Simulations using dimensionless key figures for the design and optimization of compact, hybrid MGT-SOFC systems of the “Turbo Fuel Cell” type for high efficiency

Authors

Heinz Peter Berg - BTU Cottbus-SenftenbergChair of Combustion Engines and Flight PropulsionSiemens-Halske-Ring 14D-03046 Cottbus Germany
Roland Dückershoff - Technische Hochschule MittelhessenFachbereich Maschinenbau, Mechatronik und MaterialtechnologieWilhelm-Leuschner-Straße 13 D-61169 Friedberg
Axel Himmelberg - BTU Cottbus-Senftenberg Chair of Combustion Engines and Flight PropulsionSiemens-Halske-Ring 14D-03046 Cottbus Germany
Marko Kleissl - BTU Cottbus-Senftenberg Chair of Combustion Engines and Flight PropulsionSiemens-Halske-Ring 14D-03046 Cottbus Germany
Uwe Ring - BTU Cottbus-Senftenberg Chair of Combustion Engines and Flight PropulsionSiemens-Halske-Ring 14D-03046 Cottbus Germany

Abstract

The "Turbo Fuel Cell" represents a highly integrated and highly compact technology system of a micro gas turbine fuel cell cycle (MGT-SOFC). It provides the solution for a highly efficient reverse electricity generation with an electrical efficiency of at least 68% (status 2020-21) to approx. 75-80% (in the future). In the context of industrial research on such a hybrid process, adapted, dimensionless parameters should be used in the design and optimization of the overall system. As an example, simulations of thermally optimized solutions to improve the energy yield using various dimensionless key figures are presented. Above all, heat integration measures enable an increase in system efficiency and a reduction in primary energy input. On the basis of exergetic analyzes by use of a modified Heat Balance Factor Y, as presented at ETC12, and the consideration of the SOFC enthalpy spread j, as well as a highly integrative use of the High Temperature Heat Exchanger Function F, it is shown how the hybrid cycle process efficiency can be optimized through innovative coupling of the individual heat flows. Measures to change the hybrid process can be used to deliberately shift the useful energy from the predominant heat yield in order to optimize electrical efficiency. A developed system enables primary energy to be used with the highest possible efficiency. The primary fuel used here is gaseous primary energy in the form of methane (natural gas) and hydrogen from renewable sources. Treatment mechanisms, such as the reforming of the methane used, and the targeted use of modern heat insulation and recovery mechanisms also have been considered. For the optimized hybrid system, total electrical efficiencies of more than 68% could be demonstrated and additional thermal energy for heating purposes could be extracted. Ultimately, overall efficiencies for the utilization of the energy content of the primary energy of up to 97% can be achieved. Energy converters with a maximum system output of around 200-300kW were examined. In the near future, such plants can replace existing fossil power plants being part of decentralized network systems. By their flexibility, they can guarantee the necessary security of power supply.