New York City has a rule about roofs that most of the country doesn’t. Replace your entire roof deck, or put up a new building, and the whole roof has to become either a garden or a power plant.<\/p>\n
Or both, if you can work out how to fit them on the same surface.<\/p>\n
That last part is the hard bit, and it is why roughly a hundred kilowatts of solar panels are currently standing straight up on an industrial roof in Queens. Rows of them, edge-on, like books on a shelf. Nothing tilted at anything.<\/p>\n
The hardware is Norwegian. Over Easy Solar put the array up in the Willets Point industrial pocket of Queens, on a building whose owner has not been named, and pv magazine reported it in April<\/a> as the arrival of vertical rooftop PV in the US market. The install was delivered by Sempergreen USA, which supplies pre-grown vegetation mats for green roofs.<\/p>\n That detail is the whole story. The panels are upright because the roof under them is a garden, and the garden had a legal claim on the space first.<\/p>\n New York passed Local Laws 92 and 94 in 2019. Since November 15 of that year, every new building, and every alteration where the entire roof deck or roof assembly gets replaced, has to cover 100% of the roof with what the Department of Buildings calls a sustainable roofing zone<\/a>.<\/p>\n Three ways to satisfy it: a solar system generating at least 4 kW, a green roof, or a combination of the two. Mechanical equipment and fire access paths get carved out. The rest of the roof is spoken for.<\/p>\n Most owners pick one and move on. Doing both on the same square footage is where it turns awkward, because a conventional tilted array is basically a roof over the roof. It shades the sedum and it throws rainwater off to one side.<\/p>\n Trygve Mongstad, founder and CEO of Over Easy Solar, told pv magazine the Queens project was drawn up with a conventional tilted layout first, then switched to vertical to meet the city Department of Environmental Protection’s priorities for green roof performance. Standing the modules on edge lets rain and light reach the planted surface between the rows.<\/p>\n Willets Point is a sensible place for that to matter. It is low, filled ground next to Flushing Creek, historically the auto-shop and scrapyard district known as the Iron Triangle, and stormwater retention on a roof there is not decoration.<\/p>\n The second constraint is weight. The xM3 unit Over Easy uses arrives prefabricated: four modules rated at 256 W apiece, heterojunction cells from Huasun with 95-96% bifaciality, in a frame that needs no ballast and no penetrations through the membrane. Four modules at 256 W works out to a bit over a kilowatt per unit, so a 100 kW array is somewhere near a hundred of them.<\/p>\n Dick Bernauer, VP of sales at Sempergreen USA, put the loading at 2.4 pounds per square foot and credited the system’s wind uplift resistance for letting it share a green roof without extra ballast. He also pitched it at any “generic flat roof that has low loadbearing capacity”, which is a much larger market than green roofs.<\/p>\n The generation numbers are less flattering than the setup suggests, and Over Easy handed them over anyway.<\/p>\n Mongstad told pv magazine that a 100 kWp vertical array in New York should land between 100,000 and 140,000 kWh a year, depending on albedo, azimuth and local shading. The figure pv magazine carried for the Queens roof was around 120,000 kWh.<\/p>\n Then run the comparison he offered himself. A conventional 100 kWp system on the same flat roof, tilted ten degrees and split east-west, would produce about 116,000 kWh a year in New York on the same radiation data. In specific yield, vertical lands at 1,000 to 1,400 kWh per kWp per year against roughly 1,300 for conventional east-west flat roof solar.<\/p>\n So the vertical array beats the tilted one by about a fifth at the top of its range, loses to it by around 14% at the bottom, and the middle is a coin flip. Nobody is selling this on annual kilowatt-hours.<\/p>\n A reader pushed back in the comments under pv magazine’s piece, pointing at the shadows in the project photo as evidence of how little sun the panels were catching at that hour, and arguing that comparisons to a “conventional” system are slippery when most flat-roof arrays run at suboptimal tilt anyway. Fair objection. Worth remembering that every yield figure above came from the company selling the racking.<\/p>\n Stand a bifacial module on edge facing east and west and you stop chasing noon. The east face works the morning, the west face works the evening, and the daily curve comes out with two humps instead of one.<\/p>\n That shape carries a dollar value in New York specifically. Con Edison runs a summer super-peak<\/a> from June through September, weekdays between 2 and 6 p.m., when supply prices sit well above the rest of the day. A tilted south-facing array is already sliding down its curve by then. An east-west vertical array is still working its west face.<\/p>\n We covered the same physics at industrial scale when Frankfurt Airport stood 37,000 modules along a runway<\/a> and when Germany floated 2,600 upright panels on a Bavarian gravel lake<\/a>. The rooftop version is the same trick on a much smaller surface.<\/p>\n Then there is snow, which is the argument Over Easy leans on hardest. Its own case study puts the advantage under light snow cover of up to about 4 inches, where snow on the roof bounces light into the rear face, and under partial cover of up to about 12 inches, where the modules are still standing clear of the drift. In Norwegian winters the company claims three to four times the output of conventional flat-roof mounting.<\/p>\n Vendor numbers on a vendor product, in Norway. The underlying physics is not controversial, and it is why an Austrian ski resort went vertical on a glacier<\/a> rather than fight the drifts every week.<\/p>\n In July, the next North American deployment surfaced in Vancouver. Over Easy’s first system in British Columbia sits on the roof of Science World, the domed science museum in the middle of the city: 19.5 kW across three arrays, 76 XM-3 units on ST125 feet built for gravel roofs and heavy snowfall.<\/p>\n The array is one line in a CAD 39 million retrofit, about $27.4 million, that also covers air-source heat pumps, electric chillers and five inches of insulation inside the dome. Together those measures are expected to cut the museum’s energy use by 42%.<\/p>\n Rob Baxter, co-founder of installer VREC Solar, told pv magazine<\/a> there had previously been “not a good solution for flat roofs that could not support ballast or penetrations”, and said the deciding factor here was keeping snow off the modules over winter.<\/p>\n BC Hydro is watching the numbers. The utility frames the Science World array as a way to test vertical PV in snowy, low-sun-angle conditions, with a view to more installations in parts of British Columbia where snow is a genuine problem. Over Easy also told pv magazine it has a pilot running in Quebec with Hydro-Qu\u00e9bec, comparing winter yield against conventional systems that spend the season buried.<\/p>\n Two Canadian utilities running instrumented winter tests. On the American side, one array, one roof in Queens, and no published production data yet.<\/p>\nThe roof had to be a garden and a power plant at the same time<\/h2>\n
The annual power math is closer to a tie than the pitch sounds<\/h2>\n
What you are actually buying is the four o’clock hour<\/h2>\n
The follow-through landed in Canada, not on another American roof<\/h2>\n
The July 4 deadline turned installation speed into a line item<\/h2>\n