Retrofitting of Industrial Utility Systems Considering Solar Thermal and Periodic Heat Storage

Abstract

This paper involves the development of a model that is based on mathematical programming for integrating solar thermal and heat storage with multi-period heat exchanger network (HEN) of industrial operations. The method employed entails discretising the availability of solar thermal on the basis of hourly, daily and monthly time periods using real-life climatic data for hourly solar irradiation and ambient temperature variations. Considering variability in the supply profile, a flowsheet superstructure of closed circuits including direct and indirect solar thermal utilization with periodic heat storage is first developed. Thereafter, the flowsheet is systematically connected with the modified stage-wise superstructure model formulation which allows utility selection at each stage of the HEN. The problem is formulated and solved in GAMS using Slovenia climatic data as a case study, while the objective function maximizes the solar heat output to the heat network. In average 25.9 % (139.6 kW) of hot utilities is saved due to solar thermal. The hourly profile of various climatic features considered within the model will enable more realistic solar heat forecasting for utility retrofit in existing designs and also for new designs.