My initial thought about this was that it's using fuel to make electricity, right? Rather than using sunlight/hydro/etc -- kinda like a generator, but without the mechanical aspect?
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But they say other fuels work, in which case it wouldn't be "wire-to-wire", and then it'd be more appropriate to compare this to a power generator fueled by natural gas or gasoline. A generator with no pistons or turbines, just a fuel pump, sounds fantastic, if they can make it work. But you'd have to supply sodium.