LAUSR

Abstract In view of system efficiency and environmental protection, it is important to harvest solar energy better e.g. by improving solar heating systems. A theoretically founded tool for it is mathematical modelling with the use of system transfer functions. Knowing the transfer functions, the outlet temperature of the system can be determined as a function of the system inputs (solar irradiance, inlet and environment temperatures), the dynamic analysis of the system can be carried out, furthermore, stable feedback control can be designed effectively based on the mathematical methods of control engineering. The designed control can be used e.g. to provide just the minimal required outlet temperature for the consumer and, therefore, to maximize the produced heat with minimal or without any auxiliary heating cost. Although, pipes can affect the operation of solar heating systems considerably, this effect has not been built in the transfer functions of such systems worked out already in the literature. In this study, new transfer functions for solar heating systems with pipes are proposed based on a validated mathematical model. Transfer function based control design is also given generally. As particular applications, the dynamic analysis and the design of a stable P control are presented on a real solar heating system. It is also presented quantitatively that the designed P control is faster and more precise than the most conventional on/off control. Furthermore, the presented methods can be easily adapted for any solar heating system with long pipes equipped with an external heat exchanger.