[RE-wrenches] Skystream tower heights

[Dan Fink]

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 <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
>
>
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