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I have read this question - Solar panels and hail and my question is similar. I have the possibility that neighboring kids may throw stones at my roof top solar panels to scare off monkeys which are a local pest.

What protection measures I can take as I do not think my insurance will cover that damage ?

I have been told by my neighbor to use chicken wire. Will that reduce the output of solar panels ?

Chicken wire

UPDATE Background - I stay in a rural area where monkeys are common. I also live in a hilly terrain and there are houses above and below me. So kids may accidentally throw a stone at a monkey when it is over my roof.

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    Chicken wire has a very low surface area... it would not significantly reduce the power (less than 1%). However, it's made for keeping chickens out, not rocks or hail. I suppose it would deflect some rocks.
    – Ben Welborn
    Commented Jul 21, 2016 at 12:34
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    What size stones are you talking about here? Most quality solar panels today are designed to be hail rated, meaning they can with stand a 1 inch piece of hail traveling at 50mph.
    – treeNinja
    Commented Jul 21, 2016 at 13:02
  • Do they also have BB/pellet guns? I've seen a couple panels runied that way.
    – Ben Welborn
    Commented Jul 21, 2016 at 13:35
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    Even if the panels were covered, it is likely that the cost of a single panel will be less than your deductible. It would only make sense to get insurance involved if several panels were damaged at the same time such as a catastrophic loss.
    – Jason Hutchinson
    Commented Jul 21, 2016 at 15:27
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    I would really really enjoy a picture of this problem!
    – DMoore
    Commented Jul 21, 2016 at 16:53

13 Answers 13

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The real problem is the monkeys. The collateral damage due to flying rocks would best be dealt with by trapping and relocating the monkeys. Or, it might be helpful to use an electric (chicken wire) fence to keep the monkeys off the roof. Other deterrents might be motion activated sprinklers or ultrasonic alarms.

Obviously, there is not a perfect solution, but reducing the monkey population should cut down on the number of rocks being thrown at your house.

An alternative to chicken wire would be (bullet-proof) polycarbonate. Supposing that you have a glass solar panel, I would particularly recommend replacing glass with polycarbonate, especially if they do break the glass, because polycarbonate is much cheaper and more durable. Polycarbonate will become hazy after a few or several years, so it will need to be replaced occasionally for efficiency.

Pros and cons (polycarbonate vs glass):

Pros:

  1. Polycarbonate is significantly cheaper than glass.
  2. It's durable/bullet proof.
  3. It can be cut to shape.

Cons:

  1. If you replace the glass with polycarbonate you will get about a 9% reduction in power. But you would definitely want to replace the glass, because if you use polycarbonate over glass, it will reduce the efficiency by about 20%.
  2. It becomes hazy after several years and needs to be replaced.
  3. It expands and contracts, so you need to attach it with screws and allow room (around the edge) for expansion.
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    Even when new, polycarbonate panels will reduce the efficiency of the panels, not to mention be prohibitively expensive.
    – Jason Hutchinson
    Commented Jul 21, 2016 at 15:12
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    Since the panels are already installed, I'm not sure if that is an option for them. Adding an additional layer of it over the existing panels will certainly decrease their efficiency.
    – Jason Hutchinson
    Commented Jul 21, 2016 at 15:22
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    @JasonHutchinson polycarbonate is about 4 times cheaper than glass and solar panel glass is replaceable. Glass breaks, and panels are expensive.
    – Ben Welborn
    Commented Jul 21, 2016 at 17:32
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    @Aron: yeah, but have you accounted for the light blocked by all those monkeys?
    – Steve Jessop
    Commented Jul 22, 2016 at 3:34
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    As far as I understand it, an electric fence is passing no or very little current until something conductive touches it. There probably is some standby / parasitic loss. So I don't think that would have a significant effect on overall efficiency. One approach to quantifying that would be to consider the loss of efficiency / effectiveness from a broken panel. Multiply that by the probability it will occur, and that is your expectation value. Compare that to the standby losses of the electric fence.
    – StayOnTarget
    Commented Jul 23, 2016 at 2:03
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I live in a small Himalayan Village facing the same problem. But we kept our solar panel in such a place which is not accessible to kids or monkeys. The second thing I would like to mention is that if our neighboring kids don’t have that much of vision of damage of the solar panel due to stone pelting to monkeys may broke our panel - we have to make them understand - this may be broken due to - your good throw of stones towards the panel.

We have to make them understand the process and for monkeys we have to train dogs and extend shelter to them in our homes in compassionate manners. Extend your knowledge and help for understanding the ecosystem and in between the energy needs.

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How big are the rocks and how far are they being thrown from? Panels are generally designed to be able to withstand small to medium sized hail... if kids are throwing rocks large enough to break panel glass at your house, I'd imagine your house would be taking a lot of damage as well.

Stating the obvious, but anything obstructing the sun will reduce output — but chicken wire shouldn't do so in a way that's hugely significant. I'd be surprised if you saw more than a 5% reduction even if you completely covered the panels with the wire.

Alternatively, I'd recommend security cameras and some signs pointing out said cameras. I think it could go a long way as a deterrent, and if you really wanted to pursue it you could track down the kids and talk to their parents.

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  • could range from pebbles to small stones not more than 2 inches in length.
    – user56677
    Commented Jul 21, 2016 at 13:20
  • I was assuming the kids were the problem, but really it's the monkeys! This is a really interesting problem. Chicken wire might help, but have you tried doing something to keep the monkeys away from the panels?
    – user1869753
    Commented Aug 8, 2016 at 12:48
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I would think a security camera that records, along with a phone call to the police, would be cheaper and easier than trying to figure this out. Along with the threat of legal action and jail time may come restitution for any damage to your panels.

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    Apparently the kids are performing a civic duty (volunteer animal control)... damage caused by monkeys might be worse. I wonder whether a video would help much (in gansub's country).
    – Ben Welborn
    Commented Jul 21, 2016 at 15:48
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Could you post a simple sign that asks the well-meaning kids to not throw rocks at your roof?

You would want to depict rock throwing hitting a solar panel or glass pane. I could not find a precise sign but something like these might work as inspiration: no rock throwing, hikers below

fragile glass

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OK - so you're not going to be able to stop the kids from throwing rocks at monkeys and you're not going to be able to protect the solar panels from rocks. The only solution I see is to keep the monkeys off the roof.

If the monkeys will run away from water, you can get motion detecting spriklers (available at Amazon) and mount them by your solar panels. The water will allow sun through while a spritzing may chase off the monkeys.

On the other hand, if you're in a hot climate, the monkeys might enjoy a good spraying and hang out more often.

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  • Motion activated sprinklers (and ultrasonic alarms) was my answer.
    – Ben Welborn
    Commented Jul 21, 2016 at 17:30
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    @BenWelborn - sorry I evidently didn't read through your whole answer and though it was all about the poly cover.
    – Hannover Fist
    Commented Jul 21, 2016 at 17:39
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Adding this answer to comment on the chicken wire approach. Two points:

  • The shading by the chicken wire isn't as small as it might seem.
  • The effect the wire has on the efficiency will vary with sun angle.

To calculate the % area shaded we need to know the opaque proportion of the total area of the chicken wire. Instead of doing this geometrically, it seemed easier to do this using bulk material properties:

  1. Sample chicken wire:

    • 3' x 50'
    • Weighs 13 lbs
    • 20 ga steel (0.0375 inches; ref)

  2. Total volume of chicken wire sheet if laid flat: 0.46875 cuft

  3. Density of steel: 484 lbs/cuft (there is a range but I assumed cheap lighter steel)

  4. If totally solid, the same volume of steel would weigh 226.9 lbs

  5. Therefore it has only 5.7% of the expected weight.

  6. Assuming that the chicken wire's thickness is uniform, the variance from theoretical weight must be due to only 5.7% of the surface area being present.

Therefore, at BEST, the chicken wire will reduce efficiency by 5.7%. That's not trivial.

When the incoming solar is aimed directly at the chicken wire, it will have its least shading effect (i.e., 5.7% blocked).

As the sun angle departs from best-case 90 degrees, this will get worse. Obviously if the sun were shining directly on edge to the chicken wire, it would block 100% of it. I think it would go as (1 - 5.7%) sin(angle) where angle is just the elevation from the chicken wire to the sun.

But this may be mitigated somewhat because you'd expect that the efficiency of the solar panel would also decrease as the sun angle decreases. You'd have to get that info from the manufacturer to compare.

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    Your estimate may well be in the right ballpark, but I do see a number of minor error sources. For example, 20 gauge wire is apparently not quite as thick as 20 gauge plate. On the other hand, you haven't accounted for the fact that the wires in chicken wire are twisted together, increasing the thickness (and making it non-uniform, since only part of the wire is twisted) and thus the volume of the sheet. And there probably ought to be a factor of 4/π involved to account for the fact that the wire is round and not rectangular.
    – Ilmari Karonen
    Commented Jul 23, 2016 at 17:44
  • Agreed, this was a 2D analysis and certainly contains some approximations. I think if you accounted for circular cross section of the wire, it would provide even a little more shading. So if anything, this is a lower bound. Thanks for the feedback.
    – StayOnTarget
    Commented Jul 24, 2016 at 2:24
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    I think it’s not that bad if the wire is a couple feet from the surface. The shadow is fuzzy and disappears… because the light source is larger than the wire's angle of the sky, it will not block all paths of light from the sun’s disk to the panel.
    – JDługosz
    Commented Jul 24, 2016 at 9:26
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    @JDługosz: Even a blurry shadow will still reduce the power output of the solar panels by as much (on average) as a sharp one. That said, while a 5-6% reduction in power is not completely negligible, it's also not huge compared to other shadow losses (like clouds, dust accumulation, suboptimal orientation, bird / monkey poop, etc.) that one may just have to accept depending on where one wants to install the panels. In this case, it may just turn out to be effectively unavoidable. If necessary, you can make up for it by installing one extra panel for every 20 or so.
    – Ilmari Karonen
    Commented Jul 24, 2016 at 12:39
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To answer the actual question, I think chicken wire will usefully help. The wire will have insignificant effect on solar production.

However, the bracing to reasonably support chicken wire so it is effective deterring monkeys and decreasing the damage caused by rocks will probably cast a few shadows which will have an effect. The wire will have to be suspended at least two feet/60 cm above the solar panels.

Note that large stones may still occasionally break through the chicken wire, but it is easily and inexpensively mended.

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In my experience, even the "worst of the worst" neighborhood kids can be repelled by:

  1. threatening to call their parents
  2. Actually calling their parents

If their parents "don't care", they will if you send them a bill.

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    Not sure that the kids are bad... monkeys are notorious, of course.
    – Ben Welborn
    Commented Jul 21, 2016 at 16:51
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    Context is important here. Throwing rocks at monkeys on roofs could be a culturally ingrained habit in OP's region, similar to shooing away neighbors' dogs from your lawn in western countries.
    – user46770
    Commented Jul 21, 2016 at 21:56
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You're trying to solve the wrong problem. If neighborhood kids are throwing stones at your house or solar panels, it means they don't respect or fear you. Fix that. They're just kids; you're an adult. That means you have power and authority over them in a variety of ways. Exercise it. There is ZERO reason to put up with this kind of childhood hooliganism.

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    Actually, they are thowing stones at monkeys... volunteer animal control. ps, I didn't downvote any of these answers (actually I upvoted the camera idea)
    – Ben Welborn
    Commented Jul 21, 2016 at 16:54
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It sounds like anything you put over the solar panels to protect them will reduce their power output. If that's important to you, I agree with Web Welborn about finding a way to deter the monkeys from being on the roof.

Do the monkeys loiter on top of the solar panels or surrounding roof area? Here are some deterrents used for birds which you could attach to areas of the roof. They might work for monkeys, too. In the event you need to go on the roof to perform occasional maintenance, these may work as long as you wear some sturdy soled shoes.

Good

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    Monkeys are clever. In some areas they do use glass shards in concrete as a deterrent... I learned this from a nature program about monkeys, where it showed the monkeys stepping over the glass and tangling razor wire with tee shirts so they could climb over. They were taking purses and stealing anything they could, and I heard a story from a marine about one of them stealing his rifle.
    – Ben Welborn
    Commented Jul 21, 2016 at 20:26
  • I didn't want to suggest glass shards so as to deter but not injure, but WOW! I didn't know they are so clever! A protective coating over the panels may be the most effective option. I assume arming the kids with Airsoft rifles and teaching them marksmanship would be out of the question. (Despite the name, Airsoft pellets are NOT soft on impact.)
    – MJA
    Commented Jul 21, 2016 at 21:27
  • not my personal experience, but heard and saw videos - they are definitely more clever then usual animals rats cats dogs. Actually airsoft rifles are option, although too reach one option, as I suspect, but it allows better aiming, and I doubt pellet will make significant damage to panel if any (from distance). Although it's unreal to constantly have rifle, but rocks are constantly available, cheap, and fun.
    – MolbOrg
    Commented Jul 23, 2016 at 17:43
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If you'll excuse my primate drawing skills, since we're talking about our theoretical distantly-related cousins (I must admit that they are generally better climbers than we are), monkeys do have their own physical limits.

Having this in mind, if you re already planning to spend some money, this is what I suggest:

Wide panes

Basically you can place metal (or other more appropriate material) panes around your panels preventing access to your roof. Small holes can be drilled at the bottom of these panes in order for the water to flow out. Lastly, one of those panes may be allowed to tilt down (or perhaps have a small door on it) for accessing the roof when needed.

Just in case you have other structures tall enough around your house, you may try to correct their angles like this (without covering the panels):

Tall panes

I'm not sure how viable this solution is to your case, but if it's feasible enough, you won't have to place or replace anything on your panels... And you will not have monkeys on your roof.

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    Yes; instead, you will have dead trapped monkeys and a pile of rocks sitting on your roof (blocking your solar panels). Also, solar panels are generally mounted at a 30 to 45 degree angle; any lateral obstruction to light will severely decrease their efficiency when the sun is not directly facing them. Basically, solar panels work okay as long as the entire panel is receiving roughly the same amount of light, but they really don't like to be partially shaded, which your solution would cause (at least in that blue diagram).
    – Thomas
    Commented Jul 24, 2016 at 4:44
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    @Thomas thank you for your non-constructive feedback and the downvote. It's hard to imagine how monkeys that can climb roofs would be trapped between 4 ramps leading out. The goal is that monkeys don't get in, so no point in building those if they can jump in. The other solutions where panels are modified/covered will lead to loss of efficiency. I proposed to not obstruct the sunlight at all. That's why I mentioned that if tall structures are around the house the angles of those panes could be increased, obviously w/o covering the panels or turning them into walls ("viable solution").
    – CPHPython
    Commented Jul 25, 2016 at 11:02
  • @CPHPPython just so you know, I did not downvote you; maybe you should avoid jumping to conclusions based on gut feelings.
    – Thomas
    Commented Jul 25, 2016 at 19:27
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    @Thomas someone who upvoted/agreed with your comment did then, the effect you desired to cause by commenting that way affected that someone... And by rereading your own comment, that "avoid jumping to conclusions" advice you are giving to me applies perfectly to yourself. Now that I think of it, if I'd imagine that someone would jump to the conclusion of "dead trapped monkeys and a pile of rocks" due to my solution, I might have never had the trouble to try and bring this idea... Destructive criticism, just for the sake of it, is pointless and that's what prevents people to provide new ideas.
    – CPHPython
    Commented Jul 27, 2016 at 12:23
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In an analogous situation the approach taken is the following form of social engineering:

Image of fly painted on men's urinal

EDIT: As Isemi noted in the comments, "some urinals provide painted flies or plastic soccer balls or even miniature waterwheels to induce patrons to aim properly and minimize urine spills".

Thus:

  1. Provide some decoy or other point of interest that the monkeys would prefer, rather than your roof.
  2. The kids will then throw rocks at monkeys which are not on your roof.

So its a "fly" provided to both groups of pests.

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  • I don’t get it.
    – JDługosz
    Commented Jul 24, 2016 at 9:28
  • @JDługosz , some urinals provide painted flies or plastic soccer balls or even miniature waterwheels to induce patrons to aim properly and minimize urine spills.
    – LSerni
    Commented Jul 24, 2016 at 13:05
  • If they can’t hit the basin how does adding such a feature help?
    – JDługosz
    Commented Jul 24, 2016 at 13:12
  • "How does it work" is a good question... but it does seem to. Maybe it helps maintain focus?
    – StayOnTarget
    Commented Jul 24, 2016 at 13:20