Thermal coupling potential of Solid Oxide Fuel Cells with metal hydride tanks: Thermodynamic and design considerations towards integrated systems Andreas G. Yiotis * , Michael E. Kainourgiakis, Lefteris I. Kosmidis, Georgia C. Charalambopoulou, Athanassios K. Stubos Environmental Research Laboratory, NCSR ‘Demokritos’, 15310 Athens, Greece highlights  We study the thermal coupling potential of SOFCs with metal hydride tanks.  We propose an integrated system design for self-sustainable tank operation.  We develop a numerical model for heat and mass transfer in the system.  Thermal coupling is feasible at typical operating SOFC conditions. article info Article history: Received 15 April 2014 Received in revised form 30 June 2014 Accepted 3 July 2014 Available online 11 July 2014 Keywords: Metal hydrides Solid Oxide Fuel Cell Thermodynamics Thermal coupling Integrated systems abstract We study the thermal coupling potential between a high temperature metal hydride (MH) tank and a Solid Oxide Fuel Cell (SOFC) aiming towards the design of an efficient integrated system, where the thermal power produced during normal SOFC operation is redirected towards the MH tank in order to maintain H 2 desorption without the use of external heating sources. Based on principles of thermody- namics, we calculate the energy balance in the SOFC/MH system and derive analytical expressions for both the thermal power produced during SOFC operation and the corresponding thermal power required for H 2 desorption, as a function of the operating temperature, efficiency and fuel utilization ratio in the SOFC, and the MH enthalpy of desorption in the tank. Based on these calculations, we propose an in- tegrated SOFC/MH design where heat is transferred primarily by radiation to the tank in order to maintain steady-state desorption conditions. We develop a mathematical model for this particular design that accounts for heat/mass transfer and desorption kinetics in the tank, and solve for the dy- namics of the system assuming MgH 2 as a storage material. Our results focus primarily on tank operating conditions, such as pressure, temperature and H 2 saturation profiles vs operation time. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Considerable research has been invested in recent years towards the development of non-petroleum energy carriers for use both in mobile (transportation, portable devices etc) and stationary appli- cations (backup and auxiliary power units, distributed electricity generation etc). In this direction, hydrogen has emerged as an attractive option due to its production from a variety of primary energy sources, its high energy content and clean exhaust product. Furthermore, the use of H 2 can significantly contribute to the successful penetration of renewable energy (RE) sources in the electricity grid, as it offers a promising alternative medium for RE storage, which could be subsequently used as a clean fuel for ve- hicles, as well as for distributed electricity production through the use of fuel cells, or even internal combustion engines, etc. Efficient H 2 storage remains, however, a significant technolog- ical barrier towards the widespread application of hydrogen pow- ered devices and vehicles, as the volumetric energy density of uncompressed hydrogen gas is very low. In this direction, metal hydrides (MHs) are being considered as promising hydrogen stores due to their inherent high gravimetric hydrogen content, and sig- nificant effort is devoted to the development of MH-based upscaled storage systems and their testing (in terms of storage capacity, charging/discharging kinetics, reversibility and cycling, etc.) at * Corresponding author. Tel.: þ30 210 6503408; fax: þ30 210 6525004. E-mail address: yiotis@ipta.demokritos.gr (A.G. Yiotis). Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour http://dx.doi.org/10.1016/j.jpowsour.2014.07.023 0378-7753/© 2014 Elsevier B.V. All rights reserved. Journal of Power Sources 269 (2014) 440e450