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Florida HAWT Project: Worth It?
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By DigitizeLife, Section Wind
Posted on Fri Aug 29th, 2008 at 10:04:08 PM MST
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After researching designs and doing some preliminary calculations, is it even worth attempting to build a wind-generator in Florida?
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| My family has lived on 3 acres in the rural Sarasota/Bradenton area for 30 years now. As a family of DIY'ers, we've been itching to make use of the back acre of unused pasture by raising an HAWT Generator, and maybe even help reduce our 1,500kWH/month nasty habit. We've taken the first-steps to rehabilitation by adding insulation, adopting a conservative lifestyle, and even heating our 200 gallon water heater with solar. But, we still drank about 18,000kWH last year from the local pub we call FPL (Florida Power & Light).
So, we have a bare acre of land with nothing but grass, sun, and wind for a few hundred feet in any direction (and nothing else for a few thousand feet in the E.N.E. prevailing direction). Also, three 20' sections of steel pipe, a garage full of tools and materials, and a family of resourceful builders are in our arsenal. Envisioning a 60' tower in the middle of this pasture with a wind-turbine chopping through Florida storm-winds is enough to get any green-geek like myself excited.
Wind Statistics for Bradenton/Sarasota, Florida
Although our annual average wind speed is around 9.3 MPH, during the rainy seasons in this part of Florida (and especially hurricane season), we see afternoon thunderstorms almost every other day. These storms easily produce winds of 16 MPH and can approach 30 MPH quite often. So, we are faced with two options here;
- Construct a typical HAWT to make power in the low average winds of 9 MPH.
- Take advantage of the exponential energy potential of higher wind speeds and build a rig able to make power in, and withstand the Florida storms (albeit for a much shorter duration of the year).
Assuming we can design, assemble, and erect a unit well enough to utilize about 30% of the winds total potential energy, we would have to fly a 15' diameter turbine in our 9 MPH average winds to produce a mere 206 watts of electricity. If my math is right, that's 150kWH/month; 10% of our 1,500kWH/month average. With an average utility bill of $150/month, that's a savings of $15/month, or $180/year. With such a mediocre net result, it's hardly worth mentioning the inevitable disaster that a 15' diameter HAWT would create for a first-timer.
So, is there a way to have my cake and eat it too? Can we extract the gobs of power available in our storm-winds, help offset our utiliy bill, and do it all with salvaged materials and a little ingenuity? Let's look a little closer.
Let's say optimistically, that during the rainy season, we get 2 hours of sustained storm wind every day. We would still need to generate 2,459 watts throughout the duration of the storm in order to make the same 150kWH that our 15' turbine could generate each month. That would require a HAWT & tower that could stand-up and face head-on into 25 MPH winds for two hours, and have 12' diameter blades.
That's alot of speculation and even more dangerous circumstances. So, is wind energy a feasible alternative energy source for small-scale residential use in this area? That begs & remains to be answered. With such a small amount of energy being produced, offsetting so little expense, we would have to be very resourceful and creative to keep costs down. Otherwise, it would take years to even cover the cost and of the materials.
Considering the generator will be mounted atop a 60' tower, I would be comfortable designing and building no larger than a 8' - 10' diameter HAWT in order for it to remain an affordable, safe, and durable project. Here are some approximate figures;
- ' @ 9 MPH = 91 watts * 24hrs * 30.5 days = 67kWH/month = 4.4% Savings ($6.70/month)
- ' @ 9 MPH = 74 watts * 24hrs * 30.5 days = 54kWH/month = 3.6% Savings ($5.40/month)
- ' @ 9 MPH = 58 watts * 24hrs * 30.5 days = 42kWH/month = 2.8% Savings ($4.20/month)
This means with a 10' diameter rotor we would be saving about $80 per year on our power bill. Assuming we could build it all for $300, the system would take almost 4 years to pay-off. Unless my calculations are completely wrong (which they may very well be), it doesn't look like wind energy is a very viable method of reducing energy costs for low-wind applications.
Note: Wind energy is a very new concept for me and I am only beginning to learn the fundamentals of how it all works. My methods of calculating kWH/month and potential power (watts) from wind systems is based on articles and formulas posted online. Please feel free to correct any figures or suggest better alternatives, as I would very much like to see a wind generator in my future! |
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