I’m interested in small wind turbines as one source of electrical power, for cases of short- or long-term disasters. If the power is out for only a few days, I can use the approaches already discussed in the article Using a Computer and the Internet during Power Outages. But if short-term power outages become frequent, or if the power is out for longer stretches of time, I’d like to have some additional options.
This article is not about the type of backyard wind turbine that would be tied-in to the electrical grid. That type of turbine lowers your electrical bill, but doesn’t provide power when the grid is down. It is possible to have a wind turbine that works off-grid. But this approach requires a large bank of deep-cycle lead-acid batteries and specialized electronics to turn the battery power into AC current. The grid-tied wind power systems are expensive, and the off-grid systems even more so.
There exist commercial wind turbines, often called “micro wind turbines” that are small, portable, and designed to recharge batteries, not power a home. The most common application for this type of turbine is on sailboats. Southwest Windpower has several different micro wind turbines of this type. Current pricing (as of this writing) is about $750 to $1200. The least expensive one is the Air 30, which the company says provides “approx. 30 kWh a month at 13.4 mph (6.0 m/s)” and weighs only about 13 lbs — which is light, even for a micro wind turbine.
How much power is that? A 100-watt bulb, at 10 hours per day and 30 days per month, consumes 30 kWh (kilowatt hours). The average U.S. household uses (very approximately) 30 kWh per day of electricity. So this type of turbine is aptly called “micro”. It produces a very limited amount of power, but enough to be useful.
Most backyard turbines are rated at 11 m/s or higher wind speeds, so when a wind company rates their turbine at only 6 m/s, you know that the numbers are not exaggerated. The power in the wind is determined by a formula where the velocity of the wind is cubed. So a modest increase in wind speed greatly increases the power available for the turbine to extract. However, the design of the electronics in any wind turbine, small or large, will limit how much power can be extracted from the wind on the high end of the wind speed.
A commercial micro wind turbine is one option. But even at $750 or so, the price is too high, at least for my purposes. What I’d much prefer is a DIY wind turbine, one that provides the same or greater kWh per month as the Air 30, but at a much lower cost.
I’ve already started looking into the details of this type of homemade wind turbine. More on this topic in future posts.