Wind power beats PVs for contractor

August 11, 2010

In a move unusual for its scope, a private owner has installed a 65kW wind turbine to reduce its dependence on utility-supplied electricity. The turbine is mounted atop a 125-foot-tall pole beside the new headquarters of general contractor Alberici in St. Louis.

Alberici recently moved into the 100,000-sf facility, a renovated 50-year-old steel fabrication warehouse that abounds with sustainable features. Mackey Mitchell Architects of St. Louis was the project's architect.

From the outset, the goal was to achieve Platinum level accreditation, the highest of the U.S. Green Building Council's LEED ratings, for which the building will be submitted, according to Thomas Taylor, Alberici's VP of special projects.

Alberici first looked at using a solar photovoltaic system to provide supplemental electricity, but later opted for wind power. "The same amount invested in photovoltaics probably would not harvest enough energy to capitalize on the renewable energy credits," Taylor says.

Alberici considered a residential-scale wind turbine rated at only 10 kW, but found it would have produced less than 5% of the building's total energy needs. The 65 kW unit, with a rotor diameter of 54 feet, will provide a credit for producing 20% of the building's energy requirements, says Taylor. The 20-year-old equipment was salvaged from a wind farm in California.

"The wind turbine worked out better for our payback model," Taylor says. "It was more beneficial than other renewable technologies." Because it is used equipment, Alberici will be able to claim a LEED reuse credit.

Chris Schaffner, a building systems sustainable engineer with the Cambridge, Mass., office of M/E engineer Arup, says, "Wind is on the edge of economic feasibility, whereas photovoltaics, without the benefit of subsidies, are difficult to justify economically for a private developer."

An exception might be a location that receives virtually no wind, or one that has abundant solar availability. "Solar makes more sense in Arizona than in Massachusetts," Schaffner says.

Alberici conducted a review of wind-speed data at nearby Lambert International Airport which indicated that in the past 15 years, area wind speeds typically were sufficient to generate current for 11 months of the year. Alberici's unit should provide about 70,000 kW hours of electricity annually.

Since windiness is unpredictable, Alberici's goal is to produce "green" power without tying its production to particular time periods. Even at night, when the building is unoccupied, it will be able to use the maximum amount of power that the turbine can generate. The turbine needs a wind speed of eight mph to get started and a minimum of 32 mph to generate its maximum output of 65 kW.

Missouri is considered a borderline area for wind-produced electricity, with payback periods ranging from more than 10 years to more than 20 years, according to Travis Crestwell, president of Ozark Energy Services, Joplin, Mo., which installed the turbine and put it on line last month.

But he says the cost of utility-generated power and the availability of tax credits for the purchase of equipment must also be considered to determine the true payback of a wind turbine. Alberici was unable to obtain any tax credits.

The wind turbine is only one aspect of Alberici's goal of making the building 60% more efficient than a baseline building, using the DOE-2 energy model. Others include daylight harvesting, state-of-the art lighting controls, an HVAC system with downsized chillers and boilers, and a passive solar system that preheats domestic water.

Alberici evaluated overall expenditures for green features, including the wind turbine, on the basis of a 10-year payback. All the items that were considered additive were plugged into the payback model. As a group, they provided a projected a payback of 7.7 years.

The cost of the system was more than $150,000, with the majority of the expense allocated for purchase of the equipment.

The contractor hopes that its wind turbine will not only save money on electricity bills but will also serve as a symbol of the company's commitment to sustainable development.

         
 

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