Modeling and integration of rooftop photovoltaic systems for sustainable energy access in public sector buildings in diverse climates.

The paper presents a comprehensive technical evaluation of grid-connected rooftop solar photovoltaic (PV) systems installed at two public sector buildings located in climatically diverse regions. The primary objective is to maximize the energy output of each PV system, which has been designed and optimized based on the locally-constrained conditions and the resource availability. Proposed location (PL-1) situated in a semi-arid region, was simulated using Aurora Solar, while PL-2, situated in a hilly region, was modeled with PVSYST. At PL-1, a 417.96 kWp system has been installed, estimated to generate around 594.743 MWh of energy annually, offsetting 95.52% of the building's annual energy consumption with a performance ratio (PR) of 82.6%. Similarly, PL-2 has a 63.2 kWp system, which is projected to produce 93.76 MWh, with a predicted PR of 80.1%. Under a degradation rate of 1%, the anticipated lifetime energy output is 13.214 GWh and 2.081 GWh, respectively. Environmental impact research indicates that each system achieves a carbon payback time of just 42 days, with cumulative CO₂ offsets of approximately 6606.96 metric tons (PL-1) and 1040.367 metric tons (PL-2) throughout their operational lifespan. A sensitivity analysis of degradation rates, energy output variations, and emission factor of grid emphasises the systems' resilience across diverse operational conditions. The economic evaluations show that PV systems installed at PL-1 and PL-2 have LCOE of 9.54 PKR/kWh and 9.37 PKR/kWh and payback period of around 3.27 and 3.39 years respectively, hence confirming their long-term economic sustainability. The findings validate that the implementation of rooftop photovoltaic systems in public sector buildings is both technically and economically feasible, with a combination of tailored modeling, solar resource assessment in specific locations, and a net metering policy being crucial for optimal renewable energy integration within national energy policy framework.