[RE-wrenches] Skystream tower heights

[Ian Woofenden]

Dan,

You said it so well. I'll only add that it has given the small wind 
industry a HUGE black eye to have major manufacturers pushing short 
towers. It will take us decades to overcome. On a weekly basis, I 
deal with the fallout from this, from Home Power readers, workshop 
students, clients, authorities, the general public, etc.

Too many manufacturers do not even sell a tower for the NW, since 
sites where it's appropriate to have towers shorter than 100 feet are 
quite rare here, and 140-plus is more typical if you are serious 
about kWh, not just stuff that spins, in this land of very tall trees.

I would love to see manufacturers saying "we don't sell a tower 
shorter than..." instead of "we don't sell a tower taller than..."

Thanks,

Ian

PS -- If I lived underground on the tundra, I'd buy a 60-foot tower, 
at least... ;-)

PPS -- I hope to see a bunch of wrenches at the 
<http://www.smallwindconference.com> in June.



At 9:44 PM -0600 4/28/12, Dan Fink wrote:
>Ross;
>
>The Skystream has a reputation now of a reliable performer at a good 
>price point, and your SWWP monopole towers are attractive and sexy 
>as long as a concrete truck can get to the site. But we couldn't 
>recommend a Skystream on a 34 foot monopole to anyone anywhere -- 
>violates the 30 foot rule. The 45 ft monopole would be OK assuming 
>the site has nothing taller than a wooden cow fence anywhere within 
>500 feet. That's a pretty rare situation.
>
>Single story building heights of 30 feet are the norm in most 
>places, as are tree heights of 40-60 feet. The price on your 60 foot 
>monopole is jaw-dropping for most of our clients.....but they need 
>to buy your tower to get a warranty. We are usually recommending 
>towers of 80-100 feet. This excludes your products from our 
>recommendations in all but very rare, clear sites.
>
>All I can say further is........
>V = V0 x (H/H0)^alpha
>and that alpha exponent is really a bitch. Even experienced, highly 
>qualified small wind experts underestimate it much of the time I 
>think -- I've seen some amazing wind conference presentations of 
>site photos compared to MET tower alpha measurements on this topic. 
>And then we have turbulence intensity...yet another factor.
>
>I have a great slide show we use for all of our wind power intro 
>classes (the class is called "Wind Power Reality") It's photo after 
>photo of "Good turbine, bad site." Skystreams on short monopoles are 
>80% of the photos. We have our students estimate alpha exponent, and 
>de-rate the skystream  energy curve of kWh per month. I wish we 
>could get real data to see how our estimates come out....but it's 
>ugly.
>
>We just cannot, in good faith, try to tell a Client to fly a wind 
>turbine on a tower that's too short. They will blame *US* for the 
>lack of production, not the wind turbine manufacturer. And 74 feet 
>is WAY too short in most of the cases we see.
>
>No offense intended, we see how client's jaws drop when they see 
>monopole tower prices....that gives some unscrupulous dealers an 
>incentive to be deceptive and fudge the data. But it's way cheaper 
>to increase the height of a tilt-up or guyed lattice tower from 40 
>to 80 or 100 feet, compared to doing that with a monopole.
>
>*It's all $ / kWh, on the grid or off.*
>And wind speed pays back 8:1 on your bet...or overestimating it sets 
>you back 1:8, with an angry customer too.
>But in Vegas, there's a pit boss. In Small Wind, it's the wild wild 
>west, it seems.
>-- 
>Dan Fink,
>Executive Director;
>Otherpower
>Buckville Energy Consulting
>Buckville Publications LLC
>NABCEP / IREC accredited Continuing Education Providers
>970.672.4342 (voicemail)
>
>On Sat, Apr 28, 2012 at 7:51 PM, Ross Taylor 
><<mailto:ross.taylor at windenergy.com>ross.taylor at windenergy.com> 
>wrote:
>
>Hi Bob, I'm not sure if this was a question or a good-natured (I 
>hope) jab.  But, since you asked, I think it's appropriate to 
>answer.  We sell mono-pole towers for the Skystream in heights 
>ranging from 34' to 70' and we also have guyed towers to 70' as 
>well.  Our most popular tower is the 45 foot and we actually 
>discontinued the 34 foot tower.  But, in places where that tower 
>works just fine (coastal installations, the plains, etc) our dealers 
>complained very loudly and requested that we re-instate it.  So, we 
>did and we do still sell those.
>
>I don't want to derail the original thread and I'm happy to discuss 
>tower heights with you, perhaps offline, but I would respectfully 
>submit that the right height for a wind turbine (ours or anyone 
>else's) is that height which puts the turbine's rotor in clear air. 
> That height will depend upon the terrain, vegetation, structures, 
>and the wind conditions/speed.  By better training our dealers, 
>we're hoping that they will select the right tower for that site and 
>the conditions which exist there.  And this has, indeed, led to 
>better installations.  So, this is the reason the OP won't find a 
>direct sales channel.
>
>Respectfully,
>
>Ross
>


-- 
Ian Woofenden <ian.woofenden at homepower.com>, Senior Editor, Home Power magazine
Subscriptions: $14.95 per year PO Box 520, Ashland, OR 97520 USA 
800-707-6585 (US), 541-512-0220
or download free sample issue at <http://www.homepower.com>
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