A rare, unretouched aerial photo of an offshore windfarm in Denmark clearly shows how turbulence generated by large turbine rotors continues to build with each successive row of turbines.
3D color map of wake velocity from a CFD study of a counter-rotating quad wind turbine array with 32 meter diameter rotors. Wake convergence and flow acceleration are indicated by the red areas. Theoretically, when the wakes converge, the energy of the counter rotating swirls should be converted into other forms of energy, including linear kinetic energy and a small amount of heat. The amber color represents free stream velocity of 12 m/s. (Click on image to enlarge)
Simplified 3D computer model of wake convergence and swirl cancellation behind our 1.0 meter scale model test unit. Wind direction is from left to right and the colors of the wakes show the direction of the wake swirl rotation. Wake convergence is evidently caused by differential viscous energy transfer from the energetic free stream flow. When the wakes converge, swirl will be cancelled out by the counter-rotation and rapid remixing with the free stream flow will occur, restoring the wake to free stream velocity.
News @ Greenward
10 January, 2010
Michael G. Kelly elected to the Board of Directors
Greenward's shareholders have elected Michael G. Kelly to the Board of Directors at the annual meeting.
Widely considered to be one of the wind industry's top development experts, Kelly got his start in the industry in 1981, and his experience includes wind energy development and operation, wind turbine manufacturing, rotor blade fabrication, and field service & maintenance.. He is currently the Vice President of Operations at Spinnaker Energy, a developer of utility-scale wind, solar, and transmission line projects. He was formerly with Horizon Wind, where he served as Director of Operations. Previously, Kelly held positions at Enron Wind (now part of GE), Italian Vento Power, Cannon Energy, Difko Administration (now known as enXco), Zond Systems, Inc, and Wind Power Systems, Inc. He is also on the Board of Directors of Medford, Oregon based UpWind Solutions Inc., an operations and maintenance (O&M) service provider for wind energy projects.
6 June, 2009
The print edition of WindTech International is featuring an article on our ISO-e tower technology entitled "A Tougher Tower at a Lower Price? There is also a short introduction in their online edition here
4 May, 2009
Greenward's CTO Presented Paper on Large Improvements in Wind Resource Utilization at the "Clean Technology Conference and Expo 2009"
This was the first presentation of the results of Greenward's investigation into the "Wake Convergence and Swirl Cancellation" phenomenon. (see "News" from 26 January, 2009 below) A copy of the presentation is available here
20 April, 2009
Introducing ISO-e wind turbine tower technology
This is a revolutionary new tower design and manufacturing process that will reduce the structural steel content by at least 50%, resulting in a large decrease in manufacturing cost, and should make the tower virtually “typhoon-proof” as well.Read more>
26 January, 2009
Counter Rotating Quad Arrays May Hold the Answer to Serious Wind Turbine Wake Turbulence Problems
A Computational Fluid Dynamics (CFD) study and controlled velocity testing of a 1.0 meter scale model counter-rotating quad array have provided strong support for our “Wake Convergence and Swirl Cancellation” hypothesis (WCSC). We are now starting work the third phase of this program, which will include wind tunnel testing of the scale model and the investigation of potential benefits, including:
Large improvements in the wind resource utilization factor. This is expressed as square meters of rotor disk area per square kilometer of wind resource. Our test results are indicating that this could amount to an improvement in the wind resource utilization factor of between 6 to 16 times with our “Quad Array”” concept (above left), depending on the setback requirements - the larger the setback the greater the improvement.
Preservation of the wind resource and protection of certain species of wildlife: The aerial photo of the offshore windfarm was taken under ideal atmospheric conditions for the formation of low level clouds, providing a dramatic image of the turbulent wakes left behind very large wind turbines. Turbines operating in high turbulence flow can experience accelerated fatigue damage to all components in the primary load path. This can result in a large reduction is service life. In the offshore environment, there are no terrain features to break up these turbulent wakes, and they persist for very long distances, and are reinforced in an additive manner by each row of turbines. The intensity of this turbulence is proportional to rotor torque, which is roughly proportional to the cube of the rotor diameter. Bats are equipped with a type of sonar and rarely strike physical objects, however, they are vulnerable to “barotrauma” that may result from flying through the low-pressure cores of wind turbine wake swirl. WCSC may have the potential to address this issue, and this possibility needs to be fully investigated. Read more about this here.
We are now seeking funding to continue work on this program. Please direct inquiries to:
