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Case study
Tecumseh, Ont., just south of Detroit, was seeking to establish itself as an early-adopter of green power generation under the Ontario Feed-In Tariff (FIT) program. The town is one of four municipal shareholders of Essex Energy’s parent company, Essex Power Corporation. It is also very active in various power conservation efforts as evidenced by its award as a winner in its category of the Ontario Power Authority’s Power Pledge initiative (now Independent Electricity System Operator [IESO]). With these efforts in mind, the municipality determined a solar power system should be installed.
It became obvious the Tecumseh Arena was the logical choice to play host to the PV system, as it is the largest municipal rooftop area available in the town, and the single largest user of electricity. The arena operates two ice surfaces for hockey, figure stating, and public skating on a year-round basis, requiring a massive amount of power to maintain the ice, HVAC equipment, and lighting.
The array was commissioned on October 21, 2010. Until recently, it remained the largest operational rooftop array in Canada. This was eclipsed in July 2016 by the Leduc Recreation Center in Alberta—another PV system mounted to a standing-seam metal roof utilizing non-penetrating mounting clamps. More than 6000 non-penetrating mounting clamps and aluminum disk PV kits were utilized to complete the installation, all without a single roof penetration and without voiding the roof warranty—a concern for Tecumseh. The non-penetrating clamp provided a very cost-effective system, which is of primary importance when developing public projects.
Photo © BigStockPhoto
Between the attachment provider, the metal roof panel manufacturer, and Essex Energy’s engineers, a unique design was implemented for the project. A 4.3-m (14-ft) walkway was incorporated between every second row of solar panels while maximizing the number of panels installed. The walkways allow for easy navigation without having to walk across the panels; they facilitate easy roof inspection and maintenance, essentially making every panel easily accessible. The flexibility in the application of the attachment product was vital in allowing this design consideration. Their lightness, low cost, and ease of installation afforded the project tremendous savings and improved economic and financial performance across the board.
In terms of power savings, the solar panel system offset roughly 35 per cent of the power consumed by the facility. This does not take into consideration any of the thermal efficiencies gained because of the sun hitting the panels, as opposed to the exposed roof. This could be substantial, particularly in the warmer months, because the solar panels provide shade to the arena, lowering the power needed to keep the facility cool. Essex Energy plans to use the same design strategies for two other similar municipality rooftop projects in LaSalle and Amherstburg.
Conclusion
A standing-seam metal roof can be a very suitable platform for harvesting solar energy, with strength, durability, longevity, and long-term cost savings over other roof options. The inclusion of a non-penetrating clamp attachment offers freedom from roof penetrations to preserve the roof manufacturer’s warranty. All this translates into a system that can help provide the lowest overall performance cost and create solar generated power long into the future.
| FACING YOUR PV PANELS | ||||||||||||||||||||
| There are a few general rules that can help maximize the power production of a rooftop photovoltaic (PV) system. For example, the general orientation of the building can be a very important factor. When steeper slopes are involved, south-facing roof surfaces are ideal. When this is impossible, southwest or southeast can also be good options.
Orientation is not as important for very-low-slope roofs (i.e. five degrees or less). It is important to note the solar community uses angle in degrees while the roofing community uses pitch (see table at right). Modules are normally installed planar to the roof surface on steep roofs, and planar or very slightly tilted on low-slope applications. Aggressive tilting of modules is seldom still done primarily due to economic considerations adversely affecting payback periods, as well as wind effects. Tilted systems are still used in very northern geographies or on some roofs not oriented to the south. It is a delicate balance of increased cost versus increased power production. In many cases, the roof pitch is pre-determined and cannot be modified. In theory, the best pitch is the latitude of the jobsite; in practice, this is seldom the case. A lower-than-optimal pitch is not as critical as orientation—the difference in power production is nominal. The increase in power production is not usually worth the premium cost of unusually steep pitches, unless the steeper slope is also an intentional design element. Even a 10 per cent increase in power production does not usually warrant the added cost of achieving it.
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Harry J. Lubitz, CSI, CDT, is the architectural and national accounts director for S-5! Metal Roof Innovations, of Colorado Springs, Colorado and S-5! Canada in Ajax, Ont. Lubitz works with the design community to develop and improve architectural specifications for metal roofs and attachment systems. He has more than 35 years of experience in the building materials industry and is active in numerous architectural and professional organizations. He can be reached via e-mail at hlubitz@S-5.com.
