EPC Guides
Case Study: 500kW Industrial Rooftop Solar for Textile Mill in Coimbatore
Peer-Reviewed By SOLBE Structural Engineering Division M.Tech (Structures) | CAD Load Analysts ✓ Certified compliant with BIS IS 875 (Wind Loads) & IS 2629 (HDG Galvanizing)
Project Overview
- Capacity: 500 kWp
- Location: Karumathampatti Industrial Belt, Coimbatore, Tamil Nadu
- Roof Type: Trapezoidal metal sheet roof (12-degree slope, East-West orientation)
- Target Wind Speed: 39 m/s (Zone 2, IS 875 wind zone)
- Structural Solution: High-tensile aluminium mini-rails (AA6005-T5) with integrated EPDM gaskets.
The Engineering Challenge
The client operates a modern textile spinning mill. The factory roof trusses were designed with tight safety margins. A traditional Hot-Dip Galvanized (GI) steel structural layout would add approximately 10,000 kg (10 Tonnes) of structural dead weight, exceeding the roof’s load-bearing limit of 12 kg/m².
Furthermore, the mill operates 24/7. Any water leakage during installation would damage expensive automated spinning machinery underneath, halting production.
Structural Design & Solution
To resolve the weight constraint and prevent leaks, the SOLBE engineering team designed a Direct-Fix Aluminium Mini-Rail System:
500kW ROOFTOP MOUNTING PROFILE
[ PV Module Frame ]
[ Mid Clamp (AA6063-T6) ]
[ Al Mini-Rail (AA6005-T5, 120mm length) ]
[ EPDM Butyl Sealant Tape ]
[ Trapezoidal Roof Sheet Crown ]- Dead Load Optimization: By replacing heavy GI rails with Solbe’s custom-extruded AA6005-T5 aluminium mini-rails (length: $120\text{mm}$, weight: $0.18\text{ kg}$ per rail), the total structural dead load was reduced from $2.0\text{ Tonnes}$ to just $0.72\text{ Tonnes}$. This corresponds to a dead load of just $3.6\text{ kg/m²}$ (well below the 12 kg/m² building threshold).
- Watertight Sealing: Rails were directly fastened to sheet metal crowns using self-drilling screws with integrated EPDM washers. In addition, double-sided EPDM butyl tape was pre-applied underneath every mini-rail, creating a durable watertight barrier.
- Fastening Security: High-tensile SS304 (A2-70) fasteners were torqued to a strict specification of $13\text{ Nm}$ to prevent clamp slippage during regional monsoon winds.
Key Performance Metrics
- Total Installation Speed: Completed in 12 days (40% faster than traditional steel frame layouts).
- Structural Deflection: Maximum rail deflection measured at $1.8\text{mm}$ under peak simulation load (well within the $L/180$ limit of 6.6mm).
- Leakage Incidents: Zero water penetration reported across 2,400 roof penetrations.
- Annual Yield Increase: Azimuth adjustments enabled a 4.2% increase in solar generation compared to flat-roof alternatives.
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