UCS REPORTS - Union of Concerned Scientists

UCS REPORTS

Scientists and citizens working for a healthy environment and a safe world.

1 Wind Resource Assessment U n i o n o f C o n c e r n e d S c i e n t i s t s

B r i e f i n g P a p e r s f r o m t h e U n i o n o f C o n c e r n e d S c i e n t i s t s

This report is intended to guide prospective wind farm

developers through the process of site assessment. It pro-

vides practical information on how to develop reliable

estimates of the wind resource and electricity production

at a given site. This includes information on how to

measure wind speeds and direction; how to qualify your

land’s potential for wind projects; how certain variables

affect wind production costs and return on investment;

what information is typically needed by banks and inves-

tors to finance a project; and where to look for additional

information. While our examples are based on Minne-

sota, the principles discussed can be applied to any state,

particularly other parts of the Midwest.

Wind ResourceInformation FunnelPrimary questions that anyone considering a windproject must answer are: how strong are the winds atmy site and how much energy will my prospectivewind turbine produce in these winds. In this report,we will guide potential developers through the stepsnecessary to estimate the wind resources at their sites.

These refinements are produced by examiningdata from local, short-term measurement sites and re-gional, long-term records; analyzing factors relevantto wind resources like site exposure and wind roses(also known as speed and direction distributions); andgetting consulting support. You make use of the wind

Assessing Wind ResourcesA Guide for Landowners, Project Developers

and Power SuppliersB y M i c h a e l W. T e n n i s

S t e v e n C l e m m e r

a n d J o n a t h a n H o w l a n d

Figure 1. You might think of the wind assessmentprocess as a funnel where rough estimates of windpower class from wind maps go in one end and morerefined and precise estimates of site-specific windspeed come out the other end.


resource data generated during the funneling process.The rough estimates at the beginning of the processare used to conduct a preliminary assessment of thefeasibility of a wind project and determine whetherfurther consideration of wind energy is warranted.The more refined estimates in the middle of the proc-ess can support your calculations of the cost and in-come potential from a wind project. The best esti-mates of site-specific wind speed can support a cashflow analysis of a wind energy investment, an in-vestment prospectus for potential partners and a loanapplication to a lender.

Wind ResourcesThe wind resource powering a wind project is as fun-damental to the project’s success as rainfall is to al-falfa production. The objective of this report is toprovide a concise body of wind resource data and in-formation that will support the needs of wind trainersand potential wind project developers. This informa-tion is intended to clearly and effectively communi-cate what we really know and don’t know about windresources in Minnesota. Furthermore, we providesuggestions for how would-be project developers canuse the data presented to perform a variety of criticalassessments of their wind energy investment oppor-tunities and how they might go about acquiring addi-tional information that will increase the reliability oftheir assessments or increase their understanding ofthe specific wind resources available at their sites ofinterest. We present the material in a logical mannerdesigned to allow you to quickly make the determi-nation of whether wind projects are worth your de-tailed consideration.

The wind speed data for a site is critical to boththe investor and the lender for a project. The investormust evaluate the long-term energy production andeconomic performance of the project to be assuredthat it generates an acceptable rate of return. Thelender needs assurance that the revenues generated bythe project month-to-month and year-to-year will besufficient to cover the payment on any loan that ismade. The project performance on the average is im-portant to the investor, while project performanceduring poor wind months or years are important to thelender.

Impacts on a Wind ProjectThe power in the wind is the fundamental determi-nant of wind project success. Wind energy productionfrom a particular wind turbine changes in proportionto approximately the square of the wind speed.1 Forthis reason, if you over-estimate the wind speed atyour site by 10 percent, you are over-estimating windenergy production from your project by 21 percent.2

In more concrete terms, if you expect and need$10,000 of revenue per year to pay off your loan andearn some profit, you would only earn $8,100. At thevery least, there goes your profit; at worst...

Fortunately, by developing a thorough under-standing of the factors that influence the wind re-source at a particular site—exposure, obstacles,height above the ground, etc.—you can include theinevitable uncertainties in your decision-making pro-cess and take action to get the most cost-effective per-formance from any project that you choose to de-velop.

What is the wind speed at my site?

Wind Speed and Project Value—the Critical UnknownJust as good land is fundamental to successful farm-ing, a good wind resource is essential to successfulwind project development. Different locations acrossa state, county or section are likely to “possess” dif-ferent wind resources. As a prospective wind projectdeveloper, one of your first priorities needs to be de-veloping reliable estimates of the wind resources onthe land that you control. Although wind data is notas readily available or as well understood as soil data,there is a reasonable and growing body of data thatyou can draw on to make this important determina-tion.

In Minnesota and across the upper Midwest,public entities, usually state government, have beencollecting measurements of wind speed and direction,air temperature and pressure data at prominent loca- 1 The power in the wind is theoretically a function of the cube ofwind speed. Wind turbines cannot extract all the power from thewind and, as a rule of thumb, actual power production is propor-tional to approximately the square of wind speed.2 If your estimate of wind speed is 110 percent of actual, thenyour estimate of wind energy production is 110 percent or 121percent higher than actual. Therefore, your actual energy produc-tion will be approximately 83 percent of your estimates.

U n i o n o f C o n c e r n e d S c i e n t i s t s Wind Resource Assessment 3

tions for a number of years. The number and sophisti-cation of these measurements, as well as their useful-ness in meeting the needs of a wind project devel-oper, vary from state to state and from county tocounty.

The odds are that the existing measurement sitesare not on or even near your property, so you willneed to do some research to develop estimates of yourwind resource that will satisfy yourself and yourbanker. The following sections will help you developthese estimates and give you suggestions on how toimprove the reliability of the estimates, thus increas-ing your confidence in the rest of the analysis of awind development opportunity.

The ideal wind project assessment data would bea decade long set of measurements of wind speed anddirection along with air temperature and pressuretaken above, below and at the exact height above theground of the hub of the chosen wind turbine. Such adata set would allow you to estimate the energy pro-duction of a wind turbine at that site and to describethe variability in energy production, and ultimatelyrevenue production, that you could expect from year-to-year and month-to-month and to do so with highreliability.

The wind resource assessment process describedin this report is designed to allow you to take the less-than-ideal data that you are likely to have and developreasonable and clearly explained estimates of all thewind parameters of interest. For example, if you havedata for one or two years from a nearby measurementsite, you need to determine what the long-term aver-age wind year and “poor” wind years might look like.Alternatively, if you have long-term measurementstaken 10 feet above the ground, you need to estimatehow much faster the wind blows at 150 feet (windturbine hub height) above the ground. Reliable andproven techniques are readily available to make thekinds of estimates that might be required, so don’t de-spair.

Is the wind resource in my areasufficient to warrant seriousconsideration of a wind project?

Using Existing Wind Maps to Estimate WindResource. Research performed and measurementstaken over the last 25 years have shown that wind re-sources vary considerably over the upper Midwestand that some areas are just not appropriate for winddevelopment at the current time. This information hasbeen condensed into a number of wind resource mapsor atlases which can give you a quick but generalsense for the wind resource in your area.

The oldest of these wind maps was produced byBattelle Pacific Northwest Laboratory (PNL) for theUS Department of Energy in the early 1980s (see fig-ure 2). Even after a dozen or more years, this assess-ment remains the best indicator of wind resource po-tential for much of the United States. As you can seefrom the map, wind resources appear to be highest(Wind Class 4) in the northwest and western parts ofthe Midwest, declining to Class 3 in the central partof the region and ultimately to Class 2 in the easternpart of the Midwest.3 The zone of transition betweenthe most promising wind areas and those with lesspromise occurs quite abruptly in western Minnesotaand northern Iowa, making the task for a project de-veloper in that area quite challenging.

Fortunately, there are newer and somewhat morerefined estimates of wind resources available in theMidwest which can give developers additional guid-ance regarding the wind resources in this area.

Project developers in Minnesota are very fortu-nate to have the results of more than a decade of theMinnesota Wind Resource Assessment Program(MNWRAP), sponsored by the Minnesota Depart-ment of Public Service (DPS)4, and the state’s electricutilities to draw upon. In 1981, the Western AreaPower Administration (WAPA) began providing DPSwith wind data that was collected in the WAPAservice area. Later, in 1983, Northern States PowerCompany (NSP) began recording wind data at loca-

3 Wind power class is defined as a range of wind power densities(in watts per square meter of swept rotor area, or area perpen-dicular to wind flow), at a given height above the ground.4 The DPS was merged into the Minnesota Department of Com-merce on September 15, 1999.


tions in Minnesota expected to have high wind po-tential. In March, 1994, data from all sites monitoredby NSP was transferred to DPS. For each of thesesites, DPS created databases of the available infor-mation to facilitate analysis.

In 1986, advanced equipment to monitor and rec-ord wind measurements (data loggers) were pur-chased by utilities and DPS and installed throughoutthe state. All loggers recorded wind speeds measuredat the 30-meter level. In addition, some of the sitescollected wind direction data. In retrospect, we havelearned that many of these sites were not in ideal lo-cations. In addition, the data loggers, advanced asthey were for the time, did not operate as reliably asexpected. As a result, the recorded data may not be asrepresentative of the local wind resources as wewould prefer. This phase of the WRAP programended on December 31, 1995 and the results of theentire monitoring program are summarized in Minne-

sota Wind Resource Assessment Program—October1996 Report, available from DPS.

A special study of wind and solar resources onand near Buffalo Ridge in southwest Minnesota wasconducted by DPS between October 1993 andDecember 1995. The objective of the study was tocollect wind and solar data simultaneously in order tostudy the possible benefits of combining wind andsolar facilities to meet the demand for electricity inMinnesota. The Wind/Solar study was carried outwith five more advanced data loggers that monitoredwind speeds at 10, 20 and 30- meter levels. They alsorecorded wind direction, site temperature and solarradiation. The data from this program was much morereliable in large part because the data recorded on-sitecould be checked and collected via a cellular tele-phone link built in to the data loggers.

In January 1995, DPS began installing NRG 9300cellular data loggers at various locations throughoutthe state. (See figure 3.) There are currently 24 active

C L A S S E S O F W I N D P O W E R D E N S I T YWind Power

ClassDensityat 10m(33ft)W/m2

Speed at 10m(33ft)

m/s mph

Densityat 50m(164ft)W/m2

Speed at 50m(164ft)

m/s mph

1 0-100 0-4.4 0-9.8 0-200 0-5.6 0-12.52 100-150 4.4-5.1 9.8-11.5 200-300 5.6-6.4 12.5-14.33 150-200 5.1-5.6 11.5-12.5 300-400 6.4-7.0 14.3-15.74 200-250 5.6-6.0 12.5-13.4 400-500 7.0-7.5 15.7-16.8

5-7 250-1000 6.0-9.4 13.4-21.1 500-2000 7.5-11.9 16.8-26.6

Figure 2. Source: Wind Energy Resource Atlas of the United States, Pacific Northwest Laboratory, March 1997


sites. At these sites wind speed data is collected at 30,50 and 70-meter levels. Due to improved siting tech-niques, collection methods and equipment, the datacollected at these sites and the Wind/Solar sites is su-perior to the data collected in the previous projects.This data forms a more reliable basis for the evalua-tion of wind energy projects.

The Tall Tower Wind Shear Study, a detailedstudy of the wind shear (the change in wind speed atdifferent heights above the ground) began in May1996. The purpose of the study is to develop compu-tational methods for determining wind power poten-tial at all levels of interest to the wind energy indus-try. The data from the Tall Tower Study will becorrelated with data from the 14 active WRAP sitesto determine the wind shear for regions surroundingthe project sites. Each of the four Tall Tower sitesmonitors wind speeds at 10, 30, 40, 50, 60 and70 meters and wind direction at 10, 30, 60 and70 meters.

WRAP supports the development of Minnesota’swind resources by establishing and maintaining winddata collection sites in various locations throughoutthe state. WRAP collects and organizes the data foruse by developers and others interested in Minne-sota’s wind resources, and provides an overall as-sessment of the state’s wind resources as well as amap defining Minnesota areas on the basis of theirwind energy availability.

Figure 3 shows the sites where the DPS has itsmost reliable wind measurement stations. The closeryour site is to these measurement locations, the morereliable your estimate of local wind resources will be.In 1994, DPS contracted with Minnesota’s LandManagement Information Center (LMIC) to assist inmapping the wind resource information analytically.Figure 4 is based on this analysis of wind energy val-ues from 24 WRAP sites for data collected through1998. The map supports previous estimations that alarge area of southwest Minnesota contains Class 4and Class 5 winds. The energy values for the RedRiver Valley area, however, are lower than expected;Class 2 and Class 3 winds rather than the expectedClass 3 and Class 4 winds (see map legend for windclass ratings.) In addition, some areas of the state,such as the north central, have not been monitored atall and could cause the interpolation process to pro-duce less than meaningful results. Further wind re-

source monitoring is clearly necessary, especially inthe Red River Valley area. You should locate yourparticular wind development site on this wind powermap to obtain a rough estimate of the wind class foryour project. If your land is Wind Class 5 or better onthe map and your property is clear of trees in all di-rections and higher than its surroundings (i.e. 1-2miles), then you are justified in looking further intowind project development. Conversely, if your areashows up as Wind Class 2 or less and your property isin a valley, surrounded by hills or tree covered, it isunlikely that a wind development on your site will becost-competitive. If your area shows up as Class 4 onthe map and is well exposed to the winds, you mighthave a viable wind project opportunity; however, youmay need to invest extra resources in estimating thewind speeds at your site.

Qualifying Your Land’s Potential for WindProjects. It is important to remember that the windresource at a particular spot is strongly influenced bylocal terrain, vegetation cover and man-made struc-tures. Once you have a sense for the Wind Class inyour local area, you should assess the exposure ofyour land to winds. Terrain features like valleys,bluffs and near-by hills can block or disturb windflow, reducing the winds that reach your property.Tree cover or buildings on or near your property arealso likely to reduce wind flow (more on this later).Since you will ultimately have to connect your windproject to the utility distribution or transmission sys-tem or, for a small project, to your home or farm, youshould also consider the location of existing utilitylines to your property.

The Union of Concerned Scientists used a com-puter-based mapping system to take better account ofterrain elevation in the Midwest and produced themap in figure 5 as part of their Powering the Midwestproject.5 This map shows numerous locations across

5 In UCS’s analysis, the exposure of a particular location was de-termined compared to average elevation in a 7.5-mile (12-km)radius. Twelve kilometers was chosen because it is larger than thescale over which winds may be affected by major features such asan abrupt transition from water to land or an abrupt increase interrain elevation but not so large that significant details of geog-raphy are lost. A smaller radius would not distinguish the tops ofhills from the surrounding terrain, whereas a larger radius mightencompass several hills within the averaging area.


Minnesota where local terrain is elevated above the

Figure 4.

Figure 3.


surroundings and is well exposed to the wind classesshown in the DPS map above. Exceptional terrain ex-posure could produce local wind classes in excess ofthose shown in the DPS map. Again, locate yourproperty on the terrain exposure map. If your site hasgood or better exposure, you would expect wind re-sources comparable to those mapped by the DPS. If

your site is not well exposed, you may expect windresources to be less than indicated by the DPS map.

The wind maps discussed earlier present wind re-sources in terms of wind power class. In order to de-velop estimates of the energy production and, ulti-

mately, the economic benefits and costs of a windinvestment, you need to translate your wind powerclass into a range of possible wind speeds. This windspeed range can then be used in the process andspreadsheets described later to generate a range forwind turbine energy production estimates. Table 1shows the wind speed ranges at heights of 98 feet

(30 meters) and 164 feet (50 meters) above theground for each wind power class.

Your wind investment should make economicsense when you assume wind speeds at the low end ofthe wind power class range. For example, if your site

Union of Concerned Scientists Terrain Exposure Map

Figure 5.


appears to be in Class 5, then the attendant annual av-erage wind speeds at a height above the ground of98 feet on your well-exposed site could range from aslow as 15.7 mph to as high as 16.6 mph. In order toobtain a conservative, preliminary determination ofthe viability of a wind investment at your site, youshould evaluate project economics at an average an-nual wind speed of 15.7 mph. It would be prudent toevaluate economics at a wind speed 10 percent or1.6 mph lower 14.1 mph just to understand what theimpact of over-estimating wind speeds can be. Evalu-ate project economics using wind speeds of 16.0 to16.6, the upper half of the wind power class, only toget a sense for the potential up side of this invest-ment. We are not doing you or wind energy any fa-vors by overestimating the available wind resource.

Collecting Wind Resource Information fromNearby Sites. Wind class information from windmaps is most useful in making a preliminary determi-nation of the viability of your wind project. Once youconvince yourself, based on wind map estimates, thatyou might go forward, you should then scour yourarea for good quality wind measurement information.

One of the simplest and least-costly ways to be-gin improving your estimate of the wind resources atyour location is to collect information from nearbysites where wind resource measurements have beentaken.6 If you choose to have a consultant conductthis work for you, the following sections should assistyou in defining the consultant’s scope of work andevaluating the quality and reliability of the results.Table 2 provides a checklist of the data that youshould try to acquire.

Once you have found wind measurement datafrom a nearby area, you need to determine if the datasets are valid and reliable and whether they are atleast somewhat representative of your site. In general,if the measurement system accurately collected winddata 80 percent or more of the time and if the site islocated on well-exposed terrain, well removed fromhills, valleys, bluffs or trees, the data set is appropri-ate to help you make an informed decision. If themeasurement location is near significant obstructions 6 At this point in your evaluation, you might wish to solicit theservices of an expert in wind resource assessment to develop es-timates of the wind resource at your site. Independent consultingmeteorologists are available to conduct this work. Alternatively,and with some caution, you might call on wind turbine marketersto assist you in this task. At some point in the future, we mightexpect common resources like the agricultural extension serviceor DPS to provide this type of consulting to interested project de-velopers.

Table 2. Desirable Data from NearbyWind Measurement Sites

• Site elevation

• Monthly average wind speed

• Wind rose (wind speed and direction fre-

quency data, showing directions from which

the wind is strongest and weakest)

• Site exposure (local terrain—hills, valleys,

etc., vegetation cover, and manmade struc-

tures)

• Height(s) above ground

• Data recovery (number of hours of valid data

vs. total possible hours)

• Data record (year and months with measure-

ments)

• Site location with respect to your property

(wind speeds generally increase to north and

est)

Table 1. Conversions from Wind Power Class to Annual Average Wind Speed

Wind Class At 98 ft (30m) Height At 164 ft (50m) HeightPower*(W/m2) Speed (mph) Power*(W/m2) Speed (mph)

1 0-160 0-11.4 0-200 0-12.52 160-240 11.4-13.2 200-300 12.5-14.33 240-320 13.2-14.6 300-400 14.3-15.74 320-400 14.6-15.7 400-500 15.7-16.85 400-480 15.7-16.6 500-600 16.8-17.96 480-640 16.6-18.4 600-800 17.9-19.77 >640 >18.4 >800 >19.7

*Wind power density is expressed in watts per square meter (W/m2) of swept area, or area perpendicular to wind flow.


to wind flow or the monitoring equipment capturedless than 50 percent of the data, it is not appropriateto use in the assessment of your own site.

Once you have validated the data, you use it toestimate the wind resource at your site. This task iscritical to your overall evaluation of the wind invest-ment and should receive considerable attention. Thelarger the project or investment under consideration,the larger and more expensive the effort that is war-ranted.

There are a number of factors that influence thecomplexity of this task and the ultimate reliability ofthe result. The complexity or roughness of the terrainat your site and at the site where measurements weretaken is very important. In California, where windprojects are constructed along the ridgetops of somevery rugged terrain, developers of large projects havereported installing one wind measurement system(anemometer) for every two or three turbines to ac-

quire wind resource data reliable enough to satisfylenders and investors. In the Buffalo Ridge area, youmight have seen five or six wind measurement sys-tems operating across the area that was ultimately oc-cupied by the 73 turbines of the first development in1994. For installations of single, small machines, sitespecific measurements are often forgone and deci-sions are made based on measurements taken at othersites and the judgment of the developer and a localwind turbine sales person.

In the upper Midwest, particularly away fromriver valleys or prominent geological features, we an-ticipate that reliable wind estimates can be developedusing relatively simple averaging or extrapolationtechniques.

One promising technique has been developed andused extensively in Europe to assist local landownersin evaluating the feasibility of clusters of community-owned wind turbines. This computer-based assess-ment basically takes site data like that listed in the ta-ble on the previous page for both the wind project siteof interest and wind measurements of nearby sitesand generates wind resource estimates at the targetsite based on the principles developed in the Euro-pean Wind Atlas. In Europe, where the wind commu-nity has been using this approach for some time, pro-spective owners, wind turbine sales persons andlenders have come to trust and rely on this technique.In the early stages of wind development in the Mid-west, this and other techniques will need to be testedand proven so that buyers and lenders can achieve thesame level of confidence as their European counter-parts.

Should I take measurementsat my site?

Site-specific measurements give the most reliableestimates of the wind resources for a project; how-ever, they can be quite costly and require, at a mini-mum, six months to several years to complete. As aresult, deciding whether or not to undertake a meas-urement program hinges on an assessment of the costsand benefits of such an effort.

Discussions with wind resource assessment ex-perts suggest that you might be able to contract forfour to six months of measurements from a tower ofapproximately 100 feet (30 meters), along with some

Wind Assessment for Smaller Systems

In Europe, the WINDATLAS-SYSTEM is used to

project the performance of turbines having standard-

ized power curves, for areas between locations with

well-documented wind resources. This software sys-

tem has essentially eliminated the need for wind re-

source measurements at prospective turbine sites.

Site projections and economic decisions can be made

with the help of the WINDATLAS-SYSTEM in a

matter of hours, instead of the months or years that

might be required to perform conventional wind re-

source measurements at a prospective wind turbine

site.

The WINDATLAS-SYSTEM depends on two key

elements: wind statistics from long term monitoring

stations and accurate mapping of the terrain and bar-

riers surrounding the prospective turbine sites. It is

hoped that data from existing and on-going wind re-

source assessment programs in the United States can

be utilized for wind statistics in the upper Midwest.

Once these wind statistics are in place, a Wind Atlas

can be made for the upper Midwest and we will be

able to take advantage of the WINDATLAS-

SYSTEM.

(Some wind turbine suppliers offer this type of assess-ment to prospective buyers.)


consulting to evaluate this short measurement recordwith respect to long-term data for a cost of $1,500to $3,000. For individuals considering single-farmwind turbines, it might cost $20,000 to $35,000 andgenerate $600 to $1,680 per year in revenue. This in-vestment, amounting to 5-15 percent of your windturbine investment, might be burdensome. On theother hand, for larger wind turbines and clusters ofwind turbines where investments would be at leastseveral hundred thousand dollars and annual revenueswould be at least tens of thousands of dollars, anadded expense of $1,500 to $3,000 may be better jus-tified.7 A systematic assessment of the monetarybenefit of conducting on-site measurement programsis difficult to conduct.

Indeed, many of the benefits might be difficult tovalue in monetary terms (e.g., getting faster approvaland a more favorable interest rate on a bank loan).

Measurement Programs.Large Wind Projects: Multimillion Dollar In-

vestments. The measurement program that you un-dertake should carry a cost that is consistent with theoverall size of your potential investment and with theuncertainty of the resource in your area. If you arecontemplating a multi-million dollar wind project inan area where no wind measurements have beentaken, it would be wise for you to take at least twoyears of measurements with a multilevel meteorologi-cal tower in order to confirm your wind resource. Ifthe terrain surrounding your site is rugged, it may beappropriate to install several anemometers across thesite at wind turbine hub height to assure yourself thatyou have a reliable estimate of the variation of windspeed across your site. 8 In fact, it is quite commonfor the lenders to large wind projects to require rigor-ous wind resource assessment efforts before approv-ing loans.

Medium Wind Projects: $1–3 Million Invest-ments. For projects of this scale (1-4 MW or 2-6 7 For representative project costs and revenue figures for windturbine installations 7 meter/10 kW, 30 meter/225 kW and 40meter/500 kW in size see Nancy Lange and William Grant, IzaakWalton League of America, Landowner’s Guide to Wind Energyin the Upper Midwest, 1995, pages 15-26, online athttp://www.me3.org/issues/wind/iwlaguid.html.8 Lenders to large wind projects often hire independent meteor-ologists to validate the developer’s estimates of the available windresources.

wind turbines), you should seriously consider a short-term measurement program including anemometers atseveral heights and a measurement period lasting atleast a year, combined with a careful wind data inter-polation effort. Such an effort would eliminate a greatdeal of uncertainty in your estimate of wind resourcesand give you and your banker data that can confi-dently be used to evaluate an investment of this mag-nitude. The closer, more representative and more reli-able the nearby measurements are, the moreconfidence you can have in your assessment of windresources.

Small Wind Projects: Less $1 Million. For smallprojects (one or two machines in the 250 kW to750 kW size range), large investments in on-sitemeasurements are more difficult to justify. However,the revenue generated by projects this size couldrange from $25,000 to $100,000 per year or morebased on capital investments of $200,000 to$800,000; investments of a few thousand dollars inwind resource assessment and validation are, there-fore, certainly warranted. For less than $5,000, youshould be able to have a contractor install an ane-mometer on a tilt-up tower at or near hub height, col-lect up to six months of wind data and carry out acareful interpolation with existing wind measure-ments from other representative sites.

Home or Farm Sized Wind Projects: $5,000–40,000. If your intent is to install a small windturbine sized to supply a portion of the energy needsof your home or farm, on-site wind measurements areless common. In this case, you must rely onextrapolation or projections of the wind speed at yoursite. You should consider investing $500 or more in aconsultation with a wind assessment consultant with atrack record in your part of the state. Thesepractitioners are not certified as yet, so you should beadvised to carefully review their credentials andreferences before hiring them.

Measurement Program Help. Many contractorsoffer measurement programs as part of their services.As wind projects become more common in the GreatPlains, it is possible that local economic developmentor agricultural extension services will add windmeasurement planning and support to their lists ofservices. It is also possible that utilities or publicagencies interested in promoting wind energy will of-fer anemometer loan programs whereby interested


would-be developers would borrow relatively simpleequipment and take site-specific measurements.

As the wind energy market develops in the Mid-west, we expect some of the more traditional ruraleconomic development agencies or agricultural ex-tension services to develop or acquire expertise inthis type of assessment.

Site Inspection. In California where wind proj-ects have been developed for 15 years or more, anumber of meteorologists, engineers and others havedeveloped expertise in evaluating the wind resourcesat potential wind project sites. Several of these prac-titioners have been brought to the Midwest to supportthe development of the large projects on BuffaloRidge. Some Minnesotans have also begun to offersite evaluation and inspection services to prospectiveproject developers. Wind turbine sales organizationsare also likely to offer this type of service; however,the prospective buyer should understand the biasesthat a company marketing the equipment might have.

What information do my bankerand I need?

Average Annual Versus Year-to-Year Varia-tions. Wind turbines will be like crops and have goodyears and bad years. Your banker will want a realisticassessment of the energy production, and revenueproduction of your project during a poor wind year, inorder to be sure that you can cover any loan paymentthat you have. Different bankers are likely to havedifferent perspectives on this issue; however, allevaluations need to rest on an assessment of the year-to-year variations in wind availability over the longterm.

Because we do not yet have 20 or 30 years ofwind measurements in good wind energy areasaround the state, we must take an indirect approach todetermining how much the winds at our wind sitevary year to year. This approach relies on a compari-son of short-term wind records at promising sites withthose at reference sites where wind measurementshave been taken for many years, often airports orNational Weather Service installations. Ideally, theyear-to-year changes seen at wind sites will be mir-rored by changes at the reference sites.

As an example, consider figure 6 showing the an-nual average wind speed for the years 1961 to 1995

for the Minneapolis airport along with comparableaverages for more recent years from Holland,St. James, and Rochester, Minnesota. All data isnormalized; that is, each annual average wind speedvalue is divided by the long-term average from thesite. The resulting chart shows how much, in percent,

Minimum Requirement—Site and WindResource Evaluation Report

At a minimum, you should expect the follow-ing from a site evaluation contractor:

1. Site description—including property de-scription, site elevation above sea level.

2. Site map—including property lines, topo-graphic contours, locations of existing electric-ity distribution and transmission lines androads, obstacles to wind flow—trees, terrain,buildings, etc.

3. Wind statistics from nearby representativewind monitoring stations—including:

• Measurement site description, including lo-cation relative to proposed site, elevationabove sea level and exposure;

• Annual average wind speed for as manyyears as possible up to twenty;

• Monthly annual winds based on as long arecord as possible;

• Wind speed and wind power roses showingfrequency of winds over range of windspeeds or power levels from different di-rections; and

• Wind shear coefficient or annual averagewind speeds at all anemometer levels.

4. Projected annual wind speed at the site,along with an explanation of how the projec-tion was determined.

5. Annual average wind speed that will be ex-ceeded 70%, 80%, and 90% of the time, alongwith a description of the method for determin-ing the distribution of wind speeds.


the annual average wind speed in any year might varyfrom the long-term average.

Then, let’s take a closer look to explore whetherthe wind resources at other sites follow a similarlong-term pattern as those at Minneapolis. See fig-ure 7, which shows the years 1982 through 1995 fromfigure 6.

When we compare the record from Minneapolis

with wind measurements taken for wind power pur-poses across the state, we can see that the annualaverage wind speeds at diverse sites including Hol-land, St. James and Rochester follow a similar patternto those at Minneapolis. The wind speeds at the othersites drop in 1987, 1989 and 1992, when wind speedsin Minneapolis drop, and increase in 1985, 1988 and1994, when they climb.

Long-Term Wind Variability

80%

85%

90%

95%

100%

105%

110%

115%

61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 93 95

Year

Per

cen

t o

f N

orm

al

Minneapolis Holland St. James Rochester

Figure 6.

Wind Speed Variations Across the State and Across Time

80%

85%

90%

95%

100%

105%

110%

115%

82 83 84 85 86 87 88 89 90 91 92 93 94 95 96

Year (note, data recovery low in some years)

Win

d S

pee

d (

%o

f n

orm

)

Holland

St. James

Rochester

Minneapolis

Figure 7.


This indirect assessment of good and bad windyears at our specific sites requires two steps. In thefirst, we attempt to determine whether the years ofmeasurement at the windy sites represent the long-term averages at those sites or whether they are, onbalance, better than average or worse than average. Ifthey are not representative, we should make adjust-ments so that they are. This step is intended to avoidover or under-estimating the long-term average windresource at the site because the nearby measurementsupon which we rely do not accurately reflect a long-term data record. It will also allow us to adjust the lo-cal site data up or down to better reflect the long-termaverage.

The data since 1961 for Minneapolis show thatannual average wind speed tends to cycle throughseveral years with above-average values and severalyears of below-average values. The lowest value inthe entire record for Minneapolis is 91 percent of thelong-term annual average, while there are six yearswhen the average annual wind speed was 95 percentor less of the long-term average.

Another way of expressing this information is asa frequency distribution showing the percent of thetime or probability that annual wind speeds will

deviate from the long-term average by more than acertain amount. Your loan officer will be concernedabout the lowest winds thus, electricity generationand gross revenue from power sales that your projectwill experience once or twice over the term of theloan? For example, on a ten-year loan, the question is:what is the worst wind year to be expected over theentire loan? In terms of probabilities, the question is:what wind speed is likely to be exceeded 90 percentof the time?

Figure 8 shows the probability distribution of allthe measurements at the Minneapolis airport for theperiod from 1961 through 1995. If the loan officerwants to base the loan “coverage ratio” on the worstyear in 10 percent probability, this chart would sug-gest that the annual average wind speed would bebetween 91 percent of the long-term average theworst year in the measurement record to 94 percent ofthe long-term average. In other words, a bank mightbase its determination of loan coverage ratio consid-ering annual average wind speeds that are 91–94 per-cent of the long-term average at a site. As long-termdata records accumulate at the more representativesites maintained by the DPS, we would encouragewind developers to refer to this data in answering this

Distribution of Annual Wind Measurements--Minneapolis Airport 1961-1995

80%

85%

90%

95%

100%

105%

110%

115%

120%

0%10%20%30%40%50%60%70%80%90%100%110%

Time With Wind Speed Higher Than

Win

d S

pee

d (

% lo

ng

-ter

m a

vg.)

(Based on 1961 to 1995 record at Minneapolis Airport)

Figure 8.


question.Although the lender on a project will be particu-

larly concerned with the “downside” of annual windperformance, there is an “upside” to this situation aswell. Based on the Minneapolis wind record, a proj-ect operator could expect wind speeds five percenthigher than the average 17 percent of the time ornearly two years out of every 10.

Wind speed and tower costincrease with height. How highshould my tower be?

The Benefits/Costs of Increasing the Heightof Your Wind Turbine Tower. One of the firstthings that wind researchers learned when they beganmeasuring wind speed for wind projects was thatwind speed generally increases as you get higherabove the ground. Basically, the wind is slowed downby friction where it comes in contact with the groundor ground cover. As a result, wind speeds increase atincreased heights above the ground at wind sites. Thisphenomenon, known in the wind industry as windshear, presents wind developers with an opportunityto improve the overall economics of their investment

by putting their wind turbines on taller towers. As adeveloper, your task is to determine if the extra costassociated with a taller tower will pay off in increasedwind energy production and revenue. In this section,we will describe wind shear, its effect on wind energyinvestments and the uncertainties surrounding esti-mating wind shear.

For years, wind developers used the rule-of-thumb that wind speed increased over a site accordingto the one-seventh power law. The mathematicalequation for this rule-of-thumb is:

Velocityhub ht.= Velocityanem.ht. x (hub ht./anem.ht.)1/7

Figure 9 shows a graph of wind speed as a func-tion of height above the ground, assuming the windspeed at 30 feet is 14 mph and different power lawcoefficients.9

These coefficients—1/9 (0.111), 1/7 (0.143) and1/5 (0.200)—are all consistent with measurementsthat have been taken at wind sites across the country.For reference, the impact on average wind speed ofincreasing the height of your wind turbine tower from100 feet (approximately 30 meters) to 130 feet (ap-proximately 40 meters) would be 4.2 percent, under

9 The coefficient of a power law expression is the exponent of theequation, V2/V1 = (H2/H1) coefficient.

Wind Shear Determines How Much Winds Change With Heights Above the Ground

10.0

12.0

14.0

16.0

18.0

20.0

22.0

30 50 70 90 110 130 150 170 190 210 230

Height Above Ground (feet)

Win

d S

pee

d (

mp

h)

1/5

1/7

1/9

Figure 9.


the 1/7th power law. If wind shear is greater than1/5th power, average annual wind speeds increase by5.9 percent. If on the other hand, wind shear is lowerthan typical 1/9 power, the wind speed increasewould only be 3.3 percent. Remember that wind tur-bine energy production increases by approximatelythe wind speed increase squared, meaning that windenergy increases associated with the tower height in-crease from 100 feet to 130 feet would be 6.6 percent,8.6 percent and 12.2 percent respectively. If the costof increasing the wind turbine tower height from100 feet to 130 feet increases the total project cost byless than eight percent, then the extra investment inthe tower is justified by the increase in wind energyproduction if wind shear follows the 1/7th power lawor higher. (This information should be used in speci-fying the wind turbines for a project and in estimatingtheir annual energy production.)

How does wind speed change withheight (wind shear) at my site?

During the last few years, researchers have beenmaking measurements of wind shear at promising

wind energy locations using meteorological towers

with several levels of wind measuring equipment. Wecan get estimates of the wind shear coefficient in thearea near the meteorological tower by comparing thewind speed measurements hourly and monthly or an-nual averages at different heights above the ground.

Figure 10 shows the calculated wind shear (al-pha) coefficient for 12 Minnesota WRAP sites thathave been in operation since 1995 or earlier. Thisfigure shows that instead of the 1/7 coefficient so of-ten referred to for determining the wind shear in anarea, it might be more appropriate to use a 1/5 or1/4 coefficient for wind shear calculations in Minne-sota. This figure also indicates considerable variationin wind shear from location to location and at differ-ent heights above the ground. In general, the moreopen and flat the area surrounding a potential turbinesite is, the less wind shear there will be. Sites withsignificant nearby obstructions will show greaterwind shear values at heights just above these ob-structions.

Wind turbine vendors most often offer towersthat place turbine hub height in the range of98–164 feet (30–50 meters), so you should use thecoefficients shown by the white bars for your calcu-

lations. However, in recent years, wind developers

Wind Shear Coefficients Measured at Promising Sites in M innesota

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0.350

0.400

0.450

Halloc

k

Crook

ston

Sabin

Alberta

Mon

tevid

eo

Brownt

on

Luve

rne

Currie

Brewste

r

Mou

tain

Lake

Winn

ebag

o

Nerstr

and

New W RAP Sites 11-5-96 - Data to be validated

Win

d S

hea

r A

lph

a

Coef. 30-50 m Coef. 50-70 m

1/7th Power

1/5th Power

Figure 10.


have installed turbines on towers as high 230 feet or70 meters, and towers as high as 100 meter towers arebeing developed. Under those circumstances, youmight need both coefficients to estimate the increasein wind speed produced by increasing wind turbinetower height.

If there are meteorological towers nearby andcomparable to your site, you should use the averageof the wind shear coefficients from these sites in yourcalculations of average annual energy production andin assessing whether increasing wind turbine towerheight increases the pay-off for the investment. If theterrain or ground cover around your site is less favor-able than that around the meteorological towers, youshould use a conservative value for the power law co-efficient 1/7 or smaller unless a wind resource spe-cialist can argue persuasively for a higher, less-conservative value.

For the purposes of obtaining a bank loan, youmight be justified in using one of the lower windshear coefficients measured at representative sites. Inthe absence of comparable measurements, you shoulduse the 1/7th power law expression because it iswidely accepted and likely a bit conservative at awell-exposed site in the Great Plains.

How do I choose the specific spotfor my wind project?

Choosing the actual spot on your property foryour wind project may be a tradeoff between the mostwindy and well-exposed location and the distancethat location is from either the utility distributionlines or your home or farm electrical service. In thissection, we will give you a number of pointers to helpassure that you can identify pluses and minuses ofany specific location and avoid selecting sites wherewind flow to your project is severely compromised.

Obstacles and Wind Roses. In an ideal world,your project site would be the most prominent pieceof property for miles and would have no obstructionsto wind flow nearby hills, valleys, trees or buildingswithin 2,000 feet. As a practical matter, your sitemight not be perfect so you need guidelines to avoidbad sites and highlight your best options.

Fundamental data to support this process comes froma wind speed rose or wind power rose, a chart thatconveniently shows where the strong and weak windscome from over the course of a year. In the upperMidwest, winds are generated by large-scale weatherpatterns which move in predictable patterns acrossthe region. As a result, the strongest winds are mostlikely to come from the westerly directions northwest,west and southwest. Figure 11 shows both a windspeed rose and a wind power rose for the Ruth-ton/Holland site in southwest Minnesota.

Clearly, during the period of record for the Hol-land site, the strongest winds were observed comingfrom the south/southwest direction with additionalstrong winds from the southwest, northwesterly, andnorth directions. In areas of the Midwest subject tosimilar wind regimes, it is essential that wind projectsites be very well exposed to these dominant direc-tions. Conversely, winds are infrequent and weakfrom the easterly directions, suggesting that windflow obstructions in those directions will have littleadverse effect on energy production at a site.

Wind Turbine Wake Effects If SitingMore than One Machine

If you are considering a project with several windturbines, you should use the wind roses to assess howmuch space to leave between wind turbines. Sincewind turbines are themselves obstacles to wind flow,they leave “wakes” in downwind directions wherewind energy is depleted for considerable distances.Rules of thumb suggest that wind turbines in thedominant wind power directions should be at least8–10 wind turbine diameters apart.10 In the directionswhere winds are weak, spacing of 3–5 diameters canbe acceptable. This means that wind turbines withrotors that are 82 feet (25 meters) in diameter shouldbe placed 650–820 feet apart in the dominant winddirections.11

10 Researchers have shown that the size of the downwind distur-bance to wind flow created by a wind turbine proportional to thewind turbine’s rotor diameter. For this reason, wind turbinespacing to avoid unacceptable losses in the performance ofdownwind machines is defined in “rotor diameter” terms ratherthan simply in feet or meters.

10 Wind projects to date in Minnesota and Iowa do not appear to


Again referring to figure 11 showing the windrose for the Ruthton/Holland site, it would clearly becritical to multiple wind turbines spaced at least eightrotor diameters apart in the south southwest/northnortheast direction. Based on the important secondarywind directions shown on the wind rose, turbinesshould also be spaced eight or more rotor diametersapart in the northwest/southeast direction. This wind

have strictly followed this siting guidance and we would expectthat energy production from these sites is compromised somewhatdue to wake losses between machines.

rose, with strong winds from essentially perpendicu-lar directions, does not leave much opportunity forwind developers to reduce the spacing between ma-chines, in any direction, below 8-10 rotor diameters.

Wind Energy RoseDPS Site 108, Ruthton/Holland, MN

DPS 108 30-m level wind speed10/01/93-12/31/95

Figure 11.


Set-Backs—Protecting Your WindAccessSince obstacles at considerable distances can obstructthe flow of wind to a wind turbine, it is important tocontrol the property surrounding your site so that un-obstructed wind flow is assured over the life of theproject. In the terminology of county and state plan-ners, this is described as using set-backs from prop-erty lines to assure unobstructed wind flow. The tur-bine wake effects described above and the guidelinesdescribed in the Landowner’s Guide to Wind Energyin the Upper Midwest, provide valuable guidance inthis regard.12 In general, your wind project should beset back sufficient distance from property lines to as-sure that developments or buildings on adjacent prop-erty do not reduce the wind flow and thus reduce theeconomic performance of your wind project.

Some local planning boards may have set-backsfor wind turbines documented in their codes. How-ever, these requirements may reflect safety and noiserather than wind access considerations. As a result,you should always do your own evaluation to deter-mine the set-backs that protect your access to thewind.

12 Nancy Lange and William Grant, Izaak Walton League ofAmerica, Landowner’s Guide to Wind Energy in the Upper Mid-west, 1995. A summary is available online athttp://www.me3.org/issues/wind/iwlaguid.html.

If your property is not large enough to provide thenecessary distances, you might consider purchasingwind easements from your neighbors to assure thesame protection as set-backs. The participants inlarge-scale wind projects, including the ongoing NSPprojects, often acquire easements from neighbors forthis purpose. The location and size of these easementsshould be determined considering the dominant windpower directions at your site and your expectations asto the potential scale of obstacle. If your primary con-cern is the construction of wind projects in upwinddirections, then set-backs and easements that provideyou with a buffer of around 1,600 feet should besufficient.13

Who can help me?

In Minnesota and a number of other states, pub-licly accessible wind measurement programs havebeen going on for several years. As a result, you canexpect to find a rich and growing set of wind statis-tics to help you assess your site.

ConclusionWind energy is a new “crop” for rural America and,as a result, wind project developers need to work hardto assure themselves and their bankers that wind in-vestments make sense. This work is especially neces-sary in assessing the wind speeds at a promising sitefor development. As with other crops, wind farmersshould understand what the cash flow implications ofgood and bad wind years might be and resist thetemptation to pin their investment analysis to a singlesite wind speed value. With this in mind, this reportwas designed to define a range of wind speeds uponwhich decisions can be based.

We have attempted to provide numerous ap-proaches for wind farmers to improve the reliabilityof the wind resource estimates on which they basetheir decisions by conducting on-site wind measure-ments or obtaining consultation and analysis of theirsituation from qualified outsiders. In time, we expectmuch of this support to come from the institutionsthat farmers already rely on, such as the agricultural 13 This distance is approximately 10 diameters on a 50-meter (164feet) diameter turbine. Wind machines larger than this are un-likely in the next five to 10 years.

Wind Turbine Spacing at Lake Benton

At the 1994 Lake Benton wind project, severalstrings of turbines are closer than eight diametersin the north/south direction while the differentstrings of turbines are separated by a much largerdistance from the east/west direction. This spacingrepresents the economic compromise that the de-veloper chose considering impact of turbinespacing on turbine energy production when thewinds were from the north versus the added costsof land and machine interconnection. If you areconsidering placement of several machines, youwill be faced with a similar choice. Rememberthat a wind rose for your site will give you theinformation that you need to estimate the cost andbenefit of different arrangements.


extension service and county or state government.But for today, wind farmers must do their homeworkand seek out the consultation and other support theyneed on their own. Hopefully, this wind resourceassessment report will help support these pioneeringefforts.

ACKNOWLEDGMENTS

This report was originally published as a chapter inthe curriculum, Harvest the Wind released by theWindustry Project in Minneapolis. UCS is grateful toLisa Daniels of the Windustry project and Rory Artigof the Minnesota Department of Public Service fortheir continued support and invaluable contributionsto this project.

This report was supported by grants from the EnergyFoundation, the Joyce Foundation, the McKnightFoundation, and the Office of Utility Technologies,United States Department of Energy under grantnumber DE-FG41-95R110853. The Union ofConcerned Scientists is solely responsible for itscontents.

NOTICE

This report was prepared as an account of work spon-sored by an agency of the United States government.

Neither the United States government nor any agencythereof, nor any of their employees, makes any war-ranty, express or implied, or assumes any legal liabil-ity or responsibility for the accuracy, completeness,or usefulness of any information, apparatus, product,or process disclosed, or represents that its use wouldnot infringe privately owned rights. Reference hereinto any specific commercial product, process, or serv-ice by trade name, trademark, manufacturer, or oth-erwise does not necessarily constitute or imply itsendorsement, recommendation, or favoring by theUnited States government or any agency thereof. Theviews and opinions of authors expressed herein donot necessarily state or reflect those of the UnitedStates government or any agency thereof.

DECEMBER 1999

�� Wind Resource Assessment 7 P K Q P Q H % Q P E G T P G F 5 E K G P V K U V U

Further Information on Wind Power

Minnesota

Minnesota Department of Commerce85 7th Place East, Suite 500St. Paul, MN 55101Phone: 651-296-5175Toll-Free: 1-800-657-3710E-mail: [email protected]://www.commerce.state.mn.us/pages/Energy/ModTech/windmain.htm

Provides a wide variety of information and technicalassistance on wind power, including wind monitoringdata; contact information for local wind dealers, de-velopers and utilities; guides for purchasing smallwind turbines and calculating wind power production;and information to ease potential developers throughproperty and zoning issues. Operates state Wind Re-source Assessment Program (WRAP).

Windustry™ Project2105 First Avenue SouthMinneapolis, MN 55404Phone: 612-374-2261Toll Free: 800-365-5441Fax: 612-374-2601E-mail: [email protected]://www.Windustry.org/

Non-profit organization that provides information onthe economic development benefits of wind powerand analytic models to assess the costs and benefits oflocally owned wind projects.

Minnesotans for An Energy Efficient EconomyMinnesota Building, Suite 60046 East Fourth StreetSt. Paul, MN 55101Phone: 651/225-0878Fax: 651/225-0870E-mail: [email protected]://www.me3.org/

Non-profit organization that provides information ona wide variety of wind energy topics, including re-ports, analysis, local projects and legislation.

Wisconsin

Wisconsin Department of Administration,Division of Energy101 E. Wilson, 6th FloorPO Box 7868Madison, WI 53707-7868Phone: 608-266-8234Fax: 608-267-6931E-mail: [email protected]://www.doa.state.wi.us/depb/boe/index.asp

1996 Wind Resource Map for Wisconsin:http://www.baywinds.com/new/wiscpot.html

Provides general information, programs, technical as-sistance, and wind monitoring data. Publishes Wis-consin Renewable Energy Yellow Pages with infor-mation on wind energy businesses

Renew Wisconsin222 South Hamilton StreetMadison, WI 53703Phone: 608-255-4044E-mail: [email protected]://www.renewwisconsin.org/

Non-profit organization that promotes clean energystrategies for powering the state's economy in an en-vironmentally responsible manner. Provides informa-tion on legislative issues, purchasing renewable en-ergy from your local utility, and local wind projects.

Midwest Renewable Energy Association7558 Deer Park RoadCuster, WI 54423Phone: 715-592-6595Fax: 715-592-6596E-mail: [email protected]://www.the-mrea.org/

Holds workshops on renewable energy application.Hosts annual Midwest Renewable Energy Fair, whichoffers workshops and displays small wind turbines.

7 P K Q P Q H % Q P E G T P G F 5 E K G P V K U V U Wind Resource Assessment ��


Iowa

Energy Bureau, Energy and Geological ResourcesDivision, Iowa Department of Natural ResourcesWallace State Office Building,Des Moines, Iowa 50319Phone: 515-281-8681Fax: 515-281-6794http://www.state.ia.us/dnr/energy/index.htm

Provides general information and education on windpower.

Iowa Energy Center2521 Elwood Drive Suite 124Ames, Iowa 50011-8299Phone: 515-294-8819Fax: 515- 294-9912E-mail: [email protected]://www.energy.iastate.edu/renewable/

Publishes Iowa specific wind resource, ground cover,and wind speed maps. Created a wind energy produc-tion calculator that can determine wind speed andpotential turbine generation for any area in the state.

Iowa Renewable Energy AssociationP.O. Box 466North Liberty, IA 52317-0466Phone: 319-338-3200Fax: 319-351-2338E-mail: [email protected]://www.avalon.net/~laugh/index.html

Provides information on local renewable energy busi-nesses.

Nebraska

Nebraska Energy OfficeBox 95085Lincoln, NE 68509-5085Phone: 402-471-2867Fax: 402-471-3064E-mail: [email protected]://www.nol.org/home/NEO/

Provides general information on wind power.

High Plains Climate CenterUniversity of Nebraska830728 Chase HallLincoln, NE 68583-0728Phone : 402-472-6706Fax : 402-472-6614E-mail: [email protected]://hpccsun.unl.edu/wind/

The High Plains Climate Center offers statewideweather data and four years of wind monitoring datacollected from eight sites around the state.

�� Wind Resource Assessment 7 P K Q P Q H % Q P E G T P G F 5 E K G P V K U V U


National

American Wind Energy Association122 C Street, NW, 4th FloorWashington, DC 20001Phone: (202) 383-2500Fax: (202) [email protected]

Provides a wide variety of information on windpower, including the status of projects operating indifferent states, a directory of U.S. wind energy com-panies, and policy developments.

Department of Energy Wind ProgramForrestal Building1000 Independence Avenue, S.W.Washington, DC 20585http://www.eren.doe.gov/wind/

Provides a wide variety of information, programs,education and assistance on wind power. Adminis-ter’s DOE’s Wind Powering America initiative.

Energy Efficiency and RenewableEnergy Network (EREN)Forrestal Building1000 Independence Avenue, S.W.Washington, DC 20585http://www.eren.doe.gov/RE/wind.htmlhttp://www.eren.doe.gov/state_energy/states.cfm

Provides extensive information on various state re-sources and incentives for developing wind projects.

National Renewable Energy Laboratory'sNational Wind Technology Center18200 State Highway 128Golden, CO 80403http://www.nrel.gov/wind/

Provides technical information and research on awide variety of wind energy topics including U.S.wind resource data and maps, environmental issues,and turbine technology.

National Wind Coordinating Committeec/o RESOLVE1255 23rd Street NW, Suite 275Washington, DC 20037Phone: (888) 764-9463; (202) 965-6398fax: (202) [email protected]://www.nationalwind.org/

Multistakeholder organization that publishes reportsand conducts outreach dealing with a wide variety ofwind energy topics including siting, transmission,policy, economic development and environmental is-sues.

Union of Concerned Scientists2 Brattle Square, 6th FloorCambridge, MA 02238-9105Phone: 617-547-5552Fax: [email protected]://www.ucsusa.org/

Non-profit organization that provides a wide varietyof information on wind power, including technicalresearch reports, policy analysis, updates on state andfederal efforts to promote wind development, andlinks to other resources.

Documents

UCS REPORTS - Union of Concerned Scientists