A fork of cpgfunction that has been tailored for NREL's EnergyPlus.
An open source low level (C++) implementation of Massimo Cimmino's g-function methodology. The g-function calculation has to do with the distribution of heat in a ground heat exchanger (GHE). The g-function, after computed, can be used to simulate a ground source heat pump to determine the heat pump exiting fluid temperatures after a period of time. It is of paramount importance to accurately predict the thermal response of the borefield. An improper prediction of the ground response could result in a system too large (waste of money) or a system too small (resulting in failure). The g-function is currently the only known methodology to accurately predict the thermal response of the ground.
Computing the g-function is a computationally demanding procedure. Historically, g-functions are pre-computed and stored in libraries (databases) which can be accessed in GHE design tools. This is done so that the ground source heat pump can be sized within a few seconds, rather than waiting anywhere from minutes to hours for a g-function to be computed. This code base was implemented to help solve a major limitation (problem) associated with computing large sets of g-functions for borefields containing anywhere from 1 to 1024 boreholes. Massimo Cimmino's open source implementation of the g-function calculation in Python (pygfunction) has a limitation; at times the memory consumption is inordinate. This library was implemented so that computing g-functions would require significantly less memory to increase throughput on high performance clusters which contain many "low memory" nodes, and only a few "high memory" nodes.
The g-function is greatly dependent on the boundary condition used. The following is a checklist of boundary conditions contained in this library:
- Uniform heat flux (UHF)
- Uniform borehole wall temperature (UBHWT)
- Uniform inlet fluid temperature (UIFT)
Create a build with cmake:
cd /path/to/repo
mkdir build
cd build
ccmake .. # set settings as needed, shouldn't be any of interest, configure then generate
On a Visual Studio generator this will create a solution you can launch into Visual Studio.
On makefile style generators, this will create a makefile. From the build directory, just make the project:
make -j 4 # number of processors to use to build
Then you can run the test:
ctest
On my platform this resulted in:
Test project /home/edwin/Projects/cpgfunction/cmake-build-debug
Start 1: RunTest1
1/1 Test #1: RunTest1 ......................... Passed 0.79 sec
This ran what used to just be the main.cpp built file.
The original g-function theory appeared in a Per Eskilon's PhD thesis, his advisor who helped develop that theory was Prof. Johan Claesson of Lund University in Sweden. Massimo Cimmino, Assistant Professor at Polytechnique Montreal an Canada, has built on the work of Eskilson, Claesson and others. Cimmino has developed a methodology for g-function calculations, written programs to compute the g-function and then made the program open source. The openness of Cimmino's g-function calculation is monumental.
The initial development of this library was funded by Oklahoma State University by the OG&E Energy Technology Chair. The Oklahoma State University Center for Integrated Building Systems provided further funding for integration into EnergyPlus.