Photovoltaic Rooftop Mounting Rails for Membrane Billowing
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Solution Overview
Problem
Conventional photovoltaic rooftop mounting systems face challenges in maintaining structural integrity under various forces, including billowing membranes, and often require excessive penetrations that damage the rooftop, while non-penetrating systems may fail due to pressure fluctuations.
Innovation Solution
A minimally penetrating photovoltaic rooftop support system featuring elongate rails and retractable leg assemblies that accommodate membrane billowing and provide adequate support using a combination of penetrating and non-penetrating fasteners, minimizing rooftop damage and ensuring stability under wind and snow loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional rack systems with multiple roof penetrations are used, then structural stability and wind load resistance are improved, but rooftop integrity is compromised and material weight increases
Solution Approach 1:
The leg assembly incorporates a retractable mechanism that allows the foot to move dynamically in response to membrane billowing. When upward forces from membrane movement occur, the foot retracts to accommodate the movement without creating rigid constraints that would damage the membrane or compromise structural stability.
Solution Approach 2:
The foot acts as an intermediary element between the rigid rail structure and the flexible membrane. It provides a compliant interface that can adapt to membrane movements while maintaining sufficient contact to prevent excessive membrane billowing, thus protecting rooftop integrity without sacrificing structural stability.
2Object-affected harmful factors
If lightweight non-penetrating mounting systems are used, then rooftop integrity is preserved and material weight is reduced, but structural stability under pressure fluctuations deteriorates
Solution Approach 1:
The system uses different types of leg assemblies with different penetration characteristics at different locations. Some leg assemblies have feet that penetrate the membrane to provide enhanced stability in high-stress areas, while others remain non-penetrating to preserve rooftop integrity in lower-stress areas. This localized differentiation resolves the contradiction between stability and integrity.
3Ease of manufacture
If the membrane is mechanically attached at spaced-apart pinning points, then ease of installation is improved, but membrane billowing under wind loads increases
Solution Approach 1:
The leg assemblies are positioned and configured to counteract membrane billowing before it becomes excessive. By providing distributed support points along the membrane surface, the system preemptively reduces the amplitude of membrane movements under wind loads, preventing problematic billowing while maintaining the simple pinning-point attachment method.
Data Source
AI summary
A photovoltaic array including a plurality of photovoltaic assemblies and a plurality of mounting units. The mounting units each include an elongate rail and a plurality of leg assemblies. The rail is sized and configured to maintain a portion of at least two of the photovoltaic assemblies, with the leg assemblies extending from the rail in a spaced-apart fashion and terminating in a foot for placement against a rooftop structure for minimally penetration installation. Further, at least one of the leg assemblies can include a retractable leg. When the photovoltaic array is installed to a rooftop structure including a membrane intermittently secured to a rooftop deck, the retractable leg accommodates upward billowing of the membrane under windy conditions.