On-farm wind power: Part I of a three-part series

Generating electricity is a breeze…
…When you harness this clean and renewable resource for all your residential and farm-operation energy needs

By Dan Sullivan

For more than 20 years, Mick Sagrillo has worked as a wind energy advocate, educator, and entrepreneur. In 1983, he founded Michigan Wind & Sun, LTD, a company that makes wind generator components and towers, refurbishes and repairs wind equipment, and installs wind energy systems. He’s widely published on the subject of wind technology and is a founding member of the Midwest Renewable Energy Association.
In late February, Sagrillo came to Organic University, the prequel to the Upper Midwest Organic Farming Conference in La Crosse, Wisconsin, to show us how and why this clean and renewable energy source makes sense on the farm.

Coal-generated electricity accounts for about 40 percent all manmade carbon dioxide emissions released into the atmosphere. And, although it represents less than 5 percent of the global population, the United States is responsible for about 30 percent of all planetary greenhouse gas emissions. Consider a country such as Denmark or Germany, where up to 70 percent of electricity is wind generated, Sagrillo told us. Though those countries are about half the size of Wisconsin, he said, “There are 53 [electricity generating] windmills in Wisconsin; there are more than 2,000 in Denmark. We’ve got a long way to go in this country.”

Greenhouse gas emissions aren’t the only problem, Sagrillo said; 50 percent of the mercury now polluting our lakes and rendering fish toxic to eat rains down upon us from coal being burned to make electricity.

Dollars and Sense

“Efficiency is not squandering resources,” Sagrillo said as he explained the economic advantages of investing up-front in energy saving devices such as compact fluorescent light bulbs, good insulation and double-pane window. “Each dollar spent on efficiency will save you $3 to $5 dollars in system costs.”

So now that you’ve got your home super-insulated and all your household and farm appliances are geared toward maximum efficiency, it’s time to harness the power of the wind. Basically, lift created by the movement of air turns a windmill’s rotor blades—typically there are three of them—which drive a generator, which produces electricity. “The bigger the rotor, the more wind you can collect,” Sagrillo explained. (And the more time-consuming and expensive to maintain, he added.)

Sagrillo defined three basic categories of residential/farm wind machinery. What he termed the “cabin” size, a 1-kilowatt (kW) system with rotor blades about make this 8 to 11feet in diameter and the capacity to generate 30 to 100 kilowatt hours of electricity per month; “These are relatively small machines…about 45 pounds,” Sagrillo said. “You can literally throw them on your back, climb up the tower and stick it up there.” The “home” size, a 3kW to 6kW system with a rotor blade diameter of 12 to 18 feet generating anywhere from 250-800 kwh of electricity monthly. And the “small farm” size—10kW to 65kW systems with rotors spanning 22 feet or more in diameter, and with the capacity to generate upwards of 2,500 kwh of electricity per month.

According to a cost-estimate spreadsheet Sagrillo passed out to the class, up-front costs for these larger systems—including the tower and all installation costs—can range anywhere from around $10,000 for a system that can generate around 100 kwh monthly, to just over $50,000 for a system capable of generating 2,500 kwh monthly. (Key variables such as tower height and average wind speed—which will be covered in Part II of this series—will factor heavily in actual performance.

The good news about these mid-sized systems is that there is a growing supply of fully refurbished units to meet a growing demand. “We’re just now seeing a redirection of these types of turbines in places like California,” Sagrillo said. “In California, [the utility companies] are taking out the smaller turbines and putting in the behemoths…and they’re finding a niche for this 20 year old equipment.”

That niche includes farmers and others.

“A school district in Spirit Lake, Iowa put up a 65kW turbine and expected payback in seven or eight years,” Sagrillo told us. “They paid for it in two years.”

These recycled units are being remanufactured and put back on the streets with essentially the same warranty as new equipment, Sagrillo said, adding that “there are reputable remanufactures and disreputable ones—what we call Rustoleum rebuilds.” Sagrillo counseled anyone considering a second-hand unit to do their homework before making a purchase.

“A 65kW system, installed, will cost in the neighborhood of $85,000 to $90,000; a machine like this will do 65,000 to 85,000 kwh a year, depending on where you’re at.”

Economies of scale (and cooperation)

“As you go up in size, the cost of the electricity that you generate goes down,” Sagrillo informs us.

Of course, the bigger the unit, the more complex; hence, the increased maintenance investment. “Smaller units, up to about 10kW, are direct drive,” Sagrillo said. “Over 10kW, they are pretty much all gear driven.”

The next step up from a 65kW system is a doozie; about 10 times the size, at 660kW. Now we are talking 75-foot blades on a 206-foot tower. And even this Brontosaurus of the windmill world is becoming somewhat of a dinosaur for utility companies because it is too small. The price tag on one of these units installed as new equipment? Around $1.2 million.

Though a relatively new concept in North America, Sagrillo said, cooperative purchase of such large-scale wind machinery is commonplace elsewhere. “This is old hat in Denmark…less than 10 percent [of the country’s 2,000 windmills] are owned by utilities—they’re owned by the people.”

Sagrillo told us about a project near Toronto Ontario, Canada, where a non-profit choreographed the purchase of one of these huge machines and sold shares to local residents. “Over the 20-year life of the turbine, [investors] get a check on a regular basis; they’re getting back between 7- and 8-percent return on investment.”

The beauty of cooperative investment in wind energy, Sagrillo said, is that you don’t necessarily have to have a windy site to participate. “But we don’t do things like co-ops very well in this country; the business model in this country is everybody for themselves and everybody else be damned. It’s not the best business model.”

Getting technical

Wind machines fall into two basic categories, Sagrillo said.

“Drag devices work by the wind literally blowing something out of the way,” he said, giving the examples of those quaint-looking water pumpers that are ubiquitous across the rural landscape. The drag concept has been around for nearly 3,000 years and is not the most efficient use of wind power, Sagrillo said. “These do an extremely good job of pumping water; they do a lousy job of generating electricity.”

Lift devices work very much like, and resemble, airplane wings, Sagrillo said. “Lift literally causes these blades to be pulled forward similarly to the way that an airplane is moved through the atmosphere. We’re basically taking big chunks of moving air and we’re converting it to rotational momentum to turn an electrical generator.”

Another way to visualize this concept, Sagrillo said, is to imagine dense, high-pressure air molecules under the wing or in front of the rotor blade displacing low-pressure, more scattered molecules above the wing or behind the rotor blade, thus creating lift.

Electricity is produced when coils of wire inside the generator create a pulse as they move through a magnetic field, Sagrillo said. The faster the turbines turn, he said, the faster the pulse and the more electricity produced. Gear-driven turbines enhance this efficiency, he said, because the generator spins six to 18 times for every single revolution of the blades.

Smaller, direct-driven wind-energy systems typically have a tail to keep them oriented toward the wind. These uncomplicated systems are ideal for homeowners, Sagrillo said, because they are easy to maintain and homeowners have a reputation for letting things go. “They’re relatively simple machines,” he said.

“A gearbox is a level of complexity that you add to a turbine that a lot of people can’t deal with,” Sagrillo said. But equipment maintenance is a reality of farming, he said. “Every time you add a moving part, two things happen. There’s a reduction in efficiency as energy is dissipated in heat. And there’s considerable more maintenance. The maintenance issue is why windfarm equipment and industrial equipment is so different.”

Then there is dealing with the factor of too much wind.

“The blades on a direct-drive turbine are literally bolted into place; the problem is that, at some point, the wind is going to get too strong for this machine and we’ve got to get rid of it,” Sagrillo said. “One of the ways we can do this is by pitching the blades.”

Pitching the blades— turning them out of the wind’s way—is accomplished through a few different methods, Sagrillo said. In the most basic design, a tension spring connecting the shaft of the blade to a central spider gives way under a certain amount of force. “It’s simple, reliable, and cost-effective.” More complex systems utilize hydraulics and computers. This sophisticated design is more typical of large-scale windfarm machinery, he said. Rather than having a tail to guide them, these mammoth machines—which are typically sited upwind—take their cues from a computer linked to a 3-cup anemometer (to measure wind speed) and a wind vane (to measure wind direction). “A motor moves the blades around until they are facing back into the wind.”

“You can also pitch the entire rotor upwards or sideways,” Sagrillo said, explaining that this is accomplished with the aid of an offset pivot. (This is how smaller residential wind equipment typically is protected from high winds.)

With all these incredible advances in clean energy technology, why so many environment-choking coal-burning plants online and planned for the future?

“Elecricity is the most frequently-bought product in the United States; there’s nothing we consume more and with more regularity than electricity.” That unfortunately, Sagrillo said, means huge subsidies, gigantic campaign contributions, and preserving the big-business status quo.

Dan Sullivan is senior editor at The New Farm. Mick Sagrillo is owner of Sagrillo Power and light, a Wisconsin-based consulting firm specializing in home-sized wind-turbine technology and educational workshops.