@article{Tian2026, 
author = {Shuai Tian and Jie Feng and Kai Gao and Xing Jin and Xin Zhou and Xing Shi},
title = {Hierarchical multi-objective planning for city-scale rooftop solar deployment},
year = {2026},
journal = {Building Simulation},
volume = {19},
number = {9},
pages = {2303-2321},
keywords = {urban rooftop solar systems, urban building energy modeling, multi-objective optimization, techno-economic assessment},
url = {https://www.sciopen.com/article/10.1007/s12273-026-1479-z},
doi = {10.1007/s12273-026-1479-z},
abstract = {Urban rooftop solar deployment can reduce building-sector emissions, but planning decisions must balance rooftop availability, hourly demand matching, technology configuration, investment cost, and grid export constraints. This study develops a hierarchical multi-objective planning framework for city-scale rooftop solar deployment. Building-level rooftop solar potential, hourly electricity demand from an urban building energy model, rooftop photovoltaic systems, solar water heating systems, battery storage options, operating modes, techno-economic performance, and grid export capacity limits were integrated into an integer linear programming-based portfolio optimization model. The framework compares net-present-value (NPV)-led, life-cycle-energy-saving (LCES)-led, and cost-led planning priorities through controlled tolerance relaxation of the primary objective. The case study included 7,674 buildings, with 2.32 km2 of available rooftop area, 1.40 km2 of practically installable photovoltaic area, and 308.59 MW of maximum photovoltaic capacity. Results showed that grid export capacity strongly reshaped deployment outcomes, but the benefits saturated beyond a threshold. Under the NPV-led scenario, increasing grid export capacity raised NPV by 44.12% and LCES by 51.53% before saturation at 270 MW. Under the LCES-led scenario, storage-intensive portfolios under tight grid constraints were progressively replaced by export-enabled configurations as grid capacity increased. Under the cost-led scenario, grid expansion mainly reduced initial investment by 0.25 billion CNY and improved NPV by 0.21 billion CNY, with limited additional energy-saving gains. Marginal analysis showed that modest tolerance relaxation captured most co-benefits, whereas larger relaxations produced diminishing returns. The framework provides interpretable planning evidence for city-scale rooftop solar deployment under competing priorities and grid constraints.}
}