MOLTEN SALT FUEL CELLS: Diversity and convergence, cycles and recycling

Abstract

The development of the Molten Carbonate Fuel Cell, now 65 years old in its pure molten-salt cell embodiment, has spawned a remarkable variety of designs and technologies (gas-fed fuel cells, direct carbon fuel cells, solid oxide FC hybrids, CO2 concentrating/capture and hydrogen generating systems). Sometimes these new subsets are recycling ideas from earlier stages of fuel cell exploration - which extend quite far back. Since Grove's discovery in 1840, diversification of the fuel has been a persistent lure and challenge – which led to exploration of ionic melts. Much later, after the isolation and identification of solid-oxide conductors, the path to a purely carbonate cell became conceptually clear. Its history since then has had several critical points, of diversification and convergence. Like all energy technologies, it is forever at the mercy of the economics, and politics, of primary energy resources – the balance between fossil and renewable. Is MCFC a technology whose time has come … and gone? Such a view would ignore its strong chemical fundamentals, intrinsic to a future including biofuels. But controlling and stabilizing the morphology and wetting properties of MCFC materials is vital for another cycle of re-birth and flowering.