Rooftop wind doesnt work

[Madscientist267]

I don't know the answer to most of those, but for the last one, I would have to say it's a matter of application.

VAWTs appear to do better as a small source (ie 1 or 2 on a rooftop), vs HAWT on a tall tower (or 50) for much more power.

I'm sure if one were to plot the curves, they would cross at some point.

VAWTs also seem to have physical limitations from what I can tell... When they are taller, they are less stable and need more support. While I'm sure this is somewhat of a trivial task, the cost involved probably warrants just installing a HAWT.

Steve

[B529]

From what I can tell, traditional HAWTs don't do well with turbulence.

Something needs to give between the VAWT and HAWT people.

I think it was said best earlier in the thread... 'if you're having fun'...

Steve
 

Based on my real world experience I have to disagree with the statement about HAWTS in turbulent sites..  I live at 9800' in the Colorado Rockies, very turbulent site, especially when we get the wicked "Chinook" down sloping winds. My turbine and others I've installed in my backyard are holding up, so far

What needs to give for me with the VAWT vs HAWT debate, show me a 10KW rated VAWT that will produce output like the Bergey 10KW that I linked at the beginning of this thread, I believe the Bergey 10KW  produced 190,000KW hrs last year on a 80' tower in a class 3-4 wind site.

This thread has seemed to take a turn, my intention was not to start a VAWT vs HAWT debate, rather voice my concern for the future of COMMERCIAL small wind. Sagrillo's article reflects what I'm concerned about. The vast majority of the crazy promises of output I see come from VAWT manufacturers, that's why I have a justifiable negative view towards VAWTS.

Once again building whatever design turbine for yourself, mounting it however you see fit, cool, you are having fun, learning something.

[DamonHD]

Yes, agreed entirely with the (self-)educational aspects.  My MotorWind produces tiny amounts of energy, and I funnel it all into my secondary off-grid power store, but it's nice to get a little at night, even if it is only a few percent of the time.  And I now *know* how poor a wind site we have.

I remain sorely tempted to buy a small commercial VAWT, well built so it can't/won't fly apart and maim my children or any passing neighbours, but I know in advance that £ for £ solar is better for me.

Rgds

Damon

[electrondady1]

Does a VAWT capture more energy in variable/turbulent winds?
Is a HAWT more efficient than a VAWT?
Is a VAWT quieter than a HAWT?
Do less birds get killed by a VAWT?
Which has a better $ per kW?

the answer to these questions are mostly self evident.

among those that favour hawts, there is no debate on lift vs. drag
 i have seen very few examples of those old style farm windmills
being posted.yet they are received warmly,perhaps with feelings of nostalgia

 surprisingly, among vawt adherents there is a very real divide between drag and lift.
i am firmly in the drag camp.
for me it's primarily about  aesthetics, rather than efficiency.
to that caustic designation, "yard art" used so often,  i say, yup.

 it's too bad unscrupulous salesmen can't be controlled.
its too bad people are gullible
not sure what can be done about that.
i guess if enough people get stung
 they will create some legislation that is restrictive and  does as much harm as good.
 

[Bruce S]

I don't get the hate for small wind here. I don't need gigawatts of power. A steady 20 watts would be just fine, esp. at night. 20 watts doesn't sound like much but if it's at night when the sun isn't shining it's 1/4 kwh/day of power I wouldn't have had otherwise. I do not expect to live off-grid like I could on grid. It won't happen.

As long as the output is not misrespresented and it doesn't cost $1000's of dollars, it can be useful. Even if all it did was light the property at night, that would be worth something.

Mounting it on the roof is probably a bad idea. A pole in the ground tied in one place to the side of the building should be okay, though. I can't put up a tower high enough to reach clear air, If it fell it would land to or three houses away.

If battery technology ever gets 'good' solar will be enough. I already make more than I can properly store. What I need is a battery that is affordable and will not sour if left in a partial state of charge for a long time. Maybe one day the NiMH packs from hybrid cars will come down in price. Right now at $500 for a used Prius pack the cost per kwh of storage is still about 5 times that of Pb acid.

You are missing the point of the post. The hate is not aimed at small wind. It is aimed at companies/installers grossly misrepresenting output, mounting VAWTS on roofs, and charging thousands of dollars to do so.

So what size roof-mounted VAWT (swept area) and wind speed would you need to get a steady 20 watts output?

I totally agree,bummer that we got off the main topic, my self included.
BIG problem is: where else on the 'NET or any other forum can one go; that has people who will have an honest open debate about this subject?
This forum "fieldlines" is one of few even around that people can have an honest conversation about the two without someone going fanatic about it.

Best would be to start a separate post, say VAWTs the swept area along with HAWTs and their swept area and go from there.
Include vitals like wind speed, voltage unit was built for, which type of alternator is being used .
That would be nice
Gotta go see the sunshine now before the clouds go hide it again

Cheers;
Bruce S
 

[JW]

Bruce I feel thats already been re-hashed, also, this is a good point from the previous poster-

i guess if enough people get stung
 they will create some legislation that is restrictive and  does as much harm as good.

JW

[Madscientist267]

B529 -

It wasn't my intention either to aid (or otherwise perpetuate) the whole VAWT vs HAWT thing.

What must be kept in mind, however, is that we've all seen both types precariously perched on the corner of a roof.

That's where my whole argument about application comes in. They are both sold commercially as rooftop systems.

Unfortunately, the 'debate' is intrinsic to the topic. 

Steve

PS - What part of the rockies? I used to live off Rt 9 across from the Gilpin county RE-1 School (subdivision called Missouri Lakes).

[electrondady1]

this is a good point from the previous poster-

Quote
i guess if enough people get stung
 they will create some legislation that is restrictive and  does as much harm as good.

hey! i final got one  )

well it begs the question
should those knowledgeable in such things, like this windmill community be passive about it and simply react to possible legislation.
or take a hand in forming legislation that could some how prevent  the uninformed  first time buyer from getting skinned by the crooks.
i know i'm taking a chance here , you guys might try to outlaw vawts )
 

[WindriderNM]

This is power they claim is at 33 ft high unobstructed not on a roof top. A roof top is an obstruction.
1500 kwhr/yr = 125 kwhr/mo at $0.10/kwhr =$12.50/mo this is in class 4 wind zones 12.5-13.4mph average wind speed/yr.  http://www.nrel.gov/gis/wind.html
Most of the country doesn't have this kind of wind.
MSRP of $6,495 before installation over 40yr return on investment under ideal conditions not on a roof top.

[WindriderNM]

Sorry the post i was referring to got deleted

[bradyaero]

It works if the turbine is designed for the roof....

<a href="http://www.youtube.com/watch?v=PMOQtOhFN2M" target="_blank" rel="noopener noreferrer" class="bbc_link bbc_flash_disabled new_win">http://www.youtube.com/watch?v=PMOQtOhFN2M</a>

Nice idea, but it's much too low to make use of the "sweet spot" that occurs on roofs like that.  They're getting a decent amount of non-laminar flow being that close to the roof; putting it up another 1-3 feet gets closer to where the fastest, laminar flow occurs.  Giving the wind some room to flow under the device would also help quite a bit.  A simple CFD analysis would get them much better results....until the wind changes direction

The top of the turbine is about 4.5 feet from the roof.  I think it is in the sweet spot of the laminar flow.  I could move it up further  but I think there is a low pressure zone being created on the  back side of the turbine near the roof that helps with the rotation.  And there is no sound at all from the turbine btw.
The length of the d-hawt captures non perpendicular winds quite well.  But the garage is situated that the prevailing wind comes directly accross the peak of the roof from the back field.  A fun experiment especially with no tower to deal with.

[TomW]

Sorry the post i was referring to got deleted

A post with just a link to commercial propaganda is hardly a "comment" or "discussion".

Tom

[electrondady1]

bradyaero
this new image of your mill is much better at showing the scale of your devise
this concept has been around for along time .
your the first i know to try it, and make it work.
thanks for sharing.

the area above the roof of a house is basically a low/no use zone for most people .
one of our most prolific builders and experimenters Jerry had something like 12-14
 4' hawts on the roof of his shop at one time and reported as much as 80 amps into his batterys.

noise transfer is the biggest hurdle.
there is no reason two vertical columns couldn't be placed near  the gable ends of a building ,
and a catwalk suspended between them that would act as a windmill platform .
nothing needs to even touch the house itself.

it would be easy to sweep 300sq.ft with a setup like that.


 

[DamonHD]

there is no reason two vertical columns couldn't be placed near  the gable ends of a building ,

... unless for example you live in a terrace like I do, just for a start!

Rgds

Damon

[electrondady1]

your jiggered !!
ha ha
damon,  i know people who have a terrace
i have even had brunch on a terrace.
how can you live in a terrace .
i have the feeling its a type of apartment building
nomenclature

[TomW]

Yet another instance of people sharing a common language and some terms have different meanings?

Terraced Homes:

http://en.wikipedia.org/wiki/Terraced_house

I had to look it up because here in farm country terrace has a fairly specific meaning I couldn't square with a house in / on a terrace.

Tom

[DamonHD]

Thanks for the translation Tom: your UN job goodwill ambassador role awaits...

This is our area:

http://maps.google.co.uk/maps?f=q&source=s_q&hl=en&geocode=&q=KT1+3JA&sll=53.800651,-4.064941&sspn=13.753309,27.773438&ie=UTF8&hq=&hnear=Kingston+Upon+Thames+KT1+3JA,+United+Kingdom&ll=51.406688,-0.288781&spn=0.00177,0.00339&t=h&z=18

Not great for turbines of any flavour.

Rgds

Damon

[B529]

PS - What part of the rockies? I used to live off Rt 9 across from the Gilpin county RE-1 School (subdivision called Missouri Lakes).

[/quote]

Steve, we are about 6-7 miles due west as the crow flies from there. Rt 119?

[Madscientist267]

LOL Yeah... that's what I meant... hahaha It's been a LONG time; I was 14 when we left...

Well awesome... I loved it there. Wish I could go back.

If you get curious some time, hit the neighborhood and you can see my old house... It's a 3 1/2 story box, 327 Evergreen Rd. The story calculation is somewhat of my own - 2 level basement (lower level is a full story down from the first), full walk in attic, 2 stories of living space. My parents got the place for 93K in 1981.

If you go in, go off to the right as you pass the first road (we used to own the corner lot too on the side after you cross that first road, can't remember it's name), and my house was after the A-frame on the left, right before you begin to go down the steep hill. Can't tell you the number of times I learned about gravity with a bicycle on that hill! 

Maybe if I ever get back to visit, we can exchange notes or something.

Anyways, sorry, didn't mean to jack the thread or anything. 

Steve

[electrondady1]

Kingston Upon Thames
nice address
it has a very nice ring to it.
i see your roof flashing is right up against the  neighbours wall.


 

[Madscientist267]

Not sure I follow...

Steve

[DamonHD]

ed: StreetView doesn't immediately show the right pic for us: we are end of terrace with no flashing:

Here we are with the solar panels above us: to the left at the same level is a separate house.

http://gallery.hd.org/_c/mechanoids/_more2010/_more01/solar-panels-and-light-snow-and-sunshine-and-blue-sky-in-January-in-Kingston-London-England-1-DHD.jpg.html

Rgds

Damon

PS. That set of panels more than covers our annual consumption BTW.  If we can do it, I think more or less anyone with a roof could...

[electrondady1]

are you allowed to build anything outside?
 what is the distance between the end of your section and the property line?
if you can get a variance you could cantilever something inwards over your roof.
some thing like an  exaggerated capital letter F
the trick is building it so it looks like it belongs there.
off grid in Kingston Upon Thames, that's even better.

[DamonHD]

Not allowed to alter the external appearance without permission.

Measurable wind blows here <10% of the time!

Rooftop wind would not work here with the best will in the world since the resource is too poor.  And I suspect it is so for most dense urban areas.

Rgds

Damon

[Bruce S]

Bruce I feel thats already been re-hashed, also, this is a good point from the previous poster-

i guess if enough people get stung
 they will create some legislation that is restrictive and  does as much harm as good.

JW

JW
Not sure which part has been re-hashed? 
Most of the stuff coming up for both styles on here now is re-hashed again.
More info please 

[JW]

Hi Bruce,

I made that remark at a half glance 

I thought you were just talking about pro and cons of vawt verses hawt.

My mistake 

JW

[WindriderNM]

here is a site that tested several rooftop windmills in the UK the results are interesting with lots of good research and data including claimed output vs measured and pretty charts and diagrams showing things like air flow around building. http://www.warwickwindtrials.org.uk/9.html

[Bruce S]

Hi Bruce,

I made that remark at a half glance 

I thought you were just talking about pro and cons of vawt verses hawt.

My mistake 

JW

No worries, just wanted to make sure I hadn't drifted again

[Beaufort]

here is a site that tested several rooftop windmills in the UK the results are interesting with lots of good research and data including claimed output vs measured and pretty charts and diagrams showing things like air flow around building. http://www.warwickwindtrials.org.uk/9.html

Thank you for posting a link to this study, I haven't run across that one before.  The results are pretty shocking; they make solar look good even for the UK.  Out of all the numbers, graphs, and charts in the presentations I never saw any reference to the effect of time on windspeeds and power levels.  I think they missed a valuable opportunity to analyze the anemometer data to discover why the turbines don't produce the stated power at a given windspeed.  We know in real life that wind changes direction and speed quite frequently in "urban" settings like the ones tested in the study.  HAWT's cannot react to these changes with the speed of an anemometer, there are many reasons why.  These turbine manufacturers develop the power curves based upon steady-state wind conditions in a test tunnel or on a vehicle.  From my own research, this alone can explain why results look so bad in studies like this.  There are other studies like this one that simply present the aweful results and then stop; while it's informative it doesn't help anyone make wind turbines that perform better in these environments. 

I've said before on this site that the industry needs to develop a measurement system for turbulence so we can measure the degree to which rooftop wind is wonky, and then evaluate wind turbines based upon how quickly they respond to those conditions.  I don't see any efforts like this, aside from applying general "roughness factors" to textbook topography examples.  We're putting a lot of gear up in the air that's designed for ideal conditions or wind tunnels.  We should be designing turbines that react quicker to turbulent conditions, or evaluate VAWT's to see if they give better results.  With the kind of numbers in this study, I wouldn't be surprised if a VAWT produced numbers closer to predicted.

[bradyaero]

all of those mills are hawts on roofs... how stupid is that?  Try a d-hawt designed for a roof and you might actually generate some electricity... now how innovative is that???

[DamonHD]

You might also capture a unicorn in flight.

I think the fundamental point remains that for most urbanites *the wind resource is just not there*.

No amount of magical/alternative/innovative turbine design can overcome that: in this forum we continue to obey the laws of thermodynamics.

Rgds

Damon

[bradyaero]

You might also capture a unicorn in flight.

I think the fundamental point remains that for most urbanites *the wind resource is just not there*.

No amount of magical/alternative/innovative turbine design can overcome that: in this forum we continue to obey the laws of thermodynamics.

Rgds

Damon

Wow you just solved the whole issue with one comment.  Pat yourself on the back and have a beer.