NORMAN, Okla. - Mike Bergey is sailing along in his silver sedan with the ‘‘WINDPWR’’ license plate, streaming toward one of the electric windmills he has seeded around central Oklahoma’s prairie, when a warning siren howls out of nowhere.
Five years ago, a fat tornado rolled over this stretch of plain south of Oklahoma City. It killed 44 people and scrambled 8,000 homes. At one farm, it also ripped a blade tip off a turbine made by Bergey’s wind power company.
En route to check it again today, he considers the charcoal sky, then wheels around. ‘‘I’m not superstitious,’’ he mutters, ‘‘but I’ll take my chances this way.’’
For more than 25 years, Bergey has been trying to outguess the vagaries of the winds.
They fluctuate hourly here, sway and buckle metal, and in tornado season, sometimes transplant windmill parts in a neighbor’s field.
In central Oklahoma, a little wind turbine designed for a single home or small business can generate enough electricity to pay half its yearly bill — and pay for everything in a windy spring. Giant commercial-scale machines can churn out enough power for hundreds of homes.
Yet the United States gets merely three-tenths of 1 percent of its electricity from wind. Even the American Wind Energy Association, a trade group, predicts no more than 6 percent by 2020.
In other words, wind power works — but probably can’t carry the burden when fossil fuels start running thin.
LOW TECH, OLD TECH
At its core, wind power is low tech and old tech. Blades catch passing winds to spin a generator.
Most systems forgo expensive batteries that can store power for times when winds are still. In the more common on-grid systems, wind power flows into an existing electrical box and home outlets. Any surplus flushes into the local power line for credit. When winds calm, the power line takes over.
To cut down on moving parts and upkeep, Bergey’s turbines are built with neither gearbox nor bearings needing periodic lubrication. With patience, a manual, a few helpers and a crane for some models, a buyer with the ambition can assemble one himself, mounting its 23-foot-span blades on a 100-foot tower bolted to a concrete pad.
Since the early 1980s, 37,000 wind turbines sold by dozens of companies have sprouted across the country, the industry estimates. The bigger commercial ones produce by far the bulk of the electricity. Sleek and modernistic, they poke from California ridges or alternate with oil rigs on the wide Texas horizon. A battery of 130 has been proposed for choppy waters off Cape Cod.
While less powerful, little turbines for single homes and small businesses are more abundant. Bergey Windpower has sold about two dozen in the Norman area alone.
Why aren’t there even more around the country?
First, the winds don’t blow hard or steadily enough in many places.
Then, there’s the aesthetics: Even small turbines may whew-whew-whew ceaselessly, thrumming through a restless night like a distant freight train. Also, in many towns, windmills violate height restrictions.
There are infrastructure problems, too: To make full use of wind power, the Midwest, for example, would need an expensive web of highvoltage lines between wind sites and cities, industry advocates say. Commercial farms pay penalties for power interruptions from variable winds.
While simple in theory, a durable turbine is tricky to design. The blades pivot edge-on to let storms slip by, but must be stout and slightly flexible so they don’t snap in ordinary gusts.
The first Bergey blades were made of sheet metal that cracked in high wind.The blades are now made of tough fiberglass.
Harold Klusmeyer’s little Bergey broke down twice within the first couple of years. He could have replaced parts for several hundred dollars, but it was only saving about $350 a year in electricity, he figures. He gave up and eventually traded in the generator for a photovoltaic system that converts sunlight into electricity.
Jim Hames was saying morning prayers one day when he was jolted by a crash.
A guy wire on his wind turbine tower had snapped in high winds. About 40 feet of steel had come thwacking down in his pasture. The sleek turbine nosed into the dirt like an airplane engine.
Hames felt oddly liberated: ‘‘At the time it went down, it hadn’t worked in, say, six months. I was relieved to get rid of it.’’