Replacement glass for hot water panels

[Bad Wolf]

I have 3 hot water panels roughly 3' x 6' that I picked up a couple of years ago. I never got around to installing them and now the glass is broken on two of them. (my son fessed up to dropping one while moving it, the other is a mystery.)
Anyway, the copper tube and sheeting is still OK. Is there any place to get replacement glass? I've done a preliminary google search with very little luck.

 

[semipro]

How does the existing glass look after it broke? Did if break into may tiny pieces (tempered glass) or longer sharper shards (plate glass).
Either type of glass can be ordered through a glass shop. The tempered (safety) glass usually has to be special ordered in because its heat treated. Plate glass can usually be cut at the store.
Tempered glass is stronger and more resistant to breakage from things like hail. Its required in overhead windows and those close to the ground.

 

[woodgeek]

Solar thermal panels are usually made with low-iron glass (its not green on the edges) because it has better transmission. Perhaps some of the DIY solar folks can say how important that is to performance?

 

[peakbagger]

I think most folks just go with tempered and live with the slight efficiency hit.

 

[Circus]

I built my solar water heater using greenhouse 8mm twin walled polycarbonate. Works pretty good. Can't see any reason why it wouldn't work as a replacement for glass. The only drawback is it came in 4X24 ft sheets. Cuts with a saw and it's indistructable. I think I saw thinner 4x8 sheets at a Menards once.
Update: Menards does have 6mm 4x8 twinwalled polycarbonate.

 

[woodgeek]

twinwall might have too high a stagnation temp, and damage the collector if the pump was off. Polycarbonate is hard to break, and very heat tolerant.....seems like a good choice. Worst case....it yellows over time from UV (if uncoated).