Solar panel supports: New rooftop system uses lightweighting strategies

A solar-energy start-up's prototype solar photovoltaic (PV) modules harnesses the benefits of injection-molded composites to solve problems often encountered in flat-roof solar-panel installations.

A new start-up, TULiPPS Solar B.V. (Eindhoven, The Netherlands), is currently developing prototypes of its new lightweight COSMOS solar photovoltaic (PV) module, which harnesses the benefits of injection-molded composites to solve problems often encountered in flat-roof solar-panel installations.

For conventional PV modules on flat roofs, the required panel height and angle of tilt typically necessitate a separate aluminum frame and support structure and heavy ballast, such as concrete blocks, to stabilize panels in wind gusts. Ballast installation is hard work, time consuming and costly, and it adds so much mass that the systems are often too heavy for safe use on “light” flat roofs. An alternative is to drill through the roof membrane to bolt modules to the roof understructure, but the labor cost and risk of leaks makes this approach undesirable.

Developed in partnership with leading companies in the automotive composites, roofing and PV industries, and with financial support from the province of Noord-Brabant in The Netherlands, COSMOS addresses these deficiencies. Central to its design is a thin (2-mm/0.08-inch) glass PV laminate that is integrally bonded to a composite module base and forms a strong box-beam structure that eliminates the need for an external frame and reduces weight by 50 percent or more — the roof load is less than 10 kg/m2 (2 lb/ft2). The flatter installation angle (5°) reduces shadows on units farther back in an array, allowing gaps between rows of modules as small as 0.3m/1 ft rather than the usual 0.6 to 1.5m (2 to 5 ft). “Earlier, when the cost of individual modules was high, the goal was to achieve optimum efficiency for each module,” says company founder and managing director Paul Stassen. “Module costs are now lower, but the balance of systems costs are still relatively high, so the focus is on maximizing the number of modules per roof.” Although the shallower angle is considered “less efficient” at generating energy on a per-module basis, the fact that more modules can be installed per unit area leads to a reduction in the cost per watt of generated energy and a shorter payback time on the investment.

The lighter, frameless modules are easier to carry, connect quickly to a proven roof anchor system that uses no fasteners and does not penetrate the roof membrane and leaves no edges or corners to trap dirt and dust or encourage the growth of algae. The support system — a nonconductive long-fiber thermoplastic (LFT) polypropylene (PP) composite — provides high bending strength at very low weight and requires no electrical grounding.

Preliminary flame retardance testing indicates the materials will meet Underwriters Laboratories’ current and future requirements for roof-mounted polymeric components. Because TULiPPS plans to warrant its units for 25 years, materials have been formulated for long-term weatherability and UV stability. Accelerated aging tests show that the composites retain good physical and mechanical properties. Stassen’s company has filed numerous patents, is building 300 prototype modules for customer testing and plans to go commercial next year.

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