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:[email protected]>[email protected]>
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 <[email protected]>, 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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