Rooftop wind turbines offer a relatively inexpensive way to participate in the rush to renewable energy. The principle allure is low installation cost. Typically, tower installations for larger turbines add 50-80% to the cost of the system. With a rooftop turbine, an $800 tower is replaced by a $39 roof mounted tripod, or a length of pipe attached to the side of the house.
According to Ron Stimmel of the American Wind Energy Association, “…rooftop turbines still account for only 1 percent or so of the 10,000 small wind turbines that are sold each year in the country.” For this reason, few performance statistics are available from actual owners.
It’s possible, however, to get an idea of the estimated power output of a rooftop turbine from the manufacturer’s website. For example, the Energy Performance chart for Southwest Wind power’s 200W Air Breeze predicts 20-30 kWh (kilowatt hours) per month from 10-12 mph winds occurring 6 hours per day.
To put this in perspective, 30 kWh is less than 5% of the power consumed each month by the average household. Overall, the payback from a single, roof mounted turbine in tangible financial terms leaves a lot to be desired; especially in light of the fact that unlike solar, there is no Federal tax credit for residential wind power.
But anyone thinking about installing a rooftop turbine(s) is probably aware of this already. The rooftop wind enthusiast is not motivated by financial relief, but rather the intangible rewards of pride of ownership, walking the walk, or simple satisfaction as a hobbyist.
Motivation aside, it doesn’t make sense on any level to proceed with a wind powered project unless the three following requirements are met:
1. Higher than average cost per kWh. The more you pay per kWh for electricity, the more economical wind power becomes. A rule of thumb in the wind turbine industry states a residential wind powered system shouldn’t be considered unless you pay $0.10 or more per kWh for electricity.
The easiest way to determine your cost per kWh is divide the current monthly balance on your electric bill by kWh usage (also plainly stated on your bill).
2. Building codes. Visit your building department to find out if there are any zoning restrictions for roof top turbines. Don’t build your rooftop system first and ask questions later – only to be told it violates zoning laws and must come down.
3. Minimum wind speed. Wind speed of 7 mph, or 3 m/s (meters per second) is the start up speed for just about every wind turbine. However, in order to get any “juice” out of the turbine, minimum wind speeds of 10-12 mph for 6 hours per day are necessary.
Although wind speed charts for the United States and Canada are available to help site larger turbines, they’re of little use for rooftop systems because the data is collected at a minimum altitude of 30 meters (98.4 feet).
However, you can get a good idea of the wind speed at proposed turbine locations by purchasing an anemometer (wind speed meter) for around $150. The kit comes with a rooftop sensor, 60′ of cable and mounting hardware for the read out display. These are not data logging meters, so you’ll have to keep notes on your observations.
If you’re really serious about wind speed data collection, you can purchase a data logging anemometer kit with tracking software for $400.
Depending on where you live, wind speeds generally fluctuate with the seasons. Readings taken during the hot summer months of July and August, when you’re begging for a breeze, are not usually a reliable indicator of average yearly wind speed.
Also, rooftop turbines located at the edge of a long flat roof experience much more wind than those located on roof peaks.
If, after a month or two of collecting data you determine there just isn’t enough wind for a rooftop wind turbine, you can always resell the anemometer and turn your attention towards solar.
Wow! Is it ever hard to find low cost wind turbine plans. A couple years ago when we went online looking for wind turbine plans we found plenty of sources of them.
The problem was that all of the authors seemed to want to prove to me how smart they were. I knew there was a better way to build a wind generator then going to university to learn all of the terms so we set out to build our own wind generator.
I thought it was going to be a monumental task, but in reality it only took us about 2 weekends to complete… and the best part is it could pass for one of those fancy commercial models.
Our wind generator produces 1000 watts at wind speeds of around 15MPH. We went ahead and built a second one so that our solar system wouldn’t have to be as big. Right now we could last for about a week on batteries if the sun didn’t shine and the wind didn’t blow. The funny thing is that usually if the sun isn’t shining the winds blowing and vice versa.
The goal when we built our wind generator was to build it for $500. I’m happy to say that we only spent $150. We got the motor off of eBay for cheap. The tower was free (yes, you can get free towers), the blades were made from 8″ sewer pipe cut into a special shape, and we had to buy some other assorted nuts and bolts at the hardware store.
You will also need to go to Radio Shack (or circuit city I guess) and purchase a diode. A diode is an interesting little component. It only allows electricity to flow in one direction. This little piece of hardware is crucial for your wind generator. Without it your batteries will start to spin it around instead of it producing power to fill them. I made this mistake right after we finished and I hooked it up. It was a calm day and to my surprise it started spinning like mad! After we got the diode hooked up it worked quite well though.
So the next time you’re looking around at low cost wind turbine plans on the internet just remember that the author probably wants to show you how smart he/she is. Make sure to contact them first and ask them whether or not a beginner would be able to figure them out. And remember, if we could build a wind turbine then you can to.