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Contract No. DE-AC36-08GO28308

Establishment of Small Wind 

Regional Test Centers

Preprint 

T. Jimenez, T. Forsyth, A. Huskey, I. Mendoza, 

and K. Sinclair

National Renewable Energy Laboratory

J. Smith

Windward Engineering

To be presented at the 2011 National Solar Conference

(Solar 2011)

Raleigh, North Carolina

May 17-21, 2011

Conference Paper

NREL/CP-5000-50806

March 2011
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1

ESTABLISHMENT OF SMALL WIND REGIONAL TEST CENTERS

Tony Jimenez

Trudy Forsyth

Arlinda Huskey

Ismael Mendoza

Karin Sinclair

National Renewable Energy Laboratory

1617 Cole Blvd.

Golden, CO 80401

Joe Smith

Windward Engineering

10768 S. Covered Bridge Canyon

Spanish Fork, UT 84660 USA

The rapid growth of the small wind turbine (SWT) market 

is attracting numerous entrants. Small wind turbine 

purchasers now have many options, but often lack 

information (such as third-party certification) to select a 

quality turbine. Most SWTs do not have third-party 

certification due to the expense and difficulty of the 

certification process. Until recently, the only SWT 

certification bodies were in Europe. In North America, 

testing has been limited to a small number of U.S. 

Department of Energy (DOE) subsidized tests conducted 

at the National Renewable Energy Laboratory's (NREL) 

National Wind Technology Center (NWTC) under the 

ongoing Independent Testing Project. 

Abstract

During the past few years, DOE, the National Renewable 

Energy Laboratory (NREL), and some states have worked 

with the North American SWT industry to create a SWT 

certification infrastructure. The goal is to increase the 

number of certified turbines and gain greater consumer 

confidence in SWT technology. The American Wind 

Energy Association (AWEA) released the AWEA Small 

Wind Turbine Performance and Safety Standard, AWEA 

Standard 9.1 – 2009, in December 2009. The Small Wind 

Certification Council (SWCC) and Intertek, North 

American SWT certification bodies, began accepting 

applications for certification to the AWEA standard in 

2010.

To reduce certification testing costs, DOE and NREL are

providing financial and technical assistance for an initial 

round of tests at four SWT test sites, which were selected 

through a competitive solicitation. The four organizations 

selected are Windward Engineering (Utah), The 

Alternative Energy Institute at West Texas A&M (Texas), 

a consortium consisting of Kansas State University and 

Colby Community College (Kansas), and Intertek (New 

York). Each organization will test two small wind 

turbines as part of their respective subcontracts with DOE 

and NREL. The testing results will be made publically 

available. The goal is to establish a lower-cost U.S. small 

wind testing capability that will lead to increased SWT 

certification.

Turbine installation is ongoing. Testing began in early 

2011 and is scheduled to conclude in mid-late 2012.
2

1. INTRODUCTION/BACKGROUND

The past few years have seen rapid growth in the U.S. 

small wind turbine (SWT) market. Due to a proliferation 

of incentives, SWT installation capacities (defined as 

wind turbines with a rated capacity of up to 100 kW) in 

the United States have increased from 8.5 MW in 2006 to 

more than 20 MW in 2009.(1) The growing SWT market 

has attracted numerous new entrants with products of 

widely varying quality. Potential SWT buyers face a 

wide array of choices and, for the most part, lack the 

knowledge to adequately evaluate the claims made by the 

various SWT manufacturers. State incentive fund 

managers face a similar dilemma when attempting to 

determine which SWTs should be eligible for limited 

incentive funds.

Until recently, little incentive and many barriers existed 

for manufacturers seeking to certify their small wind 

turbines. There have been no legal requirements for 

turbine certification and little market pressure to do so. 

Barriers to certification included high costs associated 

with field testing, which is required for certification of 

SWTs, and the time required for field testing, which is 

typically a year or more from the time a testing contract is 

signed. Another obstacle has been the lack of U.S.-based 

certification bodies. Manufacturers were forced to use

European certification bodies. Finally, field testing 

options were limited. The only accredited SWT test 

organizations in the United States were the National 

Renewable Energy Laboratory’s (NREL) National Wind 

Technology Center (NWTC) and DNV (formerly Global 

Energy Concepts). Therefore, certification testing that 

occurred prior to 2010 in the United States was limited to 

three to four turbines annually under the DOE-funded 

Independent Testing project.

To address this issue, the North American SWT industry 

began working in 2006 with DOE, NREL, and some 

states (IA, IL, NV, NY, OR, WI), to create an SWT 

certification infrastructure. The goals were to increase the 

number of certified turbine models and gain greater 

consumer confidence in SWT technology. The strategy to 

achieve these goals was to reduce barriers to certification 

by 1) Establishing a North American SWT Performance 

and Safety standard; 2) Establishing North Americanbased certification bodies; and 3) Encouraging the 

establishment of entities to conduct the field testing 

required for SWT certification. These efforts bore fruit in 

late 2009 and 2010. The American Wind Energy 

Association (AWEA) released AWEA Small Wind 

Turbine Performance and Safety Standard (AWEA 

Standard 9.1 – 2009) in December 2009. In 2010, two 

North American certification bodies began accepting 

applications for certification to the AWEA standard. 

Finally, as of the end of 2010, over two dozen 

organizations were offering field testing services. (2)

It is expected that many states will eventually require 

certification for SWTs to be eligible for state incentive 

funds. In addition, it is expected that over time, 

consumers will demand certified turbines and reject 

uncertified turbines.

To increase the availability and quality field testing for 

certification, DOE and NREL are providing general 

technical assistance to the SWT certification testing 

community. This assistance takes the form of organizing 

an annual SWT Testing Workshop and providing 

informational support on an informal basis. In addition,

DOE and NREL are establishing a network of Regional 

Test Centers (RTCs). The RTCs are SWT testing partner 

organizations that DOE and NREL provide with financial 

support and enhanced technical assistance. It is intended 

that these RTCs can act almost as satellite testing 

organizations to the NWTC.

2. SWT CERTIFICATION AND TESTING

OVERVIEW

The AWEA standard was developed using a consensus 

process through a group representing various SWT 

industry stakeholders. The AWEA Standard refers to, and 

closely follows, the pre-existing suite of IEC standards 

(IEC 61400-2, 61400-11, and 61400-12-1). To be eligible 

for certification under the AWEA standard, a turbine must 

have a rotor swept area equal to or less than 200 m2 (in 

general, this covers turbines with a rated power 

approximately up to 65 kW) and generate electricity 

either for grid interconnection or battery charging. 

Turbine evaluation consists of both a mechanical/loads

design review and field testing.

In addition to testing by accredited test organizations, the 

AWEA standard allows testing by non-accredited test 

organizations and manufacturer self-testing. The testing 

entity conducts the testing mandated by the test standard.

The AWEA standard designates the SWCC or a 

Nationally Recognized Testing Laboratory (NRTL) as 

certification bodies. (3) At the time of this writing, the 

SWCC and one NRTL, Intertek, are accepting 

applications for certification to the AWEA Standard.

These certification bodies will conduct the

mechanical/loads design review, evaluate the test results, 

and grant (or withhold) certification.

Performance and safety certification have several goals 

and purposes. These include:
3

• Accurately characterize the turbine

• Provide consumers with objective information 

about SWT energy production and sound levels

• Verify that the turbine’s safety features function 

according to the manufacturer’s specifications. 

(This does not necessarily mean the turbine is 

safe.)

• Provide data needed to objectively determine 

turbine eligibility for state incentive programs.

The purpose of certification is less about declaring 

whether a given small wind turbine model is good or bad,

and more about accurately characterizing the performance 

of the turbine, so that consumers can make an apples-toapples comparison between different turbine models. 

Figure 1 outlines the SWT certification process and the 

various parties involved.

Fig. 1: SWT certification process.

Field testing for certification consists of four distinct tests. 

These tests are summarized in Table 1.

TABLE 1. SWT CERTIFICATION TESTS

Duration (IEC 61400-2)

• Investigates structural integrity and material 

degradation (corrosion, cracks, deformations); quality 

of environmental protection of the wind turbine; and 

the dynamic behavior of the turbine

• “Turbines must achieve an operational time fraction 

of at least 90% over a minimum of 2,500 operating 

hours (over a range of wind speeds) with no major 

failures, significant degradation of wind turbine 

components, or degradation in power production at 

comparable wind speeds.”(4) 

• No changes are allowed to the turbine configuration 

during this test

Power Performance (IEC 61400-12-1):

• Measures electrical output of the turbine vs. wind 

speed

• Estimates the turbine’s annual energy production

• Provides an independent check of the manufacturers’ 

claimed performance.

Safety and Function (IEC 61400-2): 

• Verifies that the wind turbine displays the behavior 

predicted in the design and that provisions relating to 

personnel safety are properly implemented. (5)

Acoustic Noise Emissions (IEC 61400-11): 

• Determines the turbine’s noise-emission 

characteristics

3. REGIONAL TEST CENTER (RTC) PROJECT

In the process of conducting years of SWT accredited IEC

testing under the Independent Testing project, NREL staff 

have gained in-depth experience and expertise in this 

field. A key component of DOE and NREL efforts to 

expand U.S.-based SWT certification testing is to share

this experience and expertise. Efforts began in 2008, with 

the organization and hosting the first annual SWT Testing 

Workshop at the NWTC by DOE and NREL. This 

workshop brought together experts and interested 

stakeholders to share experiences, knowledge, and best 

practices. DOE and NREL hosted successive SWT 

Testing Workshops in 2009 and 2010. Planning for the 

2011 workshop, which will be held in July in Amarillo, 

TX, is already underway.

In addition, NREL staff responds to numerous inquiries 

related to SWT certification and testing, from both 

domestic and international entities.

In further support of SWT certification testing, DOE and 

NREL initiated the Regional Test Center (RTC) project. 

This project established RTCs capable of testing small 

wind turbines to AWEA standard. DOE and NREL 
4

selected (through a competitive solicitation) four RTC 

partners: Windward Engineering (UT), Kansas State 

University & Colby Community College (KS), the 

Alternative Energy Institute (AEI) at West Texas 

Agricultural &Mining University (TX), and Intertek 

(NY). RTC partners were selected for their technical 

excellence and the quality of their business plans. DOE

and NREL are contributing funds and technical assistance 

(through subcontracts) for the RTCs to conduct 

certification testing for two SWTs at each RTC. DOE

and NREL intend to work closely with the RTCs, who 

will act as satellite testing organizations. The test reports 

for the turbines tested under this project will be placed in 

the public domain. These test reports, along with the test 

reports created under the IT program, provide valuable 

examples for the SWT testing community.

The assistance provided by DOE and NREL to the RTCs 

includes:

• Annual SWT Testing Workshop

• Assistance with site assessment

• Assistance with selection of test equipment to ensure 

compliance with IEC Standard

• Site visits (confirm general readiness, 

commissioning)

• Assistance with data acquisition, processing, and 

management

• Review test plan and commissioning plan

• Review of draft test reports

• Informal consulting and informational support

Figure 2 shows the locations of the RTC test sites. Table 

2 gives the current project status.

RTC

TABLE 2: TURBINES TO BE TESTED AS PART 

OF THE RTC PROJECT

Turbine 

Manufacturer 

and Model

Turbine 

Type

Turbine 

Rated 

Power

Intertek Fortis 

Montana

upwind 

HAWT

5 kW

Fortis

Alize

upwind 

HAWT

10 kW

KSU/CCC Enertech E13 downwind 

HAWT

45 kW

1SkyEnergy 

(Formerly 

ARI) 7.5

upwind 

HAWT

7.5 kW

AEI /

WTA&M

Potencia

Hummingbird

upwind 

HAWT

20 kW

Nikko Eolia 

NWG-1K

downwind 

HAWT

1 kW

Windward 

Engineering

Windspire 

Energy 

(Formerly 

Mariah) 

Windspire

VAWT 1.2 kW

Endurance 

S-343

upwind 

HAWT

5 kW

Fig. 2. RTC Test Site Locations
5

At the time of this writing, two turbines have been 

installed, four turbine installations are pending, and two 

turbine installations are on-hold awaiting redesign of the 

turbines.

The Independent Testing and RTC projects have resulted 

in numerous lessons learned. A key lesson is the need for 

careful site selection when choosing a SWT test site. 

Considerations for a wind turbine test site include:

• Wind resource

• Construction privileges

• Terrain

• Surrounding area

The primary consideration for a wind test site is the wind 

resource. There must be enough strong winds to complete 

tests in a reasonable time. For example, a duration test on 

a design class II turbine (designed for moderate to high 

winds) requires operation for 25 hours in winds of at least 

15.3 m/s. In order to complete the duration test in one 

year, a site with a Rayleigh wind resource distribution 

would need an average speed of greater than 6m/s. Thus, 

a site with low wind speeds could not complete a duration 

test on a turbine designed for high winds within one year.

An important site concern is access and privileges with 

regard to construction. Test sites require substantial 

infrastructure. Beyond the turbine and the met tower, 

there will probably be a test shed to house the grid 

interconnection and data acquisition equipment. There 

also may be conduit for power and data cables. Owning 

the land or having a long term agreement is important. 

Other items to consider for a testing site include potential 

zoning requirements, as a height restriction may severely 

limit testing, and the ability to arrange for a utility 

interconnection agreement.

Another aspect when considering a test site is the terrain. 

High correlations between the anemometer and the 

turbine are critical for power performance testing. The 

AWEA standard only allows relatively flat sites, without 

many obstructions, to avoid a site calibration. A site 

calibration ensures high correlations between 

measurements from an anemometer upwind of the turbine 

and what the turbine experiences at hub height.

Calibration generally is time and resource consuming.

The surrounding area is also important to a test site. 

Convenient access to the site is important for regular 

maintenance on turbines and test equipment, construction 

equipment access, and deliveries. An unobstructed 

upwind fetch is important, too. To ensure undisturbed 

inflow, AWEA power performance testing also does not 

allow another operating turbine within two diameters 

(using the larger turbine’s diameter). For AWEA power 

performance testing, obstacles out to 20 rotor diameters 

are assessed for their impact on the test. Acoustic testing 

requires relatively low background noise; airports, 

roadways, and heavy manufacturing sites are not easily 

compatible with acoustic testing.

Other lessons learned include:

• Length of Time to set up a Test Site: It has taken 

longer than expected to move from contract signing 

to the beginning of turbine testing. The RTC 

subcontracts were signed in July 2010. At the time of 

this writing, two, out of the eight turbines to be tested 

under the project, have been installed. In two of the 

RTC test site installations, the delays stem from

delays in gaining National Environmental Policy Act 

(NEPA) approvals.

• Premature Testing for Certification: Manufacturers 

are under tremendous pressure to get their products to 

market. This may tempt some manufacturers to start 

field testing for certification purposes earlier in the 

development process before all the bugs are worked 

out. This pressure should be resisted. Any 

significant change to the turbine requires that testing 

be restarted. This will add additional cost to the 

testing process.

• Involve the certification body early: It is the 

responsibility of the manufacturer to select both the 

field test site and the certification body. The 

certification body should be selected at the same 

time, or even prior, to the field test site, especially if 

the latter is not accredited. It is much easier and less 

costly for the certification body to deal with issues 

during testing rather than after the fact.

• Study the standard carefully: It is very easy for 

individuals and organizations to interpret the 

standards differently. For example, NREL 

participated in an international Power Performance

round robin with several other testing organizations. 

Each organization was given the same set of data to 

analyze. Analysis results varied dramatically 

between the organizations. A similar site assessment 

round robin (using identical site data) also yielded 

widely differing analysis results. Given the 

complexity of the standard, it is not surprising that 

different organizations interpret the standards 

differently. Testing organizations can mitigate this 

problem by participating in periodic round robins

with other testing organizations, and by participating 

in regular discussions and meetings with other test 

organizations and the certification bodies. 

• National Environmental Policy Act (NEPA) 

Approvals: While this only affects projects that 

receive federal funding, it is worth pointing out. 

While two (of four) RTC project sites received 

NEPA approvals within four months, the approval for 
6

the final site took seven months. There appear to be 

two reasons for this delay. First, some U.S. Fish & 

Wildlife Service (USFWS) officials appear to be

conflating large and small turbines, attributing the 

environmental effects of the former to the latter. 

Second, the body of literature covering the 

environmental effects of SWTs is small. In the 

absence of a large body of literature, some USFWS 

offices want proof that a proposed SWT installation 

will not harm wildlife, particularly birds. This is 

difficult to do given the aforementioned lack of 

literature on the subject. Those working on a SWT 

project that is subject to NEPA should understand the 

process and submit their paperwork early.

4. CONCLUSIONS

The U.S. SWT industry has recently created an SWT 

certification infrastructure. The purpose of this 

infrastructure is to encourage certification of small wind 

turbines, with the ultimate goal of maintaining consumer 

confidence in SWT technology. Key components of this 

infrastructure include the AWEA SWT standard and U.S.-

based certification bodies, such as the Small Wind 

Certification Council and Intertek. DOE and NREL have 

been working to transfer NREL’s SWT certification

testing expertise to the wider SWT testing community in

support of expanded certification field testing. DOE and 

NREL are providing general technical support to the SWT 

testing community, as well as, financial and enhanced 

technical support to NREL’s RTC partners.

5. REFERENCES

(1) http://www.awea.org/documents/2010_AWEA_Smal

l_Wind_Turbine_Global_Market_Study.pdf

(2) http://www.smallwindcertification.org/pdfs/small_wi

nd_test_orgs_SWCC.pdf

(3) AWEA Small Wind Turbine 

Performance and Safety Standard (AWEA 9.1 – 2009) 

Section 1.4.1 (Page 2)

(4) IEC 61400-2 Ed.2 Design requirements for small 

wind turbines, Section 9.4 (Page 99)

(5) IEC 61400-2 Ed.2 Design requirements for small 

wind turbines, Section 9.6 (Page 107)
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Establishment of Small Wind Regional Test Centers: Preprint

5a. CONTRACT NUMBER

DE-AC36-08GO28308

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6. AUTHOR(S)

T. Jimenez, T. Forsyth, A. Huskey, I. Mendoza, K. Sinclair, and 

J. Smith

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NREL/CP-5000-50806

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14. ABSTRACT (Maximum 200 Words)

To reduce certification testing costs, DOE/NREL is providing financial and technical assistance for an initial round of 

tests at four SWT test sites which were selected via a competitive solicitation. The four organizations selected are 

Windward Engineering (Utah), The Alternative Energy Institute at West Texas A&M (Texas), a consortium consisting 

of Kansas State University and Colby Community College (Kansas), and Intertek (New York). Each organization will 

test two small wind turbines as part of their respective subcontract with DOE/NREL. The testing results will be made 

publicly available. The goal is to establish a lower-cost U.S. small wind testing capability that will lead to increased 

SWT certification.

15. SUBJECT TERMS

small wind market; SWT; regional test centers; wind turbine testing; wind turbine; certification

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