Question about Snow on collectors

 A heavily cloudy day so I wasn't surprised that I had no current flow at
9 AM from my test collector.  But I noticed that there was an inch of
new snow covering the collector, which is at about a 60 degree angle
from the horizontal.  No way is it gonna slide off.  So I brushed the
snow off and now am getting about 1/3th of the output I'd get in full
sun at this time of year, at this time of day.  Not bad.

Here's my question:  I have seen pictures of many pv installations where
the collectors lay flat on the roof of the house or only slightly tilted
from the roof's own pitch.   What do people who live in snowy climates
do when they get snow?   Some of the collectors look pretty darn big, so
a plain old floor sweeping broom would have a hard time reaching the
whole thing even if the homeowner wanted to be up on the roof when it
too is covered in snow (and possibly ice).

If one used scrapers or something, does that ruin the collector, shorten
its life or reduce its efficiency?

Could one drive current back through the collectors to melt the snow/ice?

Okay, it was more than one question,
Pete Stanaitis
--------------------