Multi-energy complementary optimization for low-carbon public buildings with thermal comfort and time-of-use electricity constraints: life-cycle cost-benefit and global sensitivity analysis

In trying to solve the surge in carbon emissions (CO₂) caused by the growth in energy demand in Chinese public buildings (PB), scholars have focused on PB's low-carbon development. However, existing research has mainly focused on the low-carbon benefits of buildings, with further investigation needed into user comfort and electricity pricing considerations. Therefore, this study develops a multi‑energy optimization framework to support low‑carbon transitions of Chinese PB while ensuring occupant thermal comfort and accounting for time‑of‑use (TOU) electricity pricing. Firstly, this study employs SketchUp and EnergyPlus to simulate the initial Energy Consumption (EC). Secondly, it develops four scenarios. Scenario 1 focuses solely on photovoltaic (PV) systems. Scenario 2 incorporates Ground-Source Heat Pumps (GSHP) as well as photovoltaics. Scenario 3 builds on Scenario 2 by improving the energy efficiency of the building envelope. Scenario 4 builds on Scenario 3 by incorporating TOU pricing. We then develop a multi-energy life-cycle cost-benefit (LCB) optimization model that includes carbon emission (ECO₂) reduction, which is solved using NSGA-II. Moreover, user behaviors are explicitly modelled and thermal comfort is quantified by Predicted Mean Vote and Predicted Percentage Dissatisfied indicators metrics to capture dynamic interactions among thermal comfort, EC and Electricity Price (EP). Results indicate Scenario 1 attains the lowest LCB, whereas Scenario 2 reduces ECO₂ by about 60.06% at a 53.25% higher LCB relative to Scenario 1, highlighting trade‑offs between cost and decarbonization. Scenario 4 is preferred by low‑carbon‑oriented stakeholders; cost‑sensitive users favor Scenario 1; balanced objectives point to Scenario 2. Under TOU, Scenario 4 moderates peak EC growth (7.83% at 10:00–12:00 vs. max 16.14% at 02:00–04:00). Global sensitivity analysis shows electricity price, peak sunlight hours and investment cost dominate system outcomes (sensitivity indices > 0.98). The findings provide practical guidance for prioritizing PV and GSHP deployment, envelope retrofits and TOU design to achieve comfort‑compliant, cost‑effective decarbonization of PB.