Rooftop solar could meet all electricity needs in Canadian homes—technically

With 15 million residential and 500,000 commercial and industrial buildings, Canada is rich in the roof space necessary for serious rooftop solar

Sunny skies are non-negotiable for rooftop solar, which means the Atlantic provinces and British Columbia won’t get as much solar output as the Prairies. City of St. Albert photo.

This article was published by The Energy Mix on Feb. 22, 2024.

By Gaye Taylor

Rooftop solar could—technically, and with lots of caveats—supply 100 per cent of the electricity consumed in Canada’s residential buildings, and nearly half of what commercial and industrial buildings need, concludes a new technical report from CanmetENERGY.

The review of rooftop solar’s technical potential “suggests that up to 300 gigawatts of PV can be installed on building rooftops, with a corresponding annual electricity generation of up to 247 terawatt hours,” write [pdf] experts at Canmet’s research centre based in Varennes, near Montreal. That’s enough to supply 76 per cent of the current electricity needs in residential and commercial and industrial (C&I) buildings in Canada, their analysis finds.

“For Canada as a whole, rooftop PV on residential buildings can supply as much electricity per year as is consumed in these buildings,” they write, while for C&I buildings, maximizing rooftop solar will supply 49 per cent of annual needs.

Putting solar panels on facades of buildings (not just rooftops) could further boost annual generation by at least 45 TWh.

Much has improved in the 18 years since co-author and renewable energy expert Sophie Pelland co-wrote a similar study in 2006, which estimated at the time that rooftop solar on suitable residential and C&I buildings in Canada could meet 29 per cent of their electricity needs. The cost of photovoltaic solar systems has plummeted by some 90 per centsince then, even as they became more efficient, so that they take up less space to produce the same amount of output. At the same time, the Canadian building stock has “grown considerably”.

The new report published in January undertakes a detailed analysis of rooftop PV technical potential in a “training set” of 11 Canadian municipalities: North Vancouver, Kelowna, Calgary, Yellowknife, Saskatoon, Winnipeg, London, Varennes, Moncton, Halifax, and St. John’s. By “technical potential,” the report means that “all building surfaces that can support PV are included, irrespective of financial viability, hosting capacity of the electricity grid, or matching of supply and demand in real time.”

The authors stress that their analysis of technical potential “is the starting point for studies of the market potential, i.e., the contribution that PV on buildings could make to Canada’s future electricity supply, once economic, grid integration, and other factors are considered.”

They make their case for technical PV potential by combining building footprint data with high-resolution images of surfaces captured by light detection and ranging (LiDAR) technology that provides a vertical accuracy of 10 centimetres. Their decision to restrict the study to 11 municipalities owed to data availability limitations: “LiDAR data and especially building footprints are not yet available for every Canadian municipality,” the authors explain.

To compensate for the limits of their sampling methodology, the researchers tried to ensure that “at least one municipality was selected per province or territory to sample from a broad range of Canadian climates and building stocks.”

Rooftop Solar is Underutilized

Even with those limitations, Canmet’s numbers suggest that rooftop solar in Canada is an underutilized resource. With 15 million residential and 500,000 C&I buildings, the country is rich in the roof space necessary for serious rooftop solar, even after accounting for the non-negotiables of flat surface and those that don’t face south, Radio-Canada writes in a recent review of the study.

“People sometimes think that, as a northern country, we don’t have much sunlight, but that’s not true,” Pelland told Radio-Canada. “If we look at the sunlight in [rooftop solar] pioneer countries like Germany or Japan, our solar resources are entirely comparable, and in some cases even better.”

Regina and Montreal receive more hours of sunlight annually (1,815 and 1,580 hours, respectively) than either Berlin (1,131) or Tokyo (1,180), Radio-Canada says.

But so far, Canada has made only small use of its solar bounty. Whereas solar power supplies nearly 25 per cent of Germany’s electricity mix, it provides only 1.7 per cent in Canada.

“The fact that electricity is fairly cheap has made it more challenging for solar to break through,” Pelland says. “But the situation is changing, what with falling costs and the active search for new clean energy sources.”

No Problem with Snow

While snow might appear to be a major obstacle to solar generation, its impact is “limited, reducing electricity production by only 2 per cent to 5 per cent,” Radio-Canada says, citing ongoing research, and even that limitation can be overcome.

“The energy loss due to snow is negligible when we compare it to the sunlight we receive in Alberta, and even in Quebec, which is higher than in France,” said Sylvain Nicolay, renewable energy development researcher at l’Université de Sherbrooke, who was not involved in the study.

Nicolay heads Sherbrooke’s 3IT.Énergies platform for developing renewables, which will spend the next three years analyzing the performance of solar panels when exposed to snow. [Writer’s note: This project is named Olaf, presumably after the winsome little snowman in the movie Frozen.]

Nicolay flags the potential use of bifacial, or double-sided, solar panels to mitigate generation losses from snow. He told Radio-Canada a double-sided panel could increase solar gain by as much as 25 per cent, while costing only 5 per cent more than a single-sided unit.

Solar Potential by Province

Snow or no snow, sunny skies are non-negotiable for rooftop solar, which means the Atlantic provinces and British Columbia won’t get as much solar output as the Prairies. Whereas the Prairies could produce up to 50.6 TWh worth of solar annually by Canmet’s method of calculation, B.C. will top out at 30 TWh, while the Maritimes might hope for 16.5 TWh.

The authors cite the International Energy Agency’s (IEA) Photovoltaic Power Systems Program as an alternate method of calculating capacity. The IEA method was, in fact, used in the 2006 analysis and is more constraining, paying particular attention to lost solar potential due to shading. When the IEA’s calculations areapplied, projected TWh capacities drop significantly, the Canmet paper shows.

Rooftops are another necessity. That puts heavily populated provinces ahead of the game, with 41 per cent of the country’s PV potential in Ontario, and another 38 per cent divided roughly evenly between Quebec and the Prairie provinces, according to Radio-Canada.

But the “put-me-(almost)-anywhere” aspect of rooftop solar makes the technology a potential disarming agent in the ongoing battle against NIMBYism, Radio-Canada notes, citing frequent local efforts to block wind and ground-based solar projects.

“We can install them in parking lots to protect cars from snow and hail,” said CanmetENERGY research manager Yves Poissant. “We can turn them into power plants on vacant or contaminated land, or even on hydroelectric reservoirs, which account for thousands of square kilometres.”

 

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