Escalating global climate change and the intensification of urban heatwaves have led to an increase in summer air conditioning cooling energy consumption. This phenomenon is particularly critical in tropical regions, as it may trigger an energy crisis. The rational setting of indoor thermal design parameters can help conserve energy to the maximum extent while ensuring thermal comfort for occupants. This study selected Haikou City, a unique tropical city in China, as the research location. Indoor environment measurements and a questionnaire survey were conducted with participants, and the outdoor thermal environment sensitivity, population attributes and differences in thermal sensation, thermal neutral temperature, and comfort range were calculated and analyzed. The following results were obtained. Based on the overall population, long-term residence, and temporary residence classification, the indoor thermal comfort needs of residents in tropical cities in Haikou were effectively identified. The actual thermal neutral temperature of the overall population is 25.7 °C, and 90% of the acceptable thermal comfort temperature range is 23.2 °C–28.0 °C. The actual thermal neutral temperature of the regular residents is 27.3 °C, and 90% of the acceptable thermal comfort temperature range is 23.3 °C–31.4 °C. The actual thermal neutral temperature of the temporary population is 25.5 °C, and 90% of the acceptable thermal comfort temperature range is 23.0 °C–28.0 °C. These research results have an important reference value for improving the setting of the temperature of air conditioning in tropical areas in summer and further reducing energy consumption, which is conducive to sustainable development.

Promoting the use of solar energy resources has always involved the challenges of instability and supply–demand mismatch. The key to solving these issues is to efficiently store and utilize solar energy resources using high-performance heat storage devices. This study designed a high-performance shell-and-tube phase-change thermal storage device and established a numerical model using ANSYS software to summarize the device’s dynamic melting law. To verify the accuracy of the numerical simulation, a performance testing platform for the phase-change thermal storage device was built to investigate the impact of various factors, such as the inlet water temperature, inlet water flow rate, type of heat storage, and initial temperature of the device, and to reveal the change law of the device’s performance. The results show that the inlet water temperature has the most significant impact on the device’s heat storage and release performance. When the device’s heat storage or release is used for heating, changing the inlet water flow rate has a weak and limited effect on the device’s performance. However, when the device’s heat release is used to provide domestic hot water, increasing the make-up water temperature and reducing the inlet water flow rate can significantly improve the device’s effective heat release. Furthermore, based on the experimental validation of the model’s correctness, this study further simulated and studied the impact of different factors on the device’s heat storage process to optimize its structural design and provide technical references for the device’s actual operation and installation. The results show that the placement of fins has a negligible effect on the performance of the heat storage device while reducing the fin spacing and increasing the fin thickness can significantly improve the melting efficiency of the phase-change material (PCM). Additionally, the heat storage characteristics of the device are significantly better in the vertical installation mode than in the horizontal installation mode. This study provides theoretical guidance and technical references for the design and use of phase-change thermal storage devices.

Energy loss and performance deterioration caused by the stack effect are emerging issues in high-rise office buildings (HROB). However, a single countermeasure may not completely remove the stack effect problems, so combinations of countermeasures are often considered in building commissioning or retrofit projects to achieve the desired results. Therefore, a comprehensive study on combinations is necessary for the final decision-making. In this study, a multi-criteria decision-making model is proposed, which is utilized to calculate the ranking of countermeasure combinations for the final decision-making index by assigning weights and conducting comprehensive analysis on four criteria: infiltration energy loss, maximum pressure difference, investment cost, and implementation resistance. Based on a two-level Fractional-Factorial design (FFD), the interaction effects between countermeasures were verified, and the regression models of infiltration energy loss and maximum pressure difference were obtained as well. The investment cost and implementation resistance were defined according to the investigation and survey. An Analytic Hierarchy Process (AHP) was applied to establish the weights of each criterion. A weighted Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) method was applied to establish the decision-making index. Through the case study of a HROB located in northern China, it was concluded that the ideal combination can reduce infiltration and pressure difference by 26.88% and 87.58%, respectively, with low-level investment costs and implementation resistance. The results indicate that the multi-criteria model provides a comprehensive ranking of countermeasure combinations, which can serve as a quantitative basis for the final decision-making. Furthermore, this multi-criteria decision-making approach can be extended to other buildings in other regions.