Stronger materials are needed to withstand high

wind speeds

•Without new materials, there will be few (or no) benefits from further scaling

•Perhaps too large of wind turbines have already been installed

38 | Presentation to PE forum, 18th Feb2011 N. Srikanth

Source: Eric HauWind turbines: fundamentals, technologies, application, economics, 2006Note: metersquared is for rotor area

Material Technology Choice for Blades

Note: Squared meters is for swept area of rotorSource Eric Hau (2006) and analysis by Srikanth Narasimalu)

Outline• Overview of Wind Turbine Costs• Theoretical Output from Wind Turbines (function of diameter squared, wind speed cubed)

• Empirical Data• Power output vs. rotor diameter• Impact of rotor diameter and other factors on rated wind

speed• Cost of wind turbines

• Implications of Analysis• New materials are needed• Are new designs needed

The “Aerogenerator:” Implementation of 275 meter diameter turbine by 2014?

Tethered Wind Turbine

Tethered Wind Turbine

What about increasing size of fins?

Final Words

•Costs of electricity of wind turbines were slowly falling

•Now cost reductions have stopped and the costs may be rising

•New materials may enable further cost reductions•But will these improvements be significant, even if the materials can be developed?

•New designs are needed, but even their benefits are unclear

•The future of wind power doesn’t look good….

Appendix