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An Introduction to Wind Energy
Frank R. Leslie, B. S. E. E., M. S. Space Technology
1/19/2002, Rev. 1.0
[email protected]; (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 declineof 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.
www.hubbertpeak.com/midpoint.htm
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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?
Cape Canaveral Plant, photo by F. Leslie, 2001
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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
From www.energy.ca.gov/education/story/story-images/solar.jpegArizona has clearer skies than Florida. Ref.: Innovative Power Systems
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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
www.nrel.gov/wind/usmaps.htmlRevised 020115
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
Ref.: FSEC
Effective wind is from 9 a.m. to ~5 p.m.
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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
Available Relative Wind Energy
0
5000
10000
15000
20000
0
23
45
68
90
113
135
158
180
203
225
248
270
293
315
338
N
S
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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
Ref.: BergeyRevised 020115
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.
Vertical Axis Wind Turbines (VAWT)
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Savonius
Darrieuswith Savonius
Panemone, 1000 B.C.
Giromill
Horizontal Axis Wind Turbines (HAWT)
Ref.: WTC Revised 020115
1.8 m
75 m
American Farm, 1854
Sailwing,1300 A.D.
Dutch with fantail
Modern Turbines
Experimental Wind farm
Dutch post mill
Middelgrunden
EnergyTransmission
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
www.strawbilt.org/systems/ details.solar_electric.htmlRevised 020115
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?
Ref.: www.freefoto.com/pictures/general/ windfarm/index.asp?i=2
Ref.: www.energy.ca.gov/edu
cation/story/story-images/solar.jpeg
Photo of FPL’s Cape Canaveral Plant by F. Leslie, 2001
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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.
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[email protected]. Wind Energy [email protected]. Wind energy home powersite elistgeothermal.marin.org/ on geothermal energymailto:[email protected] rredc.nrel.gov/wind/pubs/atlas/maps/chap2/2-01m.html PNNL wind energy map of CONUS [email protected]. Elist for wind energy experimenterswww.dieoff.org. Site devoted to the decline of energy and effects upon populationwww.ferc.gov/ Federal Energy Regulatory Commissionwww.hawaii.gov/dbedt/ert/otec_hi.html#anchor349152 on OTEC systemstelosnet.com/wind/20th.htmlwww.google.com/search?q=%22renewable+energy+course%22solstice.crest.org/dataweb.usbr.gov/html/powerplant_selection.htmlwww.zetatalk.com/energy/tengx092.htmwww.wind.enron.com/
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