Design and experimental validation of a hydrogen based sustainable multi energy system

Technological advances in energy production rise together with advances in urbanization and social development, underlying an increase in global energy demand in its different forms. In the last centuries, the exploitation of fossil fuels and the development of a centralized energy system mainly based on large-scale plants were used to enhance social and economic growth. Nowadays, modern society is facing several challenges related to anthropogenic changes in the earth environment, such as climate change, natural resources depletion, and urban environmental pollution. In this context, innovative concepts of distributed energy systems, such as Multi Energy Systems, have been developed in recent years to enhance the energy transition. Despite the advantages of introducing distributed energy systems, the achievement of the best performance in terms of cost and emission is challenging due to the interaction between different energy networks. In fact, decision-makers must face several problems to achieve a desirable target, ranging from finding a methodology for equipment sizing to developing an effective Energy Management System. Technical solutions that minimize costs or emissions of the energy system are usually preferred among the different targets employed. Several numerical models, algorithms, and computational tools have been developed in recent years to perform such analysis. The development of tools and methods must demonstrate their reliability and effectiveness to be employed in different energy sectors and applied for various power scales. Moreover, experimental verification is necessary to assess the reliability and applicability of such tools. Therefore, the motivation of this research is the development of an optimal methodology for planning and operating hydrogen-based Multi Energy Systems, that includes their modeling, sizing, energy dispatch, and experimental verifications. This concept is then applied to several case studies ranging from off-grid micro-scale applications to residential and office buildings, to assess the effectiveness of such systems for different end-users and power scales. Despite all the technologies included in the portfolio of the energy system, the focus of this study lies on hydrogen technologies. Mathematical programming techniques are used to model and optimize the Multi Energy System, including its energy scheduling and the sizing of the equipment. Experimental activities are then carried out to develop a Digital Twin framework to demonstrate the reliability of hydrogen-based systems and to perform real-time optimization of the devices most sensitive to degradation. A multi-objective parametric design method is developed to study the influence of meteorological conditions on the design of hybrid systems located in different climate zones. The availability of renewable sources showed to be one of the main drivers in multi-objective design processes while hydrogen fuel cells represented a source of reliability for off-grid systems. The performance of Rule-Based Control logics is then compared with optimization techniques, such as linear optimization and Model Predictive Control, for a residential case study. Moreover, further energy networks are included as outputs of the Multi-Energy System. Results showed that the predictive strategies can exploit the additional flexibility of Thermal Storage technologies and achieve better performance in terms of cost and lifetime of components. Moreover, 3 experimental verifications of the residential case study are carried out to assess the suitability of the Energy Management System and the reliability of the energy system for a real case study. Therefore, a Digital Twin modeling framework is developed to perform further analysis on the real operation of the components, such as fuel cells and batteries. A Health Management System is included, as low-level controller, to avoid operations that lead to rapid degradation of such technologies and perform real-time corrections. The system showed promising results in terms of reliability while the Digital Twin showed useful diagnostic tools features, since the degradation related to fuel cell start-up operation is limited by the Health Management System. Finally, after having analyzed the influence that different Energy Management Strategies and sizing methodologies have on the system performance and design, a comprehensive approach that can manage both energy scheduling and design optimization is presented. Therefore, a leader-follower optimization approach is applied to a real case office building considering a general layout of the Multi Energy System including electricity, heat, cooling, and gas networks. Results showed that hydrogen represents the key energy vector enabling deep decarbonization, but still requiring research and development activities, and that the multi-energy concept allows to decrease the overall cost of the system while achieving environmental benefits, when the number of connection nodes between different energy networks increases.