Solar shines in dead of winter – even in Edmonton, study finds

Study looks at impact of snow and angle of solar panels

Old Man Winter takes a lot of flak in Alberta for everything from costly heating bills to frozen car batteries. But when it comes to the impact on solar panels, winter gets an unjustified bad rap.

A five-year study led by NAIT’s Alternative Energy Technology program found that snowfall on photovoltaic solar panels results in about a 3% energy loss. That’s significantly less than the 20% drain that industry had traditionally estimated despite a lack of data.

Tim Matthews, a technologist and one of the leads on the study, says the results will improve modelling used to estimate solar energy production that determines return on investment. Ultimately, that means a win for consumers.

“You can take this to the bank.”

NAIT launched the reference array snow study in 2012 with the City of Edmonton and Solar Energy Society of Alberta. A system of 12 solar modules was installed atop the Shaw Theatre on Main Campus to not only measure the impact of snow on the system, but also how the tilt of each module affects energy production.

“The rule of thumb throughout industry was to design a system as if it had no snow and then wipe 20% of energy production off the slate – we’re going to lose 20% because we’re in Canada,” says Matthews. “Everybody was terrified of underestimating the impact of snow and latitude [on energy production].”

They found that the angle of the solar panels has a far greater impact on energy production than snowfall. Solar modules were fixed at six different angles – 14, 18, 27, 45, 53 and 90 degrees – which represent roof pitches commonly found on commercial buildings and homes. Six modules were cleared of snow every day, while the remaining six served as a control.

The least efficient was the module set at 90 degrees, like a wall-mount system, which saw a 24% loss in performance. The module tilted to 53 degrees was most efficient, which confirmed an industry standard that solar systems are optimized when tilted to the equivalent of a city’s latitude.

The ideal angle for maximum production with snow accumulation was 45 degrees.

Matthews cautions that even five years worth of data is a small window when dealing with fluctuating variables such as weather. But for a homeowner or business who already has historic data on their energy consumption, the tilt and snow impact clear up what had been a cloudy picture in predicting the cost-benefit of solar.

“Having this information raises the level of precision when it comes to engineering, design and production modelling,” says Matthews. “A company that’s doing solar installation and design can go to a client and say, ‘This is precise. You can take this to the bank.’”

Crunching five years of data

The work of crunching through all the data fell to students (and now grads of the class of ’18) Christian Brown and Jackson Belley as the basis of their final course project, or capstone.

That’s no mean feat considering energy performance data was collected from all 12 solar modules every five minutes every day for five years – enough to fill 6,000 spreadsheet files.

“It was an insane amount of data,” says Brown. “That was not quite half, maybe the first third of the project. Months of work. It was a lot of learning.”

Data was gradually exported by day, month, season and year, making it more digestible and user-friendly for industry, government and institutions, but also the schools and not-for-profits, who are interested in the information.

“The amount of requests that we get [for the data], it’s obvious people are interested.”

The study's findings are available online, while the students' final report with datasets will be published on the Alternative Energy Technology program page this fall. It’s already proving to be a hot commodity with requests for data coming weekly from as far afield as Russia.

“The amount of requests that we get [for the data], it’s obvious people are interested and they want to know how does snow affect solar modules,” says Belley.

Brown adds it’s a pretty cool feeling to work on a class assignment that has a major real-world impact. “The idea of solar won’t be as much of a gamble any more.”

Plans are also in the works to submit the findings for peer review and publication in a scientific journal. 

So, should I clear snow and ice from my solar panels?

After five years of getting up at all hours to clear snow from the reference array – including Christmas – Matthews is glad to be rid of that daily chore. For anyone who operates a solar system, he cautions that snow should only be cleared if it’s safe to do so, such as on a flat commercial roof.

“Should you clean the ones on your [pitched] roof? Heck no,” he says. Nor does he recommend asking a contractor to remove it. It’s just not worth it for the minimal gain in power efficiency from a snow-free solar system.

“Our recommendation is that it makes no sense. One hour of time from a professional or an apprentice is just not worth it.”

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