Letter - Another look at wind turbines

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Jim Thorn is correct in stating that the V80 wind turbine has a constant speed generator. The rotor turns at 15.5 rpm and the generator at 1,800 rpm if the turbine is producing 1 or 1,800 kilowatts.

He did, however, previously make the statement that “big commercial windmills (turbines) turn at only one of two speeds: Stopped or full-bore.” This is not accurate as “many” modern megawatt turbines (Siemens, GE, Clipper) use variable speed generators that turn at different speeds depending on the wind speed.

The Siemens 2.3 megawatt turbine has speeds of 7 rpm rotor/637 rpm generator at 1 kilowatt and 16 rpm rotor/1,456 rpm generator at 2,300 kilowatts.

A variable speed generator will produce power at different frequencies (measured in hertz) so it is necessary to have a frequency converter change the power to 60 Hz before connecting to the grid.

Having a constant speed generator (like the V80) does not mean that at 7 mph the wind turbine must consume power from the grid to keep turning. It is in fact the wind moving across the massive surface area of the aerodynamic blades that causes the turbine’s rotor to turn. At lower wind speeds the blades pitch toward an angle of 0 degrees which allows the blades to capture more wind. At higher wind speeds the blades will pitch toward 90 degrees (out of the wind) and this is how a wind turbine controls the speed of the rotor at variable wind speeds.

A wind turbine will never take power from the grid and use its generator as a motor to keep the rotor turning full-bore as Mr. Thorn states. His statement that “clearly, the power to keep the rotor turning must come off the grid” is his own assumption and not based on any manufacturers’ spec sheet.

The V80, like many wind turbines, utilizes an asynchronous generator. This means it requires a small amount of electricity (over a period of a few seconds) from the grid to create the initial electromagnetic field prior to generating power.

This is not unique to wind turbine generators as all forms of power generation (coal fired, natural gas, hydroelectric, etc.) utilizing asynchronous generators require that small amount of “excitation” current to produce power.

Don’t take my word for it, do some research and make your own conclusions!

Scott Graves

Walla Walla

Comments

GeneandCassie 7 months, 3 weeks ago

Some interesting potential benefits of using wind turbines are found at this link:

http://www.wwltv.com/news/local/Woltering-turbines-257507011.html

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dogman12 7 months, 3 weeks ago

I have looked to no avail for Florida Power net generation statistics, that would end ridiculous claims that wind machines have no net output.. It would be simple for FPL to make their point. I did find gross, not net, total figures for all of Oregon, from the DOE:

Oregon Wind Generation (GWh, Million kWh)

Year Total Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

2009 3,470 224 111 341 360 329 410 296 405 314 273 233 98

2010 3,920 172 101 326 486 460 476 432 431 274 251 240 202

2011 4,775 316 339 317 520 465 546 448 531 263 378 427 221

2012 6,066 402 450 569 487 621 666 687 608 398 391 254 539

2013 6,422 458 631 568 954 697 675 836 605 644 351

6,422 Gwh statewide in 10 reported months in 2013. Clearly there is a huge positive net generation from wind machines. The economics and generation timing are another issue. The thing is, we have to go to renewables eventually, within a couple more human generations. Let's do it before we use all the fossil fuels at steadily increasing prices and decreasing net returns.

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PearlY 7 months, 2 weeks ago

It seems to me that if, as you say, we have to go to renewables eventually, then any fossil fuels we leave in the ground, that would have been retrievable at an economically viable cost, are simply wasted. If the future is renewables, who are we saving the fossil fuels for?

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GeneandCassie 7 months, 3 weeks ago

Another option is to make like the Lone Ranger and return to the 'days of yesteryear....'

No electricity to use; minimal Fossil fuel use; campfires every night; cooking under the stars......

And no round-a-bouts......

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dogman12 7 months, 3 weeks ago

We may get there if we don't take our foot off the accelerator...

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