PVs on tower [RE-wrenches]

[Ian Woofenden, Home Power]

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Hi Jeff,

Kelly and I are working together on the same project. It will be the 
wind and PV project for SEI's NW workshops in October of this year.

I'm surprised that there's so much concern over this. It seems to me 
that it's an engineering problem, and tower manufacturers have to 
deal with this all the time. That's been proven in our contact with 
these companies. They can engineer for whatever loads we specify, and 
have no trouble supplying a tower for the wind generator and PV array 
we are planning. This project is going through the local permitting 
process (!), so it will be fully engineered for our local winds.

Kelly's recent question was about tilt angle and a compromise we were 
considering to make mounting easier and keep the array compact. Our 
original plan was to lay the modules out in a tall, narrow 
arrangement on the tower, but if they were tilted, we'd have to 
spread them much higher than we preferred to avoid them shading each 
other. We've recently decided to go with a wider layout, and to tilt 
the modules to the optimum angle, and space them to avoid shading. 
This is still under discussion, but the rough plan is to have the 
modules between 50 and 100 feet on the tower.

In our part of the country where 100 to 150 foot trees are the norm, 
siting PVs up high is a great solution. Many people put small arrays 
in trees, and larger arrays on high poles or multiple-story home 
roofs. Putting this large of an array on a tower is a new experience, 
but I feel that it's a strategy that will be copied by others because 
it makes lots of sense here. The cost of the tower increases with the 
additional wind loading, but that cost is recouped in the increased 
solar window. In wind generator installations, the purpose of the 
tower is to get the collector up into the fuel. It serves the same 
purpose in this case with the PVs.

Best,

Ian



>Hi Kelly,
>
>Did you follow the thread that Ian started on this same subject last 
>year?  A number of us chimed in with some serioius concerns about 
>mounting PVs on a wind tower.
>
>I just wanted to make sure you hadn't missed that discussion.  You 
>could check the archives (11/15-11/16 - "Tubular Towers & PV 
>Mounting").
>
>Keep us up to date with how that project goes!  Sounds like a fun one!
>
>Best,
>
>Jeff C.
>Village Power Design
>
>>Kurt & Wrenches,
>>Thanks. The PV Watts calculator confirms my efficiency assumptions for the
>>steep angle.
>>
>>Has anyone used the Sanyo modules, or have comments about 'em?
>>
>>-Kelly
>>
>>>
>>>" I'm designing an interesting off-grid system where the PV array will be
>>>  mounted on the same free-standing lattice tower (160-ft) used for the
>>>  wind turbine."
>>>
>>>  I would be more than a little worried about wind loads on the tower.
>>>  Regarding the angle of incidence, check out
>>>  http://rredc.nrel.gov/solar/codes_algs/PVWATTS/
>>>
>>>  Just enter in a city near your site and type in the degrees from
>>>  horizontal for a fixed array and you get monthly production numbers.
>>>  Not going to look very good with near vertical array.
>>>
>>>  Kurt Nelson
>

-- 

Ian Woofenden <ian.woofenden at homepower.com>, Senior Editor
Home Power magazine; Subscriptions: $22.50 per year, PO Box 520, 
Ashland, OR 97520 USA
800-707-6585 (US), 541-512-0220, or download current issue at 
<http://www.homepower.com>

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