Wind is a fact of life. When I bought my Colorado mountain property 19 years ago, the incessant winds that scoured the scantily treed hilltop were a constant source of aggravation. No matter what I attempted to do, the wind was always there to kick the difficulty level up several notches, turning any relatively simple task into a near impossibility. So when LaVonne and I moved here fulltime in 1999 to build a log home, I couldn’t wait to erect my old ham-radio steel-lattice tower and affix a 1,000-watt wind turbine to the top of it.
It was payback time.
Or so I thought. The wind, it seems, had other ideas. After hounding me during the entire installation, the air grew eerily quiescent the moment I climbed down from the tower to watch the sleek, white, fiberglass blades begin sending useful, storable wattage into our hungry batteries. But the wind was lurking in the ether, studying my every move. Finally, like a drive-by assassin, it burst forth with a flurry of sharp gusts that startled the untested new turbine to life. It was a short-lived demonstration. The blades spun furiously for all of 30 seconds before the wind, having divined what the new contraption was all about, fell into a state of unprecedented dormancy for the next four days. It must have been mulling over its next move. I, on the other hand, spent those four breezeless days cursing myself for ever thinking I could get any useful work from a force of nature as mercurial as the wind.
But that’s all changed, now. The wind and I have come to terms over the yearsI have learned to accept its whimsical behavior, while the wind, for its part, has provided us with thousands of kilowatt hours of electricity we would not otherwise have been able to reap.
Was it worth all the trouble? Many less deeply invested in the wind than I would say “No.” A wind turbine is, after all, a mechanical contrivance with numerous moving parts, all of which are placed directly into the path of a force so potentially damaging that almost every creature in nature goes out of its way to avoid it. And yet that’s exactly the reason wind power is so tantalizing: it’s laden with raw energy that begs to be exploited.
Is wind for you?
In the end, whether or not you install a wind turbine on your property will depend as much on your personal disposition toward the technology as it will on the other limiting (and enabling) factors that need to be considered. But if the idea of harnessing the wind strikes an agreeable chord inside you, you’re already halfway there.
Then it’s simply a matter of if:
- you have enough wind to consistently (though not necessarily ceaselessly) drive a turbine,
- you have enough space to safely locate a tower, and,
- you are not burdened by state, local, or neighborhood restrictions.
To get your money’s worth from a wind turbine, you will want an average annual wind speed of 10 mph or better. There are a couple of ways to determine if you have that much wind. You could, for instance, install a computerized anemometer on top of a tower at the same height as your proposed wind turbine, and chart the characteristics of the wind over the course of a year. This way is as thorough as it is impractical.
A much cheaper and quicker way is to consult the state wind resource maps put together by the U.S. Department of Energy (DOE) and available for download at: www.eere.energy.gov/windandhydro/windpoweringamerica/wind_maps.asp. These maps are detailed enough to indicate the average annual wind speed in your general area, though not at your particular site. Moreover, the wind data provided by the maps are for a height of 50 meters (164 feet) above the ground. Wind at 50 meters will, on average, have twice the power density as wind measured at 10 meters (33 feet), so unless you are planning for a very tall tower, you should downgrade your expectations somewhat.
Then there is the third method, a tried-and-true little maxim employed by everyone I know who has ever installed a wind turbine, including us:
Comparison of popular wind turbines
If there is enough wind at your site to annoy you, there is almost certainly enough wind to make good use of a wind turbine.
Quick, simple, and, unless you have an profoundly low tolerance for wind, foolproof.
Once you conclude that, yes, the wind really is an annoying presence, there is the space issue to consider. The numbers to remember here are one, fifteen, and twenty. Ideally you should have at least one acre of land, your turbine should be located at least 15 propeller diameters away from your house or your neighbor’s, and your tower should extend a minimum of 20 feet (though higher is always better) above the tallest object within 300 feet, to avoid a turbine’s worst enemy, turbulence.
As for the local laws, ordinances, and covenants…good luck. There’s not much you can do about them, unfortunately, unless there is a process whereby you can apply for a variance, or you begin a one-person crusade to overturn a nettlesome restriction.
If you’ve got enough wind, space, and freedom to erect a towerand the right stuff to embrace the fickleness of wind power, it’s time to select a turbine. (If you think I’ve skipped over the subject of towers, you’re right. For much more on these, see “Unfolding the Complexity of Wind Towers” in the November/December 2006 issue.)
Almost all residential turbines currently in use are upwind, horizontal-axis machines, looking very much like wingless, stationary airplanes pointing into the wind. They produce low-voltage 3-phase AC (alternating current) as a propeller-driven rotor with imbedded permanent magnets spins around several copper windings, collectively called a stator. If the turbine is used to charge batteries in an off-grid system, the AC will be rectified into DC (direct current) either within the turbine itself, or within the innards of a wall-mounted charge controller. In direct grid-tie operations, by contrast, the turbine’s AC output is rectified to high-voltage DC, which is then converted into grid-compatible 120-volt house current.
How much power will a turbine produce? A turbine’s nominal wattage rating is based on its power output at the rated wind speed, which is generally just below the speed at which a turbine will furl (a braking maneuver in which the turbine turns away from a strong wind). This is usually in the 25- to 31-mph rangea very stiff breeze, certainly. Most of the time the turbine’s output will be but a fraction of its rated power, so a more telling statistic is a turbine’s monthly kilowatt hour output at an average wind speed of 12 mph (see chart). Still a little optimistic, but a far better way to compare machines with similar ratings.
A peculiarity of all wind turbines is the fact that they cannot be disconnected from a load (the batteries, for instance) without facing the possibility of damage from spinning at dangerously high rpm. The usual solution is to divert the output to a heat sink once the batteries are charged. The heat produced can then be used to heat a spacesuch as a battery roomor even to heat water. Some turbines (such as our 1,000-watt Bergey XL.1) will automatically go into slow mode once the batteries reach a predetermined voltage, and will remain in that mode until the battery voltage drops.
Build to suit
If sleek, production turbines seem a little tame for your inventive spirit, you can always build your own. Plans and parts can be purchased at several different sites on the Internet. I most highly recommend www.otherpower.com; it’s run by friendly, dedicated mountain dwellers who build turbines for a living and rely on them to power their off-grid homes.
The turbine you build in your own workshop may not be the apex of high technology, but it should do what a turbine is supposed to do: extract useful power from an untamed force of nature. And there’s real satisfaction in that.
Rex Ewing is the author of several renewable energy books, including Power With Nature, Got Sun? Go Solar, (available from the Countryside Bookstore) and the newly released 2nd edition of Hydrogen: Hot StuffCool Science (available from www.pixyjackpres.com). He lives with his wife, LaVonne, in a handcrafted log home powered solely by the sun and wind in the foothills of Colorado.