Effective energy storage technologies represent one of the key elements to solving the growing challenges of electrical energy supply of the 21st century. Several energy storage systems are available, from ones that are technologically mature to others still at a research stage. Each technology has its inherent limitations that make its use economically or practically feasible only for specific applications. The present paper aims at integrating hydrogen generation into compressed air energy storage systems to avoid natural gas combustion or thermal energy storage. A proper design of such a hybrid storage system could provide high roundtrip efficiencies together with enhanced flexibility thanks to the possibility of providing additional energy outputs (heat, cooling, and hydrogen as a fuel), in a distributed energy storage framework. Such a system could be directly connected to the power grid at the distribution level to reduce power and energy intermittence problems related to renewable energy generation. Similarly, it could be located close to the user (e.g., office buildings, commercial centers, industrial plants, hospitals, etc.). Finally, it could be integrated in decentralized energy generation systems to reduce the peak electricity demand charges and energy costs, to increase power generation efficiency, to enhance the security of electrical energy supply, and to facilitate the market penetration of small renewable energy systems. Different configurations have been investigated (simple hybrid storage system, regenerate system, multistage system) demonstrating the compressed air and hydrogen storage systems effectiveness in improving energy source flexibility and efficiency, and possibly in reducing the costs of energy supply. Round-trip efficiency up to 65% can be easily reached. The analysis is conducted through a mixed theoretical-numerical approach, which allows the definition of the most relevant physical parameters affecting the system performance.

In the present study, the results of the numerical implementation of a mathematical model of a planar anode-supported SOFC are reported. In particular, model results are validated and discussed when the fuel is a mixture of hydrogen and carbon monoxide, focusing on the importance of simulating direct oxidation of carbon monoxide. The mathematical model is solved in a 3D environment and the key issue is the validation comparing with experimental data, which is made in different operating conditions to establish the reliability of the presented model. The results show the importance of simulating direct oxidation of carbon monoxide and its effect on the fuel cell performance.

The application of high temperature fuel cells in stationary power generation seems to be one of the possible solutions to the problem related to the environment preservation and to the growing interest for distributed electric power generation. Great expectations have been placed on both simple and hybrid fuel cell plants, thus making necessary the evolution of analysis strategies to evaluate thermodynamic performance, design improvements, and acceleration of new developments. This paper investigates the thermodynamic potential of combining traditional internal combustion energy systems (i.e., gas turbine and internal combustion engine) with a molten carbonate fuel cell for medium- and low-scale electrical power productions with low $CO2$ emissions. The coupling is performed by placing the fuel cell at the exhaust of the thermal engine. As in molten carbonate fuel cells the oxygen-charge carrier in the electrolyte is the carbonate ion, part of the $CO2$ in the gas turbine flue gas is moved to the anode and then separated by steam condensation. Plant performance is evaluated in function of different parameters to identify optimal solutions. The results show that the proposed power system can be conveniently used as a source of power generation.