Philadelphia architecture firm installs wild solar project to maximize onsite power production
Solar systems are primarily installed on rooftops in urban environments where open land is scarce but there are many multi-story buildings. Often the roof space of these structures is not large enough to accommodate solar systems that can cover the entire energy consumption of a building. Therefore, they are supplemented with renewable energy credits (RECs) generated by solar systems outside the city.
Onion Flats, an architecture firm, wanted to buck this trend and maximize PV performance without subscribing to RECs for its Front Flats residential project in the Kensington neighborhood of Philadelphia, Pennsylvania. The solution was to install solar panels on the roof and on most of the east, west and south facing walls of the building. In total, the solar system generates 176 kW, more than the front flats need – and that is intentional.
Front Flats has layers like an onion
The Front Flats project is located in a state and city that are not known for solar incentives. It’s an anomaly in both appearance and size.
“I wouldn’t call this a solar city,” said Tim McDonald, CEO of Onion Flats. “The renewable energy loans in Pennsylvania suck, but you go over the bridge to New Jersey and it’s a different world. There is no real financial incentive to push this forward. We’re pushing it because we think we need to be there. ”
From the second floor onwards, the windows of the 28-unit house are slightly covered by bifacial solar panels that protrude from the outer walls. These vertical panels on the east, west and south facades meet the horizontal modules, which are held on the roof by canopy supports. Tenants have access to the roof, where shade gardens are laid out, and McDonald said the bifacial modular shell still lets natural light into the building and provides additional visual privacy.
The Onion Flats management team consists of the brothers Tim, Patrick and Johnny McDonald as well as the architect Howard Steinberg. The company takes care of the development, design and construction of its projects in cooperation with subcontractors and owns the GRASS service (green roofs and solar systems), which installs PV and gardens on roofs.
The design-build company has made solar part of its new construction projects, which previously only included functional areas related to PV such as the roof roof of the front flats, but never on this scale or panel orientation. To ensure that a project of this size was installed correctly, Onion Flats brought in longtime member of the solar industry and employee Ron Celentano from Celentano Energy Services as a consultant.
“These guys are crazy – I love them,” said Celentano. “They are technicians and they build their own building. You just go anywhere and just wait for the consequences. ”
The vertically mounted solar panels are attached to rails attached to angled aluminum brackets – both made specifically for the project – and screwed into the exterior walls, adding 24 inches to the facade of the building. The substructure that holds the array in place is bolted to Boral composite planks, a cementitious material.
“The facade, which keeps all the rails away from the wall, gets in and climbs around this entire strip of aluminum, climbs between the walls and the modules,” said Celentano.
Depending on the obstacles the city block posed, the plumbers used scissor and articulated booms to move around and attach the brackets to the outside of the building. A high voltage electrical line is 6 feet from the west facing panels and an elevated railway runs along the east side of the building.
“Learning curves definitely happened when we left,” said Celentano. “We used suction cups to lift the glass at first, but after we dropped some of these things it was amazing how fast it was moving.”
The bigger problem for Onion Flats was finding a solar panel supplier. The system was developed taking into account the German bifacial modules from AE Solar. However, when that transaction failed, the company had to find an alternative. The front flats array uses Prism Solar Technologies Bifacial modules that are made in America.
The frameless panels are held in place vertically with two clips at both the top and bottom, and each clip is supported by a square support on the shelf. Mounting the panels vertically one at a time means the bottom clamp will hold all of the weight, Celentano said. Weatherproof seals have been added to prevent the glass from resting directly on metal.
The canopy section of the array is 10 feet above the roof surface, the panels at a 5 ° angle. There’s a 3/4-inch. Gap between each panel and several openings in the middle of the roof panels for additional light and air flow.
Before installing a mounting structure, the layout of the inverter and the optimizer had to be determined. The system uses five SolarEdge inverters and optimizers connected to each module that meet the requirements for a quick shutdown. Each string was directed to a single plane.
“They put optimizers in certain places and they can’t just get them afterwards,” Celentano said. “But I’ve always been pretty confident about the Front Flats project. Tim’s group has great support. “
Generate more electricity than necessary
Since the layout of the front flats array is not typical, the generation capacity is not typical either. The east-facing wall produces well in the morning, but it drops to 1 kW in the second half of the day, Celentano said. Cutting out vertical angles and maximizing the number of panels on the building compensates for this loss, allowing the array to potentially produce more solar energy than it needs and measure the net excess energy. Thanks to the solar project, Onion Flats charges its tenants a flat monthly fee of USD 40 for utilities.
The Front Flats took tenants from January 1, 2020, with half of the rooms being occupied by March. At that time, the solar system also went online.
Onion Flats will not be able to record precise annual solar generation numbers until summer 2021. However, the architects and Celentano continue to expect the system to produce more energy than necessary.
Celentano said he understood those who might wonder why one would design a system like Onion Flats. “But on the other hand, if you need enough solar power to offset your consumption, that’s exactly what you have to do,” he said.
In addition to its massive solar system, the Front Flats were built to meet the requirements of the Passive House Institute Design standards – an airtight building envelope, insulation, double or triple glazed windows, ventilation with balanced heat and moisture recovery and a low impact room conditioning system – to promote higher energy efficiency.
“I’m exhausted when I do demonstration projects for other people to say,” Yes, I can do that too, “said McDonald.” If we don’t bring buildings to a climate-neutral standard in 20 years, we’re all done. ”