Combined exergy and pinch analysis for the optimal integration of energy conversion technologies

Exergy concept combined with pinch based approach are used for studying the optimal integration of energy conversion systems. The analysis first considers the representation of the hot and cold composite curves of the process and defines the energy and the exergy requirements. The basic assumption of the DTmin required for the pinch analysis is represented as a distinct exergy loss that increases the exergy requirement of the process. The exergy composite curves put the focus on the opportunities for heat pumping in the process. The optimal integration of the utility system is then realised by extracting the energy conversion system configuration from a superstructure using a Mixed Integer Linear Programming formulation. In the latter, the heat cascade definition and the combined heat and power production balances are introduced as constraints and the exergy losses minimisation is used as an objective function. The resulting balanced exergy composite curves are used to visualise the exergy losses in the heat exchanges of both process and utilities. The analysis of the results is made using a definition of the exergy efficiency that accounts for the pinch point location, the process exergy and the exported energy services.