Without question, wind is a tough renewable energy resource to tap. The best wind resource is high above the ground, requiring tall towers. And it’s an unforgiving resource, pounding on the equipment, which needs to be robust and requires regular maintenance. Building machines that can be productive while withstanding the rigors of life at tower top is no easy task. Add to this that uneducated customers want to keep costs down, and we end up with unrealistic expectations and market pressure for lower-quality equipment. What’s a potential wind energy lover to do?
First, learn enough about the resource at your site, system design, and the equipment available, so you can approach the project with your eyes wide open. Then be realistic about the cost. Buying “cheap” is not the best idea in most cases—but with wind energy systems, it’s a very bad idea indeed. The results of buying and installing on the cheap are nonproductive, short-lived systems.
David Laino’s article on wind physics in this issue will give you the science background on the wind resource, and it will help fend off misconceptions and scams that ignore the physical realities of capturing wind energy. This article gives you specifications on the viable wind turbines in the U.S. market today, with background on the companies. It’s a good start in researching what turbines might be best for you.
But this article is just a start—we recommend you seek information from a variety of sources. An experienced wind installer is a strong resource—consult with wind experts in person or at renewable energy conferences and workshops. And the Internet is a remarkable tool for finding out which turbines are actually working, and whether manufacturers are responsive and supportive.
The criteria for inclusion in Home Power’s wind turbine buyer’s guide are straightforward. We include all the turbines sized to serve the home-to-ranch scale wind market that have U.S. sales and support, have a track record and warranty, and have shown to experienced wind energy professionals that they are viable machines. There are other machines marketed in the United States—but the ones included here have stood the test of time, and/or have certification to appropriate standards.
This is a moving target in our small industry, where companies enter the market, then change hands, change product lines, or go bankrupt. It’s not our intention to slight any model or company, or to favor any. We are trying to apply our experience combined with some objective standards to give Home Power readers the best shot at capturing wind energy successfully.
The machines in the table are ordered by swept area/diameter, from smallest to largest. In this article, the companies are listed alphabetically by company name. Information was supplied by the manufacturers themselves when possible, or estimated from manufacturers’ marketing materials.
Bergey Windpower Co. (BWC) in Norman, Oklahoma, was founded in 1977 by Karl and Mike Bergey. The family-owned company is a worldwide supplier of small wind turbines in the 1 to 10 kW capacity range.
BWC wind turbines are known for their mechanical simplicity, robustness, and reliability. BWC has pioneered key industry technologies such as integrated direct-drive generators, passive controls, pultruded fiberglass blades, and custom airfoils, and offers the longest warranties in the wind industry. BWC directly manufactures its own components, and produces tilt-up and stationary guyed towers.
BWC has shipped more than 9,000 units since production began more than 30 years ago. President and CEO Mike Bergey identifies “reliability and low maintenance” as the special qualities of BWC’s turbine line.
(EWP) is among the world’s largest manufacturers of small- and medium-sized grid-tied wind turbines. Founded in 2007 and headquartered outside of Vancouver, Canada, the company has a global installed base of more than 600 turbines. EWP manufactures turbines in the 50 to 225 kW range in Canada and the U.K. This privately held company is 40% owned by its employees, who share a long-term commitment to the products and the people who invest in them.
The first EWP turbines were 5 kW S-series machines, designed by David Laino and Dean Davis of Windward. The company started growing rapidly when it purchased a larger machine from Energie-PGE of Quebec, re-engineered it, and began building the 50 kW E-3120—first for the United States in 2009, and then for the U.K. in 2010. Cofounder and principal engineer David Laino says, “We don’t merely assemble turbines, we try to deliver products that are designed to work with the people associated with them, whether it’s the owner, installer, neighbor, or investor.”
Founded in 2001, Eocycle Technologies has been a pioneer in developing permanent-magnet electric generator and motor solutions based on the transverse flux topology. Eocycle’s generators and motors are well-suited for a variety of low-speed, high-torque applications in diverse markets, including wind turbines. For the past several years, Eocycle has focused on developing and fabricating a 25 kW direct-drive wind turbine for grid-tied wind energy applications.
The privately owned company’s first three-bladed production unit went into service in January 2012, and there was a two-bladed version prototyped for almost two years. The company has produced 12 units to date. Eric Lafleur, director of sales and marketing, says that the machine offers a “combination of dependable energy production, minimal maintenance, and very quiet operation under all weather conditions.”
British Evance was founded in 1999 by four engineers who had developed a 300 kW turbine, and took what they had learned to develop the Iskra AT-5 5 kW turbine, which was refined to become the Evance R9000. Evance is a privately owned limited corporation with key investors.
Evance has installations in the United Kingdom and Europe, the United States, and Australasia, with a network of resellers and installers around the world. The first 5 kW turbine model was launched in 2004, with the R9000 (latest model) launched in 2009.
More than 1,800 Evance turbines have been installed, and the machine is available in on- and off-grid configurations. Darrin Russell, Evance’s support coordinator for the Americas, reports that “every turbine installed is still in the field operating, and that the patented reactive-pitch blades with a steel shaft running the entire length of the blades has resulted in zero blade failures.”
Gaia-Wind is a manufacturer of small wind turbines for moderate wind speed sites. Headquartered in Glasgow, Scotland, the company has grown from its original roots in Denmark to have representation throughout the U.K. and Europe, as well as Japan, Australia, Israel, the United States, and the South Pacific.
The privately held company produced its first wind turbine in 1993, and has more than 1,000 wind turbines installed. In Denmark, 77 Gaia-Wind turbines have been running for more than 10 years. As of 2014, the first turbine manufactured has been operational for 20 years.
Gaia-Wind operations manager Craig Jones says, “Our wind turbine is designed to generate high levels of energy from medium- and low- wind-speed sites, and is ideally suited to farms, rural homes, businesses, and organizations with significant land banks. The Gaia-Wind 133 turbine is the first U.K. product of this capacity to achieve the Microgeneration Certification Scheme (MCS) accreditation, an internationally recognized quality assurance standard.”
For its first seven years, Kestrel Renewable Energy (KRE) was operated from a small factory in Johannesburg, South Africa. All design and development was done by the original owner, James Carpy. In 2006, Eveready SA acquired the company. All Kestrels are completely manufactured in South Africa.
All of the models in Kestrel’s line have been produced since 2004 and were upgraded between 2007 and 2012 with investment from Eveready. In the last 15 years, more than 5,000 Kestrels have been put in service around the world. According to Carpy, the Kestrel line includes “patented, highly reliable blade pitch control; a sealed generator with proper thermal management, heavy-duty construction, robustness; and general high reliability.”
Kingspan Wind acquired some of the assets from former wind turbine manufacturer Proven Energy of Scotland, and has combined patented, high-performance technology with long-standing expertise in the energy sector. The company is part of Kingspan Environmental, specializing in renewable energy generation, water management, and pollution prevention.
Original Proven (now KW3 and KW6) wind turbines have been in service for more than 20 years. More than 4,500 turbines have been installed in more than 60 countries, and on each continent. Kingspan marketing specialist Beata Paciejuk reports that, “Kingspan Wind turbines offer maximum energy capture and provide consistent optimum performance even in the fiercest of storms, due to their patented blade hinge design.”
Northern Power Systems (NPS) started in 1974 as North Wind Power Co. In 1978, North Wind developed its HR2 2.2 kW wind turbine. This small wind turbine soon gained international market acceptance as one of the most rugged, high-reliability wind turbines available. More than 600 HR2 (and its successor, HR3) wind turbines were sold over approximately 20 years of production.
In 2008, the Vermont-based, privately held company was acquired by its current owners, who have invested more than $100 million into NPS’s products and technology. Since then, NPS has sold more than 400 of its 60 and 100 kW grid-tied wind turbines.
Jesse Wijnberg, NPS global marketing manager, says, “Originally developed in partnership with NASA and designed for remote and isolated sites, NPS turbines have an innovative, gearless direct-drive design; permanent-magnet generator; best-in-class reliability; and pleasing aesthetics.”
Sonkyo Energy produces the Windspot turbine and is a Spanish company that completed its first installation in 2009 and sold its first commercial units in mid-2010. The private corporation released three small wind turbine models—all three-blade, pitch-controlled, upwind, passive-yaw turbines. The company has more than 25 distributors, with offices and warehouses in Spain, Taiwan, and the United States. Turbine certifications are held for the United States, U.K., Japan, France, and Denmark. The company has installed about 1,000 wind turbines.
Sales manager Javier Vidal says, “Our products demonstrate simple efficiency and reliability at an affordable price. The greatest innovation in our wind turbines is a new, patented, variable pitch system. This straightforward design and the use of high-quality materials, such as stainless steel, anodized aluminum, and bronze, result in a smooth working mechanism even in the gustiest of situations.”
Ventera Wind was founded by the late Elliot Bayly, a legend in the small wind world who designed turbines under the Whirlwind and Whisper brands. Bayly’s Ventera technology was purchased by North Coast Wind & Power, a privately held Ohio-based company, and Ventera Wind was formed in September 2011. Unlike most acquisitions in this industry, Ventera Wind has chosen to honor all previous warranties of Ventera Energy.
Ventera’s original 10 kW wind turbine went into service in 2007. The new company modified the original version on several occasions to improve performance and durability, and to reduce noise. More than 200 turbines were in service as of December 2013.
Ventera Wind touts their turbines as being environmentally friendly due to their lighter weight and use of recycled metal. President Joseph Woods says, “All of the unneeded weight is designed out of the turbine; the main frame is made with 100% recycled aluminum; and there is some recycled material in the blades. Ventera Wind has done significant upgrades to the wind turbine. Every warranty claim is reviewed, with our asking, ‘What can we do so this never happens again?’ This has led us to our current model, which we predict to have a life expectancy of up to 30 years.”
The turbines in the table are sorted by size. The information in the table was supplied by the manufacturers, and we encourage buyers to confirm claims with information from impartial users and others who have direct, real-world experience.
Name & website are listed so you can explore their published information, and we encourage you to do so.
Rotor swept area in square feet lets you compare turbine collector sizes. This is the disk described by the spinning rotor—the area that intercepts the wind and collects energy. While there is wide variation in rotor effectiveness and efficiency and the gear behind them, the swept area is a great place to start when considering wind turbines. It’s a reasonable comparative measure between turbines.
Rotor diameter is also handy for describing turbine size, though it’s not as intuitive for comparison’s sake. Dividing diameter in half to get the radius, the basic formula of pi × radius2 calculates swept area from rotor diameter.
Tower-top weight may indicate the robustness of the turbine, and also is necessary information for installation equipment and infrastructure. Heavier turbines are typically more durable.
Certification indicates which certification(s) the turbine has, or if certification is in process. See the “Why Certification is Important” sidebar for more information.
AWEA rated power is in kW at 11 meters per second (25 mph). Note that this is power at only one point on the power curve. Comparisons between machines at any one point on the curve are not apples to apples. More useful are energy (kilowatt-hours) measurements at the average wind speed at tower top at your site.
AWEA rated AEO (annual energy output) in kWh at a 5 meters per second (11 mph) average wind speed. This is useful information for comparing, but is only at one average wind speed, while residential wind sites may range between average wind speeds of 7 to 13.
Estimated AEO is predicted for 8–14 mph average wind speeds. These can give you an idea of what energy production to expect at your site, assuming:
This section of the table is perhaps the most useful because it can help you be realistic about what a wind turbine might produce at your site. Rated power (watts) or power at any specific point on the turbines’ power curves cannot give you this information.
Source of AEO is the source of the annual energy output data. The sources include data derived from the field-verified energy curves on the certified turbines—i.e., Certified Energy Curve; manufacturer-supplied data, such as from Windcad, Bergey’s proprietary, Excel-based spreadsheet calculator; and the use of an AEO calculator, depending on the turbine.
Rpm is the turbine’s rotational speed at rated power. This may indicate two important aspects of the wind turbine’s performance. A lower speed for a similarly sized rotor usually translates into less wear and tear on the turbine, and less noise.
Governing system is the type of overspeed control. Turbines should have a method to protect themselves in high winds. Because wind power increases with the cube of wind velocity, enormous forces bear on a turbine in high winds. The top end of an accurate power curve can show you how well a machine protects itself. At regulation wind speed, the power curve of a furling machine will show a significant drop as the turbine turns itself out of the wind and slows down. In high winds, a machine with active blade pitching will show a flat line on the power curve, with little or no power reduction. Turbines with auto shutdown are designed to come to a complete stop.
Governing wind speed (mph) is the speed at which the machine is fully governed. Conservative designers choose to govern at lower speeds, knowing that long-term reliability is more important than capturing rare high winds.
Grid-tie only (GTO) or battery-based (BB) indicates whether the machines are designed for direct batteryless connection to the utility or are for battery charging. Battery-based systems can also be utility-intertied, but besides needing batteries, may need additional equipment. GTO machines will not operate without a live utility connection.
Cost is shown in U.S. dollars, but doesn’t include shipping. Prices include various controls and sometimes even towers or more. Inquire with manufacturers for details of what you’ll get for your dollars.
Warranty details should be carefully scrutinized to see what is covered, and what the fine print reveals.
Too many wind energy system owners end up disappointed because of poor research, unrealistic expectations, and less-than-robust design and installation. Here’s our final advice, distilled from decades of experience installing, living with, and teaching about wind energy—and commiserating with other users:
Don’t buy cheap! Wind turbines should last at least a few decades, but they live and work in a severe environment—and you can’t just slap a bandage on them when they break. Get the very best you can afford.
Understand the resource. Get measurements or accurate predictions of the tower-top average wind speed on your site. Without this, you’ll only be able to guess how much energy a wind turbine might produce.
Go with tried and true. Our combined (40+ years) of experience in the small wind industry has shown us that people, products, and companies come and go. It’s hard enough to get reliable products and excellent support from the experienced companies in the industry. Expecting magic from a new designer or manufacturer is a recipe for disappointment or disaster.
Install it well. Even the best equipment from the best companies will be compromised if not installed properly. Cutting corners because of cost, convenience, or someone’s “better idea” can cripple a “good” system.
Maintain it! One myth about small wind is that there are products that you can put up and then ignore. It’s impossible to find such a beast. All wind turbines require regular inspection and maintenance. It may be only a loose bolt that you or the technician finds, but tightening it could make the difference between another productive year and a catastrophic failure. If you don’t visit your wind turbine periodically, it will eventually come down to visit you.
Enjoy! We have wind turbines because they make electricity. But we may have other motivations too, including clean energy goals, a preference for local energy and independence, and just plain enjoyment. If you come to small wind with a lighthearted, forgiving attitude, you will ride out the inevitable challenges more gently, and appreciate the benefits even more.
Ian Woofenden lives with and talks about small wind from his home in Washington’s San Juan Islands. He is author of Wind Power for Dummies. Along with article coauthor Roy Butler and four others, he is one of the owners and coordinators of The Small Wind Conference, the premier annual event for the industry.
Roy Butler is the owner of Four Winds Renewable Energy. His home and business have been off-grid, powered by wind and solar electricity, since 1997. Roy is active in the small wind industry, sitting on a variety of boards and providing training for several organizations.
AWEA standards page • bit.ly/WindStandards
Intertek • www.intertek.com/wind/small
ITAC • bit.ly/ITACturbines • Unified list of wind turbines
Microgeneration Certification Scheme • microgenerationcertification.org
Small Wind Certification Council • smallwindcertification.org
TUV • bit.ly/TUVnelCert