time I got up on the lower porch roof, the snow had
crusted over and it wasn’t going anywhere. It is important
to use a roof rake made for this purpose, so you don’t
scratch the panels. If the snow was soft and fluffy, I think
I could have moved it.
On Sunday (the 7th), it started to melt slightly and the
sky got brighter. Unfortunately, the following day (the 8th)
we got hit again with another five inches of snow; the
panels did not start to clear until the 11th. During most of
this time, there were sub freezing temperatures. Gradually,
production increased each day until it was about 35 KWH
on the 17th (it rained the day before and that got rid of the
remaining snow). So, snow can really make a difference.
If the snow completely covers the array, the array will
not warm up and melt the snow. Figure 15 shows the
snow just starting to clear on the right side of the array
partly due to my heroic (but feeble) attempts to clear it.
When production resumed, it was even possible to see a
plot of the power produced for a
single day (Figure 16).
During these snow and
subsequent wind storms, we did
not lose power but some of the
neighbors did. When the power is
lost to a home, the solar
photovoltaic system automatically
disconnects from the grid as a
safety precaution. If the utility
company is working on the wires,
the last thing they want to
encounter is an unexpected live
wire coming from a home.
So, if you want backup power
during an outage, you will still need
Rain and Snowmarmageddon
I learned that even on a rainy day, production can be
3-7 KWH. A cloudy day (depending on how cloudy) can
result in 5-15 KWH of production. Snow (>1 inch) pretty
much shuts down production. Last year, we got buried in
snow and broke all kinds of records in New England; it
would not have been a good winter for solar energy. How
fast the snow clears off the panels depends on the
temperature, type of snow, depth, and roof pitch.
FIGURE 13. Power produced by month.
FIGURE 14. Power produced in February 2016.
FIGURE 15. Snow covering the array.
August 2016 43