Unexpected panel problem.

[guest22972]

Was looking over my shed inverter today and thought the generation was down. it was overcast but the smaller array  less optimally positioned on the house was doing better than the much larger and better orientated arrays on the shed.

Tracked it down to one array was not producing any power.
Tested for volts, amps output to the inverter, changed the breakers and swapped trackers. All to no avail. Finally thought it must be something  on teh roof, maybe a bad connection but couldn't see how.
Got the ladder, got up there and spotted it straight off.  One panel on the top pitch of the American barn type shed had done a front flip and face planeted itself forward ontop on another panel on the lower array.

This panel is on the end where the wind normaly blows.  I had it lift before so I screwd the thing down well.  I saw the solar bracket I secured it at the top, the clamp on the side looked like it had slipped off and the L bracket on the end was now a U  bracket where the panel had done a front 180.
The panel was shattered which was annoying but I was more amazed with teh fact the wind had got under a 20 Kd panel sitting flat on a roof ( I don't use solar rails)  and torn the tek screw right out of the metal Purlin.  I though maybe I missed the purlin and only got the roof iron itself but when I got down to get what I needed for the replacement, I could indeed see it had pulled through the roof truss itself.

Amazing.

I knew the end panels got more wind and I set the thing back from the edge knowing that was where the wind came from and I secured it down in 3 places. I would have bet a lot of money that panels would never have moved.
And I'd have lost. Badly.

 I realised as well I missed some panels along that run and they are just laying there completely unsecured, or at least they were till today, but none of them had moves probably because of being flat, in a line and maybe the prevailing wind hits the end of the shed and rotates pressing them down.
Perhaps the end is worse than normal because there is a big water tank underneath and although there is a lot of hedging 25M away on the boundary fence, maybe the air  hits the tank and  creates a more powerful updraft?

In any case, I was pretty amazed to see that there was enough force to tear the thing out of the metal.

I decided to eliminate the problem and removed the old smashed panel from the end and put the replacement in the last spot I had which is tilted between the 2 roof sections.  I think I'll get back up and re arrange a few panels and there is one I noticed I'll also have to replace.

There is a junction on the panel that is quite clearly burnt and creating a hot spot.  From what I read fire potential. Longshot  I think but it will be screwing with the output of the rest of the array so I'll change it out as well.
Getting more broken panels that what I'd like but they are ok for running shed and ceiling fans and other low volt solar experiments.

I'm doing another array on the house and I think I'll take another look at the solar clamps and go back to my own DIY soloution that did hold and use the little L brackets from the hardware and screw them direct into the panels and remove and replace the roof screw with the bracket underneath. I think I had that on the flipped panel it would not have. At some time I think the clamp shifted and put the force on the top bracket which was 2 much. If 2 brackets were sharing the load and couldn't move, I don't thik they could have both pulled out.

Anyway, problem fixed.  Just one I thought I had addressed with over kill but there you go.
I know the winds are strong here and get pretty scary but the force to left a 20 KG panel and pull out a tek screw, that I didn't give credit for.

[dieselspanner]

Perhaps not as weird as it might seem, once the wind got under the panel there would have been a massive force upward from just a little pressure.

It looks like later in the year I'm off to the UK to commission a new hover barge, with a 150 tonne payload, The whole thing runs on less than 1 psi, or 0.07 bar, pretty standard for most hovercraft.  When one considers that it's planned to be 52.5 m long by 25 m wide that's a lot of square inches - 2,027,800 or so!

I'd guess, as you said, the position on the roof and the surrounding panels etc. had a lot to do with it, add in a low pressure area caused by the wind direction and the shape of the roof it's self you've got some mighty forces to contend with....

Cheers
Stef

[carlb23]

my 11.5kw array is ground mounted on a tiltable frame.  Its 10' tall and 103' wide sitting on 7 schedule 40 posts each 9' in the ground with 1.5 yards of concrete in each 30" diameter hole.  they have withstood 80 mph winds and the wind gets under them pretty good since they are 5' off the ground.  This array has been on line for 9 years with no movement or problems.
the tiltable mounting was designed by TT solar in the US.

[BruceM]

I'm a fan of seasonal tilt ground mounts. I have two DIY steel racks. The roof seems an odd choice unless trees and/or lot size requires it,  as any roof repair will require panel and rail removal. 

[carlb23]

Must be a lot of force being generated in those winds.
Pitty the panels can't be made to rotate so they become a wind generator, might make more than the solar output at the right times, especially at night!   

I had 5 Kw worth of panels on a ground mount last winter that just sat on 1" tube frames.  Never had a problem all winter, even with some I had just leaning against the bushes. Couple blew over a could of times but other than that, nothing.
I suppose the wind up high where it has a clear run si a lost stronger than across the ground. hence the reason to stick turbines up as high as they can get them.

Where are panels mounted is very open and we get some fierce winter winds that get under the back of the array, but with that much concrete and steel and being so deep in the ground its not going anywhere.  Its design spec is 150 mph.  by that time the house is gone already

[BruceM]

Where I live there are wicked spring winds every year, 90mph + gusts.  I have the panels almost flat at that time of year, which helps.  They are down the hill for security reasons; when I was building my place I wanted them out of sight.  That also reduces the wind speed by 10 mph.

Given CarlB's grid tied PV array size, I expect he's a exporter of energy. 

[carlb23]

we generate about 30mwh a year with our combined 22.5kw arrays.  We have about 4 to 5 mwh a year we sell back. we also get srec's for each mwh which we sell to the utility for about 250 dollars each

[BruceM]

Those rates in Au should be enough to make anyone think of superinsulation, geothermal, and going off the grid. 

Is your water from a well or city water, and what's the standing water depth to surface, Glort?  Water (if from a well) can be a great geothermal resource. 

[mike90045]

If you have a fairly large generator, and it's got a excellent frequency control (only inverter generators are stable enough) it has to pass a 5 minute test by the GTI for voltage and Fq stability, and "grid impedance"  That's a test pulse sent out to the generator, and if it's big enough, it "dissipates into the grid". But if there is any "ringing" or voltage/impedance spike, it fails to qualify.
  If you somehow did get a generator to become qualified, you must never allow your loads to  become less that the voltage/amps the GTI is producing.  Otherwise, the voltage will rise to the over-voltage disconnect level, and the GTI drops off, or the rising voltage frys the generator and it fails, with all the GTI feeding into it.

so generally, it does not work.   Someone may rig up a pole pig transformer and generator and get it to work, but it's going to be a lot of trouble and not reliable

[old seagull man]

So still of topic but on the GTI subject, is it possible  to start a GTI with another inverter, last year we had a 3 day blackout, yet my solar panels would have produced 25 kWh a day if i could only have got them to turn on?