Home Rooftop Solar Power System Update - Shattered Panel!

[Ian.M]

The other issue is: how would a ball end up hitting the roof at a high enough angle to cause symmetrical impact damage? 

Its unlikely to have been a high angle golf or cricket ball, as Dave hasn't commented about neighbours kids frequently needing to retrieve balls.  NSW bans hunting catapults etc., and I believe Dave's in a nice enough area that there is a very low probability of it being a ball bearing hit from a slingshot fired near vertically or of some idiot firing a firearm vertically.   In the UK there is always a risk of damage around Guy Fawkes night from rocket sticks and the metal rocket bodies from illegally fired marine parachute flares, but Australia doesn't celebrate  Guy Fawkes night and the sale of fireworks to the general public is mostly banned, largely due to the risk of bush fires, and no such object was found. There are no traces of broken mussel or snail shells, and Australia doesn't have any indigenous tortoises, so a bird dropping their prey to crack its shell theory is also highly unlikely

Its therefore most probably ice impact damage - either a freak hailstone that may have been much larger than others in the same storm, or ice falling from an aircraft.

@Dave (EEVBlog):  Do you remember any bad hail storms since the previous time you were on the roof?

[gilbenl]

I'd bet my left foot on a cricket or baseball. I also noticed that it appears your fence/neighbors are about 1.5m away from the edge of your roof. There's also a pool within arm/bat's reach as well. Its entirely conceivable that some kids were playing catch or actually hitting balls, one went up on a high arc and came down on your panel. It then rolled and took a hop off the edge of the panel itself or those terra cotta roof tiles and landed back in their yard. They retrieved it and never thought twice...

Golf ball also seems reasonable. Although small, they deform a good bit (relatively) on impact and making the crater somewhat larger than expected. You don't need to be anywhere near a golf course to see errant golf balls either. I had a friend whose windshield was shattered by one. He knew the source was a golf ball because he found it sitting on his wiper. Turns out a neighbor was hitting balls into one of those practice nets using a wedge, was set up too far back, the arc of the ball missed the net and traveled 50 or so yards to meet my buddy's windshield.

The video below shows the impact deformation of a moving golf ball on a flat surface (vs. impact leaving the club face), however, this ball was probably moving considerably faster than anything you'd encounter. It does well highlighting just how much deformation capacity/elasticity a golf ball can exhibit without breaking. Okay, it may just be a cool video, too.

https://www.youtube.com/embed/HTgSaEPdj-U

[Brumby]

I wasn't expecting THAT amount of deformation!

Is that a regular golf ball?  I would have expected the case to crack deforming that much.

[gildasd]

Aliens and magnets, especially magnets.

But seriously folks, when I was about 10, someone did manage to whack a cricket ball that endded in the windshield of the old school Land Rover of one of the teachers.
With only one bounce.
The flat glass had a plastic film on the back side.
The end result was near identical to Dave's panel.

[Rasz]

Maybe Dave could take a couple of balls up on the roof and see if there is one that fits the crater.

I dont think Dave has the balls to do it, he is not a golfer.

[SeanB]

Years ago I did see that a hard boiled egg ( boiled to Mil spec ie boil till the white and yolk are blue) is capable of breaking a windscreen when it hits it at 100kph.

As to the golf ball, you do accelerate it from zero to 200kph in it's own diameter, so yes it has to deform a lot and survive that. Drive a tank over one and it does survive, though you may have to look for where it went when it popped out under the tread.

They do not survive going through a jet turbine, though the turbine is supremely unaffected by the operation. It has to survive FOD on the runway ( small stones, errant small birds, national flowers) without incident. Geese and larger birds do tend to do damage, look at those nice RR Trent videos on YT for the aftermath.

We had quite a few engines that ingested pigeons during operation, engine makes a small puff of smoke and there is no evidence aside from a few smears of blood of the bird. Even saw one that had a first stage compressor blade snap off from a bird strike, and go through the engine without any sign aside from greatly increased vibration, which went away with increased power, so the 50 minute leisurely ferry flight went down to 15 minutes at full afterburner, where it was almost gone. Came in hot, and ran out of fuel during touch down, so had to be towed off the runway. Luckily it was off for an airframe overhaul, so the engine was coming out in any case, though it came back as cargo to the service bay for investigation and overhaul.

[RupertGo]

Here's another link to suspected meteorite damage to a PV panel - http://www.solarcurator.com/2012/06/13/module-failure-from-an-otherworldly-source/. Of particular interest, they found the contender for the crime by running a magnet around the area.

But I'd suspect a well-hooked cricket ball, from the shape and size of the depression. A decent swing plus contact can add a lot of energy and height, and the perpetrator will be keen to remove the evidence. A solitary huge hailstone sounds unlikey; that sort of hailstorm tends to get noticed. My favoured secondary explanation would be something falling from an aircraft, especially if you're in the area where the gear might be coming down prior to landing.

[max_torque]

Would some form of thin, self adhesive, transparent stick on film not be ideal for a temporary fix?

Like the stuff you use to laminate paper with etc?


I'm also pretty sure that any ball that hit that panel would bounce off and go a long way, so it ain't going to be found in the gutter or probably even in the garden!

[vodka]

I see the deformation of the panel solar, and it is almost perforated.
I believe that the projectile  (steel ball or baseball ball)path  seems as anti-tank gun, a horizontal with lightness parabolic path with an impact at high speed .
This can to explain the great deformation and the place where could be thrown(Somebody have  a building a few more elevated than Dave's home).
I suspect that somebody was doing out of the ordinary in the roof

[Ian.M]

Its definitely a good idea to make it weather-tight to maintain the system output while the manufacturer and the insurers argue about who pays how much. Get lots of photos first.  I'd say the easiest would be heavy grade clear PVC, foil taped to the rim.  I'd avoid anything stick-down to the panel itself as putting pressure on it in that condition isn't a good idea, and also the weatherproofing needs to be easily removable in case the manufacturer wants to examine it.

[l0rd_hex]

Have you ruled out terrorism? I'm thinking para-militarized llamas armed with frozen burrito cannons. I am deadly serious about this.

[MartinX]

Drunken golfers did this.

[Kleinstein]

A meteorite is rather heavy material with a high speed. This would likely give smaller impact zone and less of the big dent.
Comparing this with the damage shown from the golf ball in the other video, I would get its somthing like the cricket ball of a block of ice of similar size.

Also note the rather concentric rings around the impact. So likely the impact was rather vertical.

[Ian.M]

Have you ruled out terrorism? I'm thinking para-militarized llamas armed with frozen burrito cannons. I am deadly serious about this.

More likely Australian DSTO's combat kangaroos armed with beachballs!
http://baetzler.de/humor/killer_kangaroo.html

[EEVblog]

Have you ruled out terrorism? I'm thinking para-militarized llamas armed with frozen burrito cannons. I am deadly serious about this.

It can't be ruled out.

[EEVblog]

My favoured secondary explanation would be something falling from an aircraft, especially if you're in the area where the gear might be coming down prior to landing.

30km out from the airport.
But am within a few hundred meters of a flight path.

[Ian.M]

If my numbers are right, that means the aircraft are at about 5000' - 6000' when they fly over you, which would be consitent with ice buildups having thawed long enough to break loose.  As the aluminium aircraft skin conducts heat far better than ice does, thick buildups tend to break free rather than thaw completely.
.
See: http://www.engineeringtoolbox.com/air-altitude-temperature-d_461.html

[chickenHeadKnob]

My favoured secondary explanation would be something falling from an aircraft, especially if you're in the area where the gear might be coming down prior to landing.

30km out from the airport.
But am within a few hundred meters of a flight path.

Ha - ha (sorry) blue ice it is! I know you like to sniff things now is the chance for forensic schnuffery. If this is recent damage the crater may still have the fragrance of blue sanitizer+human waste. On the other hand if it has been a-while and there have been rains...

A damaged solar panel would be getting of lightly. Some twenty years ago a decrepit ancient DC-7, a four engined  prop plane , lost a nose wheel and it went through the roof of an apartment building near where I used to live.

[cdev]

Once I saw a coated, "shatterproof" (tinted) glass door spontaneously shatter (but of course, the coating meant it did not explode it simply became a mess of shattered glass) because it was in full sunlight and the sun must have caused some kind of catastrophic failure due to unequal heating of the laminated materials.

It was really quite spectacular. The entire thing turned into a mess of cracks in around half a second. Nobody was anywhere near it and it was shut. It was fun because I was with a bunch of scientists. We were all left awestruck by this event.

It did make a funny kind of sound.

[aroby]

Maybe an Amazon drone on a test flight dropped its package too soon ...

[Smokey]

Cricket ball?  Really?  It would essentially have to come from your close neighbors right?  Do you have a cricket playing neighbor that is such a dick that he would carelessly launch a ball out of his yard, crack your solar panel, and not own up to it?  A professional baseball home run is like 450 feet (137m).  I'm not sure how far cricket balls go, but that really limits the range it could have come from (and you pretty much know the direction).
Assuming it was a cricket ball, the damage and angle would look to me that someone was seriously trying to wack the crap out of the cricket ball, not just casually toss it over a fence.  Is that realistic? 

I don't know what neighborhood you live in, but I would hate to be looking over my shoulder for all these roving bands of cricket hooligans all the time.

[Circlotron]

Light is photons.
Photons have properties of both waves and particles.
Radio waves are electromagnetic, just like light.
Your local radio station sends electromagnetic waves.
Maybe their antenna was emitting waves and *heavy rock* particles through your property at the time?

[DrGeoff]

Cricket ball?  Really? 

Of course. Cricket balls are harder than baseballs.
Then some kid with a tennis racquet could have whacked a golf ball up in the air (now that really flies) or a rock in the air (and probably lost a string doing that) which could come down onto a panel. A golf ball would bounce away and down the street.

[Smokey]

I get what a cricket ball is.  My point was that if that was what it was, it couldn't have come from very far away.  That side of his house doesn't look like it faces the street.  Since you essentially know the direction, and you (probably) know who your neighbors are in that direction, what is the likelihood that one of those neighbors is a dick or has dick kids.

If we are talking golf balls, the average golf drive is 200 yards (182m) so look for dick neighbors that far out.

[Alexei.Polkhanov]

My bet is on a golf ball. I am waiting for another episode of Myth Busters, "can golf ball do that?" Dave still have enough panels to test all plausible theories:

Here is the Poll:
ice - 0 votes
golf ball - 1 vote
baseball/cricket ball - 0
meteorite (hard to simulate?) - 0 votes
birds - 0 votes