AE/ME Wind Engineering Module 1.2

AE/ME Wind Engineering Module 1.2
Lakshmi Sankar

OVERVIEW In the previous module 1.1, you leaned about the course objectives, topics to be covered, and the deliverables (assignments) In this module, we will first review the history of the wind turbines We will also learn some basic terminology associated with wind turbines We will also discuss what factors go into choosing sites where you may build/deploy your own wind turbines or farms. We will conduct this discussion through case studies.

History of Wind Turbines http://www1. eere. energy
Technology is old, in some respects! Wind was used to propel sail boats as early as 5000 BC in Egypt. Chinese used wind energy to pump water by as early as 200 BC Persians used wind energy about the same time to grid grain By the 11th century, people in the middle east were using wind mills for food production Traders and crusaders carried the ideas to Europe.

History of Wind Turbines (Continued..)
Dutch were looking for ways of draining lakes and marshes. Wind turbines became very popular. The technology spread to US when settler brought these ideas to America. Industrialization (use of coal to generate steam) brought a decline in the use of wind energy. Steam engines replaced wind mills for pumping water and producing electricity. Rural electrification began in the 1930s. Wind turbines had to make their case economically! Their popularity rose and fell with the availability and cost of alternative forms of energy production. Oil crisis in the 1970s and energy crisis during the past decade has brought wind energy’s potential as a clean, renewable, sustainable, energy source,

Wind Power's Beginnings (1000 B.C. - 1300 A.D.)
Persians used the drag of the blades (i.e. aerodynamic force along the direction of the wind) to generate rotation of the blades. Struts connected the sails to central shaft. Grinding stone was attached to the central shaft. Only one half of the turbine was useful at any instance in time.

Early Designs http://www.telosnet.com/wind/early.html

Lift vs Drag The aerodynamic force along the direction of the wind is called drag Early wind turbines used drag to generate the torque. The aerodynamic force normal to the wind direction is called lift. For a properly designed blade (or airfoil) lfit to drag ratio may be 100 to 1! Dutch began using lift force rather than drag to turn the rotor. Over the past 500 years, the design has evolved through analysis and experimentation.

Use of Drag to Produce Torque
Pelton Wheel uses this concept Drag Force Wind

Use of Lift forces for Torque Production
Vwind - Vinduced Lsinf Dcosf Wr f Propulsive force = Lsinf - Dcosf

Wind Turbine History in the US
During the 19th century wind mills were used to pump water. Rotor diameter reached 20 meters. Water was used to operate steam engines, Eray designs used wood as the material and had a paddle like shapes. Drag force was used. Later designs used steal blades which could be shaped to produce lift forces. The blades spun fast, requiring gears to reduce the angular velocity. Mechanisms were developed for folding blades in case of high winds. In 1888, electricity was produced using the wind turbine shown on the lower right by Charles F. Brush. By 1910s, coal and oil fired steam plants became popular, and the use of wind turbines became less common.

Installed Wind Power Generation (in MW) http://www.windenergyinstitute.com/installed.html
Rank County 2005 2006 2007 1 Germany 18,415 20,622 22,247 2 United States 9,149 11,603 16,818 3 Spain 10,028 11,615 15,145 4 India 4,430 6,270 8,000 5 China 1,260 2,604 6,050 6 Denmark (& Faeroe Islands) 3,136 3,140 3,129 7 Italy 1,718 2,123 2,726 8 France 757 1,567 2,454 9 United Kingdom 1,332 1,963 2,389 10 Portugal 1,022 1,716 2,150 11 Canada 683 1,459 1,856 12 Netherlands 1,219 1,560 1,747

Basic Terminology Vertical Axis (or Darrieus) Wind Turbines vs. Horizontal Axis Wind Turbines We will study HAWTs in this course.

Terminology (Continued) http://www. energybible
Availability Factor The percentage of time that a wind turbine is able to operate and is not out commission due to maintenance or repairs. Capacity Factor A measure of the productivity of a wind turbine, calculated by the amount of power that a wind turbine produces over a set period of time, divided by the amount of power that would have been produced if the turbine had been running at full capacity during that same time interval.

Terminology (Continued)
Rotor Comprises the spinning parts of a wind turbine, including the turbine blades and the hub. Hub The central part of the wind turbine, which supports the turbine blades on the outside and connects to the low-speed rotor shaft inside the nacelle. Root Cutout The percentage of the rotor blade radius that is cut out in the middle of the rotor disk to make room for the hub and the arms that attach the blades to the shaft. Nacelle The structure at the top of the wind turbine tower just behind (or in some cases, in front of) the wind turbine blades that houses the key components of the wind turbine, including the rotor shaft, gearbox, and generator.

Parts of a Wind Turbine Turbine controller is connected to the rotor.
Converter controller, connected to converters and main circuit breaker, is needed to control the output voltage and power

Wind Power Classification http://www.awea.org/faq/basicwr.html

The following slides are from a Presentation in 2002 by American Wind Energy Association

Clean Energy Technology for Our Economy and Environment
Wind Power is Ready Clean Energy Technology for Our Economy and Environment Wind power is a reality today. Nearly 1,700 megawatts—enough to serve about 475,000 average American homes--were installed in the United States in 2001 alone. With continued government encouragement to accelerate its development, this increasingly competitive source of energy will provide at least six percent of the nation’s electricity by 2020 and revitalize farms and rural communities – without consuming any natural resource or emitting any pollution or greenhouse gases. American Wind Energy Association, 2002 Image courtesy of NEG Micon

Wind Power Market Overview

Ancient Resource Meets 21st Century Technology
The power of the wind has been used throughout human history, to power sailboats, to mill grain, and to pump water. The steel-bladed water pumper was the workhorse of the American farm until the country’s electricity infrastructure was built in the twentieth century. Inventors first used wind power to create electricity late in the nineteenth century. Engineers have been refining the design ever since, especially in the post-war period. Today’s wind turbines are sophiticated machines that use state-of-the-art technology to convert raw power from the wind into electricity that can be contribute to the country’s power needs.

Wind Turbines: Power for a House or City
Wind turbines technology generally falls into two categories: small, or distributed turbines that provide power directly to their owner, and large, or utility-scale turbines that provide wholesale power. The small turbines (such as the one of the far right of this page), range from several watts in capacity to kilowatts. The utility-scale turbines range from about 660 kilowatts to 1.8 megawatts. Offshore turbines can be larger, in the 2-megawatt range. A 10-kW turbine has a rotor diameter of 7 meters (23 feet). It is usually mounted on a foot tower, and can produce about 16,000 kWh annually, more than enough to power a typical household. A 1.5-MW turbine has a rotor diameter of meters ( feet). They are typically installed on towers that are at least 65 meters (213 feet) tall. A 1.5-Mw turbine can produce more than 4.3 million kWh per year, enough to power more than 400 average U.S. housesholds.

Ready to Become a Significant Power Source
Wind could generate 6% of nation’s electricity by 2020. As of October, 2002, there is more than 4,300 MW of wind power capacity installed in the U.S. The 10 billion kWh currently generated by wind plants in the U.S. each year displaces some 13.5 billion pounds (6.7 million tons) of carbon dioxide, 35,000 tons of sulfur dioxide, and 21,000 tons of nitrogen oxides. The power that is produced from the wind is still less than 1% of the country’s total electricity production. With the right policy and market incentives, wind power technology can provide more than 6% of the nation’s electricity by 2020, which is roughly equal to an installed capacity base of 100,000 MW. That would produce enough electricity for 25 million homes and displace approximately 160 million tons of carbon dioxide, 840,000 tons of sulfur dioxide, and 503,000 tons of nitrogen oxides. Wind currently produces less than 1% of the nation’s power. Source: Energy Information Agency

Wind is Growing Worldwide
1. Germany: MW 2. U.S.: MW 3. Spain: MW 4. Denmark: MW 5. India: MW 6,500 megawatts (MW) of new wind energy generating capacity were installed worldwide in 2001, amounting to annual sales of about $7 billion. The world’s wind energy generating capacity at the close of stood at about 24,000 MW. Germany alone set a world and national record of more than 2,600 MW of new generating capacity installed during the year. Germany, Denmark, and Spain are demonstrating that wind can reliably provide 10% to 25% and more of a region or country’s electricity supply. currently accounts for over 70% of the world’s wind power. European countries made up two-thirds of the 2001 additions. The global wind energy market continues to be dominated by the “big five” countries with over 1,000 MW of generating capacity each: Germany, the U.S., Spain, Denmark, and India. The number of countries with several hundred megawatts is growing larger, however, and it may be that in the next several years -- if the current rafts of proposed projects are developed -- Brazil and the U.K. will see their own wind generating capacity sail by the 1,000-MW mark. Source: AWEA’s Global Market Report

Wind Taking Off in the U.S.
U.S. installed nearly 1,700 MW in 2001 Wind power capacity grew by 66% Over 4,265 MW now installed Expecting over 2,500 of new capacity in combined The U.S. wind energy industry left previous records in the dust with a blowout year in 2001, installing nearly 1,700 megawatts (MW) or $1.7 billion worth of new generating equipment in 16 states. The final tally of 1,697 MW was more than double the previous record year of 1999, when 732 MW was installed, and boosted the industry's total generating capacity by 66% over the amount in place a year earlier. As of October, 2002, installed capacity in the U.S. is 4,329 MW. The wind farms completed in 200 will generate approximately $5 million in payments to landowners annually and create some 200 skilled, long-term jobs in areas where such employment is scarce. Source: AWEA’s U.S. Projects Database

United States Wind Power Capacity (MW)
New Hampshire 0.1 Maine 0.1 Washington 180.2 Wisconsin 53.0 Vermont 6.0 Montana 0.1 North Dakota 1.3 Minnesota 322.7 Oregon 156.9 Michigan 2.4 South Dakota 2.9 Massachusetts 1.0 Wyoming 140.6 New York 48.2 Iowa 324.3 Nebraska 3.5 Utah 0.2 Colorado 61.2 Pennsylvania 34.5 Kansas 113.7 California 1,715.9 Tennessee 2.0 New Mexico 1.3 There are wind turbine installations in 26 states. California, the state that gave birth to the modern U.S. wind industry, still has the most wind power capacity installed. However, Texas came on strong in 2001, installed more than 900 MW of wind power capacity. Other states with sizable wind plants include Colorado, Iowa, Kansas, Oregon, Pennsylvania, Washington, Wisconsin, and Wyoming. Wind plants are now operating in many regions of the country. For information on wind projects in individual states, go to the AWEA project database at . Source: AWEA’s U.S. Projects Database Texas 1,095.5 Alaska 0.9 4,270 MW as of 07/31/02 Hawaii 1.6

Main Areas of Growth in 2001 1,697 MW added in 2001 Washington 180
Wisconsin 30 Minnesota 218 New York 30 Oregon 132 Main Areas of Growth in 2001 Iowa 82 Pennsylvania 24 Kansas 112 There are many reasons for wind power’s current success in the various regions of the country. A utility industry restructuring law in the state of Texas requires that 2,000 MW of new renewable energy generating capacity, about 3% of the state's electricity production, be installed by That renewables portfolio standard (RPS) encouraged more than $900 million in wind power project investment in Texas alone in 2001. The Eastern U.S. is also seeing the fruits of well-formulated restructuring legislation that is encouraging the market for green power. In the next two or three years, the West could see more than 1,700 MW of new wind projects installed as utilities seek to tap into this stably-priced, inexhaustible resource. The Midwest continues to see large projects coming on line, thanks to the great wind resource in the region. Transmission supply constraints continue to pose a challenge, however, to would-be wind developers. 1,697 MW added in 2001 Texas 915 Source: AWEA’s U.S. Projects Database

U.S. Wind Power Capacity Growth
Since 1998, the U.S. wind industry has experienced a roller-coaster growth pattern, with nearly 900 MW installed in 1999; just over 65 MW installed in 2000; nearly 1,700 MW installed in 2001; and about 400 MW to be installed in That pattern is largely the resuly of the two-year extension cycle of the Production Tax Credit. A long-term extension of the wind energy Production Tax Credit (PTC) is a vital component for continued wind development. *Source: AWEA’s U.S. Projects Database

Wind Power Economics

Cost Nosedive Driving Wind’s Success
38 cents/kWh cents/kWh The cost of producing electricity from wind energy has declined more than 80%, from about 38 cents per kilowatt-hour in the early 80s to a current range of 3 to 6 cents per kilowatt-hour (KWh) levelized over a plant's lifetime. In the not-too-distant future, analysts predict, wind energy costs could fall even lower than most conventional fossil fuel generators, reaching a cost of 2.5 cents per kWh. This dramatic reduction in the cost of energy from wind plants can be attributed largely to technological improvements and economies of scale achieved by manufacturing more and larger wind turbines. This will be discussed in more detail in the following slides. Levelized cost at excellent wind sites in nominal dollars, not including tax credit

Wind Power Cost of Energy Components
Cost (¢/kWh) = (Capital Recovery Cost + O&M) / kWh/year Capital Recovery = Debt and Equity Cost O&M Cost = Turbine design, operating environment kWh/year = Wind Resource It is helpful to look at the cost of the energy produced by a wind turbine over the life of turbine, in order to compare to other technologies, although many people acknowledge that there are costs associated with pollution and the use of conventional fuel that are not incorporated in the cost of energy. To calculate the cost of energy, one should add the cost of financing the project for a year (debt and equity costs) to the cost of operating the project for a year, and divide that by the amount of electricity produced in the year.

Capital Costs Revenue Streams Debt/equity ratios close to 50%/50%
Commodity Power Sale: $30-$45/MWh Production Tax Credit: $18/MWh “Green Credit”: New Market, Values Vary Debt/equity ratios close to 50%/50% Increased debt/equity ratios can significantly increase return Generally, a wind power plant owner can expect to receive revenue from the sale of the commodity power and from the production tax credit. Some plants are now receiving revenue associated with the attributes of the wind power over and above the value of the electricity, such as the emissions displacement benefits. The “green power” value can range from zero to $25-30/MWh, depending on the market.

Long-Term Debt Better loan terms with longer-term power purchase agreement (PPA) Loan terms up to 22 years, determined largely by PPA The financing terms can have an affect on the cost of energy. Better terms are generally received with long-term contracts to sell the power output. Receiving competitive terms in the U.S. can be a challenge because wind power projects are seen as riskier than experience has proven them to be.

Equity Considerations
Return requirements vary with risk Perceived risk of wind projects may be larger than real risk Returns evaluated after tax credit Wind energy projects can expect return in low teens (10% to 15%) To compare, returns for low-risk projects such as low cost housing are in the high single digit figures, and returns for high-risk venture capital can be more than 30%.

Turbine Technology Constantly Improving
Larger turbines Specialized blade design Power electronics Computer modeling produces more efficient design Manufacturing improvements Larger turbines produce exponentially more power, which reduces unit cost of electricity Rotor blade airfoils specially designed for wind turbines Power electronics improve turbine operations and maintenance Computer modeling produces more efficient design

How big is a 2.0 MW wind turbine?
This picture shows a Vestas V MW wind turbine superimposed on a Boeing 747 JUMBO JET Because wind turbines can extract exponentially more power the larger the rotor diameter, turbine sizes have been trending up for the past two decades. Turbine sizes are limited by transportation and manufacturing expense.

Construction Cost Elements
Sometimes it is also helpful to discuss the full cost of construction. Since wind plants do not require any fuel, the construction costs are the full costs of the project over its life, minus operation and maintenance costs. The industry benchmark is $1 million per megawatt of installed capacity, but has been reported in some cases at less than $900 per megawatt. Of that $1 million, approximately half is for the cost of the turbine itself. The other half is spent on construction, towers, financing, design, and legal fees. Controlling construction costs can have a large impact on keeping the full project costs low.

Technology Improvements Leads to Better Reliability
Drastic improvements since mid-80’s Manufacturers report availability data of over 95% 1981 '83 '85 '90 '98 % Available Year 20 40 60 80 100 The “availability” of a wind turbine measures the percentage of the time that a plant is ready to generate (that is, not out of service for maintenance or repairs). Modern wind turbines have an availability of more than 98%.

Improved Capacity Factor
Capacity Factors Above 35% at Good Wind Sites Performance Improvements due to: Better siting Larger turbines/energy capture Technology Advances Higher reliability Examples: Project Performance (Year 2000) Big Spring, Texas 37% CF in first 9 months Springview, Nebraska 36% CF in first 9 months The capacity factor assess the productivity of a wind turbine, comparing the actual production with the amount of power the plant would have produced if it had run at full capacity the same amount of time. Since a wind plant uses the wind for its fuel, and the wind does not constantly blow at full speed, modern wind turbines have capacity factors that range from 25%-40%, although they will probably achieve higher capacity factors during windy months. It is important to note that while capacity factor is almost entirely a matter of reliability for a fueled power plant, it is not for a wind plant—for a wind plant, it is a matter of economical turbine design. With a very large rotor and a very small generator, a wind turbine would run at full capacity whenever the wind blew and would have a 60-80% capacity factor—but it would produce very little electricity. The most electricity per dollar of investment is gained by using a larger generator and accepting the fact that the capacity factor will be lower as a result. Wind turbines are fundamentally different from fueled power plants in this respect. If a wind turbine's capacity factor is 33%, it does not mean that it is only running one-third of the time. A wind turbine at a typical location in the Midwestern U.S. should run about 65-80% of the time. However, much of the time it will be generating at less than full capacity (see previous answer), making its capacity factor lower.

Bottom Line 20 Years of Wind Technology Development
1981 1985 1990 1996 1999 2000 Rotor (Meter) 10 17 27 40 50 71 KW 25 100 225 550 750 1650 Total Cost $65 $165 $300 $580 $730 $1300 Cost/kw $2,600 $1,650 $1,333 $1,050 $950 $790 Capacity Factor 21% 25% 28% 31% 33% 39% MWh produced over 15 years 675 3300 8250 22,200 33,000 84,000 Amortized cost of turbine per unit of energy 9.6 5 3.6 2.6 2.2 1.5 Economy of scale reduces price per kw of capacity Technology improvements yield more energy bang for the buck At the same time larger turbines have lower the cost per unit of capacity, better capacity factors and availability have increased the amount of power that each unit of capacity can generate. These two factors combine to lower the cost of energy. Combined, they dramatically reduce turbine price per unit of energy produced

Benefits of Wind Power

Advantages of Wind Power
Environmental Resource Diversity & Conservation Cost Stability Economic Development The fact that electricity produced with wind power does not emit harmful pollutants or burn resources is an obvious advantage of the technology. In addition, it can provide cost stability to a utilty’s resource portfolio and bring income and tax benefits to rural communities.

Benefits of Wind Power Environmental
No air pollution No greenhouse gasses Does not pollute water with mercury No water needed for operations Wind energy system operations do not generate air or water emissions and do not produce hazardous waste. Nor do they deplete natural resources such as coal, oil, or gas, or cause environmental damage through resource extraction and transportation. Wind's pollution-free electricity can help reduce the environmental damage caused by power generation in the U.S. and worldwide. Sulfur dioxide and nitrogen oxides cause acid rain. Acid rain harms forests and the wildlife they support. Many lakes in the U.S. Northeast have become biologically dead because of this form of pollution. Acid rain also corrodes buildings and economic infrastructure such as bridges. Nitrogen oxides (which are released by otherwise clean-burning natural gas) are also a primary component of smog. Carbon dioxide (CO2) is a greenhouse gas--its buildup in the atmosphere contributes to global warming by trapping the sun's rays on the earth as in a greenhouse. The U.S., with 5% of the world's population, emits 23% of the world's CO2. The build-up of greenhouse gases is not only causing a gradual rise in average temperatures, but also seems to be increasing fluctuations in weather patterns and causing more severe droughts. Particulate matter is of growing concern because of its impacts on health. Its presence in the air along with other pollutants has contributed to make asthma one of the fastest growing childhood ailments in industrial and developing countries alike, and it has also recently been linked to lung cancer. Similarly, urban smog has been linked to low birth weight, premature births, stillbirths and infant deaths. In the United States, the research has documented ill effects on infants even in cities with modern pollution controls. Toxic heavy metals accumulate in the environment and up the biological food chain. Development of just 10% of the wind potential in the 10 windiest U.S. states would provide more than enough energy to displace emissions from the nation's coal-fired power plants and eliminate the nation's major source of acid rain; reduce total U.S. emissions of CO2 by almost a third and world emissions of CO2 by 4%; and help contain the spread of asthma and other respiratory diseases aggravated or caused by air pollution in this country. One 750-kW wind turbine would displace: 3 million lbs of carbon dioxide per year, equivalent to nearly 2 million miles driven in an SUV 14,172 lbs of sulfur dioxide & 8,688 lbs of nitrous oxides

Electricity Production is Primary Source of Industrial Air Pollution
Despite cleanup progress made by utilities under the Clean Air Act, power plants continue as the largest stationary air pollution source in the U.S., responsible for 70% of our nation’s sulfur dioxide, 34% of our carbon dioxide, 33% of our nitrogen oxides, 28% of our particulate matter, and 23% of our toxic heavy metals. Source: Northwest Foundation, 12/97

Benefits of Wind Power Economic Development
Expanding Wind Power development brings jobs to rural communities Increased tax revenue Purchase of goods & services Wind farms can revitalize the economy of rural communities, providing steady income through lease or royalty payments to farmers and other landowners. Although leasing arrangements can vary widely, a reasonable estimate for income to a landowner from a single utility-scale turbine is about $3,000 a year. For a 250-acre farm, with income from wind at about $55 an acre, the annual income from a wind lease would be $14,000, with no more than 2-3 acres removed from production. Such a sum can significantly increase the net income from farming. Farmers can grow crops or raise cattle next to the towers. Farmers are not the only ones in rural communities to find that wind power can bring in income. In Spirit Lake, Iowa, the local school is earning savings and income from the electricity generated by a turbine. In the district of Forest City, Iowa, a turbine recently erected as a school project is expected to save $1.6 million in electricity costs over its lifetime. Additional income is generated from one-time payments to construction contractors and suppliers during installation, and from payments to turbine maintenance personnel on a long-term basis. Wind farms also expand the local tax base, and keep energy dollars in the local community instead of spending them to pay for coal or gas produced elsewhere. Finally, wind also benefits the economy by reducing "hidden costs" resulting from air pollution and health care. Several studies have estimated that 50,000 Americans die prematurely each year because of air pollution. Each MW of wind power development provides jobs years of employment. Wind provides 1 skilled operations and management job for every 10 turbines installed. Wind plants can be a valuable source of property tax income for local governments.

Benefits of Wind Power Economic Development
Case Study: Lake Benton, MN $2,000 per 750-kW turbine in revenue to farmers Up to 150 construction, 28 ongoing O&M jobs Added $700,000 to local tax base Wind leases provide approximately $50/acre in income for all land within a wind farm boundary, even though only 3-5% is used for turbines and access roads. Wind energy helps diversify income for farmers, owners of harvested forest land. Wind farms may extend over a large geographical area, but their actual "footprint" covers only a very small portion of the land, making wind development an ideal way for farmers to earn additional income (picture at left). In west Texas, for example, farmers are welcoming wind, as lease payments from this new clean energy source replace declining payments from oil wells that have been depleted.

Benefits of Wind Power Fuel Diversity
Domestic energy source Inexhaustible supply Small, dispersed design reduces supply risk US winds could generate more electricity in 15 years than all of Saudi Arabia’s oil—without being depleted. Wind facilities consist of small generators that cannot be easily be damaged at the same time and are easy to replace. If a wind facility is damaged, there is no secondary risk to the public, such as in the release of radioactivity, explosions, or the breaching of a dam. Wind plants can be built quickly to respond to electricity supply shortages.

Benefits of Wind Power Cost Stability
Flat-rate pricing can offer hedge against fuel price volatility risk Electricity is inflation-proof One of the most attractive features of wind power projects is the fact that, with good wind resource estimates, the cost of the project is almost all in the up-front construction costs, and therefore constant over the life of the project. Utilities and electricity users are starting to value the hedge benefit that a wind plant can offer, especially as natural gas prices rise and become more volatile.

Wind Project Siting

Siting a Wind Farm Winds Transmission Permit approval Land area
Minimum class 4 desired for utility-scale wind farm (>7 m/s at hub height) Transmission Distance, voltage excess capacity Permit approval Land-use compatibility Public acceptance Visual, noise, and bird impacts are biggest concern Land area Economies of scale in construction Number of landowners The main things to look for when siting a wind farm are the wind resource, the proximity to transmission lines, the ease of permitting, and the land use. Siting for a wind farm can usually be done much faster than for traditional generation, in a time period of 6 months to a year. Land-use Guidelines Ridges: Ranges from 7.5 MW per mile for 660-kW turbines to 11.8 MW per mile for 1.5-MW turbines Arrays: For a multi-rowed array (spaced 3x10 rotor diameters), of acres of land is needed per MW of capacity. Only 5% of this area is needed for turbines, access roads, and other equipment.

Power in the Wind (W/m2) = 1/2 x air density x swept rotor area x (wind speed)3  A V3 Density = P/(RxT) P - pressure (Pa) R - specific gas constant (287 J/kgK) T - air temperature (K) Because the power that can be converted to electricity varies by the area swept by the rotor, a designer can dramatically increase the electricity output by making the blades longer. Area =  r2 Instantaneous Speed (not mean speed) kg/m3 m2 m/s

Perceived Market Barriers
Siting Avian Noise Aesthetics Intermittent Fuel Source * Bird and bat kills and other effects. Birds and bats occasionally collide with wind turbines, as they do with other tall structures such as buildings. Avian deaths have become a concern at Altamont Pass in California, which is an area of extensive wind development and also high year-round raptor use. Detailed studies, and monitoring following construction, at other wind development areas indicate that this is a site-specific issue that will not be a problem at most potential wind sites. Also, wind's overall impact on birds is low compared with other human-related sources of avian mortality—see [Avian Perspectives Paper Web address] for more information. No matter how extensively wind is developed in the future, bird deaths from wind energy are unlikely to ever reach as high as 1% of those from other human-related sources such as hunters, house cats, buildings, and autos. Wind is, quite literally, a drop in the bucket. Still, areas that are commonly used by threatened or endangered species should be regarded as unsuitable for wind development. The wind industry is working with environmental groups, federal regulators, and other interested parties to develop methods of measuring and mitigating wind energy's effect on birds. Bat collisions at wind plants tend to be low in number and to involve common species which are quite numerous. Human disturbance of hibernating bats in caves is a far greater threat to species of concern. * Visual impacts, which can be minimized through careful design of a wind power plant. Using turbines of the same size and type and spacing them uniformly generally results in a wind plant that satisfies most aesthetic concerns. Computer simulation is helpful in evaluating visual impacts before construction begins. Public opinion polls show that the vast majority of people favor wind energy, and support for wind plants often increases after they are actually installed and operating. For more information on public attitudes toward wind, see . * Noise was an issue with some early wind turbine designs, but it has been largely eliminated as a problem through improved engineering and through appropriate use of setbacks from nearby residences. Aerodynamic noise has been reduced by adjusting the thickness of the blades' trailing edges and by orienting blades upwind of the turbine tower. A small amount of noise is generated by the mechanical components of the turbine. To put this into perspective, a wind turbine 250 meters from a residence is no noisier than a kitchen refrigerator.

Actual Market Barriers
Transmission constraints Financing Operational characteristics different from conventional fuel sources The existing transmission system was built to carry power from large, centrally-planned power plants to population centers. Because the wind resource is best in remote areas, it is often a challenge for wind plant owners to receive the capacity on the tranmission network to get the power to the market. Capacity is often inadequate, and the operating rules make it more costly than for conventional generation for wind projects to use the transmission grid. Because the wind industry is a relatively new one, many of the rules of planning for expansion of generation capacity and operating the transmission system were written with convention generation’s characteristics in mind.

Wind Characteristics Relevant to Transmission System
Intermittent output Generally remote location Small project size Short/flexible development time Low capacity factor Wind power is an intermittent resource, yet many transmission policies assume that generators can control and predict their generation levels and penalize them when they do not. Plainly, these policies make no more sense for wind generators than would policies that penalize coal plant operators for their ramp rate limitations. Wind projects simply cannot control the wind in the same way a fossil or nuclear facility can control its fuel delivery. Nor can a wind generator predict the wind ahead of time as accurately as other technologies can predict their fuel supply. A second key characteristic of wind projects is that they must be located at the site of the wind resource. Wind cannot be piped or sent by rail like coal, uranium or natural gas. Moreover, good wind sites are often located remotely from electric loads. This means that wind facilities are more dependent upon long-distance transmission and less able to avoid transmission problems than other technologies. Finally, wind is a relatively new entrant to the generation marketplace. Thus, policies which favor (or “grandfather”) existing generation can be a barrier to new market entrants such as wind power.

Wind Development Issues Transmission Grid Operating Rules
What wind wants: Liquid, transparent spot market for imbalance settlements Near real time, flexible scheduling protocols Robust secondary markets in transmission rights (“flexible firm”) Postage stamp pricing allocated to load (or volumetric pricing) Statistical determination of conformance to load shape to set value What wind gets: System designed exclusively to transport firm, fixed blocks/commodity strips Rigid advance scheduling protocols/onerous imbalance charges License plate pricing allocated to incremental generation Grid balkanization/rate pancaking

Wind Development Issues Transmission Expansion
What wind wants: Pro-active regional planning with political buy-in. Programmatic expansion focused on shared goals. Public infrastructure financing repaid through user fees. What wind gets: Reactive, piecemeal gridlock decoupled from political process. Project specific expansion focused on immediate needs of existing players. Uncertain capacity rights as sole rate recovery mechanism.

Consequences of Wind Characteristics
Remote location and low capacity factor = higher transmission investment per unit output Small project size and quick development time = planning mismatch with transmission investment Intermittent output can = higher system operating costs if systems/protocols not designed properly These characteristics of wind power must be considered by policy makers in determining the fairness of transmission policies. Otherwise, even policies which are facially nondiscriminatory can have a discriminatory practical impact in the marketplace, and can frustrate the objective of fuller utilization of the nation’s wind energy resource. The five highest transmission policy priorities of the AWEA are: (1) the allocation of embedded costs of transmission facilities, (2) schedule deviation penalties in the creation of real-time balancing markets, (3) the elimination of rate pancaking, (4) the equitable allocation of congested capacity among competing users, and (5) the nondiscriminatory interconnection of new generation facilities.

Federal and State Policies to Promote Wind Power

Production Tax Credit Lowers price of electricity to make it more accessible to customers Currently provides credit of 1.8¢ per kWh Industry needs long-term extension to encourage investment Wind energy currently receives a direct subsidy, the Production Tax Credit (PTC). The PTC provides a tax credit of 1.5 cents per kilowatt-hour (adjusted for inflation, currently 1.8 cents) to the producer of electricity from wind energy. The PTC was an acknowledgement that wind energy can play an important role in the nation's energy mix. It was also a recognition that the federal energy tax code favors established, conventional energy technologies. As of October, 2002, it is set to expire at the end of The wind industry is currently seeking to have the PTC extended for another three years, to December 31, 2006. All energy technologies are subsidized by the U.S. taxpayer. Subsidies come in various forms, including payment for production, tax deductions, guarantees, and leasing of public lands at below-market prices. Subsidies can also be provided indirectly, for example through federal research and development programs, and provisions in federal legislation and regulations. For example, loopholes in the Clean Air Act currently exempt older power plants from compliance with federal pollution standards and become, in effect, a subsidy that lowers the price of electricity from coal-fired power plants.

Renewable Portfolio Standard
Requirement that U.S. suppliers get 10% of supply from renewable sources by 2020 Texas example shows how RPS can enable green power markets to flourish by creating a supply of reasonably-priced renewable energy Can create incentives to solve transmission issues The Renewables Portfolio Standard (RPS) would require each company that generates electricity in the U.S., or in a given state, to obtain part of the electricity it supplies from renewable energy sources such as wind. To meet this requirement, the company could either generate electricity from renewables itself or buy credits or electricity from a renewable generator such as a wind farm. This "credit trading" system has been used effectively by the federal Clean Air Act to require utilities to reduce pollutant emissions. Aside from the "minimum renewable content" requirement, the RPS imposes very few other requirements on companies--they are free to buy, trade, or generate electricity from renewables in whatever fashion is most efficient and economical for them. The RPS is therefore often described by its supporters as being "market-friendly," because it allows market forces to decide which renewable energy sources will be developed where, and also allows price competition. Several federal restructuring bills have included an RPS, and at least 12 states have also adopted RPS laws. Typically, the RPS gradually increases over time, by 1% per year or some such number, in order to encourage the sustained, orderly development of renewable energy industries.

Standard Market Design & Interconnection
Wind is “square peg in a round hole” Intermittent Site-specific, often rural Small, with short construction lead time SMD & Interconnection NOPRs designed to make markets more efficient, which could make a big difference in cost and availability of wind power The Federal Energy Regulatory Commission’s (FERC) is currently undertaking a landmark proposal known as Standard Market Design (SMD), which would modernize the U.S. wholesale electricity market (i.e., electricity sales between power providers) and help remove electricity transmission bottlenecks, thus allowing significantly more clean, renewable energy to flow to homes and business throughout the county. AWEA believes the proposal would represent a huge win for consumers, business, and the environment. The proposal would help encourage new investment in renewable energy technologies (biomass, geothermal, solar and wind) and help deliver cost effective electricity services to both large and small consumers.

Clean Air Act Expect to see amendment to the Clean Air Act before 2004 elections Without set-asides or direct allocation for renewables, would strip wind projects of ability to claim emissions reductions Output based compliance that includes NOx, SO2 and CO2 could add revenue stream of cents per kWh Under a cap & trade system, new renewables do not necessarily reduce emissions. Under a simple cap without set-asides for renewables, more wind power on the system will allow conventional generators to pollute more per kWh, as long as total emissions stay under the cap. Under this scenario, green power marketers could no longer credibly claim that wind power reduced pollution.

Small Turbine Incentives
30% Investment Tax Credit Net metering Congress is currently considering a provision which would provide a tax credit equal to 30% of the cost of a new small wind system to homeowners. Net metering or net billing is a term applied to laws and programs under which a utility allows the meter of a customer with a residential power system (such as a small wind turbine) to turn backward, thereby in effect allowing the customer to deliver any excess electricity he produces to the utility and be credited on a one-for-one basis against any electricity the utility supplies to him.

State Incentives State renewable portfolio standards
Public Benefits Funds Electricity source disclosure Government procurement New York government procurement (10% by 2005, 20% by 2010) Pennsylvania green power procurement Others can play a major role

Green Power Market

Green Power Market Premium prices
Places a monetary value on environmental benefits Raises visibility of renewable power & promotes customer awareness Usually small scale, short-term contracts Green power is electricity generated using renewable resources such as the sun, wind, water, heat within the earth, and organic plant and waste material that don't disappear forever when they are used to generate electricity because they are easily replenished by nature. A growing number of electric power providers offer their customers an opportunity to buy green power. It usually costs a little bit more than electricity from fossil and nuclear sources of fuel because the value of clean energy is not recognized by our pricing system and because renewable industries are much smaller than traditional energy industries, and so have not had the opportunity to enjoy the economies of scale and prolonged learning curve that benefit today's more established technologies. Premium prices

Different Ways to Buy Green Pricing Green Marketing Green Tags
Regulated utility offers customers choice to support wind power construction Green Marketing In competitive market, customers empowered to choose service providers that contract to purchase renewables Green Tags environmental attributes divorced from energy Green power programs vary, but one common approach, called "green pricing," is for a utility to offer its customers the option of buying electricity generated from wind at a premium price. For example, a customer might be able to sign up to receive a certain number of 100-kilowatt-hour "blocks" of electricity from wind each month for an extra $2 each (that is, for 2 cents per kilowatt-hour). A customer signing up for 2 blocks at $2 would pay $4 more for electricity each month and "receive" 200 kilowatt-hours of wind-generated electricity. The utility would then add enough wind capacity to its generating mix to provide the additional electricity required. (The utility cannot deliver specific electrons from any of its plants to a specific customer. Instead, its generating mix should be thought of as a pool. Power plants add electricity to the pool and customers take it out. With green power, the utility adds more wind energy to the pool based on the amount customers have said they desire to purchase.) A second form of green power is used in states that have opened their electricity markets to competition (in much the same way as long-distance telephone service is now open to competition). In these states, electricity suppliers offer electricity "products" from renewable and other sources, and customers are free to sign up for the product and company they prefer. One company, for example, might offer a product that is called "Earth Saver" that is 50% wind-generated electricity and 50% electricity from landfill gas, and charge 1.5 cents/kWh more than "system power" (regular commodity electricity from the regional generating mix). A third form of green power is called "green tags" and can be used by consumers anywhere to "green" their electricity supply. With this approach, when a certain amount of electricity (e.g., 1,000 kWh) is generated from a renewable source, a certificate called a "green tag" is created. The generator sells the electricity into the commodity wholesale market, but keeps the certificate (which represents the beneficial environmental attributes of the electricity) and sells it to an interested buyer for an agreed-upon price (e.g., $20, or 2 cents/kWh). By buying green tags that represent the amount of renewable generation equal to your electricity use, you can, in effect, "green" your power supply in much the same way that you would through "green pricing" or "green power"—you are paying extra, and extra renewable energy is being delivered to the utility system based upon your payment.

Competitive Green Market
Has encouraged about 25 MW in CA & PA to date Will encourage more than 75 MW in PA in next two years

Green Pricing Has encouraged over 15 new wind projects to serve green pricing market Smaller projects Spread throughout the U.S. – raises visibility of wind power

Small Wind Turbine Market Development

Programs for small wind development
Buy-down programs Exemptions from sales, property tax Standardized zoning requirements

Buy-down programs CA renewables fund refunds 50% of the cost of a renewable system CA sales account for over half of the small wind turbine market MA buy-down program refunds 10% capped at $100 does not appreciably affect the market

Property / Sales Tax Property or sales tax exemption offered in several states Programs to affect initial purchase price work best Net metering programs (equalizing kWh costs paid and received by residential generators) do not seem to drive purchasing decisions

Future Trends in Wind Power

Expectiations for Future Growth
2,500 MW new added by end of 2003 20,000 total installed by 2010 6% of electricity supply by 2020 = 100,000 MW of wind power installed by 2020

Wind Energy “U.S. Proven & Probable Reserves” Nameplate MW
Region On-Line In Development Developable in Reserve @$2 natural gas @$4 natural gas West 2,254 2,750 35,000 200,000 Midwest 900 500 400 350,000 East 90 330 7,000 Texas 1,016 300 --- 40,000 South 2 20 100 600 Total 4,262 4,000 36,000 600,000 The amount of wind power that is developed is directly related to the price of natural gas. AWEA’s policy director Jim Caldwell has estimated that at a natural gas price of $2/Million Cubic Feet, approximately 36,000 MW of wind will be developed. In contrast, if natural gas prices rise to $4/MCF, nearly 17 times that amount will be developed.

Future Cost Reductions
Financing Strategies Manufacturing Economy of Scale Better Sites and “Tuning” Turbines for Site Conditions Technology Improvements The wind industry does not expect future cost reductions to come from a single “silver bullet” technological achievement, but the accumulation of many small advances in materials and turbine design, as well as the cost reductions that will naturally occur as manufacturers ramp up to produce turbines on a larger scale.

Future Technology Developments
Application Specific Turbines Offshore Limited land/resource areas Transportation or construction limitations Low wind resource Cold climates The U.S. does not have any existing offshore projects, although a number are in under development on the East Coast. Europe is proving that offshore wind farms can be very productive, with minimal damage to the environment. ®Middelgruden.dk

Windmail@awea.org www.AWEA.org American Wind Energy Association
122 C St, NW, Suite 380 Washington, DC 20001

AE/ME Wind Engineering Module 1.2

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