Simulation of Thermal Building Behaviour in Modelica

1. Abstract During the past decades heating and air conditioning systems were usually designed and consequently oversized according to simplified, mostly static cal- culating procedures. The increase in primary energy costs, rising cost pressure felt by private and public clients as well as increased demands on comfort forced engineers to change the customary procedure. Thus the dynamic simulation of building and system behaviour plays an increasingly important role in planning and dimensioning heating and air condi- tioning systems. This change is supported by the growing performance of personal computers in use. This means that calculating methods which used to be too expensive and time-consuming became practica- ble and could even be improved. Building and system simulation aims at emulating the thermal and energetic behaviour of an existing or a fictitious building and of its HVAC system as well as their interaction. For this purpose the external influ- ences through the outdoor climate, user behaviour and internal loads are to be taken into account. The comprehensive building design requires the adequate description of real processes within a broad spectrum of mathematical, physical and engineering disci- plines. The model of just an uncomplicated heating system includes various components from thermody- namics, fluid dynamics, mechanics, electrical and control engineering.