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The variability and inhomogeneity of solar energy limits the development of solar heating systems (SHS) in many fields. In order to improve the utilization efficiency of SHS, this paper takes three typical cities (Xi'an, Dunhuang, Lhasa) as the research object, studies the operation state of SHS in student dormitory buildings, and puts forward a corresponding optimization strategy. The research shows that the reduction of water supply temperature will improve the operation efficiency and energy saving effect of a spontaneous combustion heat pump and that there is an optimal volume of heat storage water tank (HSWT), which can make the energy saving effect of SHS run better. The optimization of the SHS shows the water supply temperature is 35 °C, and the optimal volume of HSWT is 15 m3 in the "Resource-general area (Ⅲ)" represented by Xi'an, 25 m3 in the "Resource-rich area (Ⅱ)" represented by Dunhuang, and 40 m3 in the "Resource-richer area (Ⅰ)" represented by Lhasa. With the increase in the abundance of solar energy resources in the region, the optimal volume of HSWT also increases. Meanwhile, the solar energy contribution rate of the three regions in descending order is 61.3% (Lhasa), 32.8% (Dunhuang), and 25.9% (Xi'an). After optimization, the contribution of SHS increased by about 5%. The research results will help improve the efficiency of SHS in cold areas of China and make the system more efficient and energy efficient during operation. [ABSTRACT FROM AUTHOR]

The harsh indoor environment in winter in the hot-summer and cold-winter zones of China and the increasing demand for winter heating from residential consumers have prompted more and more researchers to address the energy-efficient heating problem in non-centralized heating areas. A computational fluid dynamics model of a typical building was developed to analyze the dynamic heat transfer characteristics and energy consumption of interior partitions under decentralized heating in this region, of which the accuracy of the established model was proved by the relative error of less than 5% compared with the experimental measurement. Then seven typical kinds of interior partition configurations with different wall thickness, wall material, and insulation layer locations were developed and evaluated through simulation analysis. Transient heat storage ratio and cumulative heat storage ratio were proposed to demonstrate the dynamic heat transfer characteristics of interior partitions. The simulation results showed that 180 mm and 220 mm solid clay bricks can reduce energy consumption by 17.56% and 30.23%, respectively, compared with 120 mm solid clay bricks. The energy consumption of fly ash aerated concrete and solid clay brick partitions were reduced by 10.18% and 19.02%, respectively, compared with porous concrete partitions. The dynamic heat transfer characteristics of internal partitions with internal insulation were similar to those with external insulation due to the reduction in unnecessary energy consumption transferred to adjacent unheated rooms by about 20% compared to that without insulation. And the heat consumption of interior partitions under convective heating was 17.3% higher than under radiant heating. [ABSTRACT FROM AUTHOR]

A hybrid ground-coupled heat pump (GCHP) is an efficient and sustainable technology for space heating and cooling. A demonstration house equipped with GCHP with a solar seasonal heat storage (SSHS) system had been built in Harbin, a severe cold zone of China. A dynamic simulation model was built for the house and GCHP with the SSHS system using TRNSYS. The model used a newly developed vertical ground heat exchanger (VGHE) module which considered coupled heat and moisture transfer (CHMT) in ground with variable soil properties (VSPs) and phase change of soil moisture (PCSM). In the simulation, a large amount of computing is consumed for VSP and PCSM, while the computing amount for moisture transfer is small. The model with the new VGHE module produced better simulated results, compared with the field data. So, CHMT-VSP-PCSM affects the performance of VGHE and system to some extent, especially CHMT. Hourly variation laws of temperatures and energy parameters were analyzed, and different characteristics were showed up at different operating stages in heating and cooling seasons for both long and short terms. The GCHP with the SSHS system can meet the heating and cooling demands of the house in general. In cooling season, adjusting the ratio of the two groups of VGHE for heat storage and cooling will increase the utilization efficiency of VGHE and make the soil temperature more balanced. [ABSTRACT FROM AUTHOR]