Within the scope of IEA-SHC Task 26 and 32 a TRNSYS model of a solar thermal system for hot water preparation and space heating support was developed [2,3]. The model was implemented in the traditional way as a simple ASCII input file. To check whether the new approach obtains same results, this model has been rebuilt in SIMULATION STUDIO according to the subsystem method described in section 2. Therefore, the system shown in Fig. 6 is divided into the following subsystems, corresponding to the hydraulic loops:

• Collector loop

• Auxiliary heating loop

• Space heating loop

• Domestic hot water loop

• Weather processing

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Building representation

The store as a main element of the model is connected to the subsystems as a “stand-alone” component.

The main difference of the subsystem based model in SIMULATION STUDIO to the manually as text file implemented reference system is the use of a lot of extra equations. This is caused by the above described way of implementing interfaces in order to connect the subsystems to each other. Furthermore, the possibility to optimize the component order automatically in SIMULATION STUDIO is used (see Fig. 7), which leads to another difference to the reference system.