Bachelor's thesis Claudius Bons


Development and exergetic evaluation of controlling strategies for solar thermal systems using Software-In-The-Loop methodology

Bachelor's thesis Bons Copyright: EBC Solar thermal system with absorption chiller

This thesis describes the development of a virtual test stand for the evaluation of control strategies of the solar controller ITE 5020 by Schüco International KG using Software-In-The-Loop methodology. The company’s in-house test bench for solar cooling (absorption chiller) of training rooms is the basis of the modeled hydraulic system of the virtual test bench. It is also used for testing the controller and for the validation of the simulation results. Within the analysis of the usage of two solar collection fields for the shared, solar thermal supply of multi-storage systems, the basics of solar cycle control and the investigated control strategies of the maximum yield and high-temperature control are explained. Furthermore, the control concept includes an internal evaluation function that interrupts the active solar operational mode, in order to evaluate the technical capacity of the collection fields for a potentially more efficient operation.

The simulation models of the solar thermal components and the weather model of the virtual test stand are explained physically and methodologically. Moreover, the interface between the simulation computer and the solar controller for the implementation of the Software-In-The-Loop is described. The components of the simulation are firstly validated qualitatively, individually with field test data of the manufacturers and records of the field test site. Next, the model of the entire field test site is validated.

The parameters of the four simulated days are presented and compared. The test preparations of the solar controller as well as the simulation platform Dymola, in particular the real-time synchronization are described.

The quantity and quality of the solar yield and its importance for the solar thermal control are analyzed in the investigation of the results of the eight simulated days. The generated cooling of a simulated day and the electricity consumption for the operation of the entire site (pumps and absorption chiller) are used for the computation of the coefficient of performance (COP). The high temperature control achieves higher values for the COP than the maximum yield control. Also, the high temperature control is more efficient when considering the remaining exergy of the storage for next day usage.