Small Ducted Turbines on the March in New York

By Paul Gipe

On 14 June the Adirondack Explorer reported that two small ducted wind turbines have been installed in the Adirondack Mountains of New York State. In Harnessing energy with small blades, the on-line journal wrote that Asgaard Farm & Dairy in AuSable Forks had installed one Ducted Wind Turbine in 2020 and Wild Orchard Farm in Essex had installed another in 2022. Later this year the company will install another unit on a lowland wooded site at Wild Center in Tupper Lake, New York.

Ducted Wind Turbines is the brain child of Dr. Ken Visser and is a spin off from Clarkson University in Pottsdam, New York.

In Visser’s most recent publication (Real-world development challenges of the Clarkson University 3 meter ducted wind turbine), he reports that “the turbine demonstrated Cpt efficiencies, based on the duct area, of up to 0.45.” The journal article goes on to say that testing “demonstrates the unit could produce Cpt values in the range of 0.40 – 0.45” during one day of testing and similar results the following day.

Note: The duct diameter is 3.7 meters. The 3 meters refers to the rotor diameter. The key parameter in a ducted wind turbine is the duct diameter. Dr. Visser explains that the Cpt is the coefficient of performance of the turbine–not the duct.

These coefficients of performance are comparable to high-performance conventional wind turbines and are well within the Betz Limit. Yet they are less than that from the last major ducted wind turbine test program for a much larger wind turbine.

In 2010 Intertek tested Ogin’s 20-meter diameter ducted wind turbine to international standards using the method-of-bins. Intertek found that Ogin’s device achieved a Cp (Coefficient of Performance) of 0.48 at average wind speeds from 9.5 m/s (21 mph) through 10.5 m/s (24 mph).

Power performance testing to international standards requires weeks if not months of testing at windy sites to gather statistically significant data.

Ducted Wind Turbines does not have certification from the Small Wind Turbine Certification Council nor does it have an application in process. There is no mention of certification or certification in process on the Ducted Wind Turbine’s web site. Intertek and other companies also provide certification but information on products undergoing certification is not public. Ducted Wind Turbines’ web site states that they are seeking certification. They do not explain what kind of certification they would pursue or who they would pursue it with.

Note: Dr Visser has responded to this post on LinkedIn.

In his recent journal article, Visser importantly referenced the duct area and not the rotor diameter in his description. Past ducted turbine ventures have often limited comparisons to the rotor diameter, giving the appearance of superior performance over conventional wind turbines without a duct or shroud. However, the company’s web site declares that “DWT’s wind turbine produces more than 2X the energy of a conventional open bladed turbine of the same size” without any substantiation.

Ducted Wind Turbines installed a unit at the State University of New York in Potsdam, New York and another unit on a factory rooftop in Rochester, New York in 2021.

Shrouded wind turbines were last installed on rooftops by Honeywell’s Windtronics and Renewable Devices’ Swift more than a decade ago. Both firms failed in part because rooftop installations seldom perform as expected. Some rooftop installations used more energy than they produced.

Ducted Wind Turbine installed one of their test units on the roof of Clarkson University’s Technology Advancement Center. The rooftop turbine has generated 34 kWh since it was installed in the spring of 2021. You can watch it in real time on the University’s web site.