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Exploiting low-carbon, clean, and stable medium-deep geothermal energy is critical to achieving clean and sustainable heating for buildings in northern China. The medium-deep U-type borehole heat exchanger (MDUBHE) system is a novel technology that has emerged recently for exploiting deep geothermal energy. However, previous studies mainly analyzed the heating characteristics of the MDUBHE system in a single building type (i.e., continuous operational conditions), and the long-term (15-year) heating performance under different operational conditions is still unclear. Moreover, the heating sustainability of the system in different regions has not been clarified. Therefore, to promote the application of the MDUBHE system, this paper conducts numerical simulations to analyze the system's long-term heating performance, thermal recovery characteristics of rock and soil, and the system's energy efficiency under different operational conditions and regions. The results show that the MDUBHE system has high heating sustainability under different working conditions. After 15 years of operation, the maximum decay rate of MDUBHE's outlet water temperature is less than 3.15 % under different operating conditions and less than 3.01 % in different regions. In addition, the maximum decay rate of total system heating capacity is less than 8.86 % under different operating conditions and less than 7.60 % in different regions. Furthermore, the intermittent operation of the system and the higher thermophysical properties of rock and soil can enhance the rock-soil's thermal recovery. The MDUBHE system can efficiently operate over the long term under different working conditions. The maximum decay rates of the system's energy efficiency are less than 1.86 % under different operating conditions and less than 1.60 % in different regions. The study could promote the application of the MDUBHE system in different regions. [Display omitted] • Heat extraction model for medium-deep U-type borehole heat exchanger system is presented. • Long-term heating performance of the system and soil temperature variation are clarified. • Intermittent operation improves system energy efficiency and promotes soil thermal recovery. • The system has robust long-term heating sustainability under different working conditions. [ABSTRACT FROM AUTHOR]

While the natural ventilation double-skin façade is a widely-used technology, its thermal performance is not yet fully understood. Hence, this paper investigates the thermal performance and optimization of double-skin façades. Previous studies focused on typical moments or standard days to evaluate the thermal performance of a double-skin façade. The current study adopts a simplified method based on Computational Fluid Dynamics (CFD) to obtain the hourly heat gain and total heat gain of a double-skin façade for an entire cooling season. The data is then used to evaluate thermal performance. Finally, based on the total heat gain of the double-skin façade with different structural parameters for an entire cooling season, this paper proposes optimization parameters for different climate zones in China. [ABSTRACT FROM AUTHOR]

Climate responsive strategies contained in traditional native dwellings can provide theoretical basis for the development of sustainable buildings. This study focused on a quantitative analysis of cliff-side cave dwellings located in cold region of China. Field measurements in summer and winter were carried out. Based on the monitoring data, thermal environment of the cave dwelling and thermal characteristics of the adobe massive building envelope were evaluated. Results showed that the cliff-side cave dwelling was well adapted to local environment for its good ability of thermal insulation under the natural conditions. Furthermore, in order to assess the whole annual thermal performance and thermal comfort level, numerical simulations on the cliff-side cave dwelling models was also performed using the software Energyplus. Results showed that 52.50% time of the year was comfortable of the living room. Meanwhile, some technical strategies of making full use of solar energy and natural ventilation was proposed in the end of this paper, which can provide technical support for the regeneration design of traditional residential buildings. • Cave dwellings with massive envelope adapt themselves to the local climate well. • 52.50% time of the year was comfortable of the cliff-side cave dwelling room. • Renewable energy using strategies on the vernacular cave dwelling were proposed. [ABSTRACT FROM AUTHOR]

Proton exchange membrane (PEM) fuel cells produce a large amount of waste heat while generating electricity through electrochemical reactions, making them suitable for driving combined heating and power (CHP) systems. According to the hourly thermal and electric loads in a typical North China household, a 2-kW PEM fuel cell-based micro-CHP system with a lithium-ion battery energy storage system is proposed in this paper. The thermal and economic performances of the micro-CHP system with a lithium-ion battery (CHPWB) and a CHP system without a lithium-ion battery (CHPWOB) are comparatively analyzed by developing a thermal and economic performance analysis model on the MATLAB/Simulink platform. The thermal-load-following strategy is adopted during the design and simulation process. The results indicate that the storage capacity of the lithium-ion battery decreases by 6.6% after one cycle. The lithium-ion battery can be charged by the fuel cell stack during off-peak hours or using commercial electricity, and the charging cycle of the system is one week long. The average total efficiency of the CHPWB system can reach 81.24% with considering the energy loss in each conversion process, which is 11.02% higher than that of the CHPWOB system. The daily hydrogen consumption of the CHPWB system can be reduced by 14.47% compared with the CHPWOB system under the same operating conditions, and the average daily costs can be reduced by 8.4% and 9.5% when the lifespan is 10 and 15 years, respectively. Image 1 • A PEM fuel cell-based CHP system for a typical household in North China is proposed. • A complete model for this system is developed using the MATLAB/Simulink platform. • The thermal and economic performances of the proposed system are comparatively analyzed. • The thermal and economic performances can be improved by 11.02% and 9.5%, respectively. [ABSTRACT FROM AUTHOR]

The Chinese Accelerator Driven Sub-critical system (C-ADS) Injector-I is designed and constructed by the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences (CAS) in Beijing, China. The test cryomodule (TCM), housing two 325 MHz spoke cavities and two solenoids and operating at 2 K, has been designed, assembled and commissioned since the beginning of 2012. The C-ADS Injector-I linac with the TCM successfully accelerated the proton beam to 3.68 MeV with the peak current of 10.1 mA in pulse mode. It is the world's first prototype of spoke cavity cryomodule with beam, and is an important step in the qualification of the cryomodule before series productions. This paper describes the detail of the design, operation and thermal performances of the prototype cryomodule. The analysis takes into account the heat loads of the main components (support posts, multilayer insulation and cavities) at various cryogenic temperature levels. The estimated heat loads of the cryomodule have been compared with the available experimental measurements, and the cryogenic deformations by simulation is verified by the experimental measurements by the wire position monitors (WPMs). The operation experiences including the cool down, alignment and heat load measurement are reported. • The 325 MHz spoke cavity prototype cryomodule has been designed, assembled and commissioned. • The thermal performance of the bottom-supported cryomodule has been proved firstly worldwide. • The cryomodule can be in a stable operation at 2 K and 31 mbar with beam. • The operation experiences including the cool down, alignment and measurement of heat loads are reported. • The linac with cryomodule had been accelerated successfully to 3.68 MeV@10.1 mA in pulse mode. [ABSTRACT FROM AUTHOR]

• A new structural design method for earth-to-air heat exchangers in greenhouses is described. • The structural design method incorporates greenhouse heat balance model to better match greenhouse characteristics. • The system is more energy-efficient and stable in intermittent operation mode. • Application of an earth-air heat exchanger is a green technology for greenhouse sustainability. An earth-air heat exchanger (EAHE) is a type of environmental regulation equipment that is suitable for greenhouses. In the future, it could be a green technique for greenhouse energy supplementation. However, EAHEs lack structural design methods for application in greenhouses. Consequently, this paper presents a structural design method for an EAHE based on the architectural characteristics of greenhouses. Firstly, the EAHE design heat exchange amount was calculated according to the greenhouse heat and cold load, then the pipe length, diameter, air velocity, and burial depth were determined by combining the heat transfer efficiency and number of transfer units (NTU), and finally the final parameters were optimized and selected according to the energy loss and construction cost. The design method was validated in a greenhouse in northern China, and the heat transfer performance was analyzed in both intermittent and continuous operation modes. The results showed that the novel structural design method could guide the application of EAHE in a greenhouse and satisfy the energy demand of greenhouses. The measured average greenhouse temperature at night increased by 1.57 °C and 1.11 °C, respectively, under intermittent operation and continuous operation and decreased by 1.19 °C and 1.32 °C, respectively, during the day. The EAHE performance coefficients for heating and cooling conditions under intermittent operation were 21.49 and 18.15, respectively, significantly higher than those for continuous operation. [ABSTRACT FROM AUTHOR]

The building envelopes are exposed to the hot-humid climate with high humidity in hot summer and cold winter zone (HSCW) of China. The moisture transfer may severely influence the conduction loads through exterior walls. In this paper, a coupled heat and moisture transfer model is developed and validated to investigate the thermal performance of exterior walls. The conduction loads through a typical exterior wall are used to evaluate the effect of moisture transfer on the thermal performance of exterior walls in HSCW zone of China. The results show that the peak cooling and heating loads are overestimated by 2.1–3.9% and 4.2–10.1%, respectively, when ignoring moisture transfer. In cooling season, the sum of the latent load accounts for 14.3–52.2% of the sum of the total load and the yearly latent load accounts for 4.9–6.1% of the yearly total load when considering moisture transfer. The total cooling, heating and the yearly load are underestimated by 9.9–34.4%, 1.7–4.0%, and 5.2–6.8%, respectively, when ignoring moisture transfer. The results indicate that ignoring moisture transfer causes significant discrepancy in predicting the conduction loads. A detailed model considering moisture transfer in building envelope is essential to accurately evaluate the building energy performance in HSCW zone of China. [ABSTRACT FROM AUTHOR]

Abstract: This paper develops an overall methodology for investigating the thermal and power behaviors of semi-transparent single-glazed photovoltaic window for office buildings in Hong Kong. In order to estimate its overall energy performance, this study is conducted in terms of total heat gain, output power and daylight illuminance. Three simulation models are established, including one-dimensional transient heat transfer model, power generation model and indoor daylight illuminance model. A typical office room reference is chosen as case study, and the weather data from 2003 to 2007 from the Hong Kong Observatory are used as the simulation inputs. By incorporating the simulation results, the overall energy performance can be evaluated in terms of electricity benefits corresponding to five orientations of the studied typical office. The priority of office orientation considering overall energy performance is: south-east, south, east, south-west and west. The findings show that thermal performance is the primary consideration of energy saving in the entire system whereas electricity consumption of artificial lighting is the secondary one. The overall annual electricity benefits are about 900 kWh and 1300 kWh for water-cooled and air-cooled air-conditioning systems respectively. The application of semi-transparent PV glazed window can not only produce clean energy, but also reduce building energy use by reducing the cooling load and electrical lighting requirements, which definitely benefits our environmental and economic aspects. [Copyright &y& Elsevier]

Recently, the structural insulated panels (SIPs) with the wood-based surfacing materials are developed in housing industry to increase the thermal efficiency of the wall system. In order to integrate the waterproof feature into SIPs, a newly designed GFRP reinforced squared tube sandwich panel (GSTPs) is introduced, where the Glass fibre reinforced polymers (GFRP) is utilized as surface material and the core is reinforced by the GFRP square tube. This paper focused on the thermal insulation performance of GSTPs. Both experimental, theoretical and numerical methods are employed to study their thermal insulation performance as roof panels. More specifically, the thermal conductivity of GFPR with three different core materials, including glass wool, Extruded polystyrene (XPS) and Polyurethane (PU) in the SIP, was first measured by hot plate apparatus (HPA) in the steady-state heat transfer tests. Then, the heat transfer coefficients of three type of GSTPs with above mentioned core materials are measured by guarding heat box (GHB) test. The theoretical and finite element (FE) method based numerical studies applied to conduct the heat transfer analyses on those SIPs. The accuracies of the theoretical and numerical studies are verified by comparing the obtained heat transfer coefficients with those from the experimental tests. The results from the present study could provide a good reference to the selection of the suitable panel thickness and core materials for different thermal regions in China. [ABSTRACT FROM AUTHOR]