Solving differential equations in TRNSYS without programming

In building simulation tools differential equations are widely used to model physical phenomena of components such as walls, air and any kind of system component in the building. Especially when simulation is used to study and optimise system control, the models used are mainly transient models solving differential equations in order to represent correctly the transient behaviour of the whole control loop. The TRNSYS simulation environment is a powerful tool allowing the simulation of a large number of problems. However, developing and/or implementing new models (called ‘Types’ in TRNSYS terminology) can be an obstacle for those users who use TRNSYS as a simulation environment and not a modelling and simulation environment. In most simulation studies, there is a need for simple models considering phenomena that are specifically important for the actual problem. Simple steady state models on the one hand can easily be implemented by the TRNSYS equation type or by calling external programs such as Excel etc. Dynamic models on the other hand can only be implemented by writing new types in a programming language such as C, C++, Fortran, Visual Basic, etc., or by coupling to other environments. In order to overcome this barrier, a new type has been developed allowing implementing and calculating, without any programming, a dynamic model. With this model, it shall be possible to define simple dynamic models such as sensors, drives, furniture, specific walls, etc.