GOLDEN - If the U.S. is going to generate 20 percent of its electricity from the wind in the next 20 years, wind turbines will need to evolve in every way - larger, taller, less expensive, more reliable and more efficient.

At NREL’s National Wind Technology Center, engineers are
preparing to install the two largest turbines ever tested at
the laboratory. Key elements of a 1.5 MW General Electric
turbine have begun arriving; instrumentation and equipment
testing should begin by late summer. Installation of a 2.3 MW
turbine from Siemens Power Generation is scheduled for late summer, too.

Both turbines will be erected on the NWTC’s eastern perimeter, where they will run for years while serving as prominent sentinels overlooking metropolitan Denver.

“We need to understand how these big turbines respond,” said senior project leader Jim Green, who is leading the GE tests. “Increasing their performance, reducing their loads, creating components that last longer – we’ll need to learn about all those things if we’re going to make more wind power.”

Supersized Wind Turbines

The GE turbine will operate atop a 262-foot steel tower. The diameter of its rotor will reach 250 feet. Its total weight, including the tower, will approach 220 tons.

The only visible part of the foundation will be the bolt circle for the tower itself, but looks can be deceiving. Covered with dirt for extra weight, its octagonal concrete foundation pad will measure 50 feet across and weigh about 500 tons. “The pad has to be that big,” Green said, “because that’s what keeps the whole thing standing upright in high winds.”

Special overland trucks started arriving at the NWTC in December carrying sections of the GE system. The trucks are up to 195 feet long – three times as long as a typical 18-wheler. They use as many as 13 axles to distribute the weight of their huge cargo.

The trucks took a designated route on major roads that are
designed to handle oversized loads and traveled at times that
would not disrupt traffic. Two of the trucks were followed by a
separate escort vehicle that remotely steered the trailer’s
rear wheels by radio signals to help the long trucks negotiate
tight corners.

In mid-December, the tower sections arrived from Tulsa, Okla.;
the blades from Aberdeen, S.D.; and the generator housing and
rotor hub from Pensacola, Fla.

During the spring, NREL will build new access roads to the
planned turbine pads and provide other site preparation. NREL
is purchasing the turbine for the U.S. Department of Energy
under a subcontract with GE.

The GE turbine is already a workhorse commercial model,
accounting for nearly half of all turbine sales in the U.S. The
NREL tests are intended to discover ways to squeeze more power
out of existing wind farms and improve the durability of the
turbine’s components.

“Any improvements we can make will have a lot of leverage in
the wind industry,” Green said. Bigger than a Football Field
The Siemens 2.3 MW turbine will be noticeably larger than the
GE. It will use a similar tower, but its rotor diameter is a
whopping 331 feet – more than the length of a football field!

Unlike the GE, the Siemens model is a late-stage prototype. It
features a novel blade design that captures more of the wind’s
energy, but is not supposed to force any more load onto the
turbine’s moving parts and control systems. It will be heavily
instrumented to produce a constant stream of data on
aerodynamics, power characteristics, vibrations, system
fatigue, acoustics and other key measurements.

The tests will be conducted in three phases through late 2011.

“These tests will verify the performance of the new blades
under real and challenging conditions,” said NREL senior
engineer, Lee Jay Fingersh, who is project lead for the Siemens
turbine.

“It looks very graceful and simple, but the aerodynamics of a
wind turbine are harder to understand than an airplane or a
helicopter,” he said.

Siemens is providing the turbine, engineering support and
maintenance from its new R&D office in nearby Boulder. NREL is
providing the site, installation services and expertise in
field aerodynamics testing, structure and reliability testing
and meteorological analysis.

The NWTC would make a poor commercial wind farm, but the
location downwind from Eldorado Canyon and the Continental
Divide provides gusty conditions that challenge turbine and
blade designs and generate data at the equipment’s limits.
Motorists on Highways 93 and 128 can expect to see the giant
turbines operating regularly.

“The turbines generate more power than we can use at the NWTC,”
Fingersh said. “We’ll become an exporter of electricity and be
able to offset some of the program’s costs.”

Learn more about NREL’s wind turbine research.

— Joseph B. Verrengia