In large-scale buildings, conventional load-based sequencing strategies often control the chiller plants to fully meet cooling demand until the end of office hours to maintain the indoor comfort, leading to significant waste of cooling energy. Stopping cooling supply earlier could significantly reduce the cooling energy use but may fail to maintain necessary thermal comfort. To address this critical issue, this study proposes an innovative and optimal “soft early-stop” strategy that optimizes the trade-off between the early reduction of cooling supply and thermal comfort. To achieve this objective precisely and reliably, the key technical challenge is to predict the cooling energy demand during the office ending hours. This is solved by introducing the novel concept of “minimum cooling energy demand,” which bridges the gap between usable cold energy stored in the building thermal mass and cooling demand during office ending hours. Usable cold storage is predicted via a resistance-capacitance (RC) model, while cooling demand is forecasted using a TPE-LightGBM model, enabling dynamic optimization of early-stop times and reduced chiller capacity. Simulation test results show that, compared to conventional load-based control, the proposed strategy achieves energy savings of 11.3% and 23.3% for indoor air temperature rises of 1 K and 2 K, respectively, by proactively reducing chiller cooling capacity 30–180 minutes before the end of office hours. This strategy provides robust performance with prediction errors below 10%, offering potential for reducing cooling energy consumption without the need for infrastructure upgrades.

Development of individual building in existing district is common in high-density cities due to the limited space. Such development affects the local microclimate naturally, but the interaction is ignored in current building design practices. In this study, a comprehensive and systematic analysis is conducted to investigate the mutual impacts between new individual building design and local microclimate considering the interaction, and to identify the major influential building parameters on both local microclimate and building energy performance in subtropical urban area. A large number of high-resolution microclimate and building simulations are performed based on advanced GIS spatial analysis techniques under different building designs for the assessment of mutual impacts. A global sensitivity analysis is conducted to identify the major influential building parameters. The results show that different building designs lead to significant variation of local wind velocity (i.e., −0.95 to +4.51 m/s) and air temperature (i.e., −0.60 to +1.17 K), while the local microclimate results in a change in the building energy consumption from −41.75 to 291.54 kJ/m². The major influential parameters on both pedestrian thermal discomfort and building energy performance are building height and overall heat transfer coefficient of the building envelope. This study provides valuable references for new building or rebuilding design in order to facilitate carbon neutrality and enhance thermal comfort in urban area.

The increasing demand for cooling energy in data centers has become a global concern. Existing studies lack a comprehensive analysis of the energy performance of widely used multi-chiller cooling systems in air-cooled data centers throughout their lifecycle,especially concerning progressive loading. To bridge this gap,this study conducts a thorough assessment of the energy performance of multi-chiller cooling systems throughout the entire lifecycle. Additionally,the impact of climate conditions on the energy efficiency of the cooling systems is analyzed,considering design variations for typical climates. Multi-chiller cooling system models are developed using the test data of cooling equipment and typical control algorithms. The energy performance of the cooling system is thoroughly analyzed under full-range cooling loads and climate conditions. Results show that free cooling time could differ up to 1442 hours at different part load ratios in the same location. Furthermore,the cooling system’s coefficient of performance (COP) varies significantly,by up to 6,at different part load ratios,corresponding to a difference in power usage effectiveness (PUE) up to 0.14. Notably,the average cooling system COP throughout the lifecycle loading is found to be only 11.7,2.9 lower than the design system COP.

One of the challenges in construction of nearly and net ZEBs is how to truly achieve the nearly and net energy goals after building occupancy. Traditional building design standards and practices are mostly based on design performance evaluation, but practices show that many designed nearly/ net ZEBs failed to achieve the energy goals after building occupancy. To facilitate the practical achievement of nearly and net ZEBs, recently most of the newly-released ZEB design standards have turned to post-occupancy performance evaluation, posing great challenges to nearly and net ZEB design. However, the detailed challenges have not be comprehensively investigated, and effective optimal design methods which can facilitate the achievement of nearly and net ZEBs under these standards are still absent. In this study, new challenges of nearly and net ZEB design under the post-occupancy performance-based design standards are fully investigated, and a risk-benefit based optimal design method is proposed to facilitate the achievement of nearly and net ZEBs under these standards. The newly-released ZEB standard in China is taken as an example to investigate the challenges and test the proposed method. Results show that nearly and net ZEBs designed using conventional design method have high risk in achieving energy goals under these standards due to high risk in satisfying the requirement regarding non-renewable primary energy consumption after building occupancy. The proposed design method is effective to facilitate achieving energy goals under these standards based on the risk that decision-makers would like to take.

Occupant behavior is an important factor affecting building energy consumption. Many studies have been conducted recently to model occupant behavior and analyze its impact on building energy use. However, to achieve a reduction of energy consumption in buildings, the coordination between occupant behavior and energy-efficient technologies are essential to be considered simultaneously rather than separately considering the development of technologies and the analysis of occupant behavior. It is important to utilize energy-efficient technologies to guide the occupants to avoid unnecessary energy uses. This study, therefore, proposes a new concept, "technology-guided occupant behavior" to coordinate occupant behavior with energy-efficient technologies for building energy controls. The occupants are involved into the control loop of central air-conditioning systems by actively responding to their cooling needs. On-site tests are conducted in a Hong Kong campus building to analyze the performance of "technology-guided occupant behavior" on building energy use. According to the measured data, the occupant behavior guided by the technology could achieve "cooling on demand" principle and hence reduce the energy consumption of central air-conditioning system in the test building about 23.5%, which accounts for about 7.8% of total building electricity use.