Energy from Thin Air
Are the Answers Really Blowin' in the Wind?
by Casey Meehan & David Plastrik
Introduction: A New Old Source of Energy
A recent report issued from the Office of Energy Efficiency and Renewable Energy (OEERE) states:
The phenomenal growth of the wind energy industry over the last decade can be related at least in part to its gaining popularity. Opinion polls conducted nationwide show that the public strongly supports the development of clean energy alternatives, and wind energy is now the fastest growing, least expensive new source of electricity generation. The connection between wind energy industry growth and its increasing popularity is due, in part, to an increase in public awareness.1
What is most striking about this is the notion that procuring energy from the wind is something novel. In fact, humans have been harvesting the wind for their benefit for millennia and, in some very fundamental ways, our methods have not changed much over that long period of time. Look inside the guts of that wind turbine, though, or consider the work that wind is being asked to do, and it becomes equally apparent that much has changed.
Table of Contents
- Humans and the Wind - a Brief History
- What (and Where) Is Wind?
- Wind Energy in the U.S.A.
- Wind Energy: Not a Clean-Cut Solution
- Seeing Wind Harvest - Present and Future
- To Learn More
- Works Consulted
Humans and the Wind - a Brief History
Humans' working relationship with wind is contentious - loved and hated, welcomed and feared. Wind power has enabled humans to build civilizations and increase trade, and destroy civilizations through conquest and colonization.
Figure 1: A modern turbine next to its iconic predecessor http://www.nrel.gov/data/pix
Around 5000 B.C.E. civilizations along the Nile were using wind to move their boats.2 For nearly 7000 years, humans continued to refine sailboats to transport larger and larger loads at increasing speeds. Europeans required massive amounts of supplies from their homelands to colonize distant places - the delivery of which was only possible by using ships driven by the wind. At their zenith in the late 19th century, clipper ships plying the East Coast of the United States could move 2000 tons at speeds of 22 knots (about 25 miles per hour).
Wind was not used by early civilizations only for transportation. By 200 B.C., people in China were using basic windmills to pump water while inhabitants of the Middle East used windmills extensively for food production. Pre-industrial uses for wind were transmitted to Europe during the Middle-Ages via increasing systems of trade and the Crusades.3
For a variety of geographic and economic reasons, windmills were not widespread in North America until the march westward into the Great Plains. With its ability to pump subterranean water to the surface of semi-arid Western lands, the American windmill was a key technology for settlers in the American West.4 The first commercially produced American windmill was the iconic Halladay model, invented in 1857 by Daniel Halladay. Halladay soon set up shop as U.S. Engine and Power Company just a short distance east of DeKalb, in Batavia, Illinois.5
By the first few decades of the 20th century, some had tried using wind for large-scale electricity generation. However, the fickleness of availability, the lack of adequate electricity storage capability, and the economies of scale that fossil fuels could provide for relegated wind-generated electricity to a much smaller scale, such as providing energy for farms located in remote regions.
Today, Americans are revisiting old ideas, turning to the wind to help solve the looming energy crisis. 125 years later, the residents of rural DeKalb County, about 70 miles west of Chicago, find themselves once again navigating their working relationship to the wind. In December, 2009, NextEra Energy Resources brought 126 wind turbines (each nearly four-hundred feet tall) online at Lee-DeKalb Wind Energy Center. Consequently, many DeKalb County residents experienced a dramatic change in their relationship to each other and the land where they live.
What (and Where) Is Wind?
We all have years of experience with the wind - watching whitecaps roll across a lake, feeling the warmth ripped away from our bodies on a gusty December day, hearing it rustle through piles of dry leaves, noting odors from farms miles off as they are blown in on a breeze - but to understand it as a source of energy, a more technical understanding of wind's origin is useful.
Figure 2: Source: U.S. Department of Energy http://www.windpoweringamerica.gov/wind_resource_maps.asp?stateab=il
Where does wind get its start? The answer, as it turns out, is not on Earth; we must look to the sun. As the sun's rays enter the Earth's atmosphere, they strike and heat equatorial regions more than the globe's poles. Warmed air expands and lightens, rising higher in the atmosphere and is eventually displaced and moves out towards the poles. This movement of heated air, global in scale, is what we call wind. When we seek to tap the wind's power, we should remember that it is, in its origin, an expression of solar power.
Once heat from the sun has put the Earth's air into motion, several factors, some global, some local, influence the way in which wind circulates. Our planet's rotation, nearly 1,000 miles per hour at the equator but nearly still at the poles, complicates what would be a steady flow of warm air to colder regions. As the Earth's axis tilts through its seasonal cycle, alternately bringing more heat to the Northern and Southern hemispheres, another complicating variable is introduced. Still, on a global scale, wind patterns are fairly predictable, especially across the oceans, which gain or lose heat slowly and over vast areas and therefore tend not to drastically effect air temperatures. This is why sailors have been able for hundreds of years to rely, generally, on certain currents of wind existing in specific regions during certain times of the year.
On land, local factors complicate the predictability of wind. If you have ever been up in the mountains, you can attest to the notion that sharp changes in altitude can seriously alter the wind's course and speed. Strong local winds result from landforms that channel or gather wind while wind shadows can result for regions hidden in low valleys or behind large rises. Quick changes in local temperature also affect the wind over land. Unlike water, which holds or releases heat uniformly, soil loses its gained heat very quickly and can, as day turns to night or vice versa, change the temperature locally enough to shift wind patterns and speed. Much of the wind we experience on a daily basis owes as much to local influences as to global wind flow. In Figure 2 (below), average wind speeds at 80 meters high are mapped across the state of Illinois (Figure 3, the wind speeds at 80 meters in Wisconsin is offered for comparison). To add to this map the average direction of the wind in equally fine detail would produce an extremely complicated graphic; every location's wind is governed by many local and global factors simultaneously.
If wind is to be a harvested resource, then from these influencing factors we can begin to develop some good ideas about where to look for it blowing strong and steady. A windmill on the equator might go days without a spin, but certain latitudes are predictably windy. We may find strong winds along ridge tops that can be reliably counted on, but should avoid areas that are blocked by surrounding topography. Where large bodies of land and water meet, the wind patterns of the water tend to prevail, so steady wind is often prevalent along coastlines as well. In the future, it may prove important that constant, strong winds blow in most regions at high altitudes.
Figure 3: Source: U.S. Department of Energy http://www.windpoweringamerica.gov/wind_resource_maps.asp?stateab=wi
Can we count on wind being where it has consistently occurred in the past? This is a question that you might closely consider if you were planning a wind farm. Millions and millions of dollars worth of equipment investments are permanently installed, so there had better be a stable wind resource, right? As we have seen above, wind is governed by typically steady factors: heat from the sun, planetary rotation, seasonal shifts and topography. None of these inputs are likely to change in the near future, we assume.
What about temperature, though? In the era of Global Climate Change, as scientists crunch data and try to plan for coming changes in temperature, it may be necessary to imagine a future where winds are still predictable but fit less with historical precedence. A recent study of Brazil's wind power potential showed that the country's resources would likely shift in the face of average temperature gains6. Though the data - windy regions likely becoming even more steadily and speedily windy - offers reason for excitement in Brazil's plans for increased wind power installations, it also indicates that the locations that we might choose for a wind farm could move towards being more or less ideal in fifty or a hundred years, thus requiring consideration of yet another complication.
Wind Energy in the U.S.A.
At the beginning of the 21st century, the U.S. production capacity for wind energy was 35,000 megawatts (MW) per year - enough to power nearly 10 million homes.7 Though this is not an insignificant amount, it pales in comparison to the estimated 8 million MW of production potential in the United States. An ambitious plan calling for wind energy to provide 20% of U.S. energy requirements by 2030 necessitates the addition of another 300,000 MW capability within the next 20 years.
How do we use the wind to produce electricity?
Wind turbines are fairly simple and take two main forms: vertical axis turbines and horizontal axis turbines. Both function in similar ways though they look quite different. Vertical axis wind turbines look somewhat like eggbeaters turned vertically towards the sky. Much more common, indeed the type of turbine used at the Lee-DeKalb Wind Energy Center, are horizontal axis turbines akin to giant pinwheels.
Figure 4: Schematic of wind turbine. Office of Energy Efficiency and Renewable Energy. http://www1.eere.energy.gov/windandhydro/wind_how.html#inside
Similar to airplane propellers, the blades on modern wind turbines turn a hub by generating lift from wind. The hub, through a system of gears, turns a generator that generates electricity.8 (Figure 4)
Electricity generated from wind can be used in several ways. The energy generated from the Lee-DeKalb Wind Energy Center, for example, is transmitted to the grid to provide base-load energy.9 The expense of constructing transmission from the (usually) remote locations of wind farms significant challenge to large-scale wind operations. This is not often a problem to areas of high need remains a for smaller scale production sites. Those used for individual household energy production, for example, may store energy in on-site batteries.
A few important axioms for generating electricity from the wind are:
- Doubling the wind speed increases the power generation eightfold.
- The higher the rotor, the better. Wind is much steadier and stronger at greater heights.
Who controls and regulates wind energy?
Similar to solar power, wind can be harvested on a variety of scales. Unlike other means of energy production such as nuclear or fossil fuel, producing energy from the wind need not occur at the industrial scale. The term "distributed wind technology" refers to smaller scale operations that produce between 1kw to 1MW of electricity. Often these operations are used at the individual consumer level or to supplement power at a single facility.10 Community wind projects represent a larger operation, usually using mid-sized turbines to directly supplement the power needed by the community running the operation. Some might consider wind operations at these two scales to be a powerfully democratic form of energy production because those directly affected by the production of electricity at these sites have a significant control over them.
Industrial-scale wind farms now dot the landscape in the Midwest (Figure 5), the Great Plains, and the mountain ranges of the West. Wind farms, run by corporate utility companies, usually employ 30-150 large wind turbines, each capable of producing 1.5 MW-2.5 MW (a 1.5 MW turbine produces about the same amount of energy required to power 300 houses over a one-year span). Wind farms represent significant capital expenditure - each turbine costs between $2-$4 million installed.11
Figure 5: These three turbines make up just a fraction of a wind farm in Central Illinois. http://www.nrel.gov/data/pix
Today, electricity produced by industrial-scale wind farms costs between $.05-$.08 per kW hour making it the cheapest new source for large-scale electricity.12 To make such low prices possible, a wind farm must be located where wind speeds average about 15 m.p.h. (6.5 meters-per-second) at a height of 80 meters. Maximum power output occurs at wind speeds of about 29 m.p.h., and most turbines stop rotation (and thus power production) at wind speeds over 49 m.p.h.13 For comparison's sake, a wind speed of 15 m.p.h. extends a light flag, blows loose paper away, and causes larger branches to sway.
So, what does it take to create a wind farm? Even beyond making the large capital investment and finding an ideally windy location, other factors must be considered. Think back to the reliably windy spots discussed earlier - certain latitudes, mountaintops, off shore in the ocean, high above the earth's surface - and you will notice that many of them are not the places we typically use lots of electricity. Wherever we generate electricity, we must be able to deliver it to the sites where it is consumed, either directly or by channeling it into the electrical grid. Nearness to electrical users is just the first constraint that must be understood when planning for a wind farm.
State and National rules and regulations about the price of electricity also dictate much of the financial feasibility of planning a new wind farm. No matter how consistently the wind blows and turns turbines, a wind farm may fail if its expenses cannot be covered by the profit of selling electricity.
In the U.S., the federal government exercises regulatory control over wind power installations, particularly those that use public land. The Department of Energy provides an array of information to help potential wind farmers recognize all the levels of regulation with which they will be expected to be familiar and complaint.14 The Bureau of Land Management offers a detailed explanation for how an entrepreneur might go about considering public lands for wind generation, as well as a list of regulations that must be met for consideration. The U.S. Fish and Wildlife Service has developed a lengthy document of both suggestions and rules aimed at minimizing environmental impact from wind installations on both public and private lands. Of primary concern is the risk that installations might pose to endangered species or habitats.
Because wind turbines occupy airspace, they are regulated in a manner that forces them to share that space with its other users. The National Telecommunications and Information Administration oversees the effort to keep wind turbines from interrupting "radio, microwave, radar, and other frequencies, disrupting critical lines of communication." The Federal Aviation Agency likewise requires that a wind farm neither obstructs necessary flight paths nor causes danger for pilots and passengers, especially in the dark of night.
Some of these limiting factors can be avoided by leasing private land for a wind installation, but the placing of turbines on other people's property, even by contract, is not without complications as noted below in the case of NextEra's Lee-Dekalb Wind Energy Center installation. States, counties and municipalities all may have their own restrictions and rules on the above issues. Due to the relative novelty of wind farming and the provisional status of some regulations, conflicts and confusions may occur between national and local rules. Planning for a wind farm is an exercise in both shrewd calculation and patient consideration.
If you are interested in capturing the wind's energy privately on your own property, you are not alone - the publication of Wind Power for Dummies, a guide to small wind generators, attests to the popularity of this endeavor. Navigating the many considerations and regulations that must be taken into account, though, will require more than a dummy's attention to detail. Wisconsin's statute regulating small wind generator installations (Statute 66.0401), for instance, is composed of almost fifty subsections, most of which merely provide constraints within which local laws must be bounded. Above certain heights, federal organizations like the FAA also have rules and regulations that must be obeyed. The combination of local, state and federal legislations is complicated and can be difficult to navigate.
As author Ian Woofenden notes, even after an individual complies with all rules, neighbors and others with local interests will likely serve as an unofficial regulatory body, so one would be wise to involve them "very early in your dreaming and scheming process," lest your wind turbine meets with unpleasant blowback.15
Wind Energy: Not a Clean-Cut Solution
Producing electricity from the wind has some promising benefits. For example, as a clean and renewable form of energy production, wind energy does not directly emit harmful particulates into the atmosphere. Furthermore, producing energy from the wind has the potential to economically revitalize rural areas and help local governments have more control over their own livelihoods. This does not come without a price. On an individual level, industrial-scale wind farms may pose significant risks to both humans and non-humans. The bottom line is that the installation of any power generating facility stirs up controversy in the communities directly affected by wind energy projects. Just ask the residents of rural DeKalb County, Illinois.
Who (and what) gains? Who (and what) loses?
From early in the 20th century, short-term high levels of air pollution put over 76 million Americans at an increased risk for myriad health issues including respiratory problems, strokes, and heart attacks.16 Currently, however, each 1.5 MW wind turbine in use keeps 2,700 metric tons of carbon dioxide out of the atmosphere, the most significant greenhouse gas in terms of volume. Consequently, by producing 217.5 MW of clean energy,17 the Lee-Dekalb Wind Energy Center displaces 587,250 metric tons of carbon dioxide. At the beginning of the 21st century the total amount of wind turbines in use on the national level displaced 44 million metric tons of emissions.18
Wind energy saves other resources, too. Generating power using fossil fuels requires vast quantities of water - a resource becoming more and more scarce because of human consumption and global climate change. By the early 2000's, thermoelectric power plants accounted for 48% of total water withdrawals.19 Wind energy, on the other hand, consumes far less fresh water. Furthermore, because it does not require mining, producing energy from the wind avoids the ecological danger and land management problems inherent in excavating resources from the earth, transporting fuel to the generating station, and dealing with damaging byproducts.20 Complicating the issue, though, is that these "green" factors are benefits less likely experienced by those living near wind farms than by those living near potential or current mining sites. Moreover, the energy produced by large-scale wind farms is typically not used in the areas in which the wind turbines are located; rather, it is directed to cities where demand for energy is greater.
Perhaps a more direct benefit for those living in close proximity to wind farms is economic. According to the OEERE, the wind industry contributes significantly to economic growth. For example, by 2008 the wind industry employed an estimated 85,000 people and contributed $17 billion to the U.S. economy. If plans to achieve 20% wind energy within the first third of the 21st century are realized, the industry could directly support 180,000 jobs and indirectly foster an additional 320,000 positions.21 Moreover, $1.5 billion in annual tax revenues would go back to local governments, and individual property owners would stand to earn over $600 million in land-lease payments.22
The Lee-DeKalb Wind Energy Center, representing the largest investment in DeKalb County, generates nearly $1.5 million in annual tax revenues for the county government. The wind farm leases land from at least 75 different property owners and expects to pay them $50 million over the next 30 years. The economic benefit is clear to David Halverson, a landowner leasing property to NextEra. Instead of renting out his land at $180 per acre for agricultural production, he chose to lease part of his land to NextEra for $9,000 a year per wind turbine. Since each turbine occupies about 3 acres total, Mr. Halverson's decision is certainly economically justifiable.23
A cleaner environment and economic revitalization are appealing but they are not the only consequences of wind energy. Energy production has ecological and health impacts, and the wind industry is no exception.
Wind farms may not be as benign as they appear. Sites are often located in remote areas such as ridgelines and plains. This requires a system of new access roads for construction and operations. Furthermore, the energy produced must be transmitted to a distribution center, necessitating the installation of electrical lines. Both the roads and system of transmission have ecological consequences, such as the removal of trees and displacement of some species, and economic ramifications, such as reduced property values. In addition, some people have concerns regarding the effect of wind turbines and transmission lines on the aesthetic beauty of a landscape.
Wind turbines adversely affect birds, bats, and other species. Studies have documented substantial numbers of bats dying near wind turbines. Surprisingly, it may not be that the bats are hitting the blades, but rather that bats suffer internal organ damage from flying too close to the drastic pressure gradients created by the moving blades.24 Overall, bat mortality has been higher than expected at a number of sites.25
Unlike bats, birds are unharmed by the pressure gradients, rather, they are hurt by collision with turbine blades, moving at speeds in excess of 150 m.p.h. Studies show that less than one in every ten-thousand birds killed by anthropogenic causes is due to wind turbines. Still, specific wind farms, like Altamont Pass wind development in California, for example, seem to be more dangerous for birds than sites located in farming regions.26
Recent anecdotal reports from DeKalb County indicate that livestock may be impacted by the Lee-DeKalb Wind Energy Center. One resident, Ben Michels, who has five wind turbines behind his home, has had nine of his goats die in the three month period since the turbines became operational. Autopsies on the goats revealed no physical problems. What is more unusual is that, for the last twenty years, he lost on average only one goat per year. While the claims that such anecdotes insinuate are dubious, whether substantiated or not, they do reflect some of the latent animosity and distrust some residents living near wind farms harbor towards this controversial technology.
The negative impacts of wind turbines on human health are perhaps the most controversial, and least researched, impacts yet. According to a joint report issued in 2009 by both the American Wind Energy Association and the Canadian Wind Energy Association, there is no conclusive evidence that wind turbines have any adverse psychological effects on nearby residents. Reports from residents around the world that live near industrial-sized wind farms, however, tell a different story.27 "Wind Turbine Syndrome," a series of physical and mental maladies caused by sleep deprivation, vertigo, migraine headaches, and nausea, appears to affect a not-insignificant number of people living near wind turbines. The symptoms seem to be linked mainly to acoustic and sub-acoustic noise and shadow flicker - the strobe-like effect of the turbine blades' shadows as they are cast on the ground and inside houses.28
Donna Nilles, who lives close to 22 turbines in the Lee-DeKalb Wind Energy Center, suffers from Wind Turbine Syndrome from the persistent shadow-flicker. She claims she would like to move; yet selling her house may be difficult given its proximity to the wind farm. 36 other individuals in DeKalb County are similarly concerned and have sued the County and the landowners to remove the wind farms based on health concerns.29
Seeing Wind Harvest-Present and Future
How do we know when we are seeing the harvest of wind power? Lounging on Memorial Union's terrace on a summer day, we are quickly reminded that our oldest use of wind, sailing, has not fallen out of recreational favor. Wander a neighborhood or drive a country road long enough and you are likely to encounter pinwheels, whirligigs and other wind-powered ornaments, possibly while the serenade of wind chimes rings from a side yard. Small wind turbines, probably privately owned and intended to partially or fully power an individual house, may be as tall as several hundred feet, though many are lower. Excepting some creative homemade designs, which some enthusiasts do design, these small turbines typically look like propeller blades fronting a bullet-shaped body.
If you hear "wind power" and imagine a towering pole with a three-bladed rotor on top, you are ready to spot virtually every large-scale site of wind-powered electrical generation in the whole world.30
Part of wind power's near future will involve deploying these familiar turbines into more locations, including some that are currently unreachable. To tap the strong, steady offshore winds that occur beyond the possibility of anchored turbines, a Norwegian company is developing floating turbines that can be tethered to the ocean floor.31 Using ballasts to keep the turbine upright - the same way in which a buoy's heavy bottom keeps it bobbing - these structures might be deployed even when the ocean is hundreds or thousands of feet deep without requiring a rigid mounting to span that gap. This technology would open up deeper seas to the possibility of electricity generation (while no doubt ushering in new complications in the process of delivering generated power to the grid). These offshore turbines would be out of sight from the shore, assuaging aesthetic concerns while capturing strong, steady wind.
Prototypes and new ideas nearing production suggest that the future of wind power will also have a more varied look, when its installations are visible at all.
The strong winds that exist thousands of feet above the Earth's surface, though steady, are not yet usable in our electricity production plans because we cannot successfully capture it, much less transmit it into the electrical grid thousands of feet below. Altitude, though, may become less of a limiting factor to our production in the near future. One potential design imagines the flying of large kites up to and back down from 30,000 feet, the force of which will turn a turbine located on the ground to produce electricity.32 A Canadian company has pioneered a design for an anchored blimp that can carry a turbine up into higher elevations and then transmit electricity back down to the ground by means of a proprietary material that should be able to tolerate the force of tethering the blimp.33 An added benefit of this design is that it can act as a portable generator, moving from site to site to match either conditions or electrical needs.
In the near future, even the millennia old method of using wind to push sailing vessels will likely take on a new look. A German company has developed prototype kites that can be attached to fossil fuel powered ships.34 Flying as high as 1,600 feet above the ship, these kites act as sails that might trim a vessel's fuel needs by up to a third. This prototype sail is, perhaps, a fitting idea with which to close this brief investigation of wind power as it highlights the innovation that shapes the human relationship with wind while recalling its ancient foundations.
To Learn More
U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy
National Wind Watch
American Wind Energy Association
20% Wind Energy by 2030: Increasing Wind Energy's Contribution to U.S. Electricity Supply published by the U.S. Department of Energy (2008).
Wind Energy in America: A History by R. Righter published by the University of Oklahoma Press (1996).
Bryce, R., The brewing tempest over wind power, The Wall Street Journal, March 2, 2010, Opinion section. http://online.wsj.com/article/SB20001424052748704240004575085631551312608.html
Federal Wind Siting Information Center. "Wind Siting Policies and Regulations." U.S. Department of Energy. http://www1.eere.energy.gov/windandhydro/federalwindsiting/policies_regulations.html
"How Wind Energy Works." The Wind Coalition. http://www.windcoalition.org. (accessed March 15, 2010).
In Wisconsin #818: Bats and wind turbines. television program. Produced by Patty Loew. Madison, Wisconsin: Wisconsin Public Television. March 4, 2010
Nextera Energy. "Nextera Energy Resources Portfolio - Region, Selected Sub-Region. February, 2010." http://www.nexteraenergyresources.com (accessed March 26, 2010).
Office of Energy Efficiency and Renewable Energy, "History of Wind Energy." U.S. Department of Energy. http://www1.eere.energy.gov/windandhydro/wind_history.html (accessed March 26, 2010).
Office of Energy Efficiency and Renewable Energy, "Wind Powering America." U.S. Department of Energy. http://www.windpoweringamerica.gov (accessed March 26, 2010).
Office of Energy Efficiency and Renewable Energy, Wind Power Today: Building a New Energy Future Washington, DC: U.S. Department of Energy National Renewable Energy Laboratory, 2009.
Periera de Lucena, Andre Frussard, Alexandre Salem Szklo, Roberto Schaffer, and Ricardo Marques Dutra. "The Vulnerability of Wind Power to Climate Change in Brazil." Renewable Energy 35 (2010): 904-912.
Righter, R. Wind Energy in America: A History. Norman, OK: University of Oklahoma Press, 1996.
Rosner, Hillary. "Wind Power." Popular Science, July, 2009.
"Turn Wind Into Profit." SkySails. http://www.skysails.info/index.php?id=472&L=2
U.S. Department of Energy, 20% Wind Energy by 2030: Increasing Wind Energy's Contribution to U.S. Electricity Supply. Washington, DC: National Renewable Energy Laboratory, 2008. http://www.nrel.gov/docs/fy08osti/41869.pdf
Wernau, J."Wind turbines stir up bad feelings, health concerns in DeKalb County." The Chicago Tribune, March 14, 2010, Business section. http://www.chicagotribune.com/business/ct-biz-0314-wind-energy--20100314,0,5077292,full.story
Woofenden, Ian. Wind Power for Dummies. Hoboken, NJ: Wiley Publishing, 2009.
1 U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Wind Power Today: Building a New Energy Future (Washington, DC: National Renewable Energy Laboratory, 2009), 21. http://www.osti.gov/bridge Also available in print form.
2 U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, "History of Wind Energy," U.S. Department of Energy, http://www1.eere.energy.gov/windandhydro/wind_history.html
4 Righter, R., Wind Energy in America: A History, (Norman, OK: University of Oklahoma Press, 1996), 24.
6 Periera de Lucena, Andre Frussard, Alexandre Salem Szklo, Roberto Schaffer, and Ricardo Marques Dutra, "The Vulnerability of Wind Power to Climate Change in Brazil." Renewable Energy 35 (2010): 904-912.
7 Office of Energy Efficiency and Renewable Energy, "Wind Powering America," U.S. Department of Energy, http://www.windpoweringamerica.gov/
8 "How wind energy works," The Wind Coalition. http://www.windcoalition.org
9 NextEra Energy, "Nextera Energy Resources Portfolio - Region, Selected Sub-Region. February, 2010" http://www.nexteraenergyresources.com/
10 U.S. Department of Energy, Wind Power Today: Building a New Energy Future,12.
11Windustry, "How much do wind turbines cost?" http://www.windustry.org/how-much-do-wind-turbines-cost
12 U.S. Department of Energy, Wind Power Today: Building a New Energy Future, 8.
13 U.S. Department of Energy, 20% Wind Energy by 2030: Increasing Wind Energy's Contribution to U.S. Electricty Supply, (Washington, DC: National Renewable Energy Laboratory, 2008), 25. http://www.nrel.gov/docs/fy08osti/41869.pdf.
14 U.S. Department of Energy, Federal Wind Siting Information Center. "Wind Siting Policies and Regulations." http://www1.eere.energy.gov/windandhydro/federalwindsiting/policies_regulations.html
15 Woofenden, Ian, Wind Power for Dummies, (Hoboken, NJ: Wiley Publishing, 2009), 323.
16 U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, 20% Wind Energy by 2030: Increasing Wind Energy's Contribution to U.S. Electricity Supply, 108.
17 NexTera Energy Resources
18 U.S. Department of Energy, Wind Power Today: Building a New Energy Future, 1.
19 U.S. Department of Energy, 20% Wind Energy by 2030: Increasing Wind Energy's Contribution to U.S. Electricty Supply, 109.
21 U.S. Department of Energy, Wind Power Today: Building a New Energy Future, 1.
23 Wernau, J., "Wind turbines stir up bad feelings, health concerns in DeKalb County," The Chicago Tribune, March 14, 2010, Business section http://www.chicagotribune.com/business/ct-biz-0314-wind-energy--20100314,0,5077292,full.story
24 In Wisconsin: Bats and wind turbines, television program, Wisconsin Public Television, March 4, 2010
25 U.S. Department of Energy, 20% Wind Energy by 2030: Increasing Wind Energy's Contribution to U.S. Electricity Supply, 113.
26 U.S. Department of Energy, 20% Wind Energy by 2030: Increasing Wind Energy's Contribution to U.S. Electricity Supply, 112.
27 Bryce, R., The brewing tempest over wind power, The Wall Street Journal, March 2, 2010, Opinion section http://online.wsj.com/article/SB20001424052748704240004575085631551312608.html
28 Wernau, J.
29 Wernau, J.
30 Hayes, Brian, Infrastructure: A Field Guide to the Industrial Landscape, (New York: W.W. Norton, 2005), 218.
31 Rosner, Hillary, "Wind Power," Popular Science 275, no. 1 (July 2009): 44-5.
32 Delft University of Technology, "Laddermill," http://www.lr.tudelft.nl/live/pagina.jsp?id=8d16d19a-e942-45aa-9b52-48deb9312e92&lang=en
33 Magenn Power Inc., "Magenn Power Air Rotor System," http://www.magenn.com
34 SkySails. http://www.skysails.info/index.php?id=472&L=2