Assessment of a fuel cell based-hybrid energy system to generate and store electrical energy

Abstract

Solid oxide fuel cells (SOFC) have significant applications and performance, and their integration into coupled and cascading energy systems can improve the overall performance of the process. Furthermore, due to the constant time performance of the fuel cell, the problem of fuel starvation may arise by changing the amount of load, which can adversely affect the overall performance of the process. In the present study, the excess heat of the SOFC is converted into electrical energy in two stages using different heat generators. The coupled energy system in the present article has a new configuration in which the relationship of its components is different from the systems reported in the literature. Furthermore, since the use of an energy storage system can improve the overall reliability, the energy produced by the coupled energy cycle is stored by a storage technology for peak consumption times. The introduced system can generate approximately 580 W of electrical power with an efficiency of 80%. The highest and lowest share in power generation is related to fuel cell with 82% and thermoelectric generator with 5%. The rest of the system power (i.e. 13%) is produced by thermionic generator. In addition, the system requires 0.025 kg per hour of hydrogen fuel. It was also found that to operate the system for 5 h a day requires a storage system with a size of 3.3 m3. Moreover, two key issues to enhance the storage system performance are: adjusting the initial pressure of the system to values close to the peak (optimal) value, and using turbines and/or pumps with higher efficiencies. With the aim of supplying 5 kWh of electrical energy, five different scenarios based on the design of various effective parameters have been presented.