Solar Energy

Solar Energy

Solar PV Rooftop System Sizing: On-Grid vs Off-Grid Engineering Guide

Solar PV Rooftop System Sizing: On-Grid vs Off-Grid Engineering Guide

Solar Photovoltaic (PV) power is an essential pillar of modern green building initiatives (GRIHA & LEED points). Properly designing rooftop solar arrays requires precise irradiance calculation, shade analysis, and DC-to-AC ratio optimization.

1. On-Grid (Grid-Tied) vs Off-Grid Solar Systems

  • On-Grid Systems: Synchronizes directly with utility grid voltage. Excess solar generation is exported via Net Metering bi-directional meters. Highest ROI and lowest maintenance due to battery elimination.
  • Off-Grid / Hybrid Systems: Integrates Lithium-ion or Tubular Gel battery storage banks to provide uninterruptible backup during grid outages.

2. Solar Array & Inverter Sizing Calculation

Recommended DC-to-AC Over-sizing Ratio (DC/AC) is typically 1.15 to 1.25. This ensures string inverters operate at maximum capacity during morning and afternoon hours when irradiance is lower than peak STC rating (1000 W/m²).

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Er. Vikas Verma

Lead Electrical Consultant at TMD Infra Engineering. Specializing in turnkey contracting, technical consultations, and curriculum mentoring.