Impact of Snow on Solar Collection

    This past weekend we received five inches of a dry, powdery snow. I was curious as to how much impact snow had on solar panel power generation. Most people with large solar arrays, have their solar panels mounted on the roof of their house and/or garage. Due to space limitations of suburban yards, that is the most logical and perhaps even the only possible place to install panels. But what happens when it snows, I have often thought. Quite a bit, actually.

    I have eight 320 watt solar panels in my ground-mount array. Two banks of four panels and they are angled slightly different to take advantage of the orientation of the sun to the panels. One set of four panels is optimized for the morning hours and the other four are optimized for the early afternoon. Under ideal conditions, the maximum output should be about 2,560 watts of power.

 

     With five inches of powdery snow on the panels, see below, at 10:08 in the morning, I was generating 153 watts of power with my main array and another 76 watts with my secondary array. That was somewhat surprising. It was a sunny morning but at ten o'clock in the morning the sun was not optimal.

 

    The snow had started to slide down the slope of the panels but they were still completely covered. Even so, enough light was getting through to generate some power, but only 6% of the rated maximum. Extrapolating to a 20,000 watt rooftop array would equate to approximately 1,500 watts of generated power. That's not nothing, but it isn't much if you are selling that power to the grid. And with rooftop solar, that is all you are going to get until the snow melts off the panels. My experience with my panels last winter was that unless the temperature went well above freezing, it would take three or four days to melt the snow IF it was sunny.

 

 

    I walked out with a soft broom and in less than a minute I cleared the snow. I went back inside and checked the numbers and my generated power had jumped to 1,820 watts, a more than 1000 percent increase in power. By noon I was well over 2,000 watts. 

 

    A ground-mount solar array will gain some additional efficiency via light reflected off the white snow. Bifacial panels will do even better since they get an addition boost of 25-35 percent from the backside of the panels. This array is monofacial panels so I don't get that.

 

    In the winter, the days are shorter and you need to generate as much power as you can in that shorter period. If I couldn't clear snow off the panels, I could not generate enough power to recharge my system's batteries.