We’ve seen wood offered as an environmentally friendly alternative to steel for the giant towers that hold power-producing turbines high off the ground. Now comes concrete as a tower candidate, although for a different reason.
The idea behind new research into concrete is driven by a desire to reach higher, where winds are stronger and less susceptible to turbulence. Today’s land-based towers generally top out at 80 to 90 meters in height, and Iowa State engineers say that to get to 100 meters, steel won’t cut it.
“We have definitely reached the limits of steel towers,” Sri Sritharan, Iowa State’s Wilson Engineering Professor and leader of the’s College of Engineering’s Wind Energy Initiative, said in a statement. “Increasing the steel tower by 20 meters will require significant cost increases and thus the wind energy industry is starting to say, ‘Why don’t we go to concrete?’”
The Iowa State team said it came up with three techniques for assembling concrete turbines from hexagon shaped segments, with six panels connected to six columns. They varied the connecting technique three ways, and in simulations found in each case the towers could withstand loads beyond what they could expect at the 100 meter height. The researchers believe that concrete could work for 100-meter towers with 2.5-3-megawatt turbines – about as big as is seen for land-based systems.
The advantages, in their view are:
- increased tower life beyond steel’s 20-year lifespan;
- easier transportation because pieces are small enough for standard trucking;
- wide availability of precast concrete across the country;
- less reliance on imported steel for turbine towers;
- ability to assemble smaller precast pieces on site in multiple ways;
- the versatile concept can be tailored for any turbine size or even a height beyond 100 meters.
According to Iowa State, the concrete tower research was supported, in part, by a $109,000 state economic development grant, with help from industry partners, including Clipper Windpower, which is headquartered in Carpinteria, Calif., and has a turbine design and manufacturing facility in Cedar Rapids; Lafarge North America Inc. of Calgary, Alberta, Canada; and Coreslab Structures (OMAHA) Inc. of Bellevue, Neb.