Past studies reveal that air infiltration through the building envelope and its impact on the indoor environment and energy consumption are significantly influenced by climate characteristics. However, little relevant information is available for buildings in southern China, where the building design traditionally follows a philosophy of being open and shaded. The present study employs both experimental measurements and numerical simulations to investigate the airtightness of buildings in Hot Summer and Cold Winter (HSCW) climate region of southern China and the associated energy consumption. The measurements and simulations are based on a typical office building in Changsha. Measurement results show that the air infiltration rate of six tested spaces at the natural pressure difference ranges from 0.10 to 0.30 h−1 with an average of 0.17 h−1 in summer, and from 0.09 to 0.32 h−1 with an average of 0.16 h−1 in winter. The operation of the air-conditioning system affects largely air infiltration, and each unit change in setpoint air temperature can result in an average of one-third or more change in air infiltration rate. Simulation results show that a decrease in air infiltration rate from 0.17 h−1 to 0.01 h−1 reduces the infiltration-related cooling energy consumption from 14.29 to 0.75 kWh/m2·year and heating energy consumption from 8.20 to 0.39 kWh/m2·year. The same change in the setpoint air temperature of air-conditioning system in summer and winter results in different infiltration-related energy consumption. The findings would contribute to an improved energy simulation and assessment of buildings in southern China.@en

The vigorous expansion of renewable energy as a substitute for fossil energy is the predominant route of action to achieve worldwide carbon neutrality. However, clean energy supplies in multi-energy building districts are still at the preliminary stages for energy paradigm transitions. In particular, technologies and methodologies for large-scale renewable energy integrations are still not sufficiently sophisticated, in terms of intelligent control management. Artificial intelligent (AI) techniques powered renewable energy systems can learn from bio-inspired lessons and provide power systems with intelligence. However, there are few in-depth dissections and deliberations on the roles of AI techniques for large-scale integrations of renewable energy and decarbonisation in multi-energy systems. This study summarizes the commonly used AI-related approaches and discusses their functional advantages when being applied in various renewable energy sectors, as well as their functional contribution to optimizing the operational control modalities of renewable energy and improving the overall operational effectiveness. This study also presents practical applications of various AI techniques in large-scale renewable energy integration systems, and analyzes their effectiveness through theoretical explanations and diverse case studies. In addition, this study introduces limitations and challenges associated with the large-scale renewable energy integrations for carbon neutrality transition using relevant AI techniques, and proposes further promising research perspectives and recommendations. This comprehensive review ignites advanced AI techniques for large-scale renewable integrations and provides valuable informational instructions and guidelines to different stakeholders (e.g., engineers, designers and scientists) for carbon neutrality transition.@en

Under China's national strategy of carbon neutrality by 2060, it is urgently necessary and challenging for the governments to proactively explore policy tools to facilitate energy-efficient renovation of existing buildings. Currently, a considerable number of studies have been conducted on building energy-efficient renovation and its derivative topics, however, a comprehensive overview on incentive initiatives related to existing renovation practices in China is still scarce, such as a lack of critical correlation analysis between national and local initiatives, a lack of the synthesis and critique towards the latest policies and related achievements, and inadequate generalization of the diverse and multi-layered barriers and challenges in building energy-efficient renovation practices. To address these issues, this paper adopts a diversified policy segmentation approach to deeply analyze the dynamic evolution of the incentive initiatives from both national and local level perspectives, as well as to establish the related network of policy linkages between national to local, and between different localities. In addition, this paper presents a critical analysis on representative initiatives in two batches of pilot cities, and proposes good practices and valuable experiences for building energy-efficient renovation. Finally, this paper further summarizes and discusses the barriers to building energy-efficient renovation from four perspectives: governments, householders, enterprises and research institutions, and proposes a series of targeted and feasible pathways and strategies. This study can provide theoretical guidance and targeted recommendations for the formulation of policies, standards and regulations for building energy-efficient renovation in China.@en

The construction industry's commitment to achieving carbon neutrality has underscored the urgency of promoting green and low-carbon sustainable affordable housing. However, the development process has encountered several challenges, including conflicts between the central and local governments arising from differences in value preferences, financial constraints faced by local governments, inadequate access mechanisms, lenient screening processes, insufficient funding, and remote locations. Despite its significance, the policies related to affordable housing, especially in the context of assembly affordable housing, have received limited systematic examination. To address this research gap, this paper presents a comprehensive review and analysis of China's affordable housing policies. Firstly, it compiles and compares recent affordable housing policies in China, serving as a valuable reference for future affordable housing construction endeavors. Secondly, it conducts an in-depth analysis of the barriers and challenges obstructing affordable housing development in China, and proposing corresponding measures for improvement. Moreover, this paper identifies significant opportunities for affordable housing development in the country and explores the potential synergy between the development of assembly buildings and affordable housing by leveraging their respective attributes. By illuminating pertinent policies and associated issues, this research aims to inform policymakers, practitioners, and stakeholders involved in the affordable housing sector. Additionally, it aims to stimulate further research and innovation in the field, contributing to effective and sustainable housing solutions for low-income communities and society at large. This paper systematically analyzes the current status of affordable housing policies, challenges and opportunities. It also discusses the application of assembly building techniques in the realm of affordable housing, proving valuable insights to address traditional housing issues.@en

Geothermal energy with abundance and large quantity can partially cover building heating/cooling loads and promote the carbon-neutrality transitions. Shallow geothermal ventilation (SGV) system, with a little initial investment cost, is one of promising technologies to partly replace the conventional air-conditioning system for air pre-cooling/pre-heating. This paper reviews applications of SGV system for improving thermal performance over latest two decades, which mainly includes the reclassification of SGV system, coupling with other advanced energy-saving technologies, application potentials for building cooling/heating under various weather conditions. Heat transfer mechanism and mathematical modelling techniques have been reviewed, together with in-depth analysis on current research trends, existing limitations, and recommendations of SGV system. Phase change materials, with considerable latent energy density, can stabilize the thermal performance with high reliability. The review identifies that optimization designs and advanced approaches need to be investigated to address the existing urgent issues of SGV system (e.g., large land occupation, difficulty in centralized collection of condensate water timely for horizontal buried pipe, bacteria growth, polluted supply air, and high construction cost for vertical buried pipe). A plenty of studies show that the SGV system could greatly expand the application scope and improve system energy efficiency by combining with other energy-saving technologies. This paper will provide some guidelines for the scientific researchers and engineers to keep track on recent advancements and research trends of SGV system for the building thermal performance enhancement and pave path for future research works.@en

Geothermal energy with abundance and large quantity can partially cover building heating/cooling loads and promote the carbon-neutrality transitions. Shallow geothermal ventilation (SGV) system, with a little initial investment cost, is one of promising technologies to partly replace the conventional air-conditioning system for air pre-cooling/pre-heating. This paper reviews applications of SGV system for improving thermal performance over latest two decades, which mainly includes the reclassification of SGV system, coupling with other advanced energy-saving technologies, application potentials for building cooling/heating under various weather conditions. Heat transfer mechanism and mathematical modelling techniques have been reviewed, together with in-depth analysis on current research trends, existing limitations, and recommendations of SGV system. Phase change materials, with considerable latent energy density, can stabilize the thermal performance with high reliability. The review identifies that optimization designs and advanced approaches need to be investigated to address the existing urgent issues of SGV system (e.g., large land occupation, difficulty in centralized collection of condensate water timely for horizontal buried pipe, bacteria growth, polluted supply air, and high construction cost for vertical buried pipe). A plenty of studies show that the SGV system could greatly expand the application scope and improve system energy efficiency by combining with other energy-saving technologies. This paper will provide some guidelines for the scientific researchers and engineers to keep track on recent advancements and research trends of SGV system for the building thermal performance enhancement and pave path for future research works.@en

Integrating phase change materials (PCMs) in buildings cannot only enhance the energy performance, but also improve the renewable utilization efficiency through considerable latent heat during charging/discharging cycles. However, system performances are dependent on PCMs’ integrated forms, heat transfer enhancement solutions, system operating modes, together with optimal geometrical and operating parameters. In this study, passive, active, and combined passive/active solutions in PCMs systems have been comprehensively reviewed, when being applied in heating, cooling and electrical systems, together with a dialectical analysis on advantages and disadvantages. In addition to novel system designs, interdisciplinary applications of machine learning have been reviewed and formulated, from perspectives of reliable structures, smart operational controls, and stochastic uncertainty-based performance prediction. Furthermore, a generic methodology with a systematic and hierarchical procedure has been proposed, with the implementation of machine-learning based technique for optimisations during both design and operation periods. The mechanisms of machine learning techniques were characterised as the simplifications of modelling and optimization processes, through the errors-driven update, the support vector regression and the backpropagation neural network. Several technical challenges were identified, such as the heat transfer enhancement, the novel structural configurations and the flexible switch on operating modes. Finally, identified challenges on machine learning include the development of advanced learning algorithms for efficient performance predictions, optimal structural configurations on neural networks, the trade-off between computational complexity and reliable optimal solutions, and so on. The formulated climate-adaptive designs, intelligent operations, uncertainty-based analysis and optimisations with interdisciplinary machine learning techniques can promote PCMs applications in sustainable buildings.@en

Integrating phase change materials (PCMs) in buildings cannot only enhance the energy performance, but also improve the renewable utilization efficiency through considerable latent heat during charging/discharging cycles. However, system performances are dependent on PCMs’ integrated forms, heat transfer enhancement solutions, system operating modes, together with optimal geometrical and operating parameters. In this study, passive, active, and combined passive/active solutions in PCMs systems have been comprehensively reviewed, when being applied in heating, cooling and electrical systems, together with a dialectical analysis on advantages and disadvantages. In addition to novel system designs, interdisciplinary applications of machine learning have been reviewed and formulated, from perspectives of reliable structures, smart operational controls, and stochastic uncertainty-based performance prediction. Furthermore, a generic methodology with a systematic and hierarchical procedure has been proposed, with the implementation of machine-learning based technique for optimisations during both design and operation periods. The mechanisms of machine learning techniques were characterised as the simplifications of modelling and optimization processes, through the errors-driven update, the support vector regression and the backpropagation neural network. Several technical challenges were identified, such as the heat transfer enhancement, the novel structural configurations and the flexible switch on operating modes. Finally, identified challenges on machine learning include the development of advanced learning algorithms for efficient performance predictions, optimal structural configurations on neural networks, the trade-off between computational complexity and reliable optimal solutions, and so on. The formulated climate-adaptive designs, intelligent operations, uncertainty-based analysis and optimisations with interdisciplinary machine learning techniques can promote PCMs applications in sustainable buildings.@en

Spatiotemporal energy interaction and sharing are promising solutions to penetrate renewable energy, enhance grid power stability, and improve regional energy flexibility. However, the current literature is restrained in a small-scale neighborhood level, without considering inter-city energy migration through spatiotemporal complementarity between renewable-abundant regions (like suburb or countryside areas) and demand-shortage regions (like city centers). In this study, the energy interaction boundary is extended from a neighborhood scale to an inter-city scale, to maximize the renewable energy penetration, demand coverage, and reduce regional energy imbalance. This study firstly proposes a holistic framework on inter-city transportation-based energy migration, consisting of a residential community with rooftop photovoltaic systems and electrical batteries, an office building, hydrogen vehicles (HVs), a hydrogen (H2) station, and local power grids, for the energy transmission between building groups in spatially different regions through the daily commuting of HVs. Optimal grid-regulation strategies are thereafter proposed and adopted to stabilize the grid power and reduce energy costs. Parametric analysis on energy trading strategies and prices has been conducted, to improve the participation motivations of different stakeholders. Results indicate that, compared to the reference case with isolated buildings and vehicles, the transportation-based energy migration framework covers 23.2 % of the office energy demand and elevates the community's renewable self-use ratio from 72.7 % to 98.6 %. Meanwhile, the maximum grid-export power in the renewable-abundant region (suburb residential community) and the annual grid-import power in the demand-shortage region (city-center office) are reduced by up to 86.9 % (from 155.7 to 20.4 kW) and 29.4 % (from 49.0 to 34.6 kW), respectively. Moreover, even considering the fuel cell degradation cost of HVs, the transportation-based energy migration framework reduces the operating costs of the office building and HVs (the H2 cost and the fuel cell degradation cost) by 16.4 % (from $52791.3 to $44154.7) and 1.7 % (from $27172.5 to $26707.4), respectively. Afterward, compared to the reference case, the peak-shaving and load-shaping grid-regulation strategies can decrease the peak grid-export power of the community by about 71.6 % (from 155.7 to 44.2 kW), and the maximum grid-import power of the office by 23.7 % (from 49.0 to 37.4 kW), respectively. Furthermore, the transportation-based energy migration framework is economically feasible, only when the renewable export price for H2 production is 0.07 $/kWh, the onsite-renewable-generated H2 lower than 6.5 $/kg for the HV owners, and the vehicle-to-building electricity lower than 0.3 $/kWh for the office building. This study provides a novel inter-city energy migration framework with hydrogen networks to enhance district energy sharing, improve regional energy balance and reduce carbon emission, together with frontier guidelines on energy trading prices to promote participation motivations from different stakeholders.@en

Ventilative cooling is an energy-saving technology to diminish thermal discomfort and overheating risk of buildings, meanwhile achieving high indoor air quality (IAQ). However, there is still no optimal control strategy in practice, which considerably limits its application. This study developed a typical office building model to evaluate the performance of ventilative cooling systems with different control parameters and strategies for five typical cities in different climatic zones of China. Results showed that, when the control parameter was selected as the upper limit of satisfied comfortable zone by 90% of the occupants, the adaptive thermal comfort (ATC) model, which outperformed the other models in terms of outdoor air utilization, was not necessarily optimal in terms of energy efficiency. The outdoor air utilization potential based on the indoor dry-bulb air temperature (Td) and indoor operative temperature (Top) control was similar, but the energy usage varies considerably, especially in the hot climatic zones. When the overheating period controlled based on the thermal comfort models was the same, the energy usage would be underestimated by 16%–38% without considering the effect of radiant temperature. The ATC-based control could have up to 37% of energy-saving compared to thermostatic control, but inappropriately low limits could make it less advantages to achieve energy-saving. The energy-saving potential associated with the PMV and ATC controls showed a completely opposite trend in the different climatic zones. The analysis results indicate that eliminating the drawbacks of the lower limit in the ATC model is an effective way to demonstrate energy-saving effectiveness. The findings of this study will contribute to the effective improvement of the application potential of ventilative cooling in different climatic zones.@en

The use of natural ventilation in buildings to reduce the energy consumption and CO2 emission has been widely investigated and practiced, but few existing studies have considered the exploration and assessment of natural ventilation in different location patterns of rural residential buildings in the mountainous terrain of China. In this paper, the representative rural residential buildings are firstly selected in Huarong, Pingjiang and Liuyang regions of northern Hunan Province to carry out on-site survey works to determine building types, physical parameters and layout forms. Then, the wind tunnel experiments are carried out to investigate the effectiveness of natural ventilation under different location patterns, and the monitored results are compared with simulated data. The results show that the experiments and simulations are in satisfactory agreement. The experimental data also indicate that when the modelled distance of 120 mm (i.e. 12 m between the building and hilly terrain in practical application) is the best option for building natural ventilation. Based on the investigation and statistical data, the natural ventilation effectiveness under different location patterns and operational conditions is simulated using CFD methods, and it is obtained the most favourable location pattern for natural ventilation. The results show that the winter ventilation of buildings in the existing location pattern is significantly obstructed in the hilly terrain, which is favourable to the indoor thermal environment, however, the natural ventilation is compromised to a certain extent in summer. Furthermore, the findings also show that, regardless of the hilly terrain's height at 50 m or 150 m, the buildings are able to avoid natural ventilation in winter to the maximum extent when the distance between the buildings and the frontier of the hilly terrain is double that of the building height (i.e. 12 m). This study could contribute to theoretical instructions for optimum design of natural ventilation of rural residential buildings in the mountainous terrain of central China.@en

Hydrogen-based (H2-based) interactive energy networks for buildings and transportations provide novel solutions for carbon-neutrality transition, regional energy flexibility and independence on fossil fuel consumption, where vehicle fuel cells are key components for H2-electricity conversion and clean power supply. However, due to the complexity in thermodynamic working environments and frequent on/off operations, the proton exchange membrane fuel cells (PEMFCs) suffer from performance degradation, depending on cabin heat balance and power requirements, and the ignorance of the degradation may lead to the performance overestimation. In order to quantify fuel cell degradation in both daily cruise and vehicle-to-grid (V2G) interactions, this study firstly proposes a two-space cabin thermal model to quantify the ambient temperature of vehicle PEMFCs and the power supply from PEMFCs to vehicle HVAC systems. Afterwards, a stack voltage model is proposed to quantify the fuel cell degradation for multiple purposes, such as daily transportation and V2G interactions. Afterwards, the two models are coupled in a community-level based building-vehicle energy network, consisting of twenty single residential buildings, rooftop PV systems, four hydrogen vehicles (HVs), a H2 station, community-served micro power grid, local main power grid, and local H2 pipelines, located in California, U.S.A. Comparative analysis with and without fuel cell degradation is conducted to study the impact of dynamic fuel cell degradation on the energy flexibility and operating cost. Furthermore, a parametrical analysis is conducted on the integrated HV quantity and the grid feed-in tariff to reach trade-off strategies between associated fuel cell degradation costs and grid import cost savings. The results indicate that, in the proposed hydrogen-based building-vehicle energy network, the total fuel cell degradation is 3.16% per vehicle within one year, where 2.50% and 0.66% are caused by daily transportation and V2G interactions, respectively. Furthermore, in the H2-based residential community, the total fuel cell degradation cost is US$6945.2, accounting for 33.4% of the total operating cost at $20770.61. The sensitivity analysis results showed that, when the HV quantity increases to twenty, the fuel cell degradation of each HV decreases to 2.50%, whereas the total fuel cell degradation cost increases to 42.8% of the total operating cost. Last but not the least, the cost saving by V2G interactions can compensate the fuel cell degradation cost when the grid feed-in tariff is reduced by 40%. Research results can provide basic modelling tools on dynamic fuel cell degradation, in respect to vehicle power supply, vehicle HVAC and V2G interactions, together with techno-economic feasibility analysis, paving path for the development of hydrogen energy for the carbon-neutrality transition.@en

Cleaner power production, distributed renewable generation, building-vehicle integration, hydrogen storage and associated infrastructures are promising for transformation towards a carbon–neutral community, whereas the academia provides limited information through integrated solutions, like intermittent renewable integration, hydrogen sharing network, smart operation on electrolyzer and fuel cell, seasonal hydrogen storage and advanced heat recovery. This study proposes a hybrid electricity-hydrogen sharing system in California, United States, with synergistic electric, thermal and hydrogen interactions, including low-rise houses, rooftop photovoltaic panels, hydrogen vehicles, a hydrogen station, micro and utility power grid and hydrogen pipelines. Advanced energy management strategies were proposed to enhance energy flexibility and grid stability. Besides, simulation-based optimizations on smart power flows of vehicle-to-grid interaction and electrolyzer are conducted for further seasonal grid stability and annual cost saving. The obtained results indicate that, the green renewable-to-hydrogen can effectively reduce reliance on pipelines delivered hydrogen, and the hydrogen station is effective to address security concerns of high-pressure hydrogen and improve participators’ acceptance. Microgrid peer-to-peer sharing can improve hydrogen system efficiency under idling modes. Furthermore, the integrated system can reduce the annual net hydrogen consumption in transportation from 127.0 to 1.2 kg/vehicle. The smart operation (minimum input power of electrolyzer and fuel cell at 65 and 80 kW) can reduce the maximum mean hourly grid power to 78.2 kW by 24.2% and the annual energy cost to 1228.5 $/household by 38.9%. The proposed district hydrogen-based community framework can provide cutting-edge techno-economic guidelines for carbon-neutral transition with district peer-to-peer energy sharing, zero-energy buildings, hydrogen-based transportations together with smart strategies for high energy flexibility.@en

The application of building information modeling (BIM) technology has effectively supported the high-quality development of building sustainability and informatization in China. However, few studies comprehensively analyzed the enacted policies, prevalent applications, and existing barriers of the latest application and development of BIM technology in building industry from building sustainability and informatization perspectives to provide effective consultation and guidelines for its rational scale application in China. This paper firstly made a statistical analysis on the policies and standards of BIM technology issued from 2011 to 2021 in China. Moreover, the latest application, development and existing issues of BIM technology in building sustainability and informatization were also comprehensively discussed and analyzed. The main conclusions indicated that the application status of BIM technology for building sustainability and informatization in China was large in quantity, wide in scope, but low in level. The existing issue and limitation in terms of BIM application in China was mainly due to the lack of standards and domestic-oriented tools. Finally, the future outlook and recommendations of BIM technology for building sustainability and informatization in China were also presented as avenues for upcoming research.@en

Smart and personalized ventilation systems have been demonstrated with high performance in creating a healthy and energy-efficient indoor environment, but they have been rarely comprehensively summarized and explored in previous studies. With the progressive development of various terminal devices and control technologies, personalized ventilation based on intelligent control is potentially a promising way to achieve efficient control and energy savings in human micro-environments. This study comprehensively summarizes and analyzes the recent studies and common utilization forms of smart ventilation and PV systems that are based on CO2 concentration control, to pave path and provide some guidelines for their integration application for reducing energy consumption and improving indoor thermal comfort. Research shows that the combination of personalized ventilation and smart ventilation is an essential development for ventilation systems. Smart ventilation with demand control logic based on CO2 concentration has been mature enough to effectively improve the effectiveness and comfortable performance of personalized ventilation. However, switching from traditional air conditioning systems to personalized ventilation still requires improved sensors and intelligent control algorithms. In addition, this paper also summarizes the exploratory studies and potential application analysis of machine-learning theories to improve intelligent control of personalized ventilation. To this end, this paper identifies future tendencies for advanced theories, integrated systems, and devices in personalized ventilation systems.@en

The energy-saving renovation of existing buildings has been attracted sufficient attention to reduce fossil fuels and mitigate global warming in Europe. The shallow geothermal for building cooling and heating, as an environmentally-friendly and cost-effective alternative, has been widely explored to promote energy efficiency of existing buildings. However, few studies conduct the comprehensive overview on the applications, developments, and existing issues of shallow geothermal promoting energy efficiency of existing buildings (SGPEEEB) in Europe. The objective of this paper is to review the current application status and future trends of SGPEEEB in Europe. First, the common utilization forms and classifications of used shallow geothermal technologies are introduced to further clarify the investigated subject. Then, the research and application status of SGPEEEB has also analyzed and discussed. At last, this study proposes the future trends and comments of SGPEEEB in Europe. @en

Shallow subterranean ventilation of earth-to-air heat exchanger (EAHE) system can improve renewable utilisation, decrease CO 2 emission and promote carbon-neutral transition. However, the conventional EAHE system has drawbacks, e.g., large occupied land area, low energy-usage efficiency, small falling gradient for buried pipe and fluctuated outlet air temperature. This study proposes a vertical EAHE integrated with annular PCM with advantages, including less occupied floor space, higher energy efficiency, better centralised discharge of air condensate water and more stable outlet air temperature. An experimental test-rig was established for online testing and the real-time monitored data was for modelling calibration to characterise the sophisticated heat transfer in phase change process. Afterwards, multivariant analysis on thermo-physical PCM parameters was conducted on cooling capacity and outlet air temperature fluctuation. A dimensionality reduction approach from redundant experiments was adopted for multivariant optimization and sensitivity analysis. Results show that PCM fusion temperature and latent heat of PCM dominate the cooling capacity with percentage contribution of 37.61% and 28.91%, respectively. PCM thickness and melting temperature dominate the temperature fluctuation with percentage contribution of 31.27% and 26.18%, respectively. This study provides benchmark and guidelines on PCM thermo-physical parameters’ selection with an efficient dimensionality reduction approach, paving path for application of the vertical EAHE integrated with PCMs in buildings. @en

Shallow subterranean ventilation of earth-to-air heat exchanger (EAHE) system can improve renewable utilisation, decrease CO 2 emission and promote carbon-neutral transition. However, the conventional EAHE system has drawbacks, e.g., large occupied land area, low energy-usage efficiency, small falling gradient for buried pipe and fluctuated outlet air temperature. This study proposes a vertical EAHE integrated with annular PCM with advantages, including less occupied floor space, higher energy efficiency, better centralised discharge of air condensate water and more stable outlet air temperature. An experimental test-rig was established for online testing and the real-time monitored data was for modelling calibration to characterise the sophisticated heat transfer in phase change process. Afterwards, multivariant analysis on thermo-physical PCM parameters was conducted on cooling capacity and outlet air temperature fluctuation. A dimensionality reduction approach from redundant experiments was adopted for multivariant optimization and sensitivity analysis. Results show that PCM fusion temperature and latent heat of PCM dominate the cooling capacity with percentage contribution of 37.61% and 28.91%, respectively. PCM thickness and melting temperature dominate the temperature fluctuation with percentage contribution of 31.27% and 26.18%, respectively. This study provides benchmark and guidelines on PCM thermo-physical parameters’ selection with an efficient dimensionality reduction approach, paving path for application of the vertical EAHE integrated with PCMs in buildings. @en

Shallow subterranean ventilation of earth-to-air heat exchanger (EAHE) system can improve renewable utilisation, decrease CO 2 emission and promote carbon-neutral transition. However, the conventional EAHE system has drawbacks, e.g., large occupied land area, low energy-usage efficiency, small falling gradient for buried pipe and fluctuated outlet air temperature. This study proposes a vertical EAHE integrated with annular PCM with advantages, including less occupied floor space, higher energy efficiency, better centralised discharge of air condensate water and more stable outlet air temperature. An experimental test-rig was established for online testing and the real-time monitored data was for modelling calibration to characterise the sophisticated heat transfer in phase change process. Afterwards, multivariant analysis on thermo-physical PCM parameters was conducted on cooling capacity and outlet air temperature fluctuation. A dimensionality reduction approach from redundant experiments was adopted for multivariant optimization and sensitivity analysis. Results show that PCM fusion temperature and latent heat of PCM dominate the cooling capacity with percentage contribution of 37.61% and 28.91%, respectively. PCM thickness and melting temperature dominate the temperature fluctuation with percentage contribution of 31.27% and 26.18%, respectively. This study provides benchmark and guidelines on PCM thermo-physical parameters’ selection with an efficient dimensionality reduction approach, paving path for application of the vertical EAHE integrated with PCMs in buildings. @en

A novel vertical air-soil heat exchanger (VASHE) is proposed, coupling with diversified energy storage components, i.e., both annular and tubular phase change material (PCM) components. Compared to traditional air-soil heat exchanger systems, advantages of the new VASHE include the space-saving, higher energy efficiency, centralized discharge of condensate water and smaller fluctuation of outlet air temperature. An enthalpy-based model is developed to characterise the underlying heat transfer mechanism of the sophisticated sensible and latent heat transfer in PCMs. An experimental platform is thereafter constructed for the calibration of the developed enthalpy-based numerical model. Systematic parametrical analysis has been conducted on PCM types, PCM structure and PCM locations. Research results indicated that, the developed enthalpy-based model was accurate to predict the system performance with the maximum relative error at 1.98%. Systematic parametric analysis indicates that, within various PCM types, the RT 20 in the tubular PCM is the most promising with the smallest outlet temperature amplitude. Furthermore, accurate PCM location is an effective solution to the contradiction between daily cooling storage capacity and outlet temperature amplitude. This study demonstrates a novel air-soil heat exchanger with diversified energy storage components, which can provide concrete guidance and pave path for the geothermal energy utilisation.@en