Snow can present a major problem for owners of solar roofs in northern climates.
As far as we’re concerned, it’s a loaded question. The reason? Frankly, solar electric (aka photovoltaics, or PV for short) is frequently not the best choice to begin with.
Don’t get me wrong. We’re not anti-PV. Quite the contrary. We install PV as well as solar thermal systems. On a personal note, we lived completely off-grid and used two small PV systems to supply electricity for our home and an outbuilding for three years before moving to the Wausau area. It was a wonderful experience in many ways and we plan to install PV in some capacity on our new home once we’ve gotten that far in the renovation process.
PV or no PV – that is the question.
However, when a customer approaches us about PV, the first question we have for them is, “What’s your reason for wanting it?”
PV is great for those wanting to be self-sufficient or completely energy independent. It’s great as part of a larger plan for those building an energy-efficient home, or as a crowning glory for those who have already gotten their energy consumption down to very low levels.
But for those wanting simply to reduce high energy bills in a cost-effective manner, it’s not great. It’s stupid. You can spend a lot less on other technologies that will take your total energy footprint down tons faster than PV, and that’s where it ought to start for those seeking value.
Now that that’s off my chest, let’s get back to the topic at hand.
Solar roofing or panels – which is better?
Well, as usual, there are pros and cons to each. Let’s take a look.
People like solar roofing primarily because of the aesthetics. It blends right in with the roof without interfering with the design qualities of the building.
Thin film solar such as solar roofing is typically far less efficient at converting sunlight to electricity – about 8-10% efficient vs. 12% to over 20% now for regular panels. However, it does continue to produce electricity at far lower light levels than traditional panels. Is it enough to make up for the lower efficiency? The debate rages in solar circles. For now the best we can tell you is we don’t really know.
Snowed by snow
One thing we do know, though, is that here in central and northern Wisconsin we get a lot of snow. Snow that doesn’t melt readily off of PV surfaces of any type. Snow that can put solar electricity generation out of commission for days on end. We figure that with a roof mount you’ll be losing 20% to over 30% of your annual production in a typical year if you don’t want to be dancing around on your roof all winter.
With a solar roof there’s not much you can do about it. But regular panels can be pole-mounted where it’s easy to brush them off with a broom. And if you use an adjustable rack you can change their angle a couple times a year (flatter in summer, steeper in winter) for greater efficiency and to shed snow more effectively.
Now, we’re not going to say one option is better than another. Every situation is different and it’s good to have options to weigh. But for most applications, in this climate we’ll place our bets on the panels.
Visit Performance Energy, Inc.
We filled Al Henrick’s solar loop on Saturday night. Night is best to prevent steam from forming. The big delay was running the electric power to the pumps from a remote PV panel. Today was the first sunny day after filling and the system worked flawlessly. By the time I left around 1:30, standard time not daylight time, the tank was around 120 degrees F. The coldest water off the bottom of the tank was 114 degrees, and the heat exchanger was returning 124 degree water to the center of the tank. This was a cold start since the system had never run before, and the starting temperature was around 55-58 degrees.
It was interesting to listen to the pumps slow down and speed up as clouds reduced the output of the PV panel and then moved away. I worked on the insulation for a little while, and the tank rose from 84 degrees when I arrived around 11:00 standard time to the 114 degrees I mentioned earlier by the time I left. The storage tank holds 105 gallons, so this is a substantial rise in temperature. All we need to do now is finish up insulating the elbows and other fittings, and then install jacketing on the exterior insulation to protect it from UV rays and we are DONE!
Dan Michelsen
