With the recent push to move away from our dependence on oil, and into an era of energy generated from clean and renewable sources and an added 30% tax credit for more incentive, many misconceptions have been generated about wind energy and turbines.
For starters though they are usually very beautiful when integrated well with the building design, they often do not produce as much power as advertised because they can't overcome the major problem of "turbulent airflow." For turbines to work optimally, they need strong "laminar winds," in which all the wind flows from one direction but on top of tall buildings, where they are often mounted, the winds come from many different directions. Bob Thresher, director of the National Wind Technology Center at the National Renewable Energy Laboratory (NREL) in Golden, Colorado, explains that as wind flow comes over the edge of a roof or around a corner, it separates into many different streams.
Ron Stimmel, wind technology expert at the American Wind Energy Association (AWEA), added to this thought saying that, this turbulent flow confuses a wind turbine, affecting its performance. “Even if it feels really windy on top of a building, it’s probably more turbulent wind than steady wind,” he said.
Another issue is that of noise and vibration, contrary to common assumptions that turbines are generally quiet. The vertical-axis machines indeed are much more quiet than rotator blades but the vibration they cause on non-concrete buildings is generally detrimental to the general comfort of the occupants.
In one of the only extensive surveys of actual performance of building-integrated wind turbines the Warwick Wind Trials Project, the only turbines able to generate close to their projected electricity output were mounted on high-rise apartment buildings. And these wind turbines remained
switched off throughout most of the test period because of complaints from the residents a
bout noise. -
www.buildinggreen.com, The-Folly of Building Integrated WindAnother problem is that of the actual measured performance Vs the projected measured performance of the turbine. Manufacturers are constantly guilty of showing slightly elevated power curves for their products than what they can actually achieve which makes the process of figuring how much energy a set of turbines on our building is going to generate. The usually leaves designers and clients very disappointed in the end. For example, the vertical axis turbine (left) is nominally rated at 10kw but tests by Madison Gas and Electric showed that it has so far never produced more than 600 watts even though it is installed at a height that might be typical for a rooftop application.
So although they look nicer and sleeker as the years go by and they make a very bold and energy efficient statement for the building design, they do not help much practically for what they are meant to do. Of course if you are looking for a sculptural element to enhance a piece of your building, wind turbines do the job well and you might as well get something out of them but keep in mind that it will be minimal.
Images obtained from: www.buildinggreen.com
Article info obtained from: Alex Wilson's "The Folly of Building-Integrated Wind"
