Methanol based Solid Oxide Reversible energy storage system – Does it make sense thermodynamically?

Hydrogen is yet to be widely accepted as a fuel for everyday operation due to stringent safety regulations involved around it. In the meanwhile, methanol could be a potential fuel of the future. In this work, an extensive thermodynamic investigation on an energy storage system with a reversible solid oxide stack at its core is presented. The current investigated system can operate either as an electrolyzer or as a fuel cell. It uses steam for electrolysis (charging mode) and methanol for fuel cell operation (discharging mode). A process model of the entire system is formulated by using Aspen Plus™. Energy and exergy efficiency have been reported for both modes of operation, along with maximum roundtrip efficiency that can be achieved for the entire system operation. Results indicate that during electrolysis mode, a maximum energy and exergy efficiency of 67.94% and 72.30% can be achieved and for fuel cell mode operation, the numbers are 74.14% and 62.61% respectively. The maximum reported value of RT efficiency is 64.32% which is quite high considering the infancy of reversible solid oxide technology and the fact that methanol is used as the fuel.