Modeling and efficiency study of large scale underground thermal battery deployment

Yingqi Zhang, Xiaobing Liu, Christine Doughty, Peter Nico

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

1 Scopus citations

Abstract

A novel ground heat exchanger design, namely, the Underground Thermal Battery (UTB) was invented at Oak Ridge National Laboratory as a low-cost alternative to the conventional vertical bore ground heat exchanger (VBGHE) for the application of ground source heat pumps (GSHPs). The UTB is comprised of a tank of water, a helical heat exchanger in the center of tank and connected to a water source heat pump, and a phase change material (PCM). Compared to a conventional VBGHE, the UTB is designed to be installed at a much shallower depth, therefore, with a cheaper cost. In addition, the GSHP efficiency is improved due to natural convection of water and additional load capacity provided by PCM. The goal of this study is to explore factors that may affect the efficiency of large-scale UTB deployment. To achieve the goal, we implement an existing one-dimensional (1D) radial model of the UTB into iTOUGH2, which is part of the TOUGH family that provides three-dimensional numerical simulations for the coupled transport of water, vapor, air, and heat in heterogeneous porous media. In addition, iTOUGH2 provides inverse analysis capabilities (e.g., uncertainty quantification, sensitivity analysis). The 1D model of the UTB was previously validated with the measured performance data of a small-scale UTB. It was also compared to the simulation results of a more detailed three dimensional (3D) UTB model and is considered a good approximation of 3D representation with large computational time savings. The next step is to use the coupled model to understand what factors have the most influence on the efficiency of large scale deployment of UTB and provide guidance on the layout of multiple UTBs, as well as insights for field characterization, monitoring and operation.

Original languageEnglish
Title of host publicationUsing the Earth to Save the Earth - 2021 Geothermal Rising Conference, GRC 2021
PublisherGeothermal Resources Council
Pages1122-1127
Number of pages6
ISBN (Electronic)0934412278
StatePublished - 2021
Event2021 Geothermal Rising Conference: Using the Earth to Save the Earth, GRC 2021 - San Diego, United States
Duration: Oct 3 2021Oct 6 2021

Publication series

NameTransactions - Geothermal Resources Council
Volume45
ISSN (Print)0193-5933

Conference

Conference2021 Geothermal Rising Conference: Using the Earth to Save the Earth, GRC 2021
Country/TerritoryUnited States
CitySan Diego
Period10/3/2110/6/21

Funding

This work was supported by Lawrence Berkeley National Laboratory (LBNL) under with funding from the Geothermal Technologies Office and under Department of Energy Contract No. DE-AC02-05CH11231. The authors would like to thank Joseph Warner, Liang Shi, and Ming Qu for developing and providing the 1D UTB MATLAB code for the UTB.

Keywords

  • Energy Storage
  • Long-Term Efficiency
  • Underground Thermal Battery

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