Coupling Subsurface and Above-Surface Models for Optimizing the Design of Borefields and District Heating and Cooling Systems

Accurate dynamic energy simulation is important for the design and sizing of district heating and cooling systems with geothermal heat exchange for seasonal energy storage. Current modeling approaches in building and district energy simulation tools typically consider heat conduction through the ground between boreholes without flowing groundwater. While detailed simulation tools for subsurface heat and mass transfer exist, these fall short in simulating above-surface energy systems.

To support the design and operation of such systems, the study developed a coupled model including a software package for building and district energy simulation, and software for detailed heat and mass transfer in the subsurface. For the first, it uses the open-source Modelica Buildings Library, which includes dynamic simulation models for building and district energy and control systems. For the heat and mass transfer in the soil, it uses the TOUGH simulator. The TOUGH family of codes can model heat and multi-phase, multi-component mass transport for a variety of fluid systems, as well as chemical reactions, in fractured porous media.

The study validated the coupled modeling approach by comparing the simulation results with one from the g-function based ground response model. It then looked into effects when the water table and the regional groundwater flow are considered in the ground, from the perspective of heat exchange between borehole and ground, and the electrical consumption of the district heating and cooling systems.

To access the simulation models, please find the links in the submission:
-- For coupled approach validation: see model Buildings.Fluid.Geothermal.Borefields.Examples.BorefieldsWithTough and Buildings.Examples.DistrictReservoirNetworks.Examples.Reservoir3Variable_TOUGH from the "Modelica Building Library" resource, branch issue1495_tough_interface, commit a2667c0.
-- For the study of the effect of water table: see model Buildings.Examples.DistrictReservoirNetworks.Examples.Reservoir3Variable_TOUGH from he "Modelica Building Library" resource, branch issue1495_tough_interface_moreIO, commit 760de49.
-- For the study of the effect of regional groundwater flow: see Buildings.Examples.DistrictReservoirNetworks.Examples.Reservoir3Variable_TOUGH from he "Modelica Building Library" resource, branch issue1495_tough_interface_moreIO_3D, commit c2a2d2a.

The coupling interface script "GrounResponse.py" can be found from the above links in the folder Buildings/Resources/Python-Sources. Also, the needed files for TOUGH simulation are in the folder Buildings/Resources/Python-Sources/ToughFiles that can be accessed through the above links. A brief description of these files is given below; detailed specifications for the first three files may be found in the TOUGH3 Users Guide (Jung et al., 2018) https://tough.lbl.gov/documentation/tough-manuals/.

(1) INCON - initial conditions for each grid block
(2) INFILE - main input file with material properties and control parameters
(3) MESH - description of the computational grid
(4) readsave - Modelica/TOUGH interface program: read the final output of TOUGH simulation after TOUGH time step and prepare for transfer to Modelica for next Modelica time step
(5) readsave.inp - input parameters for program readsave
(6) writeincon - Modelica/TOUGH interface program: write the output of Modelica after Modelica time step and prepare for transfer to TOUGH as initial conditions for the next TOUGH step
(7) writeincon.inp - input parameters for program writeincon

精确的动态能源模拟对于设计和规模化的地热交换季节性储能区域供热和供冷系统的设计至关重要。在现有的建筑和区域能源模拟工具中，建模方法通常只考虑了在没有流动地下水的情况下，通过地埋管的热传导。尽管存在用于模拟地热和物质传递的详细模拟工具，但这些工具在模拟地表能源系统方面仍有不足。为了支持此类系统的设计和运行，本研究开发了一个耦合模型，包括建筑和区域能源模拟软件包，以及用于地下详细热和质量传递的软件。对于前者，它使用了开源的Modelica Buildings库，该库包含建筑和区域能源及控制系统动态模拟模型。对于土壤中的热和质量传递，它使用了TOUGH模拟器。TOUGH系列代码可以模拟各种流体系统的热和多相、多组分的物质传输，以及裂隙多孔介质中的化学反应。通过将模拟结果与基于g函数的地面响应模型的模拟结果进行比较，本研究验证了耦合建模方法的有效性。随后，它从地埋管与地面之间热交换以及区域供热和供冷系统的电能消耗的角度，研究了在考虑地下水位和区域地下水流动时的影响。为获取模拟模型，请查阅提交中的链接：-- 对于耦合方法验证，请参阅“Modelica Building Library”资源中的模型Buildings.Fluid.Geothermal.Borefields.Examples.BorefieldsWithTough和Buildings.Examples.DistrictReservoirNetworks.Examples.Reservoir3Variable_TOUGH，分支issue1495_tough_interface，提交号a2667c0。-- 对于研究地下水位影响，请参阅“Modelica Building Library”资源中的模型Buildings.Examples.DistrictReservoirNetworks.Examples.Reservoir3Variable_TOUGH，分支issue1495_tough_interface_moreIO，提交号760de49。-- 对于研究区域地下水流动影响，请参阅“Modelica Building Library”资源中的模型Buildings.Examples.DistrictReservoirNetworks.Examples.Reservoir3Variable_TOUGH，分支issue1495_tough_interface_moreIO_3D，提交号c2a2d2a。耦合接口脚本“GrounResponse.py”可以从上述链接中的文件夹Buildings/Resources/Python-Sources获取。TOUGH模拟所需文件也在上述链接可访问的文件夹Buildings/Resources/Python-Sources/ToughFiles中。以下是对这些文件的简要描述；对于前三个文件，更详细的规定可在TOUGH3用户指南（Jung等，2018）中找到：https://tough.lbl.gov/documentation/tough-manuals/。（1）INCON - 每个网格块初始条件。（2）INFILE - 包含材料特性和控制参数的主输入文件。（3）MESH - 计算网格描述。（4）readsave - Modelica/TOUGH接口程序：读取TOUGH模拟后的最终输出，并为下一次Modelica时间步准备传输。（5）readsave.inp - 程序readsave的输入参数。（6）writeincon - Modelica/TOUGH接口程序：在Modelica时间步结束后写入Modelica的输出，并为下一次TOUGH步准备初始条件。（7）writeincon.inp - 程序writeincon的输入参数。