Suitable types of Fuel Cells for Automotive Application 2

[FuelCellEng]

Hello everyone,

I am interested in the use of fuel cells in cars. I am trying to understand the reasons why all (comercial) FCEVs use Low Temperature PEM cells. I know that some types of cells are not feasible because of their high operating temperature and therefore long startup times (SOFC, MCFC), and some like others have lower power density than PEMs. But there are also types beside PEMs that have a relatively low operation temperature like AFCs and PAFCs, why are they not considered feasible for cars?
I know that they have a lower power density, but why is that?
Since they all are basically making use of the same chemical reaction (so the usable chemical energy is the same for all of them), is the only difference the type of electrolyte they are using?
Or do they also need parts made from heavier materials maybe?

Kind regards

 

[LittleInch]

Might be better in the automotive engineering forum or the climate change engineering solutions forum as its a technical question.

Most posts here are higher level thoughts.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[BrianPetersen]

Use of acronyms without explanation aside ...

AFC = "alkaline fuel cell"

minor digging (wikipedia ... OK, bite me) "Aqueous alkaline solutions do not reject carbon dioxide (CO2) so the fuel cell can become "poisoned" through the conversion of KOH to potassium carbonate (K2CO3). Because of this, alkaline fuel cells typically operate on pure oxygen, or at least purified air and would incorporate a 'scrubber' into the design to clean out as much of the carbon dioxide as is possible. Because the generation and storage requirements of oxygen make pure-oxygen AFCs expensive, there are few companies engaged in active development of the technology."

In an automotive application, having to supply pure oxygen or having to incorporate a CO2 scrubbing apparatus in addition to all the hydrogen headaches ... would be bad.

PAFC = "phosphoric acid fuel cell"

operating temperature 150 - 210 C (needs a warm-up period in an automotive application, which eats up some energy and takes some time)

"rather low power density and chemically aggressive electrolyte" ... not favourable for an automotive application.

These are commercially available, and applications seem to be for stationary power storage rather than automotive, and there's nothing wrong with that. The lower power density doesn't matter so much, and they can be contained in a big insulated box that stays at the right temperature.

PEMFC = "proton-exchange membrane fuel cell"

these were specifically developed for transport applications ...

Ambient-ish, or at least not excessively high, operating temperature. (>100 C is desired to get the water out of the cell as steam) They can cold-start from below freezing.

Electrolyte is a polymeric membrane that stays put inside the cell and isn't a nasty strong acidic or basic liquid.

I have no inside knowledge of fuel cell tech, which means I am quite sure there are plenty of people out there with more knowledge of the subject matter than myself, but somehow it seems like the use of an arrangement specifically tailored for the application (PEM) would be hard for other technologies (AFC, PAFC) to overcome.