Seasonal Tilt Solar Mounting Structure FEA for Design Wind and Jack Tilting

A utility-scale solar developer wanted a new mounting table for thin-film modules, with a tilt angle that site crews could change through the seasons. The table had a curved tilting link between the rafter and the column, and a jack to swing the module plane to each seasonal angle. Because thin-film modules are mounted in large numbers on light cold-formed members, the developer needed proof that the frame would survive the design wind at site and also stay safe while it was being tilted.

Shirsh Technosolutions carried out the seasonal tilt solar structure FEA in ANSYS Mechanical. We checked the full table under design wind to IS 875 Part 3, checked the cold-formed members to IS 801 and deflections to IS 800, and ran a separate jack operation analysis for the tilting process. Design calculations, fabrication drawings and the bill of materials followed from the same model.

Wind loads to IS 875 Part 3. We worked out the design wind pressure from the basic wind speed with the risk, terrain and topography factors, and applied net pressure coefficients for a free-standing panel. Three wind cases were set up: uplift acting away from the panels, wind pushing towards the panels and wind along the length of the table. Each was combined with dead load of the structure and the modules.

Full-table FE model in ANSYS Mechanical. The purlins, rafters, columns, bracing and curved tilting links were modelled with shell and solid elements, so the stresses in thin cold-formed walls and at the link came out directly. Columns were braced along the row and the bases restrained as in the design. The model gave stresses, deformations and support reactions for every load combination.

Cold-formed member and connection checks. The column was checked for axial compression and combined axial and bending to IS 801. Rafter and purlins were checked for bending, shear and combined bending and shear, using effective section properties for the thin walls. Bearing was checked for the purlin-to-module clamp, purlin-to-rafter and rafter-to-column bolts, and a linear buckling analysis confirmed the table is stable under the governing wind. Member deflections were compared with the IS 800 limits.

Jack operation analysis. For the tilting process we built a single-frame model carrying the panel mass, with the jack force applied at the rafter and the column restrained at its base. The frame, the tilting link and the purlins were checked at a range of working wind speeds, so the developer knows the frame stays within limits while the tilt is being changed.

Design package and review. The structure passed the stress, deflection, buckling and bolt checks under the design wind, and the jack operation cases stayed well inside the allowable stress and deflection limits. After the developer's engineering review we updated the purlin clamp positions, rectified the reports and issued drawings and the bill of materials. A variant of the same table carrying a robotic module cleaner was checked the same way.

Common questions

Why does a seasonal tilt solar structure need a separate jack operation analysis? While the jack is changing the angle, the rafter is carried through the jack and the tilting link instead of its locked connection. The load path is different, so the frame and link must be checked for that state under the wind speed allowed during tilting.

Which codes apply to a cold-formed steel solar mounting structure in India? Wind loads come from IS 875 Part 3. Thin cold-formed members such as hat purlins and C-lip rafters are checked to IS 801, and deflections are usually compared with the limits in IS 800. FEA gives the stresses and reactions that these checks need.