I'd use some 2 inch pvc with an outlet under each bank, build a custom made high wattage heater with NiChrom and a computer fan, gentle hot air bath will be enough to loosen it all up, if it needs more up the air flow and or wattage.
Or a glycol recirculating loop with a solar heater with a back up electrical unit.
With out knowing the configuration on the roof hard to suggest the best idea.
At -30c so long as I can get over 40% of the panel cleared it will clean its self once the sun hits.
As for the defoger style grids you can buy self adhesive kits:
http://www.frostfighter.com/clear-view-defrosters-about.htmThere is a large array of options but what works for you will depend on a few factors, it all starts with the general lay out of the panels, lowest average temps and so on.
Snow is a good insulator, it allows us to build the heat up till we reach a point it all comes off, so self regulating heater wire wrapped around the frames will do quite well, 30w per foot would allow for a fairy fast defrost and pretty cool ambient temp, and since the frame will expand first then the heat will work its way through rest of the glass allowing for best expansion characteristics.
Edit: If you wanted to get retardedly fancy even a heat pump system or thermosyphone