Page 38 - North American Clean Energy July August 2015

wind power

Rooftop Wind Power in Cities is Here

by Bil Becker

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IN 2003, JUST TWELVE PIONEERING RENEWABLE ENERGY YEARS AGO, multiple wind
energy innovators in the USA and worldwide, all seemed to see the coming conluence

of technical breakthroughs that could bring on a revolution in electric wind power
technology. hat conluence continues today with little media notice. Primarily in
U.S. cities like Chicago, New York City, Los Angeles, and San Francisco, wind power
experimenters recognized a platform from which they could build and launch the next

generation in Vertical-Axis Wind Turbine (VAWT) electric power technology.

• Powerful new ‘rare earth super magnets’ became available and were helping build 96%
eicient generators, alternators and electric motors;

• Design software for the engineering needed to ‘custom build’ powerful, high-eiciency,
yet low RPM generators and alternators had also arrived and were being successfully
applied;
Figure 1: Correct S
• Grid-Interactive electric power inverters were being manufactured in Germany and Italy Rotor Graph, 1973

that could hook up solar and small wind turbines to the utility grid without the need for
batteries; and
• Quiet, low-RPM vertical-axis machines were getting urban/suburban building permits
where noisier horizontal-axis ‘propeller-type’ wind electric turbines (HAWTs) were not.

Wind experimenters, worldwide, had discovered that vertical-axis wind turbines were
quite diferent from horizontal-axis (propeller-type) wind turbines due greatly to the
research done by Gary Johnson, PhD.; a professor of electrical engineering at Kansas

State University (KSU). Under a 1972 research grant from the U.S. Energy Research &
Development Administration (ERDA); the predecessor to the U.S. Dept. of Energy, Dr.
Gary Johnson did testing, analysis, and power graphs for the various wind machines in
operation at the time, including electric generators and water-pumping machines. His

graphs of eiciency (Figure 1) helped establish the status of the diferent wind turbine
technologies.

A vital publication error
It is important to note the measured eiciencies of the vertical-axis wind turbines tested Figure 2: Incorrect S
by Dr. Gary Johnson in 1972 (Figure 1). he Savonius rotor (S-type VAWT) measured at Rotor Graph, 1974
30% eiciency peak, and the Darrieus rotor (Blade-Type VAWT) measured at over 35%

eiciency peak. High-speed, two-blade propeller-type wind turbines measured over 45%
eiciency peak, and the traditional American multi-blade type “water pumper” barely
reached a 15% eiciency peak. But, when ERDA sent this chart out for publication, a
major change had been made! A graphic artist had mistakenly made a shift in labels! or hoop-bladed Darrieus rotors from the 1970s. All this was happening in conjunction

(Figure 2) Now, the more ineicient American multi-blade rotor was labelled at 30% peak with the electronic breakthroughs occurring with the super magnet generators and super-
eiciency and the Savonius rotor was shown to be only 15% eicient; switched from Dr. eicient, grid-tied power inverters. By 2003, new VAWT patents were being iled and the
Johnson’s multi-blade rotor curve. In spite of Dr. Johnson’s many phone calls and letters growth in VAWT startups had begun worldwide.
to ERDA, and to the many publishers of this wrongly labelled graph, the wrong power

curves stuck, creating a sense of ineicient ‘S-type’ rotors, which remains to this day.
Acceptance soon came
By 2005, many prop-type HAWT manufacturers began to complain about the unreal
The results were the proof
performance of the new VAWT machines and showed the public the wrongly labelled ERDA
But, wind power experimenters at Northwestern University were building and now graphs as evidence. But as more and more VAWTs of diferent kinds found acceptance with

getting 30% (not 15%) eiciencies from typical ‘S-shaped’ rotors and nearly 35%
their 30% and better power production and capacity to receive building permits in suburbs
peak eiciencies when the ‘S’ proile had been twisted into a helix. In Holland, at Delft and cities where HAWTs were banned, the tide began to turn. Why did these VAWTs
University of Technology, a 3-bladed Darrieus rotor with twisted helical blades got close receive better acceptance in suburbs and cities?
to 40% peak eiciency and was starting up in slower winds than previous straight-bladed

38 JULY/AUGUST 2015 nacleanenergy.com