One of the big solar myths is that solar doesn’t perform well in the snow. We all knew that wasn’t true – why would Ontario, Canada have such a great solar program if solar didn’t work in snowy areas? Well, now we have proof.
The January/February 2013 issue of Solar Builder article, “Is a little snow really a big deal?”, tackles the question of how solar panels perform in snow prone areas. Turns out researchers have shown not only that production losses are low, but also that panels may actually benefit from the cold weather and reflection off the snow, generating more than they otherwise would.
Here are three tips for designing rooftop solar arrays in snowy areas:
Tip 1: Understand how the system impacts how snow ice build up and melt on the roof
Joshua M. Pearce (one of the study’s authors) makes the point that it is important to design systems with snow in mind:
“During the system design, the effects of snow on PV performance should be taken into account and not simply ignored. For all systems in snowy climates, the racking should be installed to prevent ice/snow damming ? that is to ensure that snow shedding from the panels has somewhere to go when it melts.”
When developing the system layout, consider the location of the rooftop drains in relation to the racking system. Are there places snow and ice could build up and block the flow of run-off?
Also important to consider is the spacing between the rows – is there room for snow to slide off the modules, or will it drift and eliminate the ability of the system to help melt the snow?
Tip 2: Take advantage of benefits of holding panels at a high tilt angle
While you may typically design at lower tilt angles, it is worth looking at the benefits of higher tilt angles that are unique to snow prone areas:
“In snowy areas a general rule of thumb is to choose the higher tilt angle in the performance curve if other factors allow for it,” says Joshua Pearce. “Higher tilt angles both tend to shed snow faster [and] take a greater advantage of the albedo of snow (reflected sunlight).”
Since higher tilt arrays shed snow faster, disruption in system production will be minimized, as will the maintenance costs associated with routinely needing to remove snow and ice from the panels.
Tip 3: Follow building & racking load requirements and limitations
Every building’s roofing system was developed to support a certain amount of extra weight on the roof. In snow prone areas, this “snow load” requirement is in place to make sure that the roof will hold during the most extreme of winter storms. A rooftop solar array adds extra weight, and may not leave the building with enough of the extra “snow load” capacity.
Similarly, not every solar mounting system on the market is designed to hold the same amount of weight. It is important to ask about the Positive/Downward load ratings for the system. Since the racking system is the backbone of the PV system, you will want to choose one that will be able to hold large amounts of snow and ice.
How SolarDock performs in snow prone areas
SolarDock can be made in tilt angles up to 35 degrees is always non-penetrating, even at those high angles. When we designed SolarDock we wanted to make sure that we protected the roof and the system?s bottom line. Melting snow + damaged roof = leaks. Snow + low angle = low production. Both were unacceptable to us.
SolarDock also meets the same mechanical load requirements as the solar panels being used with our system. Our system holds a UL 2703 downward design load rating of 75 lbs/sf (113 lb/sf before the safety factor is applied).