Monday, February 21, 2011

Winter - effect of snow Part2

So the snow built up until February 7th at about noon. That was when the snow guards holding back such a mass of weight said "no more". The courtyard area has a standing seam metal roof that pitches toward it and had built up with quite a curl of snow. I estimate that it was 4ft thick of ice and dense snow and went back a good 20ft from the eave toward the ridge of the roof.

Heavy snow weights about 20lbs/cubic foot. 4ft tall drift x 60ft long gutter x 20ft from eave upward = 4800 cubic feet of snow, or 96,000 pounds. That my friends is a lot of weight. Snow guards were torn free, and it crashed into the courtyard.

We have a mini excavator handy and dug a path to see what was buried. The inverter obviously took a hit on the roof as you can see from this photo. It is made to withstand outdoor environments, but never was envisioned to be under such a blast of weight. The blue canopy shown in other photos over the inverter was a light gauge cover to shelter a technician when they would service the equipment. Needless to say, it was destroyed.

The inside corner also house the air conditioning condenser unit. We created a canopy cover to protect the unit from snow during the winter time. Little did we know it would be crushed under the impact.

So my next post will discuss the recovery from the event.

Winter - effect on solar Part1

As we entered winter, I'm often asked - how does that affect the electricity generation from solar panels? Certainly the shorter daylight hours reduce the potential for kwh, but this year the question was more often related to the snow we have had. In CT this winter, our ground has been covered by snow since the Xmas-NewYear holiday until March. More than 90days! In fact, we received some record snowfalls.

Our panels are on a pitched roof and rather tightly spaced. Thus, the snow can start to slide off as you see in these photos. Our standing seam metal roof has snow guards to limit hazard below, because as you can see, when that accumulation slides, it slams (look at snow splat on pavement below). What was unexpected was how much snow we got (2ft in one storm) over the winter with no thaw period between storms. It did get to be a problem as to where snow could be pushed, and still maintain access to the yard for materials deliver.

After several storms, buildings started collapsing. Usually barns at farms or storage shed industrial structures that were light engineered on the limit of building code allowances. Still, we weren't taking any chances and started shoveling snow off our office roof (the only flat roof area we have). You can see by this photo that it was a lot of snow, up to our shoulder as we shoveled it away. The right photo is our courtyard area where some equipment for the solar array is located. The snow on the pitched roof area has curled and built up substantially. It couldn't be simply removed, and the buildup was worrisome.

It snowed and snowed and snowed!! It was quite the winter!! Despite the snow shed from our panels as shown in the above photo , we were getting a "DC fault" code causing the inverter to cease generating any electricity. We couldn't access the roof safely to confirm what was causing the fault, but the "DC" indication confirms it was at the panels. My next post will show the effects.