Thierry Stephane Nouidui

Modelica Buildings Library

This article describes the Buildings library, a free open-source library that is implemented in Modelica, an equation-based object-oriented modelling language. The library supports rapid prototyping, as well as design and operation of building energy and control systems. First, we describe the scope of the library, which covers heating, ventilation and air-conditioning systems, multi-zone heat transfer and multi-zone airflow and contaminant transport. Next, we describe differentiability requirements and address how we implemented them. We describe the class hierarchy that allows implementing component models by extending partial implementations of base models of heat and mass exchangers, and by instantiating basic models for conservation equations and flow resistances. We also describe associated tools for pre- and post-processing, regression tests, co-simulation and real-time data exchange with building automation systems. The article closes with an example of a chilled water plant, with and without water-side economizer, in which we analysed the system-level efficiency for different control setpoints.

Functional mock-up unit for co-simulation import in EnergyPlus

This article describes the development and implementation of the functional mock-up unit (FMU) for co-simulation import interface in EnergyPlus. This new capability allows EnergyPlus to conduct co-simulation with various simulation programs that are packaged as FMUs. For example, one can model an innovative Heating, Ventilation, and Air Conditioning (HVAC) system and its controls in Modelica, export the HVAC system and the control algorithm as an FMU, and link it to a model of the building envelope in EnergyPlus for run-time data exchange. The formal of FMUs is specified in the functional mock-up interface (FMI) standard, an open standard designed to enable links between disparate simulation programs. An FMU may contain models, model description, source code, and executable programs for multiple platforms. A master simulator – in this case, EnergyPlus – imports and simulates the FMUs, controlling simulation time and coordinating the exchange of data between the different FMUs. This article describes the mathematical basis of the FMI standard, discusses its application to EnergyPlus, and describes the architecture of the EnergyPlus implementation. It then presents a typical workflow, including pre-processing and co-simulation. The article concludes by presenting two use cases in which models of a ventilation system and a shading controller are imported in EnergyPlus as an FMU.

Modeling of Heat Transfer in Rooms in the Modelica "Buildings" Library

This paper describes the implementation of the room heat transfer model in the free open-source Modelica “Buildings” library. The model can be used as a single room or to compose a multizone building model. We discuss how the model is decomposed into submodels for the individual heat transfer phenomena. We also discuss the main physical assumptions. The room model can be parameterized to use di↵erent modeling assumptions, leading to linear or non-linear di↵erential algebraic systems of equations. We present numerical experiments that show how these assumptions a↵ect computing time and accuracy for selected cases of the ANSI/ASHRAE Standard 1402007 envelop validation tests.

Cyber–Physical Modeling of Distributed Resources for Distribution System Operations

Cosimulation platforms are necessary to study the interactions of complex systems integrated in future smart grids. The Virtual Grid Integration Laboratory (VirGIL) is a modular cosimulation platform designed to study interactions between demand-response (DR) strategies, building comfort, communication networks, and power system operation. This paper presents the coupling of power systems, buildings, communications, and control under a master algorithm. There are two objectives: first, to use a modular architecture for VirGIL, based on the functional mockup interface (FMI), where several different modules can be added, exchanged, and tested; and second, to use a commercial power system simulation platform, familiar to power system operators, such as DIgSILENT PowerFactory. This will help reduce the barriers to the industry for adopting such platforms, investigate and subsequently deploy DR strategies in their daily operation. VirGIL further introduces the integration of the quantized state system (QSS) methods for simulation in this cosimulation platform. Results on how these systems interact using a real network and consumption data are also presented.

BacNet and Analog/Digital Interfaces of the Building Controls Virtual Testbed

This paper gives an overview of recent developments in the Building Controls Virtual Test Bed (BCVTB), a framework for co-simulation and hardware-in-the- loop. First, a general overview of the BCVTB is presented. Second, we describe the BACnet interface, a link which has been implemented to couple BACnet devices to the BCVTB. We present a case study where the interface was used to couple a whole building simulation program to a building control system to assess in real-time the performance of a real building. Third, we present the ADInterfaceMCC, an analog/digital interface that allows a USB-based analog/digital converter to be linked to the BCVTB. In a case study, we show how the link was used to couple the analog/digital converter to a building simulation model for local loop control.

CyPhySim: a cyber-physical systems simulator

This demo provides a preview of a pre-release version of CyPhySim, an open-source simulator for cyber-physical systems. This simulator supports discrete-event models, quantized-state simulation of continuous dynamics, the Functional Mockup Interface (FMI), classical (Runge-Kutta) simulation of continuous dynamics, modal models (hybrid systems), discrete-time (periodic) systems, and algebraic loop solvers. CyPhySim provides a graphical editor, an XML file syntax for models, and an open API for programmatic construction of models.

Novel simulation concepts for buildings and community energy systems based on the Functional Mock-up Interface specification

Research and development in the fields of building technologies and community energy systems have caused in recent years a transition away from stand-alone components towards dynamically interacting systems. However, the precise modeling and simulation of such complex cyber-physical systems proves challenging for the established simulation tools. This paper illustrates the applicability of co-simulation and model exchange concepts based on the Functional Mock-up Interface (FMI) specification for the simulation of buildings and community energy systems by comparing several state-of-the-art approaches. The presented applications thereby demonstrate the suitability and relevance of such modular and flexible simulation concepts for these fields. At the same time the importance of a common simulation interface is emphasized, which allows the reuse of individual components for a diverse range of applications.