An Introduction to
Wind Energy
Frank R. Leslie,
B. S. E. E., M. S. Space Technology
1/19/2002, Rev. 1.0
f.leslie@ieee.org; (321) 768-6629
Overview
 Renewable energy is sustainable indefinitely, unlike long-stored
energy from fossil fuels
 Renewable energy from wind, solar, and hydroelectric power emits
no pollution or carbon dioxide (although the building of the
components does)
 Biomass combustion is also renewable, but emits CO2 and
pollutants
 Nuclear energy is not renewable, but sometimes is treated as
though it were because of the long depletion period
 Sustainable energy comes from the sun or from tidal forces of the
moon and sun
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Energy considerations for
2050
 Fossil-fuel energy will
deplete in the future;
took millions of years to
create that much fuel
 US oil production
peaked about 1974;
world energy will peak
about 2004-9 or so
 Renewable energy will
eventually become
mandatory, and our
lifestyles may change
 Transition to renewable
energy must occur well
before a crisis occurs
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The eventual decline
of fossil fuels
 Millions of years of incoming solar energy were captured
in the form of coal, oil, and natural gas; current usage
thus exceeds the rate of original production
 Coal may last 250 years; estimates vary greatly; not as
useful for transportation due to thermal losses in
converting to convenient liquid “synfuel”
 We can conserve energy by reducing loads and through
increased efficiency in generating, transmitting, and
using energy
 Efficiency and conservation will delay an energy crisis,
but will not prevent it
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The Hubbert Curve predicts
fossil fuel decline
 Dr. M. King Hubbert,
geophysicist,
published his
prediction that the US
oil peak would be
reached in 1970.
Later, others predicted
the World oil peak
would occur in the
first decade of the
21st Century.
 Past the production
peak, oil prices will
increase as extraction
becomes more difficult
and the price is bid
up.
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www.hubbertpeak.com/midpoint.htm
Where does our local
electricity come from?
 Our local utility, FPL, lists these for the 12
months ended May 2001:
Petroleum, 40%
Nuclear, 25.5%
Natural Gas, 20%
Purchased Power (various sources),
7.5%
Coal, 7%
 Any renewables are in the Purchased Power
category
 Will we “export our pollution” to other states
as California does?
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Cape Canaveral Plant, photo by F. Leslie, 2001
Solar Energy: Thermal




Low-temperature extraction of heat from ground; ~70° F to 80° F
Water heating for home and business; ~90° F to 120° F
High-temperature process-heating water for industry; ~200° F to 400° F
Solar thermal power plants; ~1000° F
Arizona has clearer skies than Florida. Ref.: Innovative Power Systems
From www.energy.ca.gov/education/story/story-images/solar.jpeg
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Wind Energy
 Wind energy results from uneven heating of the atmosphere
 Wind resources vary greatly worldwide, even within a few
miles
 Power is proportional to the wind speed cubed
Ref.: www.freefoto.com/pictures/general/ windfarm/index.asp?i=2
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Wind Energy in Practice
 Favorable California tax
incentives resulted in major
U.S. wind farms
 Altamonte Pass
 Tehachapi
 San Gorgonio Pass
 Other turbines are located in
Dakotas, Iowa, Texas,
Minnesota, Wyoming, Iowa,
Vermont, etc.
 Early Twentieth Century saw
wind-driven water-pumps
commonly used in rural
America, but the spread of
electricity lines in 1930s
(REA) caused their decline
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www.nrel.gov/wind/usmaps.html
Wind Energy is best suited to
the Great Plains States
 Coastal Florida has Class 2 wind energy (160 to 240
W/m^2) per the PNNL Wind Energy Atlas ― sufficient to
investigate but marginal for major wind energy systems
 High average wind speeds in the Rocky Mountain Region
(300 to 1000 W/m^2) and the Great Plains States (200
to 250 W/m^2)
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Florida has marginal wind
energy
 These wind energy maps are
available for each state and for
the World
 Coastal Florida is Class 2 with
seabreeze and storm front
passages
 Summer ground heating
results in ~10 mph seabreezes
and storms
 Winter is calmer, with frontal
storm passages averaging
every four days
From the PNNL Wind Energy Atlas
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A sample day’s seabreeze wind profile from
the FSEC MET system in Cocoa, FL
Effective wind
is from 9 a.m.
to ~5 p.m.
Ref.: FSEC
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Predominant wind energy direction
determines the site selected
 The energy rose is the cube of
the wind speed (flower-like)
rose
 In Palm Bay, Florida, this wind
data sample shows the main
wind direction at 150 degrees
azimuth
 Several years of data are
averaged to get a useful
sample; 30 years desirable
 In obstructed areas, the site
selection is critical to obtain
the maximum wind energy
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N
0
20000
338
23
15000
315
Available Relative Wind Energy
45
10000
293
68
5000
270
0
90
248
113
225
135
203
158
180
S
Energy is proportional to wind
speed cubed
 Recall that the average wind power is based upon the
average of the speed cubed for each occurrence
 The wind energy varies from trivial to disastrous!
 Precautions are needed to protect the turbine
Turbines must be turned
automatically out of destructive winds
to protect them. Some turn sideways,
while others rotate vertically. Another
way is to drag flaps from the tip of the
blades. Most turbines reject power
when the wind speed exceeds 30
mph.
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Ref.: Bergey
Vertical Axis Wind Turbines (VAWT)
Panemone,
1000 B.C.
Savonius
Darrieus
with Savonius
Giromill
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Horizontal Axis Wind Turbines
(HAWT)
American
Farm, 1854
Experimental
Wind farm
Sailwing,
1300 A.D.
Dutch with
fantail
1.8 m
Dutch post
mill
Modern
Turbines
75 m
Middelgrunden
Ref.: WTC
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Energy
Transmission
 Electricity and hydrogen are energy carriers, not natural
fuels
 Electric transmission lines lose energy in heat (~2 to 5%
as design parameter)
 Line energy flow directional analysis can show where
new energy plants are required
 Hydrogen is made by electrolysis of water, cracking of
natural gas, or from bacterial action (lab experiment
level)
 Pipelines can transport hydrogen without appreciable
energy loss
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Energy Storage
 Renewable energy is often intermittent, and storage
allows alignment with time of use.
 Compressed air, flywheels, weight-shifting (pumped
water storage) are developing
 Batteries are traditional for small systems and electric
vehicles; grid storage alternative
 Energy may be stored financially as credits
in the electrical “grid”
 “Net metering” provides the same cost as
sale dollars to the supplier; 37 states’ law;
needed in Florida
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www.strawbilt.org/systems/ details.solar_electric.html
Distributed Generation (DG)
 Distributed generation occurs when power is generated
(converted) locally and might be shared with or sold to
neighbors through the electrical grid
 Distributed generation avoids the losses that occur in
transmission over long distances; energy used nearby
 Varying wind and sunshine averages across several
houses, blocks, cities, or states
 Supply is robust, but precautions are required to protect
electricity workers when main base-load power is out
and system may feed back into powerlines
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Generic Trades in Energy
 Energy trade-offs are
required to make rational
decisions
 PV is expensive ($5 per watt
for hardware + $5 per watt
for shipping and installation
= $10 per watt)
compared to wind energy
($1.5 per watt for
hardware + $5 per watt
for installation = $6 per
watt total)
 Are Compact Fluorescent
Lamps (CFLs) better to use?
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Ref.: www.freefoto.com/
pictures/general/
windfarm/index.asp?i=2
Ref.:
www.energy.ca.gov/educati
on/story/storyimages/solar.jpeg
Photo of FPL’s Cape
Canaveral Plant
by F. Leslie, 2001
Legal aspects and other
complications
 PURPA: Public Utility Regulatory Policy Act of 1978. Utility purchase
from and sale of power to qualified facilities; avoided costs
 Power Plant Siting Act provides regulation by FERC
 Energy Policy Act of 1992 leads to deregulation
 Investment taxes favor conventional power
 High initial cost dissuades potential renewable energy users
 Lack of state-level net metering hinders offsetting costs
 Renewable energy credits needed to offset unlikely carbon tax on
fossil fuels and “externalities” (pollution, health, etc.)
 “NIMBYs” rally to insist “Not In My Backyard”!
 Need to consider beyond the first action; the results, and then
what?
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Conclusion
 Renewable energy offers a
long-term approach to the
World’s energy needs
 Economics drives the selection
process and short-term (first
cost) thinking leads to
disregard of long-term, overall
cost
 Increasing oil, gas, and coal
prices will ensure that the
transition to renewable energy
will occur ― How will we
choose to do it?
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References: Books
 Gipe, Paul. Wind Energy for Home & Business. White River Junction, VT: Chelsea
Green Pub. Co., 1993. 0-930031-64-4, TJ820.G57, 621.4’5
 Patel, Mukund R. Wind and Solar Power Systems. Boca Raton: CRC Press, 1999, 351
pp. ISBN 0-8493-1605-7, TK1541.P38 1999, 621.31’2136
 Brower, Michael. Cool Energy. Cambridge MA: The MIT Press, 1992. 0-262-02349-0,
TJ807.9.U6B76, 333.79’4’0973.
 Sørensen, Bent. Renewable Energy, Second Edition. San Diego: Academic Press,
2000, 911 pp. ISBN 0-12-656152-4.
 Duffie, John and William A. Beckman. Solar Engineering of Thermal Processes. NY:
John Wiley & Sons, Inc., 920 pp., 1991
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References: Websites, etc.
awea-windnet@yahoogroups.com. Wind Energy elist
awea-wind-home@yahoogroups.com. Wind energy home powersite elist
geothermal.marin.org/ on geothermal energy
mailto:energyresources@egroups.com
rredc.nrel.gov/wind/pubs/atlas/maps/chap2/2-01m.html PNNL wind energy map of CONUS
windenergyexperimenter@yahoogroups.com. Elist for wind energy experimenters
www.dieoff.org. Site devoted to the decline of energy and effects upon population
www.ferc.gov/ Federal Energy Regulatory Commission
www.hawaii.gov/dbedt/ert/otec_hi.html#anchor349152 on OTEC systems
telosnet.com/wind/20th.html
www.google.com/search?q=%22renewable+energy+course%22
solstice.crest.org/
dataweb.usbr.gov/html/powerplant_selection.html
www.zetatalk.com/energy/tengx092.htm
www.wind.enron.com/
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Notes