Question on Rooftop windmills

[Murlin]

I have read lots of pros and cons about rooftop windmills and had a question.

I live in an area where there is plenty of unobstructed wind.

My Idea is to use several smaller mills across the peak of my house instead of one big one.

That way if one goes down, you still have something turning.

How close together can you put your windmills without them interfering with one another?

Murlin

[DanB]

'How Many is too Many?'

I would say 1.

'roof top' wind turbines (those very small ones that companies suggest you stick up on the roof) are really too small to make much usuable power to begin with.  Furthermore they are loud - they'll most likely make all kinds of racket in your house.

Very small wind turbines are expensive when it comes to cost/KWH - putting them on the roof makes things even worse.  Better to get a larger machine and put it on a tower.  Good wind turbines should have little or no 'down' time - that really shouldn't be a concern.

[Murlin]

Thanks Dan I value your experience in these matters.

I have none what-so-ever and it is always a good idea to get all the facts so one can start off in the right direction....I was planning to build a 10'.

Would it be your opinion to just jump right in and build the larger one then?

Murlin teh newb

[wdyasq]

What you really need to do is try to get a night's sleep in a boat that has one of the small gennies stuck on a mast.  Then your first question will be a mute point.

I would be reluctant to to advise one to build over 10' without a bit of experience first. Loosing 6-8 pounds of wire and the resin/mold/time is not an inexpensive learning curve. All you learn on a smeller one can be put to use on the larger one. When it works, you can probably re-coup your costs if you choose to do so.

Tower costs are a large part(if not the largest part) of a Generator project. If you plan on a larger mill and build the tower accordingly, it wil be more safe than a minimal tower for a smaller mill.

Do a bit of cost analysis, combine it with inexperience, and you will realize building a "stater mill" makes all the sense in the world. It also has few drawbacks.

Be sure to consider and select a voltage for inverter and battery bank you can live with. It may be you want a 12V or 24V small mill and then use all the down pole wiring and such for a larger 24V or 48V mill.

Good luck, and keep a tight guy-line.

Ron

[Murlin]

There was a few things I left out on my Idea.

I am building a straw bale house. The framework for the house will be a pole barn type construction with 22" thick walls after the bales are plastered with aggstone.

The roof will be made out of 28 guage metal and could have a concrete area under the windmills so if one came apart the damage would be minimal.

Since the walls and roof will be insulated to a value of around 40 to 50 it would be quite noise resistant.  But I would have no way of knowing how much noise would actually be transmitted through the steel framework and could be felt in the main structure.

Since the framework was to be made out of steel, My original idea was to have telescoping poles inside the main uprights(possible 6" or 8" steel square tubing) inside one of the walls so there would be no guy wires. A nut and screw would raise and lower the turbines for maintenance.

A slow turning large turbine would easily be supported by such a structure.

Would this make any difference in your first opinion, as I would be mounting the larger turbines and not a small fast RPM ones?

Murlin

[Bruce S]

Murlin;

    Once upon a time, I looked into building just such a type of house, but family a work kept me from it.

Here's one point and possibly the biggest reason not to attach the 'mill to the house.

The vibrations coming from the mill will be amplified throughout the entire metal structre, combined with other than just the noise being all pervasive can in the long term lead to advanced metal fatique, cracked plaster,etc...

Mr. Tesla was able to prove this accidently during his years of building free-running multi-vibrator circuits:--)were the building metal would sync up with the vibrations at different intervals and begin causing stuff to shake apart of dance.

If you have the expertese to build this house frame then you have more than enough knowledge to rig up a tower for the gennies.

Since I live in the city, I have to go the route of building smaller lawn ornaments as they are lovingly called by he city, and then series/parallel them for and decent level of usage.

If you are confined or simply must put them on your roof , have a look at some of -Eds House mounted VAWTs. It may help in your decisions.

Either way good luck on your endeavors, and do send pics of the house as you progress I for one will be watching with great interest.

Cheers!!

Bruce

[Murlin]

Thanks guys for all your comments as I am in the planning stages of all of this and any input is welcomed with open arms.  We are currently building my fathers house and should be getting the bales of straw for that project very soon.

I guess the main reason I was trying to figure out an alternative mounting method was to eliminate the need for guy wires all over the place.

I can see that if I want to accomplish this goal, tower design will have to be the way to do it.

I will just have to build a little more expensive tower that is larger at the base like the old style windmills.

If I need to take the alternator down, I will have to disconnect it and wench it to the ground instead of taking the tower down.

So how does one determine the height of tower that is needed?

Murlin teh questions, questions     ...

[kamikaze]

Hi Murlin,

Despite what many people think, I believe roof mounted wind turbines will be a common sight in the future. The biggest problem you would face now is that there are no suitable wind turbine designs currently available for roof installation, due to the noise and vibration issues already mentioned. However some of us are busy developing designs that will address these problems.

Meabwhile, a tower mounted conventional design as favoured on this forum is probably your best bet. You can always add roof mounted mills when suitable designs become available.

Regards Kamikaze

[Bruce S]

Kamikaze;

   This is a very good idea.

 Put up what currently works then progress towards the next level. One thing that could be used would be vibration dampeners much like the V6 and V8s of old used. There are still items mostly for RVers sold through JC.Whitney that are used to take the shimmy out of out-of-balance rim/tires. These could be tried as well.

-Eds design seemed to be a very stable one and I don't think he had too many complints about the vibrations either.

Hopefully he'll chime in here and give his past data findings he's done tons of test with these units.

Cheers!

Bruce S

PS I much ( even though they are not as eff%) prefer the VAWTs , just cooler looking to me.

[commanda]

Hugh has a write-up on why not to roof mount a wind turbine.

http://scoraigwind.com/

Part way down the page.

Amanda

[windstuffnow]

  Bruce is right, not all roof top instalations are problematic.   I've had the Lenz2 on the roof since last fall with little to no problems.  You have to be in a certain area of the house and be very quiet to hear the faint hum of the alternator.   It did develop a clicking noise once per revolution which I found a loosed bearing nut.  Unfortunately I miss the click because it made it easy to count off the clicks and time it for rpm estimations.  Oh well, maybe a cloths pin and card like we did when we were kids on our bikes to make it sound like a motor cycle.  The turbine is fairly small though and only offers a couple hundred watts of extra power to my battery bank.  

  I believe the main point everyone is trying to make is that if the turbine is higher you'll get better performance.  It would be difficult to build a high speed system and keep it from echoing through the roof.

  In the case of our original poster it may not be a major problem because of the dampening effect of the structure depending on exactly where the turbine was mounted.

  It might not be the best location but there is power to be captured whenever the wind blows.

.

[vawtman]

Murlin awhile back I made a posting on rooftop vawts that I think could work and still working on.Vawts will run silently just need to design absorbers like rubber flashing through the roof and other things.Straw house hmmm watch out for the big bad wolf Lol

[Murlin]

One thing people who are against rooftops might have not considered, is that if you build a house with ideas in mind, incorporating renewable energy ideas into the design of a house may be easier, and work better than adding to a current structure.

For instance, since I am building a straw bale house where the walls are 22" thick, I might be able to incorporate tower poles inside the walls that do not actually attach to the steel structure itself and go right into the ground. it would be cushioned by the straw on the inside of the wall.  Since the hard agstone is only about 3" thick and the inside is just empty space, free standing turbine poles could run the length of the structure. The best of everything.  Less wire length to the batteries, wiring terminal, ect...Guy wires could still be eliminated and the turbine could still be mounted high enough to get above the turbulence.

But I would not want my agstone cracking all the time and have to do that much added maintenance as there will be enough already having to whitewash it every year.

But I guess one could use cement stucco instead on that wall and not worry about it.

Of course one could do wind tunnel tests and make a roof design that would actually increase the wind velocity as it moves across the surface of the roof.  Utilizing a complete 360 degree wrap around porch, the pitch of the roof could be kept to a very low profile on the outside parameter.  As long as your house in not very tall say under 20 feet tall at the highest peak on the roof and about 7 feet around the porch area, landscaping could be done to deflect any ground winds to flow smoothly over the top of your house.

These are just thoughts of theory that I have been tossing around.

I would want at least 4 turbines on the roof producing 2k+ watts each.

All of this requires more brain power than I have....

so I think the easiest is to do what others have suggested and just build a separate tower.

Murlin teh open to suggestions...keep 'em comming

thanks

[vawtman]

Where theres a will theres a way just think about it Murlin,Fun stuff

[domwild]

Murlin,

Our frequent contributor Jerry has 10 or more mills on top of the roof of his workshop. Check this forum via Google until you find Jerry's photos.

Mind you, the workshop is most likely in an industrial area where noise is of little concern. And vibrations? Only he will be able to advise you on that.

[elvin1949]

Murlin

 I have no experince with wind turbine's on

a roof,that said.I do with metal roof's.

 I have a metal roof on my house.When it rain's you can't talk to anyone because they can't hear you.

 IT IS LIKE LIVING IN A SNARE DRUM WITH SOMEONE HOLDING A PRESS ROLL ON IT.Just glad it don't rain all the time.

All wind turbine's viberate?sp  at some RPM'S

the harmonics will drive you nut's.

later

Elvin

[Murlin]

I have been living in a house that I built for the past 25 years.  It has a tin roof.

The only place it gets really loud is on the porch.  I have double insulation in the ceiling and walls.  Inside the house with the doors shut, you can barely hear the loudest of rainstorms/hailstorms.

We get marble to golf ball size hail every year and even then it is not that bad.

Now going out on the porch, well it's like you say, you ARE inside the snare drum

Murlin

[electrondady1]

placing a large windmill on a conventional house would almost garantee vibration/noise problems. but if your starting with a blank page there might be ways around it . in the case of a vawt,the devise would need to be about as big as a house anyway. if you build a large support structure for it it may be possible to suspend /isolate/vibration dampen the living quarters within the structural members.

[electrondady1]

thats not very clear, what i was trying to convey is if you create a large rigid structure,structural steel, reinforced concrete, whatever, supporting the weight, channeling vibration and moment into the ground , it would be possible by minimising the contact points to create a structure within, that was isolated from the vibration .

[Bruce S]

Murlin;

   I read this last night and thought about the task at hand all day.

I then got the bright idea to call one of my neighbors , he's a structural engineer by trade and `cylce restorer by hobby. I explained to him what you want to do with the info you put here.

At first he said, as many have already done, that it was not a good choice. He then called me back and said that if this is a must then there are a few things you can do to make this work out.

So here's what he recommends:

1. ) Don't do this, build towers instead.
   
2. ) Any steel beam you plan on using as a support for the `mill will need not to be connected to the house structure at all. This is not as hard as it sounds, merely that once you start putting in the side walls isolate these beams by building wooden frames around them and not attach any wall material to them. You will only need as little as ½" clearance on all sides to accomplish this, it would be okay if Fiberglass insulation or blow in insulation was touching tho.
   
3. )  If you build a HAWT the bottom of the blades' lowest arc must clear the highest point of the roof by no less than 10 feet. This will ensure that no one will get hit and will lessen any wind noise, plus have the added advantage of having the `mill up away from the turbulence of the roof.
   
4. ) At least one set of guy wires would be needed along with using what he called Anti-galloping springs on the guy wires and depending on the height, more wires would be better.
   
   

He gave no mention of raising and lowering the tower, he didn't want the tackle that part at this time. Except if you have the main poll inside the main support, then possibly you could build into the attic specific "holes" for raising and lowering the unit, making use of a block and tackle device, as this puppy is gonna be heavy.

Also, the wires should run down inside the poles to lessen the possibility of shorting them out on the supports.

Another idea to help with isolating the vibrations would be to use motor mounts as dampening devices.

Hope this helps;

 Bruce S

[Murlin]

Here is a crude picture to help visualize my original Idea.

I am leaning towards building a freestanding tower and constructing one large gene, instead of multiples.

But the Idea is tempting.

[wdyasq]

Still waiting to see a successful VAWT with a track record and puts out 2+kW.

Ron

[powerbuoy]

I believe that you'll be able to do it as long as you stick with a VAWT approach. It probably will come down to a Ed Lenz approach in combination with a no-cog alternator.

Everything else will, as was said before by others, vibrate away ...

Powerbuoy