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Week 10 Power: Energy Options for a Global Society Renewable Energy Principles and Applications II: Wind & Geothermal Power Wind Modern wind technology is already competitive with fossil fuels. Its ultimate limitations are only due to its intermittency. Resource Potential Power

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week 10 power energy options for a global society

Week 10Power: Energy Options for a Global Society

Renewable Energy Principles and Applications II:

Wind & Geothermal Power


Modern wind

technology is

already competitive

with fossil fuels.

Its ultimate limitations

are only due to its


  • Resource Potential
  • Power
  • Swept Area
  • Rotor Design
  • Wind Speed Distributions
  • Power Increase with Height
wind power
Wind Power
  • The power in the wind is:

Power = ½ rA V3

  • Using the density of air at sea level:

Power = 0.6125 AV3 (metric)

Power = 0.00508 AV3 (mph, ft)

  • Calculate how much more power is available at a site where the wind speed is 12 mph than where it is 10 mph
  • P ~ V3
  • P2/P1 = (V2/V1)3
    • P2 = (12/10)3P1 = 1.73 P1

1.7 x the power (almost a factor of 2 increase),

with only 2 mph increase in wind speed!

swept area
Swept Area
  • Power in the wind is also proportional to the swept area

A = pR2

  • Increase the radius from 10 m to 12 m:

A2 = (R2/R1)2 A1

A2 = (12/10)2 A1 = 1.44A1

Nothing tells you more about a wind turbine’s potential than the rotor radius.

rotor designs
Rotor Designs
  • Two blades are cheaper but do not last as long
  • Three blades are more stable and last longer
  • Options include:
    • Upwind vs downwind
    • Passive vs active yaw
  • Common option chosen is to direct the rotor upwind of thetower with a tail vane

Darrieus Vertical Axis

Fan Mill Horizontal Axis





  • Two Speed

Cut-in Wind Speed:  2.5-3.5 m/s (7 mph)Rated Power:  900 KW - 1.65 MWCut-out Wind Speed:  32 m/s (75 mph)

  • Type:  3 Blade UpwindRotor Diameter:  82 m (270 ft.)

Swept Area: 5281 m2

Rotor Speed: 10.8-14.4 rpm

the lift force only turns windmill blades for useful power output
The lift force (only) turns windmill blades for useful power output
  • Can think of a windmill as a fan running backwards.
  • The pitch of the blade causes a difference in air pressure on either side.
  • This difference in air pressure is what provides the “lift force” (similar to aircraft), and causes the rotors to turn.
wind drag
Wind Drag
  • If the angle of attack of a blade is too large, the wind simply pushes against the blade, exerting a drag force but no lift. When the drag is too great, a stall occurs.
  • Wind mills are designed to operate in winds up to 35 mph, but must be able to survive 100 mph gales.
  • Random turbulent winds create strong torques that can fatigue the structure.
wind speed frequency distribution
Wind Speed Frequency Distribution
  • Wind speeds occur at different values
  • Total energy from a turbine depends heavily on the maximum speeds because Power increases with the cube of the speed

“The average of the cubes is greater than the cube of the average.”

approximating wind distribution using rayleigh distribution
Approximating Wind Distribution Using Rayleigh Distribution
  • Suppose we only know average speed
  • e.g. 12.8 MPH (5.7 m/s)
  • Wind has been observed to follow a Rayleigh distribution in many places, i.e.

Prob. (Windspeed < v) = 1 – exp[(-/4)(v/vaverage)2]

e.g. P (0) = 0, P (300 MPH) = 1

wind power24
Wind Power
  • The power in the wind is:

Power = ½ rA V3

  • Using the density of air at sea level:

Power = 0.6125 AV3 (metric)

Power = 0.00508 AV3 (mph, ft)

a utility grade 1 65mw turbine a 5281 m 2
A Utility-Grade 1.65MW Turbine A = 5281 m2
  • @4.5 m/s
    • Power = 0.6125 AV3 = 295 KW
  • @5.5 m/s
    • Power = 0.6125 AV3 = 538 KW
  • @ 6.5 m/s
    • Power = 0.6125 AV3 = 888 KW
wind speed frequency distribution26
Wind Speed Frequency Distribution

Total energy from a turbine depends heavily on the maximum speeds because Power increases with the cube of the speed

wind speed power curves
Wind Speed & Power Curves

Rayleigh Distribution

Turbine Power Profile

Cut-in Speed


Wind Speed & Power Curves

Total Energy in 1 Year:

~1.7 million kWh

Blades will be turning:

80-90% of time

Cut-in Speed 2.5 m/s (5.6 mph)

Cut-out Speed 32 m/s (72 mph)

how to calculate wind speed increase with height
How to calculate wind speed increase with height
  • Conservative Approximation:

V2 = (H2/H1)aV1

  • a is the Roughness exponent
    • Smooth terrain value (water or ice): 0.10
    • Rough terrain value (suburb woodlands): 0.25
    • Grasslands: 0.14
  • Consider doubling the height of your tower from 10 m to 20 m.

V2 = (H2/H1)aV1 = (20/10).14 V1 = 1.1V1

  • The power available increases to:

P2 = (H2/H1)3aP1 = (2)3aP1 = 1.34P1

  • If you multiply height by a factor of 5:

P2 = (H2/H1)3aP1 = (5)3aP1 = 1.97P1

  • You live in a forested area. Calculate how much more power you can get from a turbine at 87meters than a turbine at 30meters.

V2 = (H2/H1)aV1 = (87/30).25 V1 = 1.3V1

  • The power available increases to:

P2 = (H2/H1)3aP1 = (2.9)3(.25)P1 = 2.22P1

  • Small wind turbines can seldom deliver more than 30% of the energy in the wind
  • Most people live where average wind speeds are 4-5 m/s (9-11 mph)
  • Strangely, at extremely windy sites small wind turbines produce more energy but are less efficient at capturing the energy in the wind (10%)
  • Very important to locate turbines where winds speeds are highest and turbulence is at a minimum
high technology large turbines can achieve up to 46 efficiency
High technology large turbines can achieve up to 46% efficiency
  • The spinning of a windmill causes a “backwind” which is maximum at the blade tip.
  • This affects the efficiency of the turbine.
  • Thus, one factor in the design is the tip speed vs. wind speed ratio.
wind power resource potential36
Wind Power Resource Potential
  • Potential includes all the
  • factors we’ve covered:
  • wind speed
  • wind speed distribution
  • roughness of terrain
  • height of rotors
  • wind turbulence
  • etc.
  • Most turbines do not operate
  • at full capacity – 20% is typical
factors to consider when designing a wind system
Factors to Consider When Designing a Wind System:
  • Company specs relevant to the machine only
    • Company specs may claim 2.4 KW
    • But does the wind carry that much power?
  • The site must be tested for wind speed optimization, turbulence minimization
    • Height of turbine
    • Design of turbine
    • Wind speed at which the rotor furls


  • Wind turbines effective at night and in stormy weather
  • Both effective on a windy day
  • Solar effective on a clear windless day
wind farms
Wind Farms
  • Wind farms funded in the 1980s helped tremendously to mature the technology to make wind power competitive with traditional fuels
  • California gave huge tax incentives for wind farms
  • Largest turbine produced 3.2 MW




1 madison windpower llc
1. Madison Windpower, LLC
  • Town: Madison
  • County: Madison
  • Project Owner: PG&E Generating
  • # of Turbines: 7
  • Turbine type: Vestas V66- 1,650kW
  • Rotor Diameter: 66m
  • Hub Height: 67m
  • Total Capacity (MW): 11.55
  • Annual Expected Energy (MWh): 24,000
2 wethersfield
2. Wethersfield
  • Town: Wethersfield
  • County: Wyoming
  • Project Owner: CHI Energy, Inc.
  • # of Turbines: 10
  • Turbine type: Vestas V47-660kW
  • Rotor Diameter: 47m
  • Hub Height: 65m
  • Total Capacity (MW): 6.6
  • Annual Expected Energy (MWh): 19,000
3 fenner windpower llc
3. Fenner Windpower, LLC
  • Town: Fenner
  • County: Madison
  • Project Owner: CHI Energy Inc.
  • # of Turbines: 20
  • Turbine type: GE Wind- 1,500kW
  • Rotor Diameter: 70.5m
  • Hub Height: 65m
  • Total Capacity (MW): 30
  • Annual Expected Energy (MWh): 89,000
more about fenner
More about Fenner
  • Noise from individual turbines: 50 dbA (as measured from closest non-site owned area)
          • Comparable to hearing airplane in distance
  • Area: 2000 acres
  • Average wind speed: 17mph
  • Total height: 328 feet
  • Weight: 375,000 pounds
  • Resident response: mostly positive: educational, clean, approve of appearance,
4 calverton
4. Calverton
  • Town: Calverton
  • County:
  • Project Owner: Long Island Power Authority
  • # of Turbines: 1
  • Turbine type: AOC 15/50
  • Rotor Diameter:
  • Hub Height:
  • Total Capacity (MW): 0.5
  • Annual Expected Energy (MWh):
5 lorax energy
5. Lorax-Energy
  • Town:
  • County:
  • Project Owner: Harbeck Plastics
  • # of Turbines: 1
  • Turbine type: Fuhrlaender 250
  • Rotor Diameter:
  • Hub Height:
  • Total Capacity (MW): 0.25
  • Annual Expected Energy (MWh):
tax incentives
Tax Incentives
  • The Renewable Energy Production Incentive entitles Wind and PV systems to annual incentive payments of 1.5 cents per kilowatt-hour (1993 dollars and indexed for inflation) for the first ten year period of their operation, subject to the availability of annual appropriations in each Federal fiscal year of operation. - www.dsireusa.org.
  • For our turbine, this could mean 1.7 million kWh * 1.5 cents/kWh = $25,500 per year
maple ridge wind power project
Maple Ridge Wind Power Project

New York Needs Wind

The use of renewable energy sources such as wind power for

the commercial generation of electric power is an explicit energy

policy objective of New York State. The New York State Energy

Research and Development Authority (NYSERDA), for example,

has a program designed to invest some of the proceeds of the

System Benefits Charges in commercial wind projects, and the

Flat Rock Wind Power Generating Facility has been chosen for

funding by NYSERDA under this program. More recently,

Governor Pataki has instructed the Public Service

Commission to develop regulations that will require all electric

utilities to substantially increase their sourcing of power derived

from renewable energy sources. The goal: for 25% of New York's

electricity to come from renewable energy by 2010.

Why Tug Hill?

Tug Hill is in many respects the ideal location for New York's

largest wind energy project. This site consists of approximately

12,000 acres of hilltop pasture and feed-crop land at an average

elevation of 1600-1800 feet. Tug Hill is an ancient geologic

formation that lies just downwind of the eastern shore of Lake

Ontario, separated from the Adirondacks to the east by the Black

River Valley. At a maximum elevation of 2000 feet above sea

level, the Tug Hill plateau experiences strong lake-effect weather

patterns and has long been known for its exceptional wind


maple ridge turbines
Maple Ridge Turbines

Main Components: The tower, the nacelle (machine house atop

the tower), and the rotor

Height of Maple Ridge Wind Turbine Towers: 260 feet

Number of Towers: 150

Rotor Blade Length: 130 feet

Rotor Blade Speed: 14 RPM (revolutions per minute)

Electricity from each 1.65 MW wind turbine generator is fed

through numerous 34.5-kilovolt power underground cables that

come together at the wind farm substation near Rector Road.

These cables channel the electricity via a step-up transformer

and dedicated ten-mile power line into the New York electricity

grid at the 230-kilovolt Niagara Mohawk Adirondack line.

Pollution Offset: We estimate that 1 MW of wind generation

capacity is the equivalent of 1 square mile of new forest, in terms

of offsetting or displacing carbon dioxide from conventional

generating sources.


Maple Ridge Wind Power

Transmission Plan

FRWP proposes to construct approximately 10.3 miles of a

single circuit 230 kV overhead electric transmission line to

transmit power from the proposed 240 MW Flat Rock Wind

Power Generating Facility to the Niagara Mohawk Power

Corporation (NMPC) 230 kV Adirondack-Porter Transmission

Line. FRWP proposes to construct a substation in the Town of

Martinsburg (Rector Road 230 kV Substation).

The Transmission Facility will be comprised of approximately 77

tower structures and a three-phase, single circuit 230 kV line to

transmit power from the Rector Road Substation to the Chases

Lake Road Interconnect Facility. Actual spans will vary to

accommodate geographical considerations. Tower structure

types were selected to minimize visual impacts of the facility and

to further reduce impacts to agricultural areas and other sensitive

resources in the study area. Tower structures will be of three

general types: wood pole H-frame structure, three-pole wood

structure, and a single steel pole structure. Typical structures

range in height from approximately 65 to 105 feet.

  • Milliken Station Coal Power Plant:
    • 200 MWe
    • 1$ per watt generating capacity – capital cost
    • Fuels, emissions, maintenance additional
  • Flat Rock Wind Power Project:
    • 240 MWe
    • $4.20 per watt generating capacity – capital cost
    • No fuels, no emissions, low maintenance
  • Wind technology is here
    • Prices are competitive with fossil fuels
    • History of development included enough tax incentives and federal funds to ensure cost competitiveness.
  • Solar technology is almost here
    • Prices are not yet competitive with fossil fuels
    • History of development did not include federal actions over long enough time span to ensure cost competitiveness.
Energy Content of Fuels

GJ per tonne

North Sea Crude Oil 42.7

LPG (Liquefied

petroleum gas: Propane,

Butane) 46.0

Petrol (Gasoline) 43.8

JP1 (Jet aircraft fuel) 43.5

Diesel / Light Fuel oil 42.7

Heavy Fuel Oil 40.4

Orimulsion 28.0

Natural Gas 39.3 per 1000 Nm 3

Steam Coal 24.5

Other Coal 26.5

Straw 14.5

Wood chips 14.7

CO2 Emissions from Fuels

kg CO 2 per GJ kg CO 2 per kg fuel

Petrol (Gasoline) 73.0 3.20

Diesel / Light Fuel oil 74.0 3.16

Heavy Fuel Oil 78.0 3.15

Orimulsion 76.0 2.13

Natural Gas (methane) 56.9 2.74

Coal 95.0 2.33 (steam coal) 2.52

bird hazard
Bird Hazard
  • One concern of Wind Power is the increase in bird mortality
  • Studies show that it is possible to construct wind turbines to minimize bird deaths
    • Location
    • Design
  • Modern turbines turn very slowly (speed of blades is not visibly blurred) so that birds can see them and avoid them
  • The wind itself will likely drown out the sound of the turbines - at least farther than 1,000 feet away. At that distance, the environmental assessment predicts the noise level will range between 45 and 50 decibels, depending on wind speed.
  • To put that in perspective, 30 decibels is as loud as a soft whisper, and 40 decibels compares to the noise in a library.
  • Belyaev, L.S., O.V. Marchenko, S.P. Filipov, S.V. Solomin, T.B. Stepanova, and A.L. Kokorin (2002) World Energy and Transition to Sustainable Development. Kluwer Academic Publishers.
  • Fowler, J.M. (1975) Energy and the Environment. McGraw Hill.
  • Gipe, P. (1999) Wind Energy Basics: A Guide to Small and Micro Wind Systems. A Real Goods Solar Living Book. Chelsea Green Publishing Company, Vermont.
  • Howes, R. and A. Fainberg (1991) The Energy Sourcebook: A Guide to Technology, Resources, and Policy. American Institute of Physics, NY.
  • New England Solar Electric Inc., (1998) The Solar Electric Independent Home Book. Revised Edition, Fourth Printing.
  • Renewable Energy Annual 2001. Department of Energy – Energy Information Administration publication number DOE/EIA-0603(2001).
  • Ristinen, R.A., and J.J. Kraushaar (1999) Energy and the Environment. John Wiley and Sons.
  • Smith, E.R.A.N. (2002) Energy, the Environment, and Public Opinion. Rowman & Littlefield.
  • Vanek, Francis, personal communication.
  • Watts, R., Editor (2002) Innovative Energy Strategies for CO2 Stabilization. Cambridge Univ. Press.
resources on wind
Resources on Wind
  • 1. http://www.sandia.gov/wind/ -- info about wind turbines
  • 2. http://eereweb.ee.doe.gov/windandhydro/wind_technologies.html -- wind energy technologies
  • 3. http://www.awea.org/ -- the website of American Wind Energy Association
  • 4. http://www.nrel.gov/wind/ -- National Renewable Energy Laboratory - Wind Technology Center
  • 5. http://www.town.ipswich.ma.us/ub/wind/Ipswich%20WTG%20Report.pdf – this is a report on a townships' plan to construct a wind turbine.
  • 6. http://www.aceny.org/media/New%20York%20WindPower.wmv – a 17 minute DVD erasing myths and fears about wind power in NY State.
  • 7. http://www.awea.org/wpny/index.html --Wind Power NY's website.
  • 8. http://www.awea.org/pubs/factsheets/10stwf_fs.PDF -- building a wind farm – steps to take and things to consider.