Modelica Library for Building Energy and Control Systems

The Modelica Buildings library is a free open-source library with dynamic simulation models for building energy and control systems. The library contains models for

• air-based HVAC systems,
• water-based heating systems,
• controls,
• heat transfer among rooms and the outside, and
• multizone airflow, including natural ventilation and contaminant transport.

The primary use of the library is for flexible and fast modeling of building energy and control systems to accelerate innovation leading to cost-effective very low energy systems for new and existing buildings. The library is particularly suited for

• rapid prototyping of new building systems,
• analysis of the operation of existing building systems,
• development, specification, verification and deployment of building controls within a model-based design process, and
• reuse of models during operation for functional testing, for verification of control sequences, for energy-minimizing controls, fault detection and diagnostics.

All development is open-source and we welcome contributions.

The models in this library are implemented in the Modelica language, which separates the concerns between modeling (i.e., defining the model equations) and simulation (i.e., computing a numerical solution to the equations). Such a separation allows a

• high degree of model reuse,
• graphical "plug and play" modeling since modular models can be connected in an arbitrary way,
• the integration of models from different domains (controls, thermodynamics, heat and mass transfer, fluid flow, electrical systems, etc.),
• the coupling of models with fast dynamics in the order of seconds (local loop control) and slow dynamics (energy storage),
• the coupling of models whose evolution is described by continuous time equations (for the physics and local loop control), discrete time equations (for supervisory control), state events (for control that switches when a threshold is reached), and finite state machines (for control that transitions between different modes of operations),
• the exchange of models with other simulation platforms,
• the use of state-of-the art numerical solvers.

By using the Building Controls Virtual Test Bed, the models in this library can also be coupled to other simulation programs such as EnergyPlus, Radiance and MATLAB/Simulink, as well as to building control systems using a BACnet or analog/digital interface.

How to contribute

At this stage, contributions are particularly needed for

• expanding the model library (see the download page for the current state),

• validating existing models,
• expanding the documentation, and
• improving the numerical robustness of large system models.

The development site is https://github.com/lbl-srg/modelica-buildings. If you would like to contribute, please send email to Michael Wetter.

License

The models are available under the following open-source license.

Contact

For help, send email at https://groups.google.com/group/modelica-buildings. This is an open group and everyone can join it. No invitation is needed.

Michael Wetter
Lawrence Berkeley National Laboratory
Simulation Research Group
MWetter@lbl.gov