Mark Johnson is no Don Quixote humbled by windmills. He makes wind turbines beg for forgiveness.
Johnson is in charge of engineering and testing GE wind turbines, including the largest ones that generate the same thrust at the world’s powerful jet engine and have their blade tips flying at 190 mph, faster than the takeoff speed of a fighter jet. “They must handle huge forces and hurricane wind gusts,” says Johnson, wind engineering leader at GE Renewable Energy. “I’d rather have a torture chamber in the lab than in the field.”
Johnson’s got his wish last fall, when GE partnered with Clemson University in North Charleston, SC. Clemson’s new wind turbine testing facility holds the world’s most advanced rig for trying and validating wind turbine drivetrains, the machinery that connects the spinning main shaft and gearbox to the electricity generator.
Clemson’s test bed will allow Johnson and his team to put GE’s next-generation drivetrains through 20 years of stress in just a few of months.
A wind turbine nacelle in the bay of a test cell at Clemson. Top image: The site also includes a massive grid simulator nicknamed Stargate, after the science-fiction movie.
The team starts the test by attaching the drivetrain to a powerful motor, switchgear and variable frequency drive built by GE Energy Management. The set-up is capable of delivering 7.5 megawatts of power and subjecting the drivetrain to hurricane-force torques. “Imagine putting a seven-ton Mack truck on a lever arm that’s more than a football field long,” Johnson says. “That’s how much torque we can deliver.”
The largest wind turbine blades weigh as much as 13 tons and the rig can also simulate groaning real-life bending momenta created by the blades in bad weather. “This rig is similar to what we have for certifying jet engines in Ohio,” Johnson says. “We take the turbines to their limits.”
GE’s wind design and component and development test teams install over 200 sensors inside the turbines. They gather design and performance data during the test from the gear box, bearings, generator and other technology, and feed it to a GE computing center for analysis. Workers tear down each turbine after they finish testing and inspect it for denting, pitting, rubbing and other internal damage.
The Clemson site also includes a 15-megwatt grid simulator that will allow Johnson and his team to mimic grid conditions the turbines may encounter around the world. The turbines must be able to handle disturbances sail through interrupted grid service. “When you go to countries with weaker grids, like India, you have to prove to local regulators that your machines can turbines can work there,” Johnson says.
Wind energy is fast becoming a key part of global energy generation. In U.S. alone, wind farms have delivered 30 percent of all new power generating capacity for the last five years. Wind also supplied more than 4 percent of all U.S. electricity for the first time in 2013. States like Iowa and South Dakota now get more than a quarter of their power from wind.
“Testing and validation allows us to drive down the costs of electricity and maintain high reliability,” Johnson says. “Clemson will help us push the edge of what’s possible.”