With politicians pushing adoption of renewable energy in the United States and Europe, the last few years have seen a surge in plans for wind farms–both on land and sea. But wind power isn’t viable everywhere, and prime coastal spots are often already de
So some wind-turbine makers are shifting their focus toward
building bigger wind turbines that can harvest the lower-speed winds
that are more readily available. This next generation of wind turbines
is no small matter: their rotors have a diameter the size of a football
In general, wind turbines get more powerful and efficient with
taller turbine towers and larger areas swept by the blades, according
to the American Wind Energy Association. A turbine’s swept area is a
key indicator in how much power output potential the turbine has.
“Lower wind-speed turbines certainly open up more land for
development,” said Rich Reno, platform leader for General Electric’s
new 2.5-megawatt wind turbine. “Larger turbines open up the opportunity
to get more megawatts out of a given piece of land.”
new sites for wind farms is essential to the sector’s growth because
many of the places with the most attractive wind conditions tend to be
developed already. More efficient turbines also make wind power a more
realistic option for countries like Germany, which is not very windy
and has relatively limited shoreline, where winds tend to be stronger.
Despite those obstacles, the country has the world’s second largest
installed base of wind power.
Wind farm development continues to push into new regions–particularly
in the U.S. and parts of Europe, where politicians are encouraging
“We see continued growth in Europe, notably because of EU legislation
to derive 20 percent of its energy from renewable sources,” Victor
Abate, vice president for the renewables arm of GE Energy, told Reuters
in an interview. The European Union issued a directive in December 2008
to have 20 percent of its energy come from renewable sources by 2020.
Europe contains more than half of the world’s installed wind power
The U.S. is now the country with the world’s largest installed base of
wind power, according to the World Wind Energy Association. More than
8,300 megawatts of wind power was installed in 2008, expanding the
nation’s total wind power generating capacity by 50 percent in a single
Although that growth is expected to slow in 2009, according to both the
AWEA and investment bank HSBC, the wind industry is still getting
support stateside. As part of the economic stimulus plan signed in
February, President Obama extended tax credits for wind and increased
the amount the government will spend on those credits by 30 percent.
Industry watchers predict much of the growth in the wind market will be
in the low- to medium-wind segments. And as that trend continues, wind
turbines in general have been increasing in size–from typical 18-yard
rotors 25 years ago to about 110 yards in recent years. The average
wind turbine installed in 2007, with a capacity of 1.6 megawatts, is
twice as powerful as the average wind turbine installed in 2000 (0.76
MW), according to AWEA.
Several manufacturers are rolling out new low-speed turbines to help
meet that demand. Siemens, Vestas, and Nordex all recently released
new, large wind turbines directed at low-wind markets. Last year,
General Electric released its largest turbine for low-wind use.
Siemens predicts that the low-wind market alone should represent
one-third of the total global wind-power market in the coming years.
Its new turbine, the SWT-2.3-101, has a “nominal” (that’s maximum in
wind-engineering speak) power output of 2,300 kW, enough to power
approximately 700 homes, depending on wind conditions. The turbine is
enormous, with a 110-yard rotor diameter–larger than an American
Designed to harvest weaker winds, SWT-2.3-101 has a swept area of
86,111 square feet, 17 percent larger than Siemens’ previous 2,300 kW
“The new wind turbine will open up many potential new sites for our
customers,” Andreas Nauen, CEO of Siemens’ Wind Power Business Unit,
said in a statement.
Danish wind-power company Vestas recently unveiled its V 112,
a 3 MW low-wind turbine the company claims is the world’s largest
mass-produced wind turbine for low- and medium-wind-speed sites.
The wind turbine has a nominal power output of 3,000 kW, the
same as the company’s previous largest turbine. But because of its
larger blade diameter, it’s able to reach that potential with lower
speed winds. It can generate electricity at wind speeds as low as 6.7
miles per hour and reach maximum power at about 31 mph. The previous
model required 8.9 mph winds to deliver power, and 34 mph to attain
Three factors have made it possible to make modern turbines so
big, according to General Electric: controlling the load on the grid,
new blade design, and new materials to reduce the weight of the
“As the technology increases in those areas it allows advancement,” said Reno, of GE Energy.
New materials and construction techniques make it possible to build
even larger wind turbines. Siemens says it uses a proprietary
manufacturing process, which casts the 53-yard, fiberglass-reinforced
epoxy blades in one piece. The process eliminates weaknesses from
gluing parts together, as is done with traditional blades and thus
makes it possible to make turbines this size.
Vestas is increasingly using composite materials and has a
low-weight-design philosophy. In March, Vestas teamed up with U.S.
aerospace company Boeing for projects in areas such as aerodynamics and
composite-materials fabrication processes, design, and analysis.
But there are limits to how big these turbines can get. GE says
the grid’s ability to handle more powerful loads is one limiting
factor. And in the future, problems with transportation could limit the
size of new land-based turbines. Going around road corners and narrow
bridges with 50-yard blades is already a problem, and the only thing
that could alleviate that would be technology for making multiple-piece
blades. Offshore this transport problem doesn’t exist so the turbines
could be bigger there. GE thinks the size increase of the turbines will
plateau, but that won’t happen for a while.
“I think 70 meters (77 yards) was a pretty big rotor 10 years
ago. Today 110 is out there,” Reno said. “Can they grow another 30
meters (33 yards) in 10 years? I think it is possible.”