Clemson Energy Innovation Center is ENR's Editors' Choice Winner for Best Of The Best 2014
While constructing Clemson University's $110-million wind-energy test center in North Charleston, S.C., the project owner and its builders were often working toward a "moving target." From the start of construction in July 2011 through completion in 2014, the first-of-its-kind facility's design changed several times, says Jim Tuten, project director with the Clemson University Restoration Institute (CURI), the project owner.
Back in 2011, "we didn't have a clear set of specs," says Tuten, who served as project manager. And while a poorly defined scope can be a project killer, for the team building the SCE&G Energy Innovation Center (as it's now called), this early lack of definition sharpened their commitment to designing and constructing a facility that would function as ideally as possible for its end users. That's because, in reality, Clemson and its builders were fashioning an entirely new type of facility, built largely upon the wishful requests of the wind-turbine manufacturers that were asked to envision an ideal test center.
Located within a decommissioned U.S. Navy warehouse on a rehabilitated brownfield site—chosen for CURI's redevelopment and sustainability mission—the 82,300-sq-ft facility supports the testing of offshore wind turbines by giving manufacturers the capability to simulate an estimated 20 years of field conditions in just a few months. And while other wind-turbine drivetrain test facilities exist, Clemson's LEED Gold-certified center goes several steps further.
The inclusion of a 15-MW hardware-in-the-loop grid simulator, for instance, lets manufacturers evaluate their devices' impact on the grid. By recycling the electricity produced by the drivetrain testing—thus avoiding grid impacts—the center became the world's first facility capable of evaluating 60-Hz equipment, intended for North America, as well as 50-Hz units, designed for global markets.
Despite that early, undefined scope, the construction clock was ticking from the start. A $47-million Dept. of Energy grant, backed by deadline-centric stimulus funds, pushed the project owner and general contractor Choate Construction Co. to get shovels ready.
The project team wasn't completely building blindly, though. Working off early industry feedback, CURI and AEC Engineering began design work by using estimates of the testing-induced forces the building would likely experience, based on factors such as torque capacity and blade loading capabilities. With typical turbine blades measuring as much as 300 ft in length, the facility would have to endure massive, fluctuating vibrations created by the 7.5-MW and 15-MW test rigs, which simulate real-life stresses of offshore conditions.
And even though the site was located next to the Cooper River, atop typically mucky Charleston soil, the builders figured the 39-ft-tall structure could accommodate the giant machines.
But as the facility began moving toward reality, industry's needs—and DOE's suggestions—changed, growing to be "a lot more than anybody had anticipated," Tuten says. Since the test equipment ended up being significantly stouter than expected, one of the first major increases in scope resulted: a redesign of the foundation system.
The site's swampy soils provided a challenge as well. As Tuten told ENR Southeast at the time, "We had heavy loads on muck in a seismic area with flooding potential and high wind loads due to hurricanes on a brownfield site."
Accommodating these greater-than-expected loads and retrofitting the existing structure to current wind and seismic codes required contractors to beef up the foundation by installing 432 steel H-piles, ranging from 46 ft to 57 ft in length.
The research center is built around two massive pieces of equipment, with the smaller of the two driven by a 7.5-MW gearbox, and the other a 15-MW, 341-ton gearbox that is considered to be the world's largest. In addition to being more stout, the foundations—which use friction piles, considered a first for this type of facility—needed to function independently.
"The foundations required isolation from the existing structure such that external vibrations were not induced into the test specimen and test vibrations were not transmitted to the facility," Thomas Lorentz, senior vice president with AEC Engineering, told ENR Southeast during construction.
The 7.5-MW rig required a 10-ft-deep concrete foundation, and the 15-MW unit needed a 13-ft-thick base. Supporting the 7.5-MW section are 40 35-ft-long steel shoring piles, 88 70-ft-long steel piles and an estimated 250 tons of reinforcement steel, ranging in size from No. 4 to No. 11 bars. For the larger test rig, 54 35-ft-long steel piles and 115 75-ft-long concrete piles form the base, along with 650 tons of reinforcement steel.
For the concrete placement, only self-consolidating concrete would work, says Chris Palmer, Choate's project manager.
"With that amount of rebar, it would prove impossible to get traditional concrete and vibrators down 13 ft and know you have a solid foundation," says Palmer. Concrete contractor Cooper River Contracting, which had used the method on another area project, sold AEC on the approach.
Without that method, "I don't think we would've gotten [the foundations] built," Palmer adds. The 7.5-MW section required 880 cu yd of concrete, while the larger one consumed more than 3,600 cu yd.
Also, due to the height of the existing building, the piles' depth required crews to modify the pile-driving rig to drive the piles 20 ft at a time. "We would then have to full-pin moment weld the next 20-ft section, which took about three hours per weld."
By summer 2012, the budgetary impact of the redesigned foundation systems began to sink in with project officials and brought about another "significant redesign," Tuten says. To get back under budget, CURI was forced to eliminate the planned second-floor mezzanine, which accommodated offices. The team also had to settle for a more "industrial" interior aesthetic, instead of the originally planned high-end laboratory finish.
An even bigger challenge was getting the gearboxes for the test rigs into the building. The equipment was so much bigger than originally planned that only the smaller of the two units barely fit within the existing structure.
To accommodate the larger rig's installation, the contractors left unbuilt a roughly 20-ft-by-20-ft portion of the facility. That meant that installing items such as flooring and utilities, located in the easternmost portion of the building, couldn't begin until the 341-ton, 15-MW gearbox—the mechanical centerpiece of the test rig—was in place.
Once the gearbox arrived at the nearby Port of Charleston, it took roughly one month to get it in place. Says Tuten, "A 341-ton gearbox does not go anywhere very fast, and if it does, you're in real trouble."
Construction of the 15-MW test rig's load application unit (LAU) structure—the vertical structure that houses the gearbox and drivetrains—was another feat, requiring extreme tolerances. "There were hundreds of individual components that went into building these, all of which had to relate back to each other to within one-sixteenth of an inch in every dimension: X, Y and Z," Palmer says. Failing to meet tolerances would result in the drivetrains not aligning with the test rigs, he adds.
For the LAU, "we had to anticipate the theoretical deflections during construction [versus] during service," Lorentz explained. That meant estimating the deflections for both before and after concrete placement.
So far, the project's final design is working well, says Nikolaos Rigas, the facility's director. "Reception by industry has been very positive," he says. General Electric was the first manufacturer to initiate testing, using the 7.5-MW unit; it concluded testing in late 2014. Currently, Clemson is readying the larger rig for its first round of testing.
However, what started as a wind-energy test center is still evolving and broadening its reach. The university is working to develop what could be the world's first virtual test bed for wind-turbine drivetrains, which would enable manufacturers to evaluate designs as a precursor to physical testing.
Arguably more significant is the school's pending creation of a solar-array simulator, which eventually will be integrated with the existing grid simulator, so manufacturers can study how best to deploy their equipment and how that equipment might affect the grid.
Says Rigas, "We're pretty excited."
Project Team
Submitted by Choate Construction Co.
Owner Clemson University Restoration Institute
Lead Design Firm AEC Engineering
General Contractor Choate Construction Co.
Architect, MEP Engineer Davis & Floyd
