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Front. Energy Res. | doi: 10.3389/fenrg.2018.00139

A cogeneration system based on solid oxide and proton exchange membrane fuel cells with hybrid storage for off-grid applications

  • 1École Polytechnique Fédérale de Lausanne, Switzerland

Solid oxide fuel cells (SOFC) have developed to a mature technology, able to achieve electrical efficiencies beyond 60%. This makes them particularly suitable for off-grid applications, where SOFCs can supply both electricity and heat at high efficiency. Concerns related to lifetime, particularly when operated dynamically, and the high investment cost are however still the main obstacles towards a widespread adoption of this technology.

In this paper, we propose a hybrid cogeneration system that attempts to overcome these limitations, in which the SOFC mainly provides the baseload of the system. The introduction of a purification unit allows the production and storage of pure hydrogen from the SOFC anode off-gas. The hydrogen can be stored, and used in a proton exchange membrane fuel cell (PEMFC) during peak demands. The SOFC system is completed with a battery, used during periods of high electricity production. In this paper, we propose the use of a mixed integer-linear optimization framework for the sizing of the different components of the system, and particularly for identifying the optimal trade-off between round-trip efficiency and investment cost of the battery-based and hydrogen-based storage systems. The proposed system is applied and optimized to two case studies: an off-grid dwelling, and a cruise ship.

The results show that, if the SOFC is used as the main energy conversion technology of the system, the use of hydrogen storage in combination with a PEMFC and a battery is more economically convenient compared to the use of the SOFC in stand-alone mode, or of pure battery storage. The results show that the proposed hybrid storage solution makes it possible to reduce the investment cost of the system, while maintaining the use of the SOFC as the main energy source of the system.

Keywords: SOFC (solid oxide fuel cell), PEMFC (proton exchange membrane fuel cell), CHP (combined heat & power), Off-Grid Energy System, Hybrid propulsion system, energy storage

Received: 18 Aug 2018; Accepted: 03 Dec 2018.

Edited by:

Peiwen Li, University of Arizona, United States

Reviewed by:

Kas Hemmes, Delft University of Technology, Netherlands
Miguel A. Laguna-Bercero, Universidad de Zaragoza, Spain  

Copyright: © 2018 Baldi, Wang, Pérez-Fortes and Marechal. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Francesco Baldi, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, francesco.baldi86@gmail.com