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Building Simulation: An International Journal

Article Title

Influence of geometry on the thermal performance of water pit seasonal heat storages for solar district heating

Authors

Yakai Bai, Key Laboratory of Solar Thermal Energy and Photovoltaic Systems, Chinese Academy of Sciences, Beijing 100190, China;Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, China;University of Chinese Academy of Sciences, Beijing 100049, China;Department of Civil Engineering, Technical University of Denmark, Brovej 118, 2800 Kgs. Lyngby, Denmark
Ming Yang, Key Laboratory of Solar Thermal Energy and Photovoltaic Systems, Chinese Academy of Sciences, Beijing 100190, China;Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, China;Joint Laboratory, Institute of Electrical Engineering, Chinese Academy of Sciences and Guangdong Five Star Solar Energy Co., Ltd., Beijing 100190, China
Jianhua Fan, Department of Civil Engineering, Technical University of Denmark, Brovej 118, 2800 Kgs. Lyngby, Denmark
Xiaoxia Li, Lanzhou University of Technology, Gansu 730050, China
Longfei Chen, Key Laboratory of Solar Thermal Energy and Photovoltaic Systems, Chinese Academy of Sciences, Beijing 100190, China
Guofeng Yuan, Key Laboratory of Solar Thermal Energy and Photovoltaic Systems, Chinese Academy of Sciences, Beijing 100190, China;Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, China;Joint Laboratory, Institute of Electrical Engineering, Chinese Academy of Sciences and Guangdong Five Star Solar Energy Co., Ltd., Beijing 100190, China
Zhifeng Wang, Key Laboratory of Solar Thermal Energy and Photovoltaic Systems, Chinese Academy of Sciences, Beijing 100190, China;Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, China;University of Chinese Academy of Sciences, Beijing 100049, China;Joint Laboratory, Institute of Electrical Engineering, Chinese Academy of Sciences and Guangdong Five Star Solar Energy Co., Ltd., Beijing 100190, China

Keywords

water pit, seasonal heat storage, truncated cone, storage capacity, thermal stratification, coordinate transformation

Abstract

The aim of the study is to investigate the influence of geometry on the thermal capacity and stratifications of a water pit heat storage for solar district heating. A TRNSYS component model for a truncated cone water pit was developed based on the coordinate transformation method and validated by experimental results from the water pit heat storage in Huangdicheng in 2018. The thermal performance of 26 water pits with different heights and side wall slopes was calculated for 10 consecutive years. It takes four to six years for the water pit to reach steady-state operation. The operation data from the tenth year was selected to evaluate the thermal performance of each configuration. The results show that because of the thermal insulation on top of the water pit, the height to diameter ratio of a water pit with minimum annual heat loss was always smaller than 1.0. The annual storage efficiency of a water pit increases with side wall slope due to the reduced side wall area. There is an almost linear increase in the thermal stratification number of a water pit with height. With an increase in the height, thermal stratification in water pits with a steeper slope increased more gradually than water pits with a lower slope. The findings in this paper are relevant for the design optimization of water pits as seasonal thermal energy storages.

Publisher

Tsinghua University Press

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