SEARCH BLOG: WIND
In a recent post critical of Al Gore and his hyperbole about wind turbine generated electricity, I hinted at issue of these generators actually having a parasitic relationship with the rest of the power grid.
You may be interested in the following: A Problem With Wind Power by Eris Rosenbloom and the subsection: Energy consumption in wind facilities.
Among the wind turbine functions that use electricity are the following:†sThese articles are three years old, so there will be a lot of "yes, but" new technology, etc. Those same "yes, butters" will gladly point to 40-year old fossil fuel or nuclear plants and deride the technology employed therein.
It may be that each turbine consumes more than 50% of its rated capacity in its own operation. If so, the plant as a whole -- which may produce only 25% of its rated capacity annually -- would be using (for free!) twice as much electricity as it produces and sells. An unlikely situation perhaps, but the industry doesn't publicize any data that proves otherwise; incoming power is apparently not normally recorded.
- yaw mechanism (to keep the blade assembly perpendicular to the wind; also to untwist the electrical cables in the tower when necessary) -- the nacelle (turbine housing) and blades together weigh 92 tons on a GE 1.5-MW turbine
- blade-pitch control (to keep the rotors spinning at a regular rate)
- lights, controllers, communication, sensors, metering, data collection, etc.
- heating the blades -- this may require 10%-20% of the turbine's nominal (rated) power
- heating and dehumidifying the nacelle -- according to Danish manufacturer Vestas, "power consumption for heating and dehumidification of the nacelle must be expected during periods with increased humidity, low temperatures and low wind speeds"
- oil heater, pump, cooler, and filtering system in gearbox
- hydraulic brake (to lock the blades in very high wind)
- thyristors (to graduate the connection and disconnection between generator and grid) -- 1%-2% of the energy passing through is lost
- magnetizing the stator -- the induction generators used in most large grid-connected turbines require a "large" amount of continuous electricity from the grid to actively power the magnetic coils around the asynchronous "cage rotor" that encloses the generator shaft; at the rated wind speeds, it helps keep the rotor speed constant, and as the wind starts blowing it helps start the rotor turning (see next item); in the rated wind speeds, the stator may use power equal to 10% of the turbine's rated capacity, in slower winds possibly much more
- using the generator as a motor (to help the blades start to turn when the wind speed is low or, as many suspect, to maintain the illusion that the facility is producing electricity when it is not,‡ particularly during important site tours) -- it seems possible that the grid-magnetized stator must work to help keep the 40-ton blade assembly spinning, along with the gears that increase the blade rpm some 50 times for the generator, not just at cut-in (or for show in even less wind) but at least some of the way up towards the full rated wind speed; it may also be spinning the blades and rotor shaft to prevent warping when there is no wind§
The big difference is that new technologies have been deployed that fix 40-year old problems, but the problems of three years ago remain. It might be worthwhile having some real systemwide analysis for wind turbine electric power generation before following Al Gore's advice and installing the products in which he has investments and is hawking under the guise of the next energy answer.