Experimental assessment of a PV-direct-connected DC LED lighting system for enhanced energy efficiency in existing buildings

This study presents a Photovoltaic-Direct-Connected Direct Current (PDCD) lighting system designed to enhance energy efficiency and renewable energy utilization in existing buildings, without requiring modifications to the conventional Alternating Current (AC) infrastructure. The system was implemented in a real-scale experimental environment and operated in parallel with a conventional AC-based Light-Emitting Diode (LED) system under identical conditions. Key performance indicators—including lighting energy consumption, illuminance performance, and photovoltaic (PV) energy utilization—were quantitatively evaluated based on measurement data. The results show that the PDCD system reduced lighting energy consumption by 10.3 % compared to the conventional AC system, while maintaining comparable illuminance levels under the same operating conditions. In addition, reliance on AC grid power was reduced by 25.7 %, and by 20.4 % when normalized for differences in PV generation. These outcomes demonstrate the system’s effectiveness in enhancing renewable energy utilization and reducing grid electricity dependence through a simplified power-supply architecture. Unlike simulation-based studies or full-scale Direct Current (DC) infrastructure proposals, this research empirically validates a partial DC implementation that is compatible with existing AC systems. The proposed approach offers a practical, scalable, and energy-efficient retrofit strategy for existing buildings and contributes to the advancement of sustainable lighting systems. This work contributes to bridging the gap between theoretical models and real-world implementation of DC-based lighting systems.