Mini-turbines spell hope for building-integrated wind power
Until recently, the only viable option for harvesting wind for power was to erect one of those colossal propellers commonly found on rural wind farms.
Several building owners have successfully integrated industrial-sized wind propellers to help power their facilities. In early 2005, St. Louis-based general contractor Alberici installed a 125-foot-tall, 65kW wind turbine at its new headquarters to provide about 20% of the 100,000-sf building’s energy. Similarly, a 120-foot-tall, 250kW wind turbine installed in late 2002 at Harbec Plastics’ factory in Ontario, N.Y., provides about a quarter of the electricity needed to operate the building and the equipment it houses.
But these cases are few and far between. Besides the shockingly high upfront costs and ongoing maintenance expenses associated with owning one of these monstrous propeller systems, the shear size of the units limits the applications for on-site building power generation, especially in urban environments. Even small propeller systems cannot be placed on rooftops (the vibration and turbulence inherent with propellers can disturb building operations and occupants), and they require open expanses and extreme heights for optimum performance. Norman, Okla.-based Bergey WindPower, for instance, recommends an acre of open space and at least a 60-foot-tall tower for its 10kW propeller system—hardly ideal for a tight, urban site.
A Building Team in Chicago is experimenting with a new type of wind turbine specifically designed for dense urban and suburban environments. The cylindrically shaped units, each weighing less than 250 pounds and just 5x10 feet in size, will be mounted on the roof of the Ford Calumet Environmental Center, planned along Lake Calumet on Chicago’s Southeast side. Developed by University of Illinois-Chicago professor William Becker and marketed by his company, Aerotecture Ltd., Park Forest, Ill., the 1.5kW turbines produce energy at wind speeds as low as 6 mph and continue generating in winds exceeding 70 mph. The innovative helical-blade design minimizes noise and vibration and harnesses the “chaotic, turbulent winds” common in dense urban environments, says Becker.
“Wind power applications for buildings require that because winds tend to whip around buildings,” says Becker. “These machines really ‘enjoy’ variable, gusting winds.” Because the units are small and virtually silent, they can be placed almost anywhere atop or within a building, at heights as low as 20 feet. The steel frame permits the units to be situated in any direction—horizontally, upright, and diagonally—and they can even be stacked. At the Ford Calumet Environmental Center, which is set to break ground in November 2006, 12 units will be placed vertically atop cone-shaped ventilation stacks on the rooftop, according to Jeanne Gang, AIA, principal and founder of Studio/Gang Architects, Chicago, design architect on the project.
Gang says the unit’s low profile and inherent safety features make the technology ideal for the building, which is being designed to achieve a LEED Platinum rating. “We needed something that was bird-safe, because the building is located in a migratory bird path, and the site is habitat for all types of wildlife,” says Gang. Each unit will be wrapped with a metal mesh screen to prevent birds and other wildlife from coming into contact with the blades. Even if the screen is breached, the blades rotate at a much slower rate than traditional propeller systems, minimizing harm to animals.
Sachin Anand, PE, LEED, lead engineer on the project with Chicago-based consulting engineer CCJM Engineers, says the wind turbines will be tied directly to ventilation fans inside each stack. In the warm months, the heated air will collect in the 12 “chimneys” and will be extracted out of the building by the ventilation fans. In the winter, the ventilation stacks will be closed and the fans reversed to direct the warm air back down into the interior spaces. “Instead of using an intermediate mechanism to convert wind into energy to power the ventilation fans, the turbines will be coupled directly to the fan,” says Anand. He says this approach will greatly reduce electrical demands for air circulation for the building. The Building Team is considering using the wind turbines to generate power for the building at times when the ventilation fans are not needed, but Anand says this “integrated” approach may prove too costly. “My gut feeling is that we probably won’t use the systems for power generation,” he says. Regardless, Anand sees much potential in the technology for building-integrated applications. “These turbines are not as expensive as wind-farm propeller systems, and they’re much more quiet,” says Anand.
As for the cost, Becker says individual units go for $5,000-$10,000, depending on the features, but he expects the costs to dip much lower as production ramps up.