Power from the wind

American wind resources

Not all areas of the United States are equally suited to supplying energy from wind. The

map below (Fig. E21.3.1 a) shows the regions that have significant resources. The

availability ranges from very low (white) to deep blue (the greatest areas of wind

availability). It is clear that the upper east and west coasts of the country are full of wind

resources. There are seven categories of wind resources ranging from 1 (none) to 7

(superb, 800 to 1600 W/m2 at 50 m height). At this time, only resources in categories 5

(excellent, dark purple, 400 to 600 W/m2 at 50 m height), 6 (outstanding, red, 600 to 800

W/m2 at 50 m height) and 7 (superb, blue) are being exploited commercially.

Fig. E21.3.1 The wind resources of the United States. Darker areas have more wind.(U.S. Department of Energy Refs. 30, 54)

Additionally, the upper Midwest (the Dakotas, Minnesota, Iowa, Nebraska) have the

greatest potential to sustain wind energy. It is for this reason that the Dakotas are

sometimes called the Saudi Arabia of wind energy in America. The Texas panhandle and

Oklahoma also have significant resources for wind energy. Archer and Jacobson have

reevaluated possible wind power at 80 m at 8,000 sites globally and in the United States.

They determined North America to have the greatest potential to supply wind energy,

but identified many sites around the world.(a)

Many farmers and landowners in these areas are leasing their land to power companies

that site windmills there. Farmers may earn around $2,000/yr for each wind machine on

their land.(55) The turbines use only about 500 square meters of land (about 1/8 acre), and

farmers can farm the rest unhindered.(55) Crops net the farmers less than their rent, so it’s

very attractive.

Others are taking advantage of the wind as well. Sr. Paula Larson, prioress of the Sacred

Heart Monastery in Richardson, ND, and Sr. Bernadette Bodine have written of the good

experiences with the two used 100 kW wind turbines the sisters installed.(56) In 1999, the

Monastery produced 242,870 kWh, of which 162,530 kWh was used and 80,340 kWh

were transferred to the local co-op utility. They saved $14,920 in electricity costs and

made $916 from sales to their co-op. These nuns spent $125,000 and had saved the

Monastery well over $25,000 in electricity costs for the two years 1998 and 1999, about

a 10-year payback.(56) The turbines should easily last another 20 years with proper

maintenance, allowing the Monastery to save to buy newer, more efficient turbines when

the present ones are retired.

In 1999, the Monastery paid the co-op a bit over 9 cents per kWh, and obtained just a bit

over 1 cent per kWh for the energy given the utility, saving a large sum. The nuns of

Sacred Heart Monastery would be even happier, though, if North Dakota had required

their co-op to pay them the same rate they had to pay. This is called “net metering.”

With net metering, the person or organization would pay the going price for electricity for

the net amount of energy used. If net metering had been a North Dakota law, the

Monastery would have saved $22,300—over $7,000 more than they did—in 1999 alone!

If net metering were law, the Monastery would have needed only a bit over 5 years to

have paid off their investment. One of the most important suggestions in the report

Repowering the Midwest is that net metering be instituted in all midwestern states not

currently having it as law.(57) This is seen as very important in encouraging alternative

energy producers (and of course makes sense for all states, not just the midwestern states,

which are the focus of Ref. 57).(58) Many states, including Ohio and California, do have

net metering laws.

Fig. E21.3.2 A Darrieus windmill on the test site of Southern California Edison.

a.

b.

Fig. E21.3.3 Energy from wind in the U.S. a. By region. b. By state.(U.S. Department of Energy, Ref. 15)

Southern California Edison for some years tested various devices at its site in the San

Gorgonio Pass (Figures E21.3.2) near Palm Springs. This is indicative of the approach to

electricity generation in California. The Pacific Region of the country is the predominant

region in renewable energy overall, as seen in Fig. E21.3.3 a. This is basically because the

region contains California. Over the years, the state of California has led the rest of the

United States in embracing renewables, as Fig. E21.3.3 b shows, producing roughly two-

fifths of all America’s renewable energy.

In the 1970s, wind turbines were the focus of government-supported research in the wake

of the energy crisis.(35,42) The producers of renewable went into building facilities in a big

way in the 1980s, constructing large wind farms because of newly-available government

subsidies and tax breaks, both from the Federal Government and the state of California.

Wind was much more expensive at that time than it is now, and the technology not so

robust. (35)

Fig. E21.3.4 Windmills in the San Gregornio Pass near Palm Springs, California.(U.S. Department of Energy, National Renewable Energy Laboratory)

a.

b.

Fig. E21.3.5 Wind resources in California are located quite near the two largest cities.(California Energy Commission)

As a result, wind producers struggled for some years, and as described below, it was only

in the 1990s that the market recovered in the U.S. Southern California Edison continues to

buy a lot of energy from wind farm producers in the San Gregornio Pass area (Fig.

E21.3.4 and Fig. E21.3.5 b). Another private company put more than 700 wind machines

in the Altamont Pass near San Francisco in the 1980s to sell to Pacific Gas and Electric

(Fig. E21.3.5 a).

The Reagan administration decided that wind energy research in the 1970s had reached

commercialization and abruptly stopped further research. Instead, they put tax incentives

in place to cause investors to build wind energy installations. About 900 MW was built

through 1985, when the federal investment tax credits and California credits expired.(41,42)

What was the result? Oil prices dropped from the mid-1980s through the mid-1990s as a

result of the effectiveness of conservation measures in the United States and the rest of

the developed world and the perceived threat to oil of these renewable resources. Natural

gas prices tracked oil prices and remained low until the late 1990s. One result is that the

amount of money saved by these renewables was much lower than it would have been if

prices hadn’t dropped, as was projected when they were constructed.

In addition, the Reagan administration assumptions about the maturity of wind turbine

design was unwarranted. The problem is that the turbines were not as robust or well-

constructed as had been thought by the politicians who intervened to stop the research

for ideological reasons. Some California windfarms experienced low capacity factors of 5

to 10% because of mechanical failures and poor turbine design.(41) In addition, people

who would have been expected to be supportive objected to the ugly tower framework,

the number of birds killed by flying into the blades, and the loudness of the humming

noise coming from improperly mounted or poorly designed blades.(41,42,59)

Typical wind farm machines of the 1980s were in the 50 to 75 kW range. Recently, things

have changed. Nowadays, wind turbines are generating much more power, as discussed in

Extension 21.3, How a windmill works .

Wind energy has become more widespread because of the globalization of the wind energy

companies.(35,42) In the early 1980s, California possessed over 90% of all installed wind

turbines in the world! While California still looms large with some 14,000 wind turbines

producing about 1.8 GW (about 1% of California’s total electricity, and about 10% of the

world’s total wind capacity), other states, especially in the midwest and southwest are

catching up. Iowa now has the nation’s largest windfarm (Buena Vista County, rated at

112.5 MW),(15) and Minnesota also is increasing its use of wind energy (Pipestone

County, 103.5 MW).(15) Between 1998 and 2001, these two states have added 500 MW

of wind capacity.(57) Texas has around 50 MW installed. The California Energy

Commission in the late 1990s and early 2000s authorized subsidizing almost 1 GW in

new wind installations in California. Ironically, American producers sell most of their

production abroad, and American firms import wind machines from Europe.(60)

This is part of the nationwide explosion of interest in wind. Even though wind is only a

small part of the total renewable energy picture in the United States—and the world—at

present, this interest, and the perception of environmental friendliness among most

people, is pushing worldwide growth. Figure E21.3.6 (next page) shows the worldwide

growth of wind energy.

Fig. E21.3.6 Wind energy capacity.(U.S. Department of Energy, National Renewable Energy Laboratory, Ref. 30)

Apparently, about 2 construction jobs per megawatt installed are created. Possibly as

many as 5 permanent jobs for every 100 MW of installed capacity are also created, so the

local economic impact is not limited to the lease fees farmers receive.(30)

In Antarctica, where electricity grids are not common, Admiral Byrd used a windmill in

the 1930s to power his Antarctic base, Little America.(42) Several modern 280 kW

windmills are also being used to replace dirty diesel generators at the Australian Antarctic

base.(61)

The manufacturing picture

When the first wind machines were being installed in the 1980s, many American

companies entered the market, but the most successful sellers sold Danish wind machines.

As a result of Danish turbine popularity, despite their unreliability, many fledgling

American companies ultimately went under. By 2000, only Zond (bought out by Enron

in 1997, operating now as part of GE Wind Corporation) of Tehachapi, California,

Kenentech, and the Wind Turbine Company of Belleview, Washington are companies still

producing windmills in the United States. New companies have been formed, such as

Bergey Windpower, Northern Power Systems, and Atlantic Orient Corporation.

The reason for the German Renewable Energy Sources Act that sets the German subsidies

(and those of other European countries)? According to the explanation attached:(18) “In

three European countries – Germany, Denmark and Spain – national legislation has been

adopted to introduce minimum prices for feeding into grids electricity generated from

renewable energy sources. It is owing exclusively to the national legislation of these three

countries that the European Union witnessed the emergence of a wind turbine

manufacturing industry which offers cutting-edge technology in the world market today.”

The report goes on to note that this focus created 20,000 jobs in Germany alone.(18)

The original German renewable energy law, the Stromeinspeisungsgesetz für Erneuerbare

Energien (Law on Feeding Electricity Generated from Renewable Energy Sources into the

Grid) of 1 January 1991 set subsidies that were responsible for huge growth in the

German wind energy sector. The Act stated that “as much as approximately 4,400

megawatts had been installed within the territorial scope of the Act, accounting for about

one-third of the capacity installed world-wide.”(18) That was followed by a second

renewable energy act that mandated further subsidies, which was translated in Ref. 18. At

present, Germany has 7,500 windmills already operating in the windiest states—

Schleswig-Holstein, Niedersachsen (Lower Saxony) and Mecklenburg-Vorpommern

(West Pomerania) on the North Sea—and more in other states as well.(51) By 2004,

Schleswig-Holstein produced almost 30% of its electricity from wind. The grand plan is

to have 25 GW of wind machine capacity installed by 2030.(51)

The Danish wind turbine manufacturers have cornered over half the world market.(62)

Danish companies employ 12,000 in Denmark, and estimate another 6,000 are employed

in other countries servicing and installing Danish turbines.(62) The three-bladed design is

sometimes called the “Danish concept.” The active and longstanding industry is the

reason that Denmark harvests 14% of its energy needs from the winds using some 5,700

turbines.(62) Additionally, the Danish people themselves have embraced wind energy. It is

grass roots. Over 100,000 Danes own shares in windmill co-operatives.(26) Over 80% of

Denmark’s windmills are owned by such co-operatives.(63)

The Dutch, as with the other coastal European countries, are installing turbines offshore

to harvest relatively steady ocean breezes. They have also installed individual building

windmills in large numbers.The mills are so small and weigh so little (mass ~200 kg) that

they can be installed in an afternoon.(64) Wind supplies Europeans with a significant

portion of their electricity, with 20 GW installed on land alone, and that proportion is

growing rapidly.(65)

The Germans have the largest installed wind capacity in Europe (the Danes still lead in

per capita wind capacity). The Germans are so committed to the future of wind that they

installed a windmill in the Galapagos Islands to serve the inhabitants who currently use

diesel generators. The Galapagos are extremely windy, and this windmill will reduce the

environmental impact on these historic islands.(66)

Large-scale wind energy possibilities

The same person who proposed the chain of windmills through the Midwest (as

discussed in the Chapter), W. E. Heronemus, also proposed floating offshore

windmills.(42,67,68) The winds are three to five times as strong just offshore of New

England as on land.(68) Heronemus proposed using the wind energy to dissociate water

and pipe the hydrogen ashore to be burned in place of natural gas (see Chapter 23). Such

offshore windmills were considered in great detail in the report of the EUROCEAN

group.(69)

Offshore wind energy is attractive because of many factors, most discussed in Ref. 70.

New types of foundations have been designed using more steel and less concrete, making

the materials that have to be transported smaller (and saving up to 35% of the cost). The

foundations should last long enough to support several generations of windmills. All wind

turbines recover their complete full-cycle energy cost in the first few (usually three)

months of operation. Research has shown that the wind turbines do not interfere with sea

birds. Further, the winds are steadier over the water because it is so flat, and the wind

blows about 20% faster over water than over land. There is less air turbulence over water

than over land. Turbines operating over water are expected to need less maintenance than

those over land, and to last 25% longer. And real windfarm turbines outperform the model

projections by 20% to 30%, giving about 50% to 70% greater output than equivalent

turbines on land.

Large-scale turbines can make the projects even more cost-effective.(70) Cabling for larger

transmission lines are not a lot more expensive or fragile than those for smaller lines.

Offshore machines can operate at higher speeds (and so at greater efficiency) than those

onshore, where there is a need to keep the noise level lower. The size of the foundations

does not scale as the size of the turbine.(71) With greater capacity, there are fewer turbines

to maintain and fewer connections to have to make.

It may have just been dreaming when Heronemus proposed offshore wind farms, but the

Danes actually have built the first three offshore wind farms—at Vindeby, in the Baltic

just off the Danish coast in 1991, at Tunø Knob in the Kattegat Sea in 1995, and

Middelgrunden, near Copenhagen in 2000.(70-73) The Dutch, famous for windmills in

history, are also planning real offshore energy farms.(74) Kema, a Dutch engineering firm,

has built wind turbines and an underwater carrier that can carry the turbines out to sea.(74)

The carriers are to be built by the Dutch engineering firm Mammoet. Some British

researchers have even proposed floating offshore wind generators.(75) The Norwegians are

installing a wind-to-hydrogen facility on Utsira Island.(76) This obviates the need to run

electric cables to the facility; the hydrogen is stored in tanks until needed.

With moderate restrictions on land use, only about 0.6% of the U.S. land area would be

available for wind energy devices today (mostly in North Dakota, Wyoming, and

Montana); however, this area could produce 25% of present electricity use.(40) With

similar restrictions, Canada could produce about 18 times current electricity consumption

(from the Northwest Territory District of Keewatin and the provinces of Quebec,

Manitoba, and Newfoundland).(40) Based on assumed advances in technology, 13% of the

U.S. land area would be exploitable for wind, producing 4 times current electricity use,

and Canadian production would climb to 70 times current use.

As mentioned in the Chapter, wind turbines could be built by a new federal program

absorbing a total of about 4% of one year’s budget. As the resulting electricity was sold,

this money could be paid back to the Treasury.(77) This loan from the American people

to the American people could help us make the transition to obtaining a substantial

fraction of energy use in the form of renewable energy at no overall cost. In fact, in later

years, the income would be a new revenue source.

The Australian engineer Bryan Roberts has big plans to tap the wind energy in the jet

streams, the cross-continent rivers of air in the upper troposphere. This idea has been

referred to as “wind farms in the sky.”(78) So-called gyromills will be lofted to 4500 m

altitude and tied down to harvest energy from the 500 km/h jet stream. The power

density in the jet stream is 15 to 20 kW/m2 compared to 400 W/m2 at ground level.(78) A

gyromill is an unpowered helicopter. The electricity could be brought down to Earth by

wires accompanying the tethers. Roberts has tested model gyromills, and calculated that

20 MW machines would be profitable, although many are skeptical.(78)

Another interesting idea is the “solar chimney,” which would wrest energy from desert

air.(79) The tall chimney would connect the hot surface air through a tall chimney to cooler

air some distance aboveground (1.5 km up). It should be capable of producing 24 hours

per day because the hot desert air passing into the turbine warms the ground beneath, and

the base would be 7 km across. The idea is the brainchild of German architect Jörg

Schlaich, who conceived the idea decades ago when working on a cooling tower.

This chimney runs on the same principle that draws air up houses’ chimneys and up

power plant cooling towers. The tall chimney might be constructed soon in Northern

Cape Province in South Africa.(79) The incredible height is necessary because the updraft

needed to power the turbines was found to be disappointing in the 50 kW test chimney

built in Spain a decade ago (about 15 m/s). The best way to increase the updraft is to

increase chimney height. The 1.5 km design would experience a 15 m/s (over 50 km/h)

wind in the middle of the chimney. The design should produce between 1.4 and 1.8

TWh/yr (160 to 200 MW).

Drawbacks of wind energy

While there are not many drawbacks to wind energy, there are a few. Birds have been

killed flying into windmill blades. The 5,400 wind machines in Altamont Pass (capacity

580 MW) have been particularly studied, and it was found that about 44,000 birds had

been killed during the first 20 years of operation.(80,81) As Ref. b points out, there are

consequences beyond the bird deaths: “When birds and bats collide with electrical power

line infrastructure, their electrocution also can result in electrical outages, affect service

reliability, and cause wildfires.”

Ref. b mentions the legal problems that can result from the bird deaths. “Nearly all of the

birds that are being killed are protected by the Migratory Bird Treaty Act, the Bald Eagle

and Golden Eagle Protection Act, and a series of state Fish and Game codes. These birds

include raptors and non-raptors.” The report also points out that “[n]early each bird

killed results in a violation of one of these laws. Bird deaths also impact the species and

can result in litigation.” Ref. b also reports that bats are being killed by windmills based

on a survey done in Solano County. This may be another concern that needs to be

addressed.

The major California wind areas are the Altamont Pass, Solano County, the Pacheco Pass,

the San Gorgonio Pass, and the Tehachapi Pass. The Altamont Pass and Solano COunty

windmills have known problems with avian deaths. The California Energy Commission

identified land-use practices close to turbines, turbine location, and the degree of turbine

clustering as factors in bird deaths at Altamont.(b)

The studies show that fewer, larger turbines are generally less deadly than more, smaller

ones (though this is site-specific)(b) so the companies hoping to expand their wind

capacity will be expected to use the larger turbines (which are generally more efficient

anyway, see Fig. E21.3.7 for the experience in California). An industry report points out

that many millions of birds are killed every year in collisions with cars, communication

towers, and windows on buildings, while the toll from windmills is in the tens of

thousands. (81) These large “background” numbers of avian deaths due to human actions

are, of course, no excuse to kill more birds than absolutely necessary.

Fig. E21.3.7 Numbers of wind turbines in California, 1985 to 2003, by size class of turbine.(M. Dorin and L. Spiegel, California Energy Commission, “Assessment of avian mortality from collisionsand electrocutions,” CEC-700-2005-015, June 2005, Table 1)

Research has shown that birds generally avoid windmills.(c) As mentioned above, it

appears possible to reduce the already low effect on birds by using fewer, larger turbines

and by locating them carefully.(d) This is occurring naturally (Fig. E21.3.7) in response to

economic forces.

We have already discussed noise.(41,42,59) Despite complaints, where machines emit noise

as specified in the design, no noise problems were observed at nearby houses.(59) To date,

many of the complaints associated with noise from wind turbines have been attributed

either to a lack of appreciation at the design stage of the importance of designing for low

noise or else to defects in components or manufacture. Most problems with noise

occurred where wind farms were put up quickly, and few commissioning tests were run

(in the U.S. particularly, investor impatience was a factor).(59) In general, there are no

significant noise problems for homes located more than 350 to 400 m from a turbine.(59)

Putting the windmills in ecologically or noise sensitive places could be a problem, but this

is possible to address easily in the planning stages.

Some object to the visual image of the turbines, but many find the windmills esthetically

more pleasing than, say, transmission lines. If the sites are some distance from areas of

natural beauty, this should generally not be a problem. The windmills cannot be readily

distinguished from the surroundings if they are more than 10 km away.(59) Canny choices

of colors, tree and vegetation plantings, and layouts can play a large role in the perception

of observers.

As was found for the Danish offshore sites for windfarms, birds do not generally have

problems with windmills. However, three projects, the Altamont and Solano wind farms

in California (two of the biggest projects, as pointed out in Ref. 59) and the Tarifa wind

farms near Cadiz above the Strait of Gibraltar in Spain, occupy hills on bird migration

routes.(59,82) Raptors (bird predators) were the most affected, presumably because they

were accustomed to use trees and other high structure as spy platforms. The most

important lesson to be learned from these rare experiences is the necessity of study before

siting decisions are made. While the windmills often kill insects, there seems little concern

about this, except (as we’ve mentioned) for the drop in output from dirty turbines.

One research article claims that there is the possibility of “nonnegligible climatic change

at continental scales.”(e) However, in their simulation, wind farms cover 10% of the land

area of Earth. The study estimates that if wind supplies 2 TW of electricity Earth’s mean

temperature could rise by 0.5 °C.(e) The authors are not advocating against use of wind

energy. Indeed, they write, “[p]reliminary calculations using assumptions common in

such models consistently show that, by reducing CO2 emissions, the indirect benefits of

wind turbines exceed the costs (or benefits) arising from their direct climatic effects.”(e)

None of that positive experience changes minds of people opposed to having wind

generators in their back yards. Even where state law is encouraging (such as in California),

local residents can oppose the project and make it drag on.(83)

Several companies plan to put windmills off the shores of Nantucket, Martha’s Vineyard,

and Cape Cod.(84) This has been especially notable in the protests accompanying the plan

to put offshore windmills off the Massachusetts coast.(85,f) Despite this protest, a test

windmill has been built, the state has approved the idea, and the plan is proceeding

apace.(86,g) In upstate New York, residents of Cherry Valley tried to prevent a wind

energy installation from being built.(87) A company wanted to build windmills in

Farmington, Maine, but local residents opposed the plan.(88)

While America seems home to NIMBYs, and Europeans (with the exception of the

British) are much more accepting of the windmills, many windmill proposals in Great

Britain have aroused opposition on the scale seen in the United States. One windmill

proposal in the Scottish Highlands met with fierce resistance.The giant windmills are

being built near the villages of Ardnamurchan and Morvern on the scenic northwest coast

of Scotland, long recognized for spectacular natural scenery.(88,89,h) Another plan for a

huge windmill farm in Cumbria(i) and on the Isle of Skye(j) also met resistance.

However, Britain has several operating windfarms. The first to be installed in the United

Kingdom was the Blyth windmill array, mounted on the harbor wall in the port at Blyth,

Northumberland, in 1992.(16) One windmill at Blyth had its blade snap in 2002.(90) There

is also has a windfarm on the Kintyre peninsula. The Carradale power station has 46

turbines and can generate 30 MW.(91)

A huge windfarm with 1,000 turbines is to be constructed in the Greater Wash in the

Thames estuary and off the northwest coast.(92,j) The 270 1 gigawatt wind turbines will

generate approximately 1% of the energy needed for the United Kingdom.(k) It will be

around 20 km off the coast and has met with less resistance because of that separation.

On the other hand, despite a few mishaps, Wood County, Ohio residents mostly

welcomed the windmills into their community.(93) The credit for that success apparently

goes to Daryl Stockburger, the utilities director of the city of Bowling Green, Ohio.(l) A

Toledo Blade news article quotes Sara Ward, head of the Ohio Department of

Development’s office of energy efficiency: “Daryl Stockburger has been an unwavering

champion of utility-scale wind power in Ohio ... He has methodically proven that wind

power works here and he has done it without large government incentives.”(l) The state

of Ohio, after learning that it is second only to California in the possibility of wind

energy-related jobs, is supporting the development of possible sites.(l)

Wisconsonites seem to accept the windmills, too.(94,l) Local farmers are most vocal in

support.(m) Colorado farmers are asking for windmills to be placed on their land.(95)

Farmers struggling financially see no drawback in hosting windmills that will pay some

bills without harming the productivity of the farm.

Avian deaths in perspective

In pointing out these drawbacks of windmills, it must be mentioned for comparison that

power company transmission lines cause collisions that kill or injure birds and can

electrocute them. The California Energy Commission notes that “utilities, researchers, and

the resource agencies have documented that electrical power line infrastructure has caused

avian collisions and electrocutions. ... Recent research suggests that up to 85 percent of

collisions and electrocutions may go undetected by the utilities.”

One way utilities detect such events is through outages. Eskom, the South African electric

utility, observed 200 to 350 such bird-induced events every year. Almost 40% of

Eskom’s outages are bird-related (lightning is second with 24%).(n) The electrocutions are

possible only for birds with sufficient wingspan to come into contact with the wire

pair—these large birds are mainly raptors (birds of prey such as hawks or eagles).(o)

A study in New York of birds and transmission lines found 4,960 interaction events

(birds entering a line’s airspace) but identified no collisions. Only seven dead birds were

found in the study area.(p)

The effect of windmills on birds needs to be kept in perspective. The California PIER

Program Project Summary estimates total bird mortality from collisions with electricity

transmission lines in the United States at between 10,000 and 174 million! Raptor deaths

from windmills were estimated in 2001 to be 488 in the United States, (468 in

California).(q)

References in addition to those listed for this chapter are shown in red in the text, and

listed below:

a. C. L. Archer and M. Z. Jacobson, “Evaluation of global wind power,” J. Geophys.Res.–Atmospheres 110, (2005), to be published. See also their analysis of the UnitedStates wind energy potential, C. L. Archer and M. Z. Jacobson, “Spatial and temporaldistributions of U.S. winds and wind power at 80 m derived from measurements,” J.Geophys. Res. 108, 4289 (2003).

b. M. Dorin and L. Spiegel, California Energy Commission, “Assessment of avianmortality from collisions and electrocutions,” CEC-700-2005-015, June 2005.

c. R. Black, “Wind farms pose low risk to birds,” BBC News dispatch, 8 June 2005.

d. J. Kay, “Taming the deadly wind farm,” The San Francisco Chronicle, 19 December2004.

e. D. W. Keith, J. F. DeCarolis, D. C. Denkenberger, D. H. Lenschow, S. L. Malyshev, S.Pacala, and P. J. Rasch, “The influence of large-scale wind power on global climate,” Proc.Natl. Acad. Sci. 101, 16115 (2004).

f. C. Dean, “Much heat and deep split over a Cape Cod wind farm,” The New YorkTimes, 12 January 2005.

g. B. Daley and S. Allen, “Wind farm gets initial state OK, but data sought,” The BostonGlobe, 5 March 2005.

h. P. Kelbie, “Wind turbines threaten to become a blot on the landscape of Scott andStevenson,” The Independent (UK), 7 March 2005.

i. N. Pyke and S. Carrell, “Bragg tilts at Britain’s biggest wind farm,” The Independent(UK), 10 April 2005. M. McCarthy, “Cumbrian wind-farm plan generates heat amongdivided environmentalists,” The Independent (UK), 20 April 2005.

j. P. Kelbie, “Police called in as Skye islanders go to war over wind farm scheme,” TheIndependent (UK), 1 June 2005.

k. H. McCormack, “World’s biggest wind farm planned for London,” The Independent(UK), 8 June 2005.

l. T. Henry, “Alternative energy forms fascinate him,” The Toledo Blade, 20 June 2005.

m. R. Mertens, “In Wisconsin, tilting at windmills is a serious matter,” The ChristianScience Monitor, 25 April 2005. M. Vickerman, “Next to other energy sources, wind isenvironmental winner,” (letter to the editor), The Madison Capital Times, 7 February2005.

n. H. Vosloo, “Birds and power lines,” ESI 3, 38 (2003).

o. C. Platt , “Raptors vs. lethal lines,” Environmental News, November 2002, Universityof Alberta Environmental Research and Studies Centre.

p. New York Power Authority, “Estimates of bird mortality associated with transmissionlines,” September 2004.

q. R. Carlton, “PIER Program Project Summary,” Electric Power Research Institute,2001.