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The rising energy consumption in residential buildings within the hot summer and cold winter (HSCW) climate zone, driven by occupants' pursuit of improved thermal comfort, necessitates effective energy conservation measures. This study established urban building energy models for 32,145 residential buildings in Changsha City, China, and conducted a comprehensive retrofit analysis of seven energy conservation measures (ECMs). Additionally, the study assessed the impact of residents' conscious energy-saving behaviors concerning air conditioner (AC) control. The research commenced by creating six baseline models representative of the diverse building stock. Identifying seven commonly used ECMs, the study examined the potential of each measure for enhancing energy efficiency. To facilitate the analysis, a dedicated toolkit, AutoBPS-Retrofit, was developed to efficiently modify the baseline model for each ECM. Furthermore, the investigation delved into the investment cost of implementing the ECMs and evaluated their simple payback year (PBP) and net present value (NPV). The results demonstrate that tailored retrofit plans are essential when addressing envelope improvements, varying according to building types and ages. Retrofits targeting lighting systems offer both promising energy savings and favorable economic viability, albeit subject to residents' preferences. Alternatively, upgrading the AC systems emerges as the most energy-efficient approach, yet the economic assessment raises concerns. The study's findings offer practical insights for governments seeking to establish effective carbon reduction goals and policies. Moreover, the research can assist energy-saving institutions, real-estate companies, and stakeholders involved in renovation projects by offering guidance in making informed decisions to enhance energy efficiency in city-scale residential buildings. [ABSTRACT FROM AUTHOR]

• An approach that assists policymakers for more equitable decisions regarding UGS. • Incorporate population activity intensity effect to analyze UGS equity. • Offer insights into UGS renewal by assessing cost to UGS updates. • Advances in understanding UGS dynamics for more sustainable urban environment. Urban green space (UGS) plays a pivotal role in enhancing citizens' living standards, well-being, and overall physical and mental health. As urbanization continues to progress, ensuring equitable access to UGS becomes increasingly vital in addressing the social resource disparities. This paper proposes an innovative approach to inform UGS planning and updates, placing a strong emphasis on equitable UGS distribution. In pursuit of a more balanced UGS layout, we present a novel recreational demand model that can evaluate the citizen's recreational preferences by taking into account the population activity levels and the agglomeration effect. Leveraging point of interest (POI) data within the geographic information system (GIS) platform, we quantitatively analyze these factors. Additionally, we propose a refined resistance model, enhancing the accuracy of UGS update cost estimation. Applying these models, we undertake a case study in Changsha City to advance UGS update strategies. Our findings reveal disparities not only across different city sectors but also within individual spaces, underscoring the unequal distribution of diverse UGS resources. The proposed models can effectively guide the incorporation of new UGS points in urban planning, mitigating the challenge of inequitable UGS resource allocation. The study provides a new approach to more comprehensively evaluate the UGS quality and offers additional valuable insights for improved UGS planning, and therefore, contributes to fostering a more just, inclusive and sustainable urban environment. [ABSTRACT FROM AUTHOR]

• A PV assisted ground source heat pump and air source heat pump (PVGSHP-ASHP) system was proposed. • Performance for three GSHP systems were simulated and compared in depth. • Economic optimization of the integrated operation of the PVGSHP-ASHP system was carried out. • The proposed system can solve the load imbalance problem in hot summer and cold winter zones while improving the COP of GSHP and reducing the system cost. The ground source heat pump (GSHP) system is widely recognized as an efficient, clean and economical renewable energy technology for buildings, and can be utilized for building cooling, heating and hot water supply. In the hot summer and cold winter zones of China, however, the total thermal load (heating load and hot water load) of GSHP systems is greater than the cooling load, which may cause a significant soil temperature drop and GSHP performance deterioration. To solve the above problems, a photovoltaic (PV) assisted GSHP and air source heat pump system (PVGSHP-ASHP) was proposed. This paper investigated the performance and feasibility of the PVGSHP-ASHP system, using a case campus building in Changsha city, China. The PVGSHP-ASHP system was firstly established by TRNSYS, and then, its operational performance was evaluated and compared with the PV assisted GSHP (PVGSHP) system and the PV assisted GSHP and electric heater (PVGSHP-EH) system. Finally, the economic optimization of the integrated operation of the PVGSHP-ASHP system was carried out with the combined simulation of TRNSYS and GenOpt. The results showed that for the PVGSHP system, the soil temperature reduced from 18.1 °C to 11.8 °C after 15 years of operation, which caused a decrease in the annual coefficient of performance of the GSHP (COP GSHP) and an increase in the annual electricity consumption. Although the PVGSHP-EH system can solve the load imbalance problem, its annual lifecycle cost (ALCC) increased by 39.3 % due to the low efficiency of the EH. The PVGSHP-ASHP system can solve the appeal problem with high annual COP GSHP and COP sys values of 3.49 kW/kW and 4.69 kW/kW, respectively, and only 71,700 kWh of the annual electricity consumption, while its ALCC was the lowest at 99,223 CNY, which was 8.1 % lower than the PVGSHP system. After optimization, the ALCC of the PVGSHP-ASHP system reached the minimized value of 91,158 CNY, with a reduction of 8.1 %. These findings can provide new ways to solve the load mismatch problem of GSHP systems while enhancing the system efficiency in the hot summer and cold winter zones of China. [ABSTRACT FROM AUTHOR]