When wind dies down, cost of energy goes up 

On a recent trip to West Texas, I went to the horse’s mouth on wind-powered energy and spoke with the manager of a 100-unit wind farm. He reminded me that wind, the most successful of the alternative methods of generating electricity, accounts for 2 percent of the total U.S. supply.

Consider for a moment the specifics of wind farming. The latest towers stand 280 feet high, their blades approach 100 feet in length, and they cost about $3 million to purchase and install. To maintain a set speed of about 20 rotations per minute, a computer controls the blades to adjust their pitch angle. Wind speeds of 10 miles per hour can set the blades in motion, and the top usable wind speed is about 70 mph, beyond which point the blades feather like the propeller on an airplane to avoid damage. In West Texas, the turbines can operate about 40 percent of the time.

Owners of the land where wind turbines stand receive a royalty on power generated, usually 4 percent of the total, an amount ranging from $300 to $700 per month per turbine. The blade noise presents a problem, says my contact, but only to neighbors who do not have turbines on their property. To their hosts, the turbines “sound like money.”

Money also goes to the wind companies as a subsidy called a Production Tax Credit. The amount of the credit varies depending on the amount of power generated, but it goes to repay 30-52 percent of loans incurred to build the turbines. Wind power has fallen on hard times lately, with competing natural gas prices down to one-third of the price two years ago. Yes, the wind is free, but the payments on construction loans continue.

In recent developments, wind power has literally taken to the skies. A dozen small companies have designed kites and other contraptions to reach the faster, more dependable winds at higher altitudes. The Federal Aviation Administration restricts the maximum height for these flying turbines to 2,000 feet. There, steady winds blow with more than twice the strength as those blowing at ground level. Significantly, each doubling of wind speed produces far more than twice the amount of power.

The primary drawbacks to depending on wind power or enlarging its contribution remain its variability and the necessity of maintaining backup, gas-fired generators with equivalent capacity to step in when wind speed varies. Without this “insurance,” brownouts and interruptions inevitably occur. The cost of wind-generated power must include the expense of idle gas-fired plants which could have produced the electricity at a lower cost to start with.

To bring the discussion closer to home, a 30-mile-wide swath running the length of the Tennessee-North Carolina border contains the only usable wind conditions anywhere in the Tennessee Valley Authority sphere of influence. It lies dormant with “no current plans to exploit it,” says the TVA spokesperson I reached.

TVA may save us money by not investing in costly, inefficient wind power.

Gerry Calhoun of Nashville is an energy consultant and a petroleum geologist. He has taught on energy and climate in the adult learning department at Vanderbilt University.