Improvement of energy utilization in residential districts at the early design stage: Achieving lighting self-sufficiency of buildings through a PV-DC power distribution system

• An evaluation framework was proposed for optimizing residential energy planning. • Lighting self-sufficiency in residential buildings was the optimization goal. • Standard number of building floors was defined to evaluate lighting self-sufficiency. • Surplus PV power can be transferred by battery delivery to buildings in demand. • A case study was conducted to present how to identify the optimal residential proposal. Improvement of energy utilization through effective technologies and reasonable distribution plays an important role in the construction of energy residential districts. Many studies have proposed different decision tools for improving the solar energy potential based on detailed residential information. However, there is still a lack of decision-making tools to use less residential information for optimizing energy planning towards achieving energy self-sufficiency at the early design stage. Therefore, this study proposed an evaluation framework to divide energy groups in residential districts, aiming to achieve the lighting self-sufficiency of residential buildings from a photovoltaic-direct current (PV-DC) power distribution system. This distribution system can transfer surplus PV power from power-rich buildings to power-deficient buildings. An evaluation index (the standard number of building floors) was defined to estimate the surplus PV power for residential buildings and optimize energy proposals. A real residential district in Nanning City was selected as a case study to demonstrate the process of the proposed evaluation framework. The analysis results revealed that nine out of 10 residential areas are lighting self-sufficient using the PV-DC power distribution system. Moreover, even if the lighting electricity demand increases by 50% and PV conversion efficiency decreases by 25%, the identified energy groupings in the study district can still achieve zero-energy lighting with low delivery distance cost and high PV power redundancy. Therefore, the proposed evaluation framework can be used as a design support tool for urban designers to identify residential proposals with zero-energy lighting at the early design stage, which is conducive to further improving energy utilization in the construction and operation stages.