wind Q & A


additional information

Midwest Renewable Energy Association: Located in Custer, Wisconsin, the MREA offers many courses and workshops about renewable energy and sustainable living skills.

American Wind Energy Association: A national non-profit organization based in Washington DC, AWEA is a national trade association representing wind power project developers, equipment suppliers, services providers, parts manufacturers, utilities, researchers, and others involved in the wind industry.

Windustry: A non-profit organization based in Minnesota, Windustry is a non-profit organization working to increase wind energy opportunities for rural landowners and communities by providing technical support and creating tools for analysis.

Wisconsin Renewable Quarterly, Summer 2005, Volume 10, No. 2 (PDF): Published by RENEW Wisconsin, this issue features articles on wind, including a letter from Doug and Cindy Decker.

Wisconsin wind maps:

Focus on Energy Wind Maps and Data

Focus on Energy Wisconsin Wind Map

Focus on Energy Renewable Energy Program

Federal government sites:

U.S. DOE's Energy Efficiency and Renewable Energy offers a full range of information resources

U.S. DOE, National Renewable Energy Laboratory in Golden, Colorado is the primary U.S. government research facility for renewable energy technologies

Energy Information Administration Kids Page: Wind Energy — Energy from Moving Air

Turbines at the Byron site

How the turbines work

Concerns about wind turbines


Turbines at the Byron site

Why did you build them here?
Economics and energy production are optimized when you place wind turbines at the place with the highest, steadiest wind speeds. (The energy produced is related to the cube of the wind speed.) Wisconsin isn't the best state for wind, but the areas along the Great Lakes and the Niagara Escarpment offer some of the highest average speeds in Wisconsin. The Byron site is on the Niagara Escarpment, a limestone ridge that's about 300 feet higher than the land to the north and west. As winds blow across the area, the escarpment forces them up, which increases their speed.

Why don't you build more?
Many wind projects are underway in Wisconsin. And in June 2007, construction began on the largest wind project in Wisconsin - We Energies Blue Sky Green Field wind project, which is now complete and operational. This wind project is designed to generate 145 megawatts of electricity - enough to power approximately 36,000 average residential homes.

Electricity generation via traditional power plants using coal, natural gas, or nuclear fuels is still cheaper than wind power, so some additional incentive is needed to build wind power. Currently, the federal government offers a Production Tax Credit that encourages wind energy development. We Energies also offers financial incentives for customer-owned renewable energy projects to not-for-profit organizations and business customers.

What is the average wind speed at this site?
14 mph.

What prevents the towers from tipping over?
The weight of the towers (104 tons each) is a major factor in keeping them in place. The foundations are also very heavy, steel-reinforced concrete cylinders, which are socketed into the limestone bedrock below. Bedrock lies 3 feet below the ground surface at Byron, while the foundations are 16 feet deep. Additional anchors from the concrete into the bedrock create a very stable base.


How the turbines work

Why do they spin some days but not others?
When the wind isn't blowing, the blades don't spin. We don't turn turbines on and off. The wind needs to reach a sustained 4 mph for the blades to turn.

How does the electricity get out?
The electricity generated travels down the tower, then underground, through an electrical cable to the local distribution feeder that serves our customers in the area. If the turbines are not operating, those customers get electricity from our other power plants via the high-voltage transmission system. If the turbines are producing more electricity than the local demand needs, the excess electricity will flow back to the transmission substation where it can serve other customers.

Does one wind turbine cast a "wind shadow" on the other downstream turbine?
Sometimes. In winter, when winds are predominately from the north and west, the south turbine output is slightly less. In summer, when the winds are predominately from the south and west, the north turbine output is slightly less.

Why do the two turbines always seem to spin at slightly different speeds?
While these turbines are designed as "constant speed" turbines, with a rotor speed of 28.5 revolutions per minute, there is some variation for several reasons:

  • The wind always varies and is therefore slightly different on each turbine. Also, if one turbine is directly upwind of the other, it can create a "wind shadow" effect that reduces the wind at the downstream turbine.
  • These turbines actively vary the pitch of their blades to modulate their speed and power output. They also have "variable slip" generators to allow the turbine to smooth out power surges due to wind gusts. These actively controlled systems cause some fluctuations in the rotation speed.

If wind speed and therefore energy output are variable, how do you maintain constant voltage?
These turbines regulate power output and voltage several ways:

  • The pitch, or angle, of the blades is adjusted constantly to match wind speed. At lower wind speeds the blade is turned fully into the wind. At higher speeds, the blade is rotated slightly out of the wind by the hydraulic system in the nacelle to reduce the wind force on the blade. At extremely high wind speeds, the blades are turned completely out of the wind. This allows maximum energy capture at low wind speeds and modulates the power at higher wind speeds.
  • The generators have resistors that allow "variable slip" operation. In other words, the magnetic field on the generator rotor is also constantly adjusted to reduce the power surges from wind gusts. This keeps the power output more constant.
  • Thyristors and capacitors (electrical components) in the control cabinet adjust power factor to balance real power output with reactive power output from the generators (volts versus vars).

On days when it's not too windy, can you use one of the turbines as a fan and blow air to the other turbine to produce energy?
No, for two reasons:

  • These generators are not designed to be used as motors, so you can't power the blades like a fan.
  • Even if you could motor these turbines, it would not be efficient to use one turbine to blow wind past the other turbine. You'd get back less energy than you put into the system.

Is lightning a problem?
Yes and no. Being the tallest object on the highest point in the immediate area means you will be a magnet for lightning strikes. The turbines are protected by lightning receptors and conductors embedded in the blades. These are then grounded to the tower through the hub. The tower is connected to deep earth grounding through the foundation. Lightning is directed through these conductors to the earth where it dissipates harmlessly. The towers have been struck by lightning multiple times with only minor effects.


Concerns about wind turbines

Are there problems with birds?
Bird mortality has been an issue at some wind turbine sites, but is not a problem here to our knowledge. Turbines with lattice towers and/or guy wires provide many roosting or nesting sites and may attract birds. The Byron turbines have solid tower shells to avoid this. Modern wind turbines also rotate at slower speeds, which appears to reduce bird collisions. This location was chosen to avoid known bird migration routes. To date, we have not observed any bird mortality at this site.

Isn't ice buildup on the blades a problem? Do the blades fling ice chunks at passing cars?
No. Ice can build up on the blades, but it sheds and disintegrates into small pieces before it gets very thick. If it did get thick, the turbine hub would become unbalanced and the controller would shut down the turbine due to vibration.

How do wind turbines affect groundwater?
They don't. This question probably stems from the historical use of windmills to pump water in rural areas. These turbines don't pump water.

Can the blades come off?
No. The likelihood of a complete structural failure is extremely low. The bolts are designed with much greater strength than is needed to hold the blades on.