INNOVATIVE APPLICATIONS OF EXERGY ANALYSIS AND THERMOECONOMICS IN CHEMICAL, THERMAL AND COOLING ENERGY CONVERSION SYSTEMS

Since 70s, the world has been becoming more and more concerned about energy and environmental issues. The need of meeting the current energy demand by guaranteeing the ability of future generation to satisfy theirs have been pushing research not only to exploit alternative energy sources such as renewable energies, but also to improve the efficiency of energy conversion systems. To this regard, developing systems that use efficiently energy is of paramount importance especially in those countries which rely on non-renewable energy sources such as oil, natural gas, and coal. In fact, the reduction of energy consumption will lead not only to the saving of unrestorable and limited energy resources but also to some environmental benefits, such as the reduction of carbon dioxide emissions. To this am, a lot of methods have been developed across scientific research. Among them, Exergy Analysis and Thermoeconomics are well-recognized for supporting the analysis and design of any energy conversion system. This thesis deals with innovative applications of Exergy Analysis and Thermoeconomics in chemical, thermal and cooling energy conversion systems. It aimed at demonstrating the capabilities of both methods to provide insights into design alternatives and operation strategies of energy conversion systems. Exergy Analysis of Reverse ElectroDialsysis process is carried out. This innovative energy system converts salinity gradient into electricity, by interposing selective membranes between two solutions at different concentrations. The analysis aims at providing insights into the effects on the exergy performance of the current membrane properties and of some design and operating parameters. Results will be useful for the future development of this system. A further exergy analysis is focused on the integration of Reverse Electrodialysis process with Multi-effect Distillation Unit. This innovative system allows for the conversion of low-grade heat into electricity. Efforts are still needed to improve the energy performance of this system and to this aim, exergy analysis allows for evaluating the effect of some design and operating parameters. Thermoeconomic Cost Accounting is applied to Multi-Effect Desalination (MED) process, of which energy consumption highly affect the operating costs. In order to gain insights into the cost formation process of the produced freshwater, a thermoeconomic analysis of this system is carried out by adopting a high disaggregation level. The analysis allows for understanding at which extent the irreversibility occurring at each subprocess affects the cost of freshwater. Then, the same system is supposed to be operated in a cogenerative asset realized by coupling it with a steam power plant. In this case, Thermoeconomics provides a method for apportioning cost on electricity and freshwater produced. Another innovative method investigated in this thesis is the Thermoeconomic Diagnosis of energy systems. This Fault Detection and Diagnosis Technique has been extensively applied to thermal power plants, but only recently it has been extended to Heating, Ventilation and Air Conditioning Systems (HVAC). With this respect, most of results achieved so far have been based on a set of virtual-experiments thus not allowing to account for real operation of these system. For the first time, the method is tested using experimental data obtained from a packaged rooftop air conditioning unit. Last but not least, the applications of exergy-based methods to environmental analyses is considered. To this regard, an innovative approach based on integration of Thermoeconomics and Life Cycle Assessment (LCA) is here proposed. The procedure combines the capabilities of these two techniques to account simultaneously for aspects related to thermodynamics of energy conversion processes and to the overall impacts along the plant life cycle, i.e. from raw material extraction to the disposal of facilities. The capabilities of this approach are illustrated by applying it to a water-cooled vapor compression chiller.