http://www.pddnet.com/news/2015/08/how-building-better-wind-turbine-began-styrofoam-balls
Scientists at GE Global Research spent the last four years building a more efficient wind turbine. The result rises 450-feet above the Mojave desert in California – almost half the height of the Eiffel Tower — and looks like it has a silver UFO stuck to its face.
It may appear strange, but you are looking at the future of wind power. The team explains how it came about.
In 2011, Mark Little, GE’s chief technology officer and the head of the GRC, challenged principal engineer Seyed Saddoughi and his team to build a rotor that could harvest more wind.
Michael Idelchik, who runs advanced technology programs at the GRC, gave them another clue: “Since we know that the inner parts of wind turbines don’t do much for energy capture, why don’t we change the design?”
The team came up with the idea of putting a hemisphere on the center part of the wind turbine to redirect the incoming wind towards the outer parts of the blades. “The biggest unknown for us was what size the dome should be,” Saddoughi says.
The group decided to do some experiments. They bought on the Internet a 10-inch wind turbine and a bunch of Styrofoam balls of different sizes, then took the lot to a wind tunnel at GE’s aerodynamic lab (see above). “By cutting the Styrofoam balls in half, we created our domes of different sizes and then stuck these domes on the center of the small wind turbine and ran our experiments at different tunnel air speeds,” Saddoughi says.
The team hooked up the turbine to their instruments and measured the amount of voltage it produced. “Invariably we got a jump in voltage output with the dome placed at the center of the wind turbine; albeit the increases differed for different size domes,” Saddoughi says.
The scientists reached out to a colleague who did simple computer simulations for them and confirmed that even a full-size turbine was more efficient with a nose upfront.
“Of course overjoyed by the very limited experimental and computational results, we wanted to come up with a name for this design, such that it really represented the idea – and was also something that everybody would remember easily,” Saddoughi says. “The team gathered in my office again, and after an hour of playing with words the name Energy Capture Optimization by Revolutionary Onboard Turbine Reshape (ecoROTR) was created.”
Saddoughi is attaching differently shaped noses and turbine blades in Stuttgart. All image credits: GE Global Research and Chris New (ecoROTR)
The team then built a 2-meter rotor model of the turbine and took it for testing to a large wind tunnel in Stuttgart, Germany. The tunnel was 6.3 meters in diameters and it allowed them to dramatically reduce the wall effects on the performance.
The researchers spent couple of months working in Stuttgart. “We conducted a significant number of experiments at the Gust wind tunnel for different tunnel air velocities and wind turbine tip-speed ratios with several variations of domes,” Saddoughi says. “The wind tunnel was also operated at its maximum speed for the blades in feathered configurations at several yaw angles of the turbine to simulate gust conditions.” They ran the turbine as fast as 1,000 rpm and carried out surface dye flow visualization experiments (see below).
When dye hits the fan. Saddoughi after the dye flow visualization.
When they came back in the second half on 2012, they started designing the actual prototype of the dome that was 20 meters in diameter and weighed 20 tons. The size presented a new batch of challenges. “Unlike gas or steam turbines that are designed to operate under a relatively limited number of set conditions, wind turbines must operate reliably and safely under literally hundreds of conditions, many of them highly transient,” says Norman Turnquist, senior principal engineer for aero thermal and mechanical systems.
They ran more calculations to make sure that GE’s 1.7-megawatt test turbine in Tehachapi, Calif., would be able to support the dome. They looked at performance during different wind speed and directions, storms and gusts. They also designed special mounting adapters and brackets to attach the dome. “The design looked really strange, but it made a lot of sense,” says Mike Bowman, the leader of sustainable energy projects at GE Global Research.
The team then assembled the dome on site. “Early on, it was decided that the prototype dome would be a geodesic construction,” Turnquist says. “The reason is simply that it was the construction method that required the least amount of unknown risk.”
For safety reasons, the workers assembled the dome about 300m from the turbine and used a giant crane to move it to the turbine base for installation. But there was a hitch. “After the adapters were mounted to the hub it was discovered that bolt circle diameter was approximately 8mm too small to fit the dome,” Turnquist says. The team had to make custom shims to make it work.
The dome went up in May on Memorial Day and the turbine is currently powering through four months of testing. “This is the pinnacle of wind power,” says Mike Bowman. “As far as I know, there’s nothing like this in the world. This could be a game changer.“
