12. Generating a Modelica Model from Semantic Model

In this section, we will specify how to generate a Modelica model from a semantic model of a building or a Heating, Ventilation and Air Conditioing (HVAC) system. This Modelica model then serves as the format from which control sequences (CDL and CXF), point lists, etc. can be exported.

Building semantic models provide information about the equipment topology and how they are connected. Semantic models enable assigning machine-readable metadata to control points and enable the development of portable analytics and control applications.

12.1. Workflow

The current workflow for generating a Modelica model (along with the control sequences) leverages the Templates package of in the Modelica Buildings Library (https://simulationresearch.lbl.gov/modelica/releases/v11.0.0/help/Buildings_Templates.html). As of Buildings version 11, there are three system templates - one for an Air Handling Unit (AHU), one for a Variable Air Volume (VAV) terminal and one for an air source heat pump plant. As the templates are used to generate the Modelica models, only these types of systems are covered. The process is described in Fig. 12.1

Fig. 12.1 Flowchart describing the workflow of generating a Modelica file from a semantic model of a HVAC system.

The software that implements this workflow is available at https://github.com/lbl-srg/obc/tree/master/software/s223ToMo.

12.2. Example

From a ASHRAE Standard 223P semantic model that describes two VAV boxes, Fig. 12.2 describes the workflow to query the necessary sensors and instantiate the corresponding Modelica models using the VAVBox template from the Modelica Buildings Library.

Fig. 12.2 Flowchart describing the workflow of generating a Modelica model of two VAVBoxes described using the proposed ASHRAE Standard 223P.