Not mentioned here is that molten carbonate fuel cells are very sensitive to sulfur poisoning – sulfur levels in the anode stream have to be much less than 1 ppmv. (When firing natural gas they even have to remove the odorant mercaptans with a guard bed upstream of the anode.) I’ve not yet seen anybody address the issue of what to do about the sulfur present in the cathode stream if they’re using flue gas from a coal plant in a hybrid arrangement. Instant death to the electrolyte, unless you remove it all, which you can’t do at all easily because you don’t want to cool the flue gas down, scrub it, and then reheat it. Not a mention of cost in the piece, either, plus these things are huge – power densities are very low – not scalable, in my opinion. It’s really hard to visualize a 1 GW MCFC system….