GHEtool 2.0.3

Python package for borefield sizing

GHEtool: An open-source tool for borefield sizing in Python

What is GHEtool?

GHEtool is a Python package that contains all the functionalities needed to deal with borefield design. It is developed for both researchers and practitioners. The core of this package is the automated sizing of borefield under different conditions. The sizing of a borefield is typically slow due to the high complexity of the mathematical background. Because this tool has a lot of precalculated data (cf. infra), GHEtool can size a borefield in the order of tenths of milliseconds. This sizing typically takes the order of minutes. Therefore, this tool is suited for being implemented in workflows where iterations are required.

Graphical user interface

GHEtool also comes with a graphical user interface (GUI). This GUI is prebuilt as an exe-file (only for Windows platforms currently) because this provides access to all the functionalities without coding. A setup to install the GUI at the user-defined place is also implemented and available here. This graphical interface is made by Tobias Blanke from FH Aachen.

Screenshot of the GUI.

Requirements

This code is tested with Python 3.8 and requires the following libraries (the versions mentioned are the ones with which the code is tested)

• Numpy (>=1.20.2)
• Scipy (>=1.6.2)
• Matplotlib (>=3.4.1)
• Pygfunction (>=2.1.0)
• Openpyxl (>=3.0.7)
• Pandas (>=1.2.4)

For the GUI

• PyQt5 (>=5.10)

For the tests

• Pytest (>=7.1.2)

When working with Python 3.9 and higher, installing a newer version of pygfunction (>=2.1.0) can lead to problems due to the fact that its dependency CoolProp is not compatible with Python 3.9 and higher (see also https://github.com/CoolProp/CoolProp/issues/1992 and https://github.com/CoolProp/CoolProp/issues/2119). If one wants to work with the newer version of pygfunction and with Python 3.9 or higher, one can install a development version of CoolProp using

pip install -i https://test.pypi.org/simple/ CoolProp==6.4.2.dev0

Quick start

Installation

One can install GHEtool by running Pip and running the command

pip install GHEtool

or one can install a newer development version using

pip install --extra-index-url https://test.pypi.org/simple/ GHEtool

Developers can clone this repository.

It is a good practise to use virtual environments (venv) when working on a (new) Python project so different Python and package versions don't conflict with eachother. For GHEtool, Python 3.8 is recommended. General information about Python virtual environments can be found here and in this article.

Check installation

To check whether everything is installed correctly, run the following command

pytest --pyargs GHEtool

This runs some predefined cases to see whether all the internal dependencies work correctly. 9 test should pass successfully.

Get started with GHEtool

To get started with GHEtool, one needs to create a Borefield object. This is done in the following steps.

from GHEtool import Borefield, GroundData

After importing the necessary classes, one sets all the relevant ground data.

data = GroundData(110, # depth of the field (m)
                  6,   # distance between the boreholes (m)
                  3,   # ground thermal conductivity (W/mK)
                  10,  # initial/undisturbed ground temperature (deg C)
                  0.2, # borehole equivalent resistance (mK/W)
                  10,  # number of boreholes in width direction of the field (/)
                  12)  # number of boreholes in the length direction of the field (/)

Furthermore, one needs to set the peak and monthly baseload for both heating and cooling.

peak_cooling = [0., 0, 34., 69., 133., 187., 213., 240., 160., 37., 0., 0.]   # Peak cooling in kW
peak_heating = [160., 142, 102., 55., 0., 0., 0., 0., 40.4, 85., 119., 136.]  # Peak heating in kW

monthly_load_heating = [46500.0, 44400.0, 37500.0, 29700.0, 19200.0, 0.0, 0.0, 0.0, 18300.0, 26100.0, 35100.0, 43200.0]        # in kWh
monthly_load_cooling = [4000.0, 8000.0, 8000.0, 8000.0, 12000.0, 16000.0, 32000.0, 32000.0, 16000.0, 12000.0, 8000.0, 4000.0]  # in kWh

Next, one creates the borefield object and sets the temperature constraints and the ground data.

# create the borefield object
borefield = Borefield(simulation_period=20,
                      peak_heating=peak_heating,
                      peak_cooling=peak_cooling,
                      baseload_heating=monthly_load_heating,
                      baseload_cooling=monthly_load_cooling)

borefield.set_ground_parameters(data)

# set temperature boundaries
borefield.set_max_ground_temperature(16)  # maximum temperature
borefield.set_min_ground_temperature(0)  # minimum temperature

Once a Borefield object is created, one can make use of all the functionalities of GHEtool. One can for example size the borefield using:

depth = borefield.size(100)
print("The borehole depth is: ", depth, "m")

Or one can plot the temperature profile by using

borefield.print_temperature_profile(legend=True)

A full list of functionalities is given below.

Functionalities

GHEtool offers functionalities of value to all different disciplines working with borefields. The features are available both in the code environment and in the GUI. These functions are listed in the table below, alongside with a link to an example document where one can find how these functionalities can be used.

Functionality	Example document
Sizing the borefield (i.e. calculating the required depth) for a given injection and extraction load for the borefield (two sizing methods are available).	main_functionalities.py
Calculating the temperature evolution of the ground for a given building load and borefield configuration	main_functionalities.py
Using dynamically calculated borehole thermal resistance (this is directly based on the code of pygfunction)	sizing_with_Rb_calculation.py
Optimising the load profile for a given heating and cooling load	optimise_load_profile.py
Finding the optimal rectangular borefield configuration for a given heating and cooling load	size_borefield_by_length_and_width.py
Importing heating and cooling loads from .csv and .xlsx files	import_data.py
Using your custom borefield configuration	custom_borefield_configuration.py

Comparisons	Example document
Comparison in calculation time and accuracy between the simplified L2 sizing methodology and the more accurate L3 method.	sizing_method_comparison.py
Comparison in calculation time and accuracy between using the precalculated gfunction data or not.	speed_comparison.py

Precalculated data

This tool comes with precalculated g-functions for all borefields of type nxm (for 0<n,m<21) for which the boreholes are connected in parallel. For these borefield configurations, the g-functions are calculated for different depth-thermal conductivity-spacing combinations. The ranges are:

• Depth: 25 - 350m in increments of 25m
• Thermal conductivity of the soil: 1 - 4 in increments of 0.5W/mk
• Spacings (equal): 3 - 9m in increments of 1m

Here a burial depth (D) of 4.0m is assumed even as a borehole radius of 7.5cm for all the precalculated data.

It is possible to calculate your own dataset to your specific project based on the pygfunction tool and use this one in the code.

License

GHEtool is licensed under the terms of the 3-clause BSD-license. See GHEtool license.

Contributing to GHEtool

You can report bugs and propose enhancements on the issue tracker. If you want to add new features and contribute to the code, please contact Wouter Peere ([e-mail]).

Main contributors

Wouter Peere, KU Leuven & boydens engineering (part of Sweco), [e-mail]

Tobias Blanke, Solar-Institute Jülich, FH Aachen, [e-mail]

References

Development of GHEtool

Peere, W., Picard, D., Cupeiro Figueroa, I., Boydens, W., and Helsen, L. Validated combined first and last year borefield sizing methodology. In Proceedings of International Building Simulation Conference 2021 (2021). Brugge (Belgium), 1-3 September 2021.

Applications of GHEtool

Coninx M., De Nies J. (2022) Cost-efficient Cooling of Buildings by means of Borefields with Active and Passive Cooling. Master thesis, Departement of Mechanical Engineering, KU Leuven, Belgium.

Michiels E., (2022) Dimensionering van meerdere gekoppelde boorvelden op basis van het type vraagprofiel en de verbinding met de gebruikers. Master thesis, Departement of Mechanical Engineering, KU Leuven, Belgium.

Vanpoucke B. (2022) Optimale dimensionering van boorvelden door een variabel massadebiet. Master thesis, Departement of Mechanical Engineering, KU Leuven, Belgium.

Haesen R., Hermans L. (2021) Design and Assessment of Low-carbon Residential District Concepts with(Collective) Seasonal Thermal Energy Storage. Master thesis, Departement of Mechanical Engineering, KU Leuven, Belgium.