# NG Fuel cells



## Sunking (Aug 10, 2009)

It has been about a year since I last looked at this around the same time the Bloom Box came out. They are certainly nothing new.

Anyway what I found the first time around is you get twice as much energy out of NG by burning it, rather than combining it with a reactant like oxygen. So I do not see them as any real solution as they are less efficient than burning, and they release just as much or more Co2.


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## Duncan (Dec 8, 2008)

Hi Kelmark

I am a bit suspicious of the 250,000 miles - last time I had concrete evidence the membranes lasted less than a year - even less if the fuel was not really pure


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## Tesseract (Sep 27, 2008)

Sunking said:


> Anyway what I found the first time around is you get twice as much energy out of NG by burning it, rather than combining it with a reactant like oxygen. ...


You got that backwards, Sunking... Fuel cells are at least twice as efficient at converting chemical energy into electrical than an internal combustion engine. Also, both systems combine a fuel with oxygen to release the energy of formation (enthalpy) - the fuel cell uses a catalyst to liberate the energy as electrons while a heat engine liberates the energy and is subject to Carnot's Rule. 

A third means of combining the two reactants - e.g., fuel and oxygen - which is even more efficient is nuclear fusion... needless to say, that's probably not coming to a store near you anytime soon.



Duncan said:


> I am a bit suspicious of the 250,000 miles - last time I had concrete evidence the membranes lasted less than a year - even less if the fuel was not really pure


Depends on the fuel cell. The higher temperature types like Solid Oxide and Molten Carbonate have very long operational lives, don't need exotic noble metal catalysts and are very tolerant of impurities in the fuel/air stream feeding them, but they are - as you might guess - only suitable to fixed installations.

Lower temperature cells like Alkaline (used in space flight) and Polymer Electrolyte Membrane (the type mentioned here) are much less tolerant of impurities in the feedstock, particularly sulfur compounds. The PEM type also needs to be kept at the proper humidity level to maintain ionic conductivity of the special sulfonic acid-polymer membrane (e.g. - DuPont's Nafion) without flooding the gas passages with liquid water. Once you solve all these physical problems the PEMFC is remarkably robust and should pump out power for decades - 250k miles should be trivial in such a case. 

PEMFCs would make an almost ideal range extension generator in a series hybrid if it weren't for one thing.... their cost. PEMFCs require very active catalysts (e.g. - precious metals) because of their low operating temperature, the plastics used for the ion exchange membrane are difficult to manufacture and the electrode materials have to withstand high humidity in the presence of a potential difference (ie - subject to galvanic corrosion) so they are inevitably made of expensive materials like machined graphite.

All of this issues are potentially solvable, we just ain't there yet.


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## Kelmark (Oct 26, 2009)

Tesseract,

Are the new ceramic ng fuel cells the same as PEM or PEMFC's or are they something different all together?

link;
http://www.cfcl.com.au/Assets/Files/Gennex_Brochure_(ENG)_Mar-09.pdf


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## Tesseract (Sep 27, 2008)

They are solid oxide types... using a sintered ceramic and metal oxide catalyst/substrate to perform the redox reactions. These are typically low-activity catalysts so they need to operate at high temperatures. Not really appropriate for on-vehicle use, though they are great for semi-portable and fixed power installations.


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## Duncan (Dec 8, 2008)

Hi Tesseract

_*All of this issues are potentially solvable, we just ain't there yet.*_

The funny thing is fuel cell technology is well over 100 years old!

_*You got that backwards, Sunking... Fuel cells are at least twice as efficient at converting chemical energy into electrical than an internal combustion engine. Also, both systems combine a fuel with oxygen to release the energy of formation (enthalpy) - the fuel cell uses a catalyst to liberate the energy as electrons while a heat engine liberates the energy and is subject to Carnot's Rule. *_

That is all very good - BUT - you first re-form the fuel (NG) into hydrogen - and I believe you lose a lot of the available energy in that step - the quoted efficiencies I have seen range from 80% to below 30%


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## resago (Sep 28, 2010)

NG is H + C, of course you need to liberate the H.


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