An urban experiment in renewable energy

Monday, February 15th, 2010

Location: Sloan Valve Company, 10500 Seymour Ave., Franklin Park, IL

Developer: Aerotecture

Builder/General Contractor (for Sloan Valve Site): Englewood Construction

By William Olson

The Chicago region has been a natural laboratory of sorts for sustainable design, having earned itself the moniker of the “Green Roofs City” and a top rating among US cities for its number of LEED-certified buildings.

Now with a number of wind turbines sited in the city and its neighboring suburbs, a local developer looks to inspire new meaning into Chicago’s reputation as “The Windy City”.

Atop the US Social Security Administration building sits a prototype wind system developed by Aerotecture, a Chicago-based company focused on urban wind power. To gauge the performance of the system, the company has installed a monitoring system that will trace its performance for the span of a year, determining at what times and under what conditions optimal power generation occurs.

What is more, Aerotecture is carrying out a parallel experiment at Sloan Valve’s corporate headquarters in neighboring Franklin Park, Ill., which will further refine their understanding of the potential for the technology given the two sites’ different heights and variability in wind speeds.

Monitoring aside, efficiently harnessing “urban junk wind” has proved to be an elusive target, and for material cause.

“There is a barrier of physics,” explains Ron Stimmel, Legislative Affairs and Small Systems manager of the American Wind Energy Association (AWEA).

In addition to significantly lower average speeds in urban areas, the wind resources around buildings Stimmel explains, “tend to be unpredictable and very turbulent.”

Thus, it’s not merely the challenge of leveraging weaker urban winds that hinders viable wind development. The turbulence, gusts and other natural risks in a city—such as lightning—add a some perceived risk in densely populated environments.

But Bil Becker, Aerotecture’s founder and CEO, insists Aerotecture’s patented technology has vitiated most risks. The key to his claim is in its design, which would impress even Watson and Crick: Helical geometry. The shape of the rotors, Becker insists, essentially limits the maximum speed at which the blades will spin, creating an inherently self-regulated system. Brakes have been installed in his system, should disaster strike, but he maintains that, “mechanical failure is impossible.”

With a chunk of the risk in urban wind turbines attenuated, there still remains the issue of wind speed. Systems tend to perform best in open, windy corridors as total power generation equates roughly to a cubic function of wind speed. This means that lower-speed winds return a disproportionately lesser generative capacity than higher winds. Kevin Borgia, executive director of the Illinois Wind Energy Association, is particularly skeptical of the potential of Aerotecture and other small wind systems in urban sites. He is hopeful that they can someday be viable, but cautions that, “because of wind conditions and sheer created by buildings, current wind technologies are more suitable for rural environments.”

Borgia admits the extent of urban pioneering in wind technologies is underway, but holds that, “a few more years of engineering are needed before someone gets it right.”

Still, Becker is moving forward. And to make up for some of the slack urban wind engenders, he’s paired his turbine with solar panels at the suburban site, describing the system as a hybrid. The idea is to soak up the sun during the warmer and less breezy months, and harness the wind through the seasons of lesser light.

“We’d like to see people not have to pay a utility bill,” Becker states, adding, “Our goal is to get to zero-electric buildings.”

The hybrid concept installed at Sloan is roughly dependent on both sources of energy, each of the two turbines measuring approximately 2,500 watts in capacity, with the solar panels at 2,100 watts. The turbines stand roughly 12 feet in height and spread 7 feet in width. Englewood Construction served as the general contractor and managed the structural reinforcements to the roof for the project, which entailed boring into it and employing steel I-beams for support.

And it’s not just at Sloan’s headquarters and the SSA building that Aerotecture’s turbines are cranking up new power in the region. Elsewhere around the city, the helical wonder is pumping new swagger into Chicago’s windy atavism, including installations at Sankofa House, Pepsico-Chicago, the colossal Greenworks Wind Tower and, among others, the Helmut Jahn-designed Mercy Lakefront SRO.

By August of this year, all the data at the Sloan and SSA sites will be captured and, pending analysis, Mr. Becker intends to publish a ‘white paper’ disclosure as part of the experiment’s cost-benefit analysis—a document sure to become a new tool of sustainable urban development.

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