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• A seasonal solar thermal energy storage system is developed for space heating. • Ground coupled heat pump and solar collectors are integrated into such a system. • A validated TRNSYS computer simulation model of the system was applied. • The system performance parameters in six cold climate locations were identified. The performance of a seasonal solar thermal energy storage system for space heating in cold climates was investigated. The system includes a double U-tube vertical borehole thermal energy storage integrated with a ground coupled heat pump and evacuated tube solar collectors. A validated TRNSYS model for six cold climate locations: Lukla, Dras, Sivas, Harbin, Ulaanbaatar and Verkhoyansk was applied. The hourly typical metrological year (TMY) data of each location was used. The house model for each location was based on the typical local dwelling. The annual heating loads per unit floor area (GJ m−2) was found in the range of 0.71–2.59 (1.71, 1.79, 0.71, 1.19, 1.45 and 2.59 for Lukla, Dras, Sivas, Harbin, Ulaanbaatar and Verkhoyansk respectively). The sizes of the system components such as solar collector area, borehole length, number of borehole and heat pump capacity were determined for each location. The analysis covered both heat charging and discharging. It was found that the average ground temperatures were stable in each location with solar charging. However, if the system was not charged by solar energy, the average ground temperatures were decreased over the years. The seasonal compressor heating coefficient of performance coefficient of performance were found to be more than 5.8, that shows the potential benefit of the system. The proposed system could fulfil more than 93% of the space heating demand in all selected locations. The results of the study reveal the potential benefits of utilising seasonal solar thermal energy storage system in cold climate locations. [ABSTRACT FROM AUTHOR]

Abstract A number of seasonal thermal energy storage (STES) systems have been deployed for heating in cold climate zones due to potential utilisation of solar energy. It overcomes the drawback on intermittency of solar energy and contributes to storing heat from summer to be used in winter. Heat pump and solar collectors with low-temperature storage are the influencing factors to improve the system performance. This paper investigates STES systems integrated with heat pump and solar collectors for heating applications in cold climate zones based on the current available literature. Furthermore, various simulation models and software tools related to STES system were reviewed. This study discusses potential STES systems for space heating system in cold climate zones based on various parameters such as heating demand, climate conditions, and availability of solar resources, storage temperature, energy efficiency, and life cycle cost (LCC). A simple calculation method was applied to demonstrate the potential contribution of different STES options. The double U-tube borehole thermal energy storage (BTES) integrated with ground coupled heat pump (GCHP) and evacuated tube solar collector (ETSC) system was found to be most appropriate for space heating in cold climate zones. The analysis indicated that the system could have higher overall energy efficiency than the traditional space heating systems. Furthermore, a decision support flow chart was presented based on STES options. Highlights • Seasonal thermal storage systems overcome the drawback on intermittency of solar. • Heat pump and solar collectors with low-temperature storage improve the performance. • Climate, storage temperature, energy efficiency, and life cycle cost are discussed. • A decision support flow chart is presented for selection of system options. [ABSTRACT FROM AUTHOR]

• A validated simulation model was used to optimise a heating system. • The system consists of a borehole heat exchanger, solar collectors and a heat pump. • Solar energy is collected in summer and stored in the ground for used in winter. • The objectives functions to be minimised are life cycle cost and GHG emissions. • Pareto fronts (sets of solar collector area and borehole length) were identified. Seasonal solar thermal energy storage (SSTES) system is a promising technology to minimise greenhouse gas emissions (GHGE) by harnessing solar energy for space heating applications. The SSTES system in this study includes double U-tube borehole heat exchanger, ground-coupled heat pump and evacuated tube solar collectors. The aim of this investigation is to optimise the design variables of a SSTES system for space heating in cold climate locations. Six cold climate locations were studied namely: Lukla (Nepal), Dras (India), Sivas (Turkey), Harbin (China), Ulaanbaatar (Mongolia), and Verkhoyansk (Russia). The optimisation variables considered are the total solar collector area and total borehole length. There are three separate optimisation investigations: two single-objective and one multi-objective for the SSTES system. The first investigation is to minimise total life cycle greenhouse gas emissions and the second investigation is to minimise total life cycle cost included cost of GHGE. The third investigation is to minimise both life cycle cost of SSTES system and cost of GHGE (multi objectives). The simulation model was developed using TRNSYS 17 and the Multi-Objective Building Optimisation (MOBO) tool was applied for optimisations. The optimal set of design variables and the corresponding value of the objective function were determined for each single-objective optimisation investigation. Pareto front for each location was also identified for the multi-objective optimisation investigation. The technical and financial performance were also analysed and presented. [ABSTRACT FROM AUTHOR]