Small Wind Turbines
Fulfill Their Promises


Now that the Small Wind Certification Council (SWCC) has given green lights to two small wind turbines with more approvals coming soon, the whirling blades may start popping up on lawns and fields across the U.S., powering homes, farms, and small businesses.

A standard national certification process is expected to fuel sales because it facilitates rebates and incentives offered to end users. Some of these from government bodies and utility companies can amount to paying for half of the initial cost. Installation of a system using a larger size turbine [still in the "small" classification] can be in the $60,000 range.

Funded by the U.S. Department of Energy and New York State Energy Research & Development Authority as well as by fees charged to applicants, the certification organization was set up by the industry in 2006 as an independent testing authority to confirm that a turbine has been tested and designed according to the requirements of the American Wind Energy Association standard. Certification, which takes at least a year, includes an evaluation of the turbine design and six months of field testing for performance, sound, safety and durability.

The council also issues consumer labels that allows for easy comparison among different manufacturers and models.

Council Reviews

Brent Summerville, the council's technical director, says the turbines with applications for certification have an operating record. For those the process takes about a year to complete while those that are new often take closer to 18 months.

"[That's because] manufacturers of the new turbines learn more about the design through the certification process and will often do some design improvements," he says.

In addition to the field testing, the council reviews the engineering design file. "It's a fairly complicated mechanical engineering task involving aerodynamics of the blades that work under extreme conditions in the wind. Twenty years of operating in the wind leads to fatigue and corrosion. [We do] a structural analysis of these components and the overall design [to make sure it is] most efficient in converting wind to electricity and tough enough to stand up to the conditions."

Certification is becoming increasingly important because several government and utility programs offering incentives to those installing small wind turbines require it for eligibility, and many, if not all, others are expected to mandate certification soon.

Southwest Windpower Skystream 3.7 is one of the first to obtain certification. Image source:

The industry is in transition, Summerville says. "Everyone wants certified turbines but there aren't that many that have gone through the process, and agencies that want to require certification are still waiting and deciding when to require it. In the U.K., it's mandatory to have a certified turbine to receive any rebates, and that day is coming soon in the U.S." Without the incentives, it's difficult to find customers willing to invest tens of thousands of dollars, he indicated.

The first two certified are the Bergey Windpower Excel 10 and the Southwest Windpower Skystream 3.7. As of July 2012, of the 29 other turbine models seeking certification, 11 are under test and five have been granted conditional temporary certification based on certification from a U.K.'s certification organization.

"The Bergey Windpower Excel has been around since the 1980s and has seen many incremental improvements," says Summerville, "so it didn't have that many issues."

Simulating Turbines

Some of the work being done to test blades for large turbines may also benefit small turbines. Dr. Fernando Ponta, an associate professor in the Department of Mechanical Engineering, Engineering Mechanics, at Michigan Technological University, is developing cost-effective ways to test innovative new wind turbine technologies. The National Science Foundation-funded research involves a virtual test environment in which innovative prototype blades can be tested at "real" full-scale conditions by combining two advanced numerical models implemented in a parallel high-performance computing supercomputer platform.

In principle, this model can be used to simulate turbines of any size, including small, says Dr. Ponta, although "the full potential of its contribution will be in dealing with the extreme design challenges of next-generation super-turbines."

Nancy Giges is an independent writer.

Everyone wants certified turbines but there aren’t that many that have gone through the process, and agencies that want to require certification are still waiting and deciding when to require it.

Brent Summerville, technical director, Small Wind Certification Council


September 2012

by Nancy Giges,