Development of a Dual-Operation Grid-Connected Rooftop PV System with Capacity and Space Optimization under NEM Guidelines in Bangladesh

Bangladesh government took a significant step towards achieving clean energy solution with the introduction of Net Energy Metering (NEM) guideline in 2018, later revised in 2019. However, due to capacity limitations and technical challenges that currently restrict the full utilization of rooftop space for PV systems, revising the existing framework is essential to overcome these barriers and encourage more consumer participation. In this context, this study investigates two grid-tied rooftop PV systems designed for the Science Library Building at the University of Dhaka - Case 01, following the existing NEM scheme, and Case 02, a dual-operational rooftop PV model which integrates NEM with a Feed in Tariff (FiT) mechanism for enhanced energy output ensuring maximum utilization of available roof space, using the PVsyst 7.4 software. Upon comparing the two scenarios, it is found that Case 02 significantly reduces carbon emissions by about 243.991 metric tons of CO2 per year, exhibiting a higher return on investment (55.2% vs. 49.1%) with a high energy production of 524.014 MWh/year despite having slightly lower performance ratio and higher maintenance cost. Therefore, the proposed model offers more sustainable and economically viable solution for future rooftop PV installations, though further investigation is needed to address the technical challenges for more efficient renewable energy integration.