Squirrels, birds, and bees Oh my

[hardwired]

So someone I know was inquiring about customer service job for a solar company and told them there would be ongoing client service after the install.

I questioned it thinking once it's installed and no equipment issues no need for call backs. But their response was customer calls for squirrels and birds.

So is something needed to keep the squirrels and birds at bay and out from underPV panels. I have ongoing problems with bees so yet another pest to deal with?
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[bcroe]

So is something needed to keep the squirrels and birds at bay and out from
underPV panels. I have ongoing problems with bees so yet another pest to deal with?

The problem is solved here by using a ground mount, panels many feet in the clear. Bruce Roe

[blueman2]

Great question. As new system owner myself, I was just thinking about this. We have lots of squirrels and rats in our area and I was concerned about making a home under the panels. I have heard about critter guards, but also know you need to keep good airflow under the panels to keep them cool in summer.

For roof mount, do most people go without critter guards of any type? I am just hoping the wires are made out of something that rats and animals do not like to eat. I do have experience with some wires (indoor rated coax under my house, for example) that rats LOVE to eat.

[SunEagle]

Great question. As new system owner myself, I was just thinking about this. We have lots of squirrels and rats in our area and I was concerned about making a home under the panels. I have heard about critter guards, but also know you need to keep good airflow under the panels to keep them cool in summer.

For roof mount, do most people go without critter guards of any type? I am just hoping the wires are made out of something that rats and animals do not like to eat. I do have experience with some wires (indoor rated coax under my house, for example) that rats LOVE to eat.

Keep your cat on your roof.

[PugPower]

Plenty of ground squirrels in my area, never seen one on the roof. Have had buried wire chewed by critters. My installer says that it gets too hot for birds to live under the panels. Maybe in winter time? My roof panels are installed quite low to the roof, but I have seen others which have more room underneath and might make a good home for critters.

[hardwired]

Plenty of ground squirrels in my area, never seen one on the roof. Have had buried wire chewed by critters. My installer says that it gets too hot for birds to live under the panels. Maybe in winter time? My roof panels are installed quite low to the roof, but I have seen others which have more room underneath and might make a good home for critters.

Apeaking of panel height off the roof, what should be the gap in between? What is "low"?

Also, what are the skirts I see on the edges called on some installs that give that clean look? Are these considered "guards" to keep the animals out?

Also. Can an should you do gapless between the panels (i.e. But up against each other). What's needed for snow?

[J.P.M.]

Apeaking of panel height off the roof, what should be the gap in between? What is "low"?

Also, what are the skirts I see on the edges called on some installs that give that clean look? Are these considered "guards" to keep the animals out?

Also. Can an should you do gapless between the panels (i.e. But up against each other). What's needed for snow?

The optimal roof deck to bottom of panel dimension is a compromise of several things.
- More clearance means lower cell operating temps. which improves cell efficiency and so array output.
- If high enough clearance, it's easier to get under the array for maint./service as well as cleaning out critters/nests.
- Some folks don't like the aesthetics of high clearance.
- If very large clearance, some additional considerations may be necessary for wind loadings.

"Low" might be 0 gap (flush) to maybe 5 cm. or so. "High" might be something like ~ 25 cm. +/- ~ 5 cm. or so.
FWIW, my array clearance is ~ 25-28 cm. to bottom of panel, depending on where it's measured with 1" concrete tiles, but that was by design.
A lot of data and published stuff leads to a consensus that small panel to roof deck gaps of, say, 4 - 6 cm. or so will add maybe ~ 3 - 5 deg. C. to the NOCT because the back side of a panel gets less circulation and so cooling is less efficient and so the panel is warmer than with a larger gap.
Also, gaps beyond 15 cm seem to provide little in the way of lower NOCT's or in service cell temps. compared to a 15 cm. gap.
Basically, for typical roof applications, a 15 cm. gap seems a good number.

In spite of what some folks may think and what some peddlers will try to B.S. customers about, the skirts are mostly cosmetic, and in a lot/most applications, and for reasons rooted in fluid mechanics, may actually inhibit/reduce cell/panel cooling . Beyond some aesthetic appeal to some folks, they seem to be a gimmick.
They also have no advantage with respect to reducing wind loads in any measurable way and depending on array tilt and wind vector may actually increase wind loadings.
I suppose if the leading edge of such guards were to be very close to the deck they might tend to make it more difficult for some varmints to find a home, but at what cost in lost array output and inaccessibility of the array as well as no way to see/know if something is going on under the array ?

Gap vs. gapless also has +/- 's. The underside of the array probably stays a bit drier with no gaps - but still not bone - but the array temps. will most likely be a bit higher. Reason: with the usual vertical gaps of a couple cm. or so between panels the gaps will tend to increase air turbulence on/under/"through" the array which will tend to decrease panel temps. That increased mixing will also tend to have an effect on the uniformity of fouling/dirt over the entire array, but that's most likely a lesser consideration and probably impossible to quantify.

Bruce may well have more informed opinions about gap/gapless with respect to snow loading and gap vs. gapless behavior in snow. My semi informed guess is it won't matter much in the bigger scheme of things, but I'd defer to his opinion on that.

[emartin00]

There are a number of "critter guards" available for solar panels. Most are simply a coating wire mesh that gets attached around the edges of the array. They are actually required in a few jurisdictions.
The wire mesh allows plenty of air flow, but you do need to make sure that leaves don't collect at the top of bottom of the array.

[peakbagger]

FYI, in high wind zones off the shelf racking may not be available or more costly. Wind Uplift starts to factor in on calculation and most companies just dont want to mess with it.

[PugPower]

It is my understanding that if you don't leave a small gaps between the individual panels for them to contract and expand with heat, you risk warping them. I am no expert, but that makes sense.

[J.P.M.]

It is my understanding that if you don't leave a small gaps between the individual panels for them to contract and expand with heat, you risk warping them. I am no expert, but that makes sense.

For most attachment methods that use clips, the thermal strain induced from the assembly to operating temp. differentials coupled with the temp. differentials between racking (usually operating relatively cooler) and panel frames (usually operating relatively warmer) will be present pretty much regardless of panel spacing gaps. The clip/attachment method may/may not give the assembly a bit more strain tolerance.

If I was designing such an assembly, I'd certainly check for thermally induced stresses and consequences, but I'd not expect it to be a problem needing a design change for applications such as most rooftop PV arrays.

[hardwired]

So what is the consensus on spacing and rail systems?

15cm roof to under panel gap is 5.9" which seems pretty big. Most proposals I
am seeing are 3" gap and a number are using iron ridge system.

Which systems use clips? Do the clips protrude above the panel and work to hold snow?

What system has has a small gap and no protrusions?

Mic you go with edge skirts should they be top and/or bottom? Got a proposal that only has them on the bottom??

[PugPower]

I don't think 5.9" is very high. I only see systems with edge skirts on the bottom. I was told edge skirts are for cosmetic purposes only.

[J.P.M.]

So what is the consensus on spacing and rail systems?

15cm roof to under panel gap is 5.9" which seems pretty big. Most proposals I
am seeing are 3" gap and a number are using iron ridge system.

Which systems use clips? Do the clips protrude above the panel and work to hold snow?

What system has has a small gap and no protrusions?

Mic you go with edge skirts should they be top and/or bottom? Got a proposal that only has them on the bottom??

There's some information around that halving the roof to bottom of panel clearance from 6" to 3" will increase the actual operating circuit temp. by ~ 3-6 C., depending on wind regime. Research is spotty and IMO only , a lot of it is not well done. More gap is better, but it seems beyond ~ a 15 cm. or so gap, cell temps. don't drop all that much more.

On skirts: They are almost entirely cosmetic and have little effect on panel operating temps. and can actually increase wind loadings. Therefore, getting them with the idea or goal of attaining a performance improvement is a waste of money. If aesthetics are a concern, get black frames.

[PugPower]

If my system was on the front facing roof of my property and I was concerned about aesthetics, I would have probably gotten all black panels and skirts. Fortunately, no one can see my panels besides the neighbor behind me so aesthetics were not a priority. But I totally understand why some people would want to do this since IMO is does provides a nicer upgraded appearance.