Impact Resistant Solar PV Panels

You could try a mosquito tone generator to irritate and repel teenagers up to 30 feet away. Only people under 25 can hear it.(16-18.5 kilohertz)

You may need to boost the output with a amplifier to increase distance and effectiveness if is not beyond their throwing distance.

Here is a link:

https://mosquitoloiteringsolutions.com/us/

And if you want to get REALLY Serious,and money is no problem,try this:

https://youtu.be/XN9GeNmIMeU

Your ideas are good, hard plastic or chicken wire. Maybe video surveillance might also be cost-effective.

“…possible solutions on preventing projected small rocks/pebbles from damaging rooftop mounted Solar PV Panels.”

If the pebbles are gathered from some local waterway

1) perhaps fence off public access to the waterway.

2) perhaps pave a local section of the waterway

3) perhaps introduce a population of freshwater crocodile in the affected area… this suggestion has a few possible problems that may prove more troublesome than your current problem, so consider carefully before proceeding

4) perhaps a basketball court or two in the area of concern… give the miscreants something else to do… teen center, small music and dance venue, one of those skateboard park type areas… baseball diamond maybe

5) perhaps some sort of vertical screen on the building, so the PV panels are not visible from the street… this may limit solar exposure of the panels (undesired) and usually only works if installed before the kids know there is something behind the screen that can be vandalized

I feel your pain, Ron, I really do. The mindless and often determined nature or vandalism is extremely difficult to combat. If you cover with lexan sheets, the vandals will select bigger and bigger stones… or balloons filled with paint… or whatever they can think of next.

I would extend the perimeter to 100 yards with a 12' fence if possible thus putting the panels out of throwing distance...failing that then video surveillance with guards monitoring your grounds...loud speakers to threaten intruders would be helpful too I think,,,Dogs can also be utilized for perimeter security....

How far away are the offenders?

What is their range?

Calculate the parabola based on that distance and put your shield there for best effect.

A solar panel I furnished was positioned about 100 yards offshore in a lake where it was subject to gunfire. We added a 1/4" thick polycarbonate shield, spaced off the panel by a few lengths of 1-inch diameter Tygon tubing that spanned the whole panel.

Seems irrelevant the biggest cause of damage here is from hail storms not rock chuckers.

If polycarbonate is used what has been done to stop UV yellowing like on headlights?

This might help

https://webstore.iec.ch/en/publication/68735

IEC Technical Specification 63397

IEC TS 63397:2022 Photovoltaic (PV) modules - Qualifying guidelines for increased hail resistance IEC TS 63397:2022 defines additional testing requirements for modules deployed under applications or in environments where PV modules are likely to be exposed to the impact of hailstones leading to higher stress beyond the scope of the IEC 61215 series. This document aims to assist in the selection of modules for deployment in specific regions that have a higher risk of hail damage and to provide tools for improving module design.

But they only seem to be talking about hailstones one inch in diameter travelling at ~50 miles an hour. I think the average thug could manage a lot more.

In your analysis you seem to be concentrating on force rather than impact energy. Whatever the energy when the rock leaves the vandals hand (½mV²) you need to subtract the potential energy due to the height of the solar panels (mgh).

I hope the thugs aren't reading this thread, because, Doorman has identified a threat (paintballs) which will render all protection parallel to the panels useless. Therefore I think the best defence will probably be a vertical screen of chicken wire.

From a purely engineering viewpoint, my initial preference to protect these solar panels is to use wire mesh (chicken wire) to deflect accidental stones from damaging these solar panels. The plausible crazing, cracking, and clouding of "transparent" panels can easily turn protective material into a blocking filter.

Let me now focus on my choice of the word "accidental." If these damaging stones are not from simple accidents, then no amount of shielding can protect them. The vandals will just escalate from river rocks.

Our OP question is:

“What would be the best solution to prevent small river rocks being projected onto rooftop solar PV panels?”

If these rocks were of cash value, I believe very few of them would be tossed up onto the roof.

Pay for the river rocks. Just buy them from the kids. A dollar a pound. For a sanity check, an American baseball is about 145 grams, stated average of 26 odd grams is largest class of the sampled stones, so I am guessing the PV panels are pretty high above the ground, so 40 or 50 gram max mass will be paid for. After a period of time eligible rocks will be pretty scarce around the subject area, the offer to buy sunsets… end of trouble. Dollar a pound for driveway gravel, but this should prove considerably less money than replacing one PV panel.

Disguise this gravel purchase as something… “We are using the stones as donated aggregate for repair of aged and damaged concrete at local hospital… library steps… boat launch ramp…”

This crazed scheme

1) is implementable within a day or so of decision to proceed. No waiting two, three, six months for parts to arrive.

2) is anticipated to be lower overall expense than anything else… certainly less expensive than doing nothing, or hand wringing over a decision until 50% of the panels need to be replaced

3) might actually work.

4) consequence of unsatisfactory result is pretty low… that is to say, should not cost very much money or time to try, especially compared to PC panels installed, protective screens erected (stone hits screen, bounces back toward street, stone breaks out automobile windscreen… now who pays?), ruined PV panels…

I dunno, this rather loopy suggestion has several issues.

Well, if you were to shoot one or two of them, I bet they would stop.

Gotta get their attention.

Put up concentric circles of large rat traps, the spring loaded type, to throw the rocks back when hit. A slight modification of the snap lever would do, similar to a sling shot pouch, and adjust spring tension according to results. Build a prototype and test it for results.

You could go larger and sling a whole cup full to make sure you get them all. No boulders, just small pebbles. Enough to sting but not really hurt anyone.

Or, as someone else suggested, shoot them with paint balls.(Just kidding ).