Wind Turbine Noise

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Wind Turbine Noise

Postby Power4nico on Wed Jul 16, 2008 6:08 pm

Hi there!
I am considering installing a Wind turbine at my house, in a suburb in the city.
My concerne is:
1. Are there any restrictions to such installations in a built up area?
2. Do they make enough noise to bother the neighbors?

Anyone care to give me some answers?
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Re: Wind Turbine Noise

Postby windgat on Wed Jul 16, 2008 6:19 pm

Hi Nico. In Cape Town there are no specific restrictions. Normal property boundary and height restrictions apply, as for any construction.

The noise level depends on the design, mainly the blades. Mine is practically silent: in low wind it makes no detectable noise and a nearby tree produces more noise in a strong wind.
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Re: Wind Turbine Noise

Postby Power4nico on Wed Jul 16, 2008 6:31 pm

Hi windgat,
Thanks for the reply. I have been going thru the forums postings, and your name comes up all over. Are you the main guy on this forum?
I would greatly appreciate any info you can give me on a suitable wind turbine. I live in Kimberley, and I have already installed a 2400w solar array, complete with Outback Charge controller, 2 x 3kw Inverters, a 660AH Battery bank. This supplies my home with power during the day, and at night I change over to eskom power. Works very well! However, we have many days (and nights when the wind blows, so I want to try to suppliment my system with a W/Turbine, I'm thinking a unit around 2-3Kw.
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Re: Wind Turbine Noise

Postby windgat on Wed Jul 16, 2008 8:18 pm

Have you an idea of wind speeds there? If you give me a specific windspeed, I can estimate the size of the turbine blades you will need to get 2-3kW. Its probably around 3-4 metre diameter, which is big to have in suburbia. Maybe there is space for a couple of smaller ones?

PS: Yes, I'm the guy who made the stuff on the website.
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Re: Wind Turbine Noise

Postby Power4nico on Sat Jul 19, 2008 7:59 am

Hi windgat,
mmmmm....Wind speeds? You know, this is a bit difficult. There are days when there is hardly a breath of wind, yet there are days when it really pumps (around 30 to 35 km's/h), but on average I would say that 3 out of 7 days are windy and maybe the speeds are around 2 - 20 km's/h.
You make me worry when you say that wind turbines bigger than 3-4m dia. is not suitable for a suburban installation! Please give reasons?

When I look at some of the perforomance curves of W/Turbine outputs at various wind speeds, I note that the bigger units produce more Kw at lower wind speeds. My thinking is that this is the way to go, rather than trying to use a smaller unit which needs an average of 20 or so Km's/h to give a decent output.

One other reason why I want to go for a wind turbine is that this "alternative energy thing" is a hobby of mine, and a hybrid system would really tickle my fancy.
If the wind can produce maybe up to 50% of my yearly power requirement, I would be happy. I am even looking at the "feul cell" technology. I have designed (from info I've gathered) a workable Feul Cell Hydrogen production unit and genertor. But I want to go for the wind first! It blows around my place and it eats me when I know that's "lost power" going by!

I'm Honoured to be talking to the main guy!

Regards
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Re: Wind Turbine Noise

Postby windgat on Sat Jul 19, 2008 5:15 pm

Like all compromises, its hard! Unless you have variable pitch blades, they will be optimised for a particular wind speed. 2km/h wind has such low power density that its really not worth worrying about it. Working with 20km/h = 5.5m/s:

Wind power available is about 0.6 Av^3 (or 0.6 x A x v x v x v).

So for a 3m diameter: area A = 7sq.m, and power is 0.6 x 7 x 166 = approx 700watts.

Now that is the kinetic energy in the wind, of which 0.6 is available for conversion = approx. 420watts.
A good generator will get 80% of that into electricity = 335W.

So now you can follow the above calculation with various wind speeds and diameters. You will see why manufacturers often quote power at 10m/s! (Other deceptive advertising will quote the rating of the generator - nothing to do with the power actually produced). You will also see why small systems (<1m diameter) are very limited.

A turbine larger than 3m diameter is big, and therefore heavy. Safety considerations, such as consequences of large blades becoming detached in a storm, and also engineering issues, such as how to get something that heavy onto the top of a pole, are behind my thinking about suitability for suburbia. If you have a small holding or large garden, and space to lower the pole horizontally, that is different.
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Re: Wind Turbine Noise

Postby Power4nico on Sun Jul 20, 2008 9:04 am

Hi windgat, Thanks for the reply and calculation on wind energy, I did not know that. However, my good friend, getting poles up with "heavy" objects on top of them, is no problem (even in a small space). I'm in the engineering game with a 35 ton mobile crane.
I'm very interested to see what you've done. Is it possible for you to send me pic's of your installation on this forum somewhere, or direct to me at njnel4@telkomsa.net.
Now you mention "large blades becoming detached" in storms! Is this somethng that happens to well made W/Turbines? When building roof tops are ripped off, big trees blown over, etc. is a W/Turbine expected to survive such extreme winds?

Tell me, would a "multi-bladed" rotor not develope more torque, than say a two or three blade prop for a given diameter? Similar to a typical "wind-Pomp"
What about a "double" or even a "trebble" prop or rotor? Has anyone attempted to make something like this?
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Re: Wind Turbine Noise

Postby windgat on Mon Jul 21, 2008 9:47 pm

Wow, ok, a crane like that makes a difference. Of course not all of us have access to such a device...

There are loads of pics on the site - have you looked under Photo Galleries?

Re Storms: Well I have not yet seen a roof ripped off in Cape Town! I was thinking more of the risk of a flaw in the manufacturing, which is possibly a concern to the home DIY'er.

Re Blades: It helps others follow and find postings if we keep on topic... would it be possible to post the question under "Blades and Hub"? Your question raises important issues, and I would very much like to post a reply there.
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