Transcript Wind Energy - Engineering Extension

Wind Energy
Resource, Advantages, and
Constraints
Dr. Richard Nelson
Engineering Extension
Renewable Resources
and Technologically Viable End-uses
Wind - electricity and
hydrogen production
Insurance Against
Conventional Fossil-based
Price Risk
No Greenhouse Gas Emissions
No Sulfur Dioxide (SO2),
Nitrous Oxide (NOx), or
Mercury Emissions
Why Wind Energy?
Wind, for now, is the renewable energy resource/technology of
choice
“Free” resource
A “clean” resource due to:


Replacement of a “dirty” energy source (coal) and,
No emissions associated with its use
Can be utilized on underutilized land or on lands currently in
commodity crop production (“harvest” on the surface and “harvest”
above the surface)
Will primarily be used for electricity generation for
immediate end-use or as a “driver” for hydrogen
production
Energy Production and the Environment
Energy use in power plants accounts for:
 67% of air emissions of SO2, the primary cause of
acid rain. SO2 causes acidification of lakes and
damages forests and other habitats.
 25% of NOx, which causes smog and respiratory
ailments.
 33% of Hg (mercury), a persistent, bio-accumulative
toxin which increases in concentration as it moves up
the food chain, e.g. from fish to birds, causing serious
deformities and nerve disorders.
SOURCES: Union of Concerned Scientists (UCS)
Wind Energy
Benefits
No air emissions
No fuel to mine, transport,
or store
No cooling water
No water pollution
No wastes
Wind Resources in the United States
 Wind resources are characterized by windpower density classes, ranging from class 1 (the
lowest) to class 7 (the highest).
 Good wind resources (class 3 and above) which
have an average annual wind speed of at least
13 miles per hour, are found along the east
coast, the Appalachian Mountain chain, the
Great Plains, the Pacific Northwest, and some
other locations.
Wind Resources in the United States
 Wind speed is a critical feature of wind resources, because the
energy in wind is proportional to the cube of the wind speed.
Kansas Wind Potential
Kansas is one of the three best
wind states in the country
Total “windy” land equals more
than 108,000 square kilometers
(about 1/2 of state)
Total Energy Potential = 1.07
trillion kWh or 121,900 MWa
Most of that potential probably won’t
be developed . . .
Wind Energy Basics
Physical & Engineering Aspects
Wind Power Equation
P = ½ * air density * Area Swept by Rotor * Wind Speed3
P = ½ * ρ * A * V3
1)
Power in the wind is correlated 1:1 with area and is extremely sensitive to wind speed
(the cubic amplifies the power significantly)
2)
If the wind speed is twice as high, it contains 23 = 2 x 2 x 2 = 8 times as much energy
3)
A site with 16 mph average wind speed will generate nearly 50% more electricity and be
more cost effective than one with 14 mph average wind speed (16*16*16) /
(14*14*14) = 1.4927
4)
Therefore, it “pay$” to hunt for good wind sites with better wind speeds
Energy from the Wind
 Turbine output drives wind economics and output is a strong function of wind
speed
 Wind speed increases with height above the ground

Power = 1/2 × (air density) × (area) × (wind speed)
³
 Energy in the wind increases as height increases (theoretically)
V2/V1 = (H2/H1)1/7
Wind Turbines
Turbines: Different Sizes and Applications
Small (10 kW)
• Homes (Grid-connected)
• Farms
• Remote Applications
(e.g. battery changing, water
pumping, telecom sites)
Intermediate
(10-500 kW)
• Village Power
• Hybrid Systems
• Distributed Power
Large (500 kW – 5 MW)
• Central Station Wind Farms
• Distributed Power
• Offshore Wind
Large Wind Systems
 Range in size from 100
kW to 5 MW
 Provide wholesale bulk
power
 Require 13-mph average
wind sites
Technology Overview
Large Wind Projects
Over 98-99% availability
Can deliver power for less than 5 cents/kWh
(with Production Tax Credit) in many locations
~6,000 MW to be installed nationwide at end of
2003
In 2004, will generate about 3x Vermont’s total
use
165-220 ft TOWER
Apx. 100 ft.
1.3 to 1.8 MW rated capacity
Rotor diameter 60 to 80 meters
Tower height 60 to 80 meters
Turbine footprint 10 m x 10 m
Lowest ground clearance is at
least 100 ft.
245-330 ft. TIP
Typical Turbine Size
Next Generation Wind Turbines
Wind Turbine Schematic
Nacelle for 1.65-MW turbine
Cross section of blade for 1.65-MW turbine
Variability
Quantifying Wind Power Performance
99%
Availability
>90%
Operating Time*
30 – 40%
Capacity Factor
* Lake Benton, Minnesota Analysis of Windfarm
Operation
Expected Output/Capacity Factor
 The capacity factor is simply the wind turbine's
actual energy output for the year divided by the
energy output if the machine operated at its
rated power output for the entire year
 A reasonable capacity factor would be 0.25 to
0.30. A very good capacity factor would be 0.40
 Capacity factor is very sensitive to the
average wind speed
Power Curves
The turbine would produce about 20% of its rated power at
an average wind speed of 15 miles per hour (or 20
kilowatts if the turbine was rated at 100 kilowatts).
Operating Characteristics of
Wind Turbines
0.66 MW
Vestas
1.5 MW
GE
1.8 MW
Vestas
2.5 MW
GE
3.0 MW
Vestas
Hub Height (m)
55
80-85
67-70
80
80-90
Rotor Diameter (m)
47
70.5
80
88
90
1,735
3,904
5,027
6,082
6,362
Cut-in Speed (m/s)
4
3
4
3
4
Cut-out Speed (m/s)
25
25
25
25
25
Rated Speed (m/s)
15
12
16
12
15
Swept Area by Rotor (m2)
“Value” of Wind Energy
The value of a wind turbine or wind farm
depends upon many factors
location
terrain
wind speed = f(location, terrain)
cost of competing energy source
rate structure of competing energy source
Wind Insures Against
Fuel Price Risk
 Platts “conservatively
estimates that generating
electricity from renewable
sources can ultimately
save consumers more
than $5/MWh (1/2¢ per
kW-h) by eliminating fuel
price risk”*
*4/8/03 announcement re “Power Price Stability:
What’s it Worth?”
 Value of domestic fuel
source (wind) would have
a direct benefit on the
Kansas/community
 Wind energy “Fuel” is
inflation-proof; therefore
impervious to fuel price
hikes
Wind - Natural Gas Comparison
Wind
Low Operating Cost
High Capital Cost
Non-dispatchable
No Fuel Supply/Cost
Risk
No Emissions
Natural Gas
High Operating Costs
Low Capital Cost
Dispatchable
Fuel Supply/Cost Risk
Smog, Greenhouse
Gas Emissions
Wind Power Costs
Wind Speed
Assuming the same
size project (total
MW installed), the
better the wind
resource, the lower
the cost; capture
more energy for the
same capital/
installed/
maintenance cost
Wind Power Costs
Project Size
Assuming the same
wind speed, a larger
wind farm is more
economical;
economy-of-scale
associated with wind
farm installation
Wind Power Isn’t Perfect
 Wind Power output varies over time; it isn’t dispatchable
 Wind Power is location-dependent (rural vs. urban where
it is needed most)
 Wind Power is transmission-dependent for tie-in to the
grid
 Wind Power has environmental impacts (pro / con)
 Wind Power can only meet part of the electrical load
Common Misunderstandings
Wind turbines are
only generating
electricity about
one third of the
time.
Wind turbines generate
electricity essentially all
the time, but only at their
rated capacity about 3040% of the time
Wind Web Sites
• www.awea.org
• www.wwea.org
• www.windpower.org