Q: Why can't we install windmills in our backyards and trap the power individually for our personal use? Is the limitation how to store it and feed it into my electrical circuits, or what? Is it cost, or sound pollution to my neighbors, or has a household system just not been developed yet?
Asked by Maria Schmidt, '79, Fort Worth, Texas
Your question conjures up a vision of neat rows of houses generating all the electricity they need through gracefully turning backyard windmills—and what a delightful vision that is!
Unfortunately for most, this windmill-covered neighborhood will likely remain a dream. That is, unless your neighborhood is blessed with powerful winds, liberal building codes and generous tax subsidies. While there are several commercial suppliers for small household wind turbines, they simply do not make economic or environmental sense for most suburban or urban homes.
When it comes to wind energy, bigger is better. Windmills need a certain amount of wind to get their blades turning; even the smallest wind turbine needs about a five-mile-per-hour blow just to start. That's about the minimum for kite flying, too, and it's a rare backyard that has consistent kite-flying conditions—and trees and other tall obstacles only get in the way more. This wind obstruction may explain why the one rooftop windmill in my San Francisco neighborhood is never turning no matter when I check.
You may then ask: What about building upward? Wind speeds do get faster with altitude, which is why the towers for freestanding turbines tend to be at least six stories high. The roof of a typical house doesn't come close, however, and those who set residential zoning codes tend not to look kindly upon structures that shoot up four or more stories further into the air.
There is a little good news though—the other obstacles you mention are really just hiccups. Connection to the energy grid is generally easy for a trained electrician, and the ambient sound from small windmills is usually no louder than a refrigerator. Backyard windmills aren't cheap, but the ultimate cost can drop dramatically, depending on tax breaks from local, state and federal governments.
Alas, there's a still greater problem: physics. A wind turbine's electricity output depends on its size as well as the speed of the wind. And anything that could fit in a backyard—even six stories up—would produce only a fraction of the typical household's electricity consumption. In fact, to rely solely on homemade wind power, you might need to install something like 17 typical backyard turbines. In fact, some argue that micro wind turbines never generate enough electricity even to offset the energy used—and emissions generated—in their production, shipping and maintenance.
This is to say nothing of economics, where the numbers are no more encouraging. One small wind turbine could shave around $200 a year from your electricity bill. At that rate it would take, oh, about 150 years to pay off the $30,000 investment you made to install the turbine in the first place. You could save nearly as much just by using the wind—rather than a clothes dryer—to dry your laundry.
And maybe that's the real point. It may not make environmental or economic sense to install personal windmills, but there are lots of things you can do to reduce your electrical consumption in the first place. Adding insulation, upgrading heating and cooling systems, replacing incandescent light bulbs with fluorescent—as well as good old-fashioned using less—are all guaranteed to lower your utility bill and your carbon footprint. These things may not be as much fun as installing your own backyard windmill, but unless you live in champion kite-flying territory, they'll sure be a lot less frustrating.
Rachel Adams is a PhD candidate in biology.
