Analysis of Solar Array Support Rack

Typical Solar Panel Array. OCEI performed structural analysis on a solar array support structure.
Typical Solar Panel Array. OCEI performed structural analysis on a solar array support structure.

Hurricane Winds Caused Structural Issues on Solar Array

O’Donnell Consulting was asked to investigate structural issues on a solar array support rack after Hurricane Sandy caused damage at the facility.

The investigation included issues caused by design, fabrication, and shipping and handling deficiencies – considering loads as deadweight, wind, snow, ice, live loads, and combinations thereof. Some of the identified problems can cause rack structural instability. The Facility consists of 6,847 individual solar racks – capable of generating approximately 40 MW of electricity. Each solar rack consists of 24 Photovoltaic (PV) Panels attached to a series of horizontal and vertical beams (referred to as members or rails) with module clips. The horizontal and vertical members connect to each other with tee head (T-head) bolts. The horizontal beams are supported by two tilt brackets which in turn are attached to cylindrical support columns (piles). The horizontal beams are attached to the tilt brackets.

The first part of the investigation involved determining structural integrity under design loading. This evaluation was based on generally accepted Codes and Standards, as well as specifications cited on drawings and in documents provided by the rack designer and other companies.

Structural Analysis

The inspection of design and fabrication related structural problems in the rack structure supporting solar panels was documented. The rack design was evaluated for structural integrity of the individual components and strength of the connections and their ability to resist slipping. To determine the suitability of the rack design for the intended design loads, calculations were performed according to the Codes and Standards. Some components and connections did not satisfy the design criteria.

The rack evaluation was based primarily on component forces and moments determined by finite element modeling and analysis. Beam elements were primarily used in constructing the model for compatibility with evaluation methodologies of the AISC Code. Refinements to the model and more explicit modeling of design features may reduce conservatisms and enable demonstration of compliance of some reported overstressed components with Code requirements. These calculations indicate that remediation of the rack structures was needed. Potential solutions were then presented.

O’Donnell Consulting Performs Engineering Design, Analysis and Troubleshooting for Clients in Industries including Manufacturing, Petrochemical and Energy.

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