Development of Model Components for Thermal Simulation of Buildings by Means of Bond Graphs

Introduction

However, all these programs have in common that they are closed software systems that can only be used for the purpose, for which they had originally been designed.

For this reason, we decided to construct a new program on the basis of bond graph technology that should support all of the features of the older programs, that should be as easy to use as the earlier programs, that however should be considerably more flexible, as its users should be able to exchange models at will and/or supplement new ones. In addition, the new program should be much more easily understandable in comparison with its predecessors, because all of the model equations are openly available in the models in source code.

To this end, a modular thermal building model for Dymola/Modelica was created, making use of the bond graph library.

Historical Development

• In 1989, Spyros Andreou developed in his MS Thesis a first version of a building model. It was the model of an experimental house with active solar heating that had been built in Aachen, Germany in the last seventies. An earlier model of this building had been developed at ETH Zürich as part of a disploma project in the early eighties. In contrast to Andreou, the previous student had not employed bond graphs for the modeling. It indeed turned out that his model had been badly flawed, as the energy conservation laws were violated at the interfaces between the modules.

• The model by Spyros Andreou was presented in the appendix to chapter 8 of the book Continuous System Modeling (). Also this model turned out to be still faulty, because a correct modeling of the water loops would have required to consider the mass flow as well, not only the entropy flow, i.e., the water loops should have been modeled as convective flows, a methodology that hadn't been developed yet in those days. A corrected version of the model of the water loops can be found in Powerpoint presentation #22 () of my lectures concerning the mathematical modeling of physical systems.

• In 1992, Markus Weiner developed a model of another experimental building in his MS Thesis. His was a model of a building with a passive solar heating that had been constructed in Tucson in the early eighties. He himself identified the model parameters from measurements that he took, and he developed in parallel models coded in Dymola, in Calpas3, and in DOE-2. He compared the models and simulation results in his thesis. Passive solar heating systems are a bit simpler to model, as they do not require any convective flows to be considered. Markus Weiner's student exchange visit with the University of Arizona had been financed by the Deutscher akademischer Austauschdienst (DAAD).

• In 2001, I ported Weiner's model over from its original non-graphical version of Dymola to Dymola/Modelica Version 4 employing a graphical user interface.

• In 2005, an improved and fully documented version of the model was included with the bond graph library as a standard sample program.

Most Important Publications

1. Andreou, S. (1990), Simulation of a Solar Heated House Using the Bond Graph Modeling Approach and the Dymola Modeling Software, MS Thesis, Dept. of Electr. & Comp. Engr., University of Arizona, Tucson, AZ.

2. Cellier, F.E. (1991), Continuous System Modeling, Springer-Verlag, New York.

3. Weiner, M. (1992), Bond Graph Model of a Passive Solar Heating System, MS Thesis, Dept. of Electr. & Comp. Engr., University of Arizona, Tucson, AZ.

4. Weiner, M., and F.E. Cellier (1993), Modeling and Simulation of a Solar Energy System by Use of Bond Graphs, Proc. 1^st SCS Intl. Conf. on Bond Graph Modeling and Simulation, San Diego, CA, pp.301-306.

5. Cellier, F.E. and R.T. McBride (2003), Object-oriented Modeling of Complex Physical Systems Using the Dymola Bond-graph Library, Proc. ICBGM’03, 6^th SCS Intl. Conf. on Bond Graph Modeling and Simulation, Orlando, Florida, pp. 157-162.

Sponsors

• Deutscher Akademischer Austauschdienst (DAAD)

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