Hail Protection / Weather Protection in General

[Aelric]

I really do like the group, I have been reading it for about 2 months or so now and you guys have lots of really good articles.   I have done a few searches, both here and on google for hail protection for solar panels.  I don't have any panels yet but I am curious how you would protect them.  I live in Oklahoma and we on occasion have had hail as large as baseball size, that is why I ask.  Even tempered glass will shatter with enough force, and plexiglass has its limitations too.

Also on weather protection, what are some of the best ways to keep water out of the panels, silicone sealant?  I remember IFred mentioning something about surrounding his panels with mineral oil, but I was just wanting to know a bit more about how it could be made water tight.

[wpowokal]

For hail simply insurance.

[Snoprob]

In OK City the sun's summertime maximum degree-angle is 78~, or close to level as far as hail is concerned, I guess. I'd know I'd use plexiglass with a couple of cross braces or center posts so vibration would xfr to the frame, plus acrylic sag-memory in high temperatures would be lessened. I would be more worried about the other 97% of storms with high straight line winds pulling the whole units apart or off. At 78 degree orientation solar panels are wings with huge lifting surfaces.

[ghurd]

I never saw the glass broken on a factory made PV from hail or baseballs.

Never even seen baseball size hail though! 3/4" is big here.

I've seen quite a few blown off and smashed. Thats what I worry about most.

Maybe a layered armour approach. Add a extra front glass, 1" above the real front glass. The force needed to break the extra front would slow the hail enough for the next layers to survive?  Just a thought.

G-

[John II]

I have not tried this, but I think the best hail protection would be to build a deck on your house either out of wood or better yet concrete and provide storage channels underneath to retract your Photo Voltaic panels into. You could use steel tracks and something like garage door openers to power them out from under the deck into the sun light, or back in under the deck for protection. This would probably be the ultimate protection from tornados or severe hail. Your deck would have to be high enough off of the ground, so you could have each panel pre-tilted to face the sun at the right angle.

As far as keeping home made Panels from leaking, I can't give any advice there. Commercial panels don't leak as they are filled with some form of jellow consistency silicone.

John II

[nothing to lose]

I like your idea of retractable pannels. I been thinking on something like that when I build a house. Kinda a wall in a wall or roof over roof. Open when I want sun, closed when I don't want it.

I think if a person built something like that for solar panels using a motor to open and close it you could make a wind meter and have it close automatically at a set wind speed like 70-80mph if wanted.

For my roof over roof I was thinking a light sensor. Open summer nights to lose heat, closed durring the day to block sun. Oposite durring the winter. Then I also have a nice clear view of the sky on clear summer nights.

Manual switch to of course in case I want to watch an eclispe or comet on a cold winter night sometime

[Snoprob]

John II's above post has alot of merit - I especially like the idea of a 'panic button' that will recall the panels back under shelter if I see the sky go black from one of our midwest thunderstorms. Having the panels parked at night & during snow storms could be worthwhile also. Mostly I guess fears of getting the PV's ripped off makes me want them corraled at night - I guess I gotta stop thinking like a city boy, eh?

[Aelric]

One Idea I had while thinking about this, what if you took apart one of those weather radio's that turns on when there is an alert.  I know there are several weather radio's out there that come on whenever that alert comes on of severe weather.  If you could link that into your switch so anytime there was severe weather it would auto retract your solar panels into a steel or concrete shelter.   I dunno just an idea.   I had thought of something similar for a wind turbine to check weather alert against windspeed and when it is low enough brake and lock down the turbine to protect it from tearing itself apart in high winds.   Just a few ideas.

[tcrenshaw]

What about insted of building retractable panels, build a tracking system that will tilt the panels 90 degrees to the sky. Hit your panic button and all the panels turn pretty much sideways. I have seen hail fly saidways but the angle should allow the panels to survive. Once the storm passes, flip the panels back into sun tracking mode. Of course now you have to deal with a very strong mounting system because the panels are not laying flat on a roof and have just become wings!

[tcrenshaw]

What about those roll type garage doors? Wonder if anything like that can be made so insted of pulling the panels under a cover, the cover rolls out over the top of the cells.

[nothing to lose]

That sounds interesting if your not in an area that might get alot of false alarms.

I am kinda in the middle of alot of stuff here. Everything hits all around us, but we miss most of it. I think I myself would get alot of false alarms. I have been just 8 miles away and thought houses were about to blow away, it was still dry and dusty when I got home, not hardly a drop!

[Aelric]

True False alarms would be bad but my thinking on it is that if it is bad enough to be a false alarm (we get maybe 1 or 2 a month) the sky's will most likely be overcast anyway which would limit the output of the panels.  I was just thinking maybe to auto retract, or even the garage door idea is good too, and then have a switch to open it back up after the danger is past, or if it is a false alarm.  (besides I'd rather be inside if it was bad weather anyway)  This would simply make it so if it was bad weather you wouldn't have to worry about the panels, the would protect themselves, then after its clear you can go hit the switch and start collecting energy again.

[earthshaker]

Use a weather radio with S.A.M.E., capability, this way when an alert is issued, it can be set for only your county, this will minimize alerts for other areas, around yours. Use a light detector in series with the alert signal control circuit, when the light level is low (ie: thunderstorm)and the alert sounds, your PV array recedes into its "den" for protection. A lot of the newer weather radios use an X10 type external alert output, and some use a "dry contact". Both of these could be used with the proper support circuitry, to accomplish the retraction scenario.

The mechanics could be as simple as a small dc powered winch to extend and retract the array (looped cable)or as complex as desired, make sure to use your backup power for the whole thing, so when the grid falls on its face and causing a blackout situation your array can still be retracted.

[nothing to lose]

Thanks,

I never used those weather warning radios (I like suprises) so I didn't know you could set them by county.

I have been thinking about one recently but hadn't bothered due to my thoughts on false alarms here.

 Although as close as 8 miles away has had really nasty storms while it never rained here a drop, they are in a different county also (actually 6 miles is a different STATE).

 Question is though I geuss, how acurate are they at geussing the counties effected? Would they still call out my county when a really nasty storm is just 8 miles away even though we may not get any of it. Most people probably are not sitting on the edge of about 4 small counties like I am and would not have to worry so much about it.

 I guess the light sensor is a good idea since normally if the suns not out you don't need the panels anyway. In my case I might not use the radio, but would use the sensor.

May get a radio though anyway now and just turn it on when I see the storms comming to find out what they may be, or find out whats in my area that I am NOT getting

How hard are they to change counties on? Like a digital clock maybe, punch a couple buttons? Might be nice for traveling this area to know whats on the other end when I get there. This time of year I have hit NASTY blizzard only 100 miles away, no snow at all at home when I left or when I got back. When I say nasty I mean cars in ditches everywhere and 2 spun out in front of me. I don't worry about the weather, I worry about the other drivers!!

[earthshaker]

The setings vary from area to area, but the basics are the same, the FIPS code (punch this in Google and you will find several lists) typically a code of all 9's will be all areas. Then when you find the code for your county/state all you have to di is (consult the instructions that came with your radio)enter the channel of your NWRt (national weather radio transmitter)from 1-7 then the code of the area you are interested in. For eample for my area is 031047 then save that info in your unit. Some S.A.M.E. radios have several areas that can be programmed, in my case I live just 3 miles from one transmitter's coverage area but it is not the transmitter for my area, that one is 25 miles away, but with different areas programmed I can change transmitters at will. The receivers will cost around $70.00 for the better grade radios there are some cheaper ones available, but they may not be able to support different area channel/code combinations. Here is a link that I found with google

http://www.nws.noaa.gov/nwr/indexnw.htm

One editorial comment every home should have a weather radio alert receiver. If you aren't interested in all the other counties alerts in your area, get a receiver with SAME capability.