Fuel Cell Technology

[smith70]

Hi every body
I need some information about fuel cell technology and its working mechanism. according to my googling, I found that only water and heat are the byproducts of these cells. is that right or there are other byproducts or enviromental issues?
thanks for any help and/or information about fuel cells
.

 

[MikeClay]

Unless I'm mistaken, steam reforming natural gas produces carbon dioxide. For each 4 H2 molecule produced, there will be 1 carbon dioxide produced. In addition, this reaction is endothermic,which means that some of the hydrogen will have to used to produced the energy needed to sustain the reaction to produce the hydrogen. While the stream may be not have any particles or ash, it does have a definite carbon footprint.

--Mike--

 

[moltenmetal]

MikeClay: as you've correctly pointed out, you get a lot less than 4 mol H2 per mol CO2 from an SMR. The process is endothermic and you obtain that energy by burning fuel.

http://www-pord.ucsd.edu/~sgille/mae124_s06/27637.pdf

Table 4 of this reference from NREL shows that typical hydrogen production operations generate about 10.6x0.84 = 8.9 kg of CO2 per kg of H2 produced. That's about 2.5 mol H2 per mol CO2.