[RE-wrenches] Hurricanes Forces

Mon Sep 18 09:31:28 PDT 2017

I took a U-tube flight in a copter and a couple U-tube car rides in the
Keys yesterday. Pretty hard for me not to believe that if your number was
up, it did not matter how much effort was put into the installation for
above average quality. There were a few solar installations on houses up
on piers where the whole roof was gone. It was hard to tell what the
trailer parks were to begin with.
I think Jason is right about the direction of the wind and not just the
speed. Especially a 180 degree shift near the eyewalls. I still have not
heard back from my client there...

Dave Angelini Offgrid Solar

> I can't rule out loose hardware, but most of the modules that were plucked
> show evidence of significant bulging from wind uplift. We use impacts, but
> go back over them after installation is complete because things can shift
> around and loosen hardware.
>
> Small tornadoes, high gusts, and even Venturi effects between adjacent
> buildings are plausible explanations for some losses I've seen. I went to
> a
> home with a damaged solar pool heater. It wasn't bad - one panel was torn
> up, but their pool cage and the pool cage on two adjacent homes were a
> total twisted mess. Damage is very localized - much like you see with
> tornados that seemingly pick winners and losers. It's not just the speed
> of
> the wind, but the direction.
>
> There is a beer distributor in town that recently had a 1.1MW rooftop
> array
> installed by a competitor from out of town. My understanding is that it's
> a
> total loss. Worse yet, the panels punctured the roof in so many places
> that
> the facility has to shut down completely. This appears to be the biggest
> solar disaster from the storm, but I have not looked into the 2MW solar
> field at the local university or any utility owned fields. Early reports
> still seem to indicate relatively few issues in percentage terms.
>
> Jason
>
>
>
>
> On Sat, Sep 16, 2017 at 9:12 PM, Ray <ray at solarray.com> wrote:
>
>> Is it possible there may have been loose mounting hardware here and
>> there?  I've found quite a few loose clamps over the years on many
>> different systems from myself and reputable dealers.  I've found that
>> using
>> a impact driver really causes trouble; I now hand tighten everything.
>> Many
>> of the threaded aluminum type blocks can seize up when tightened at
>> speed
>> with a driver, and no lube.  They seem tight, could pass a torque wrench
>> test, but actually are seized up.
>>
>> We've recently had a pole mount that ripped modules right off their
>> still
>> tight mounting bolts, which I could only explain by a mini tornado.
>> This
>> could be the explanation in your random failures too.  Another
>> possibility
>> are a vortex  or turbulence created by the nearby trees or the structure
>> itself in very high winds.  We like to model wind loading as a simple
>> vector force, when we all know the reality is extremely dynamic.
>>
>> Ray Walters
>>
>> Remote Solar
>>
>> On 9/16/17 8:15 AM, Jason Szumlanski wrote:
>>
>> I generally agree on all points. I'd love to use three rails on all
>> systems, but there is an economic factor, and as Tom mentions, a third
>> rail
>> doesn't necessarily stop glass being sucked out or a tree landing on the
>> array. At what point do we cease over-engineering the mounting structure
>> and the module itself? I can see hardening backup systems and critical
>> infrastructure (utility scale solar included), but residential grid-tie
>> systems should be built with an acceptable loss criteria. I know I might
>> take some heat for that statement, but given the anecdotal evidence of
>> the
>> small percentage of issues relative to the installed base we have, I
>> think
>> it's the right answer.
>>
>> Also, one thing we are seeing (small sample size) is modules being
>> plucked
>> from random parts of the array, not necessarily on the lower or side
>> edges.
>> Very odd.
>>
>> Jason
>>
>>
>>
>> On Fri, Sep 15, 2017 at 3:52 PM, Tom Lane <tom at ecs-solar.com> wrote:
>>
>>> Hurricanes wind create both suction up lift and direct pressure against
>>> the glass frame wall of the module -- if a module is to be held
>>> securely it
>>> must be attached 1/3 or 1/4 of the way from top to bottom by each of
>>> the
>>> two rails . If modules are facing due South and the wind force comes
>>> from
>>> the east or west the force will start pealing off one module at at time
>>> .
>>> For example if the winds shearing force is from the west the first
>>> module
>>> on that end should have an extra rail in the middle with two extra
>>> clamps
>>> BECAUSE when that first one goes it will start peeling off each one one
>>> at
>>> a time until that wind band passes . It is critical on raise systems on
>>> flat roofs that the two end modules use the struts with two ( 11/2 sets
>>> of
>>> mounting hardware per module) and the first three or at least first two
>>> modules be X braced with aluminum L bars bolted with 3/8 bolts across
>>> the
>>> back struts in front of and back of the struts with the L bars to
>>> prevent
>>> peeling down the row or bank of modules the same as modules mounted
>>> flat on
>>> a roof . Enough suction force from high wind speeds can suck the glass
>>> right out of the frame wall - using three rails per module , two each
>>> 1/4
>>> of the way from the top and bottom and one directly in the middle can
>>> help
>>> . I also suggest using only 60 cell modules in wind zones over 150 MPH
>>> with
>>> two rails minimum maybe even three on high rises .The frame walls on 72
>>> cell modules is trying to hold too much glass in place for just two
>>> rails
>>> .  On ground mounts that are adjustable lower the array to 15% or less
>>> and
>>> on smaller home owner ground arrays attach motorcycle tie down straps
>>> on
>>> the end corners and middle hooked to extra D rings attached to the
>>> array (
>>> especially to the corners of Top of Pole Racks ) to mobile home screw
>>> in
>>> ground anchors AND if possible strap plywood over the glass front .
>>> GatorTom PS : having insurance is a good investment when a monster 100'
>>> Live Oak tree topples forward onto your array . Or a car or boat gets
>>> blown
>>> onto your roof .
>>>
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Dave Angelini Offgrid Solar
"we go where powerlines don't"
http://members.sti.net/offgridsolar/
e-mail  offgridsolar at sti.net
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