Do wind towers use more energy than they should?

FARGO N.D. — The editor of a mechanical engineering periodical recently lamented about the amount of energy a wind tower consumes. He studied the inner workings of a modern wind tower and pondered whether any net energy is produced.

Components

Some of the devices inside a wind turbine that consume power include:

Rechargeable batteries — Large wind turbines contain a number of rechargeable batteries to power the electrical systems when the wind is not blowing. These systems include aircraft lights, brakes, blade control devices and weather instrumentation. If the wind doesn’t blow for an extended period, these batteries must be recharged with power off the electrical grid.

Heaters — Gearboxes in wind turbines contain fluids that must be kept warm in frigid climates. Turbine blades also have built-in heaters to prevent icing, which the author suggested could consume up to 20 percent of the electricity produced by the turbine.

Motors – A common misconception is that the blades of a wind tower sit still when the wind is not blowing. In fact, a tower uses its generator in reverse as a motor to spin the blades slowly. The movement of the blades is almost imperceptible to the naked eye.

The blades move to prevent brinelling (grooving) of the bearings on the main shaft. This occurs when bearing components rock back and forth without much movement. Consequently, electricity is taken either from the storage batteries or off the grid to power the blades during these periods.

Wind turbine manufacturers don’t report how much electricity is consumed internally or must be purchased externally. The amount is likely to be quite variable because system designs vary by manufacturer. Moreover, there likely are both good and bad economics of operation as turbine sizes increase.

So, is this really an issue to be concerned about? The editor concluded his article by saying, “We’ve commissioned so many wind turbines that we will need to build new coal-fired power plants to run them.”

Solution?

The problem could be solved easily if tower net metering was available. Net metering monitors the quantity of electrical power flowing in both directions. Overall, the point is rather moot, though, because the editor failed to realize that wind turbine generators are rated on a net power-producing basis.

In other words, each turbine has a nameplate with its power rating listed on it. What is a more important consideration is the power curve that describes the level of electricity produced at various levels of wind speed. Wind speed is highly variable in each geographic area, so that is a more important factor to consider.