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October 20, 2005



Couldn't the heat generated by the fuel cells be used?

It would seem rather pointless to create a fuel cell that wastes so much of it's potential output on heat. If it wasn't significantly better than other fuel cell technologies in some other ways.


Error in title: there is no zinc used in these fuel cells. They are SOLID oxide fuel cells, using ceramic electrolytes rather than metal fuel.

Robert McLeod

Sure you can use the heat from the exhaust to run a cogenerated process. If you need industrial heat for example. Or if the unit is mounted in an apartment or office tower it can produce space heat or hot water. A particularly large solid oxide fuel cell can run a combined cycle by burning the fuel and then using the exhaust to boil water and run a steam Rankine cycle.

James Fraser

Oops, sorry about the zinc. I have edited the post to take out all references to zinc. I don't know where that came from, it must have been from the Z in Zirconia, but that is no excuse.

About the heat - The heat from these cells has always been used, or rather proposed, to be used for the purposes mentioned. These researchers have been trying to adapt the battery for use in vehicles, where the higher heat is hard to isolate. Even there it could be used to drive a Stirling engine or a turbine, but that probably would be too complex. I don't know how the weight and power density of these cells compares to PEM cells but the researchers claim they are more efficient.


It really sounds like this technology is best suited for larger applications where they can take advantage of the heat as opposed to trying to get rid of it to fit it into a car.

Granted removing the necessity for gasoline in cars is of paramount importance but using fuel cell technology to reduce the need for things like coal-electricity generation or massive hydro-electric projects does have value too.


Current cars get about 17% efficiency.  If you can boost the prime mover from ~20% up to 60%, you don't care much about the waste heat; you're making a heck of a lot less than before.  Such a fuel-cell car could dump all its waste heat out the exhaust, eliminating the need for a conventional cooling system.

It would indeed revolutionize stationary generation so long as it could tolerate impure fuel gases (too fussy and the energy cost of gas cleanup gets too high).  Combined-cycle plants are already hitting 60% efficiency, but these units look like they could be home-sized.  If homes could generate electricity from e.g. the operation of the furnace and water heater, the potential for efficiency gains is enormous.


It's good to have options for car applications of fuel cells and if they have better power/wieght densities, I don't see why we shouldn't go with these over PEMs. I guess it also comes down to which is easier to manufacture.

However, the Solid Oxide fuel cells described in this post still use platinum as a catalyst (just like PEM cells) which could be a major problem. Platinum is in pretty short supply and is more valuable than gold. It is particularly useful as a catalyst for lowering the temperatures necessary for the reactions that go on in fuel cells which is why it is used both in PEM cells and these low-temp Solid Oxide cells. What we really need though is a cheap and readily available replacement for the platinum and until we get that, I'm not sure we'll be able to mass-produce fuel cells at a low enough cost. Anybody know more on this?

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