Re: PEM Fuel Cells and Thier Cost.
Carbon_Rod, Sat May 28 2016, 08:52AM

Most current polymer based cells are based on an accidental discovery from the 90's.
The largest manufacturer was gutted for the patents, and driven into bankrupted obscurity.

So today, you can buy an expensive PEM based cell that will slowly get poisoned by trace CO, and eventually stop working well.


The DoE has done extensive feasibility studies on variants of both low and high temperature catalyst based fuel cells.
Some new research seems to think they can solve the storage issues with high concentration, room temperature, and low pressure liquid peroxides. However, I seem to recall a generation of rocket scientists that failed to make it safe enough for general use.


Primarily, Hydrogen gas is problematic to handle even if corrosion issues are solved:


Best of luck,

Re: PEM Fuel Cells and Thier Cost.
Patrick, Sat May 28 2016, 07:01PM

what about mitigating hydrogen embrittlement using fiberglass or carbon ? could that be effective ?

and Horizon seems to be a large player in this market. i keep running into them. i keep running into them.

and, what lifecycle do the PEM's have before the CO poisoning really effects performance ? just an order of magnitude, like 10, 100 or more hours to decrease by 10%. or is there some formal way the industry describes this reduction in useful life.

My purpose is for small ground and under water bots. so 2 or 3 hours at a time. maybe 1000 hours total life of the stack.

Re: PEM Fuel Cells and Thier Cost.
Carbon_Rod, Sun May 29 2016, 12:32AM

"what about mitigating hydrogen embrittlement using fiberglass or carbon ? could that be effective ?"
The prototype H2 vehicles from the local facility generally use carbon-fiber composite wrapped storage tanks.
At the time, I didn't ask about the metal alloy they used for the pressure vessel.

"and Horizon seems to be a large player in this market. i keep running into them. "
Indeed, they seem to be one of the few groups still trying to make it practical for consumer use.
A few years back...I seem to recall thinking their $2k 200W kit was outrageously overpriced...


"and, what lifecycle do the PEM's have before the CO poisoning really effects performance ?"
I was told it was a trace contamination problem, but can't recall much of the research on the chemistry.
We were more interested it the support hardware at the time:


"My purpose is for small ground and under water bots. so 2 or 3 hours at a time. maybe 1000 hours total life of the stack"
Having built on both platforms, I can assure you that there are quite a few design differences in these systems.

Mass and energy density are important for "ground" vehicle range:
A 24v 20ah LiFePO4 e-bike power pack already comes with a charger system, and you could buy over 100/pcs for the price you were quoted.

The range estimate is "1 mile per amp" for e-bike users, but I seem to recall around 2Ah/km of flat terrain for autonomous robots.

"under water bots" mean the Buoyant Mass == Ballast (energy density is less important for surface craft):
There are now full sized craft using LiFe power systems, but in water these things have an endless list of trade-offs.
Note, automotive style lead acid industrial marine batteries have well over 200 Ah, and for the unit price one gets 4x the run-time for much less hassle. Note, Pb cells don't state they need venting, but precautions should be taken seriously.

1000 hours is a long run-time unless the units are in standby, and you may need to start thinking about generation/sail options.
The Li cells will last 2k+ charge cycles, as long as you don't deep cycle discharge over 20% of the labelled capacity.

Good luck,

Re: PEM Fuel Cells and Thier Cost.
Bored Chemist, Sun May 29 2016, 09:40AM

Then don't put CO in them.

Re: PEM Fuel Cells and Thier Cost.
Patrick, Mon May 30 2016, 02:17AM

It slowly appears.

ANd on a seperate note:


How do methanol fuel cells age? is it similar to one of the above graphs ?

Re: PEM Fuel Cells and Thier Cost.
Bored Chemist, Mon May 30 2016, 12:00PM

How?
Where does the carbon come from?

Re: PEM Fuel Cells and Thier Cost.
klugesmith, Tue May 31 2016, 06:50AM

This thread is the first time I heard of CO poisoning of hydrogen fuel cells.

Many people, apparently including Elon Musk, think that the "hydrogen economy" is supposed to use hydrogen made by electrolysis of water. Pretty darn inefficient way to store electricity.

Ask a big user of hydrogen (e.g. for making ammonia or refining petroleum, not little stuff like space shuttle fuel tanks) where it comes from. They'll say "the vast majority is prepared by steam reforming of natural gas".

So hydrogen is primarily a low-density fossil fuel product, noteworthy for low carbon emission at the time & place of consumption as fuel.

Here is a small format self-powered reforming system, using methanol, that produces enough H2 to run 2.5 to 7.5 kW of fuel cells. I would not be surprised if told that its output includes measurable traces of CO.

Re: PEM Fuel Cells and Thier Cost.
johnf, Tue May 31 2016, 06:51AM

Because you are stripping ions in the PEM you get active ions looking for mates with enough energy to break up a happy couple. For air 300ppm co2. "O" ion with energy looking for mate has the chance to steal an "O" from co2 to form CO and O2.
Even worse for the methanol based cells as there are much more carbons to play with M2CentsW

Re: PEM Fuel Cells and Thier Cost.
Patrick, Tue May 31 2016, 05:30PM


Yes, here in California, without enormous government subsidies fuel cells and solar cells wouldn't last at all in the market place. Solyndra in my home town of Fremont CA, comes to mind. We have a political class here that just has to cram this tech into the market place. We have endless commercials on our radio and TV wanting to install wind or solar, at almost no cost, theres a lot of fine print though on those contracts.

Re: PEM Fuel Cells and Thier Cost.
Carbon_Rod, Tue May 31 2016, 08:23PM

"without enormous government subsidies fuel cells and solar cells wouldn't last at all in the market place"
This may hold true for domestically manufactured stuff...
However, classic thin film Amorphous silicon cells are part of China's internal Energy policy, and this feeds into the consumer market production chain. Recall, communist governments will often fully subsidize labour costs for state projects, and more than one domestic company has foolishly attempted to compete in this market. A gov subsidy will not change this global market dynamic, as your competition will be dumping the stuff in volumes you could never scale up to meet.

Panel manufacturers are now so prolific due to the cell price drop, that they started to omit reverse bypass diode cell array protection for large panels. Note, if one cell is shaded (e.x. bird droppings) or fails with no bypass path, in rare cases it can cause a hot spot intense enough to cause a fire. If your panels are not made out of glass/metal, done at home, or cheap stuff out of China/India... hope it is low power enough to be irrelevant. However, commercial enterprises use Thermal imaging on RC quads to inspect for failing cells.

As with any technology, there is no universal solution that is optimal for every scenario.
I believe Hydrogen is a great idea for aerospace, but liquid Peroxide researchers have some valid (albeit old) arguments too.

@Bored Chemist
There are a few books that cover the chemistry in detail, and document about a dozen or more other common side reactions.

"Explanations exist; they have existed for all time; there is always a well-known solution to every human problem — neat, plausible, and wrong." ( H. L. Mencken )

Re: PEM Fuel Cells and Thier Cost.
Patrick, Wed Jun 01 2016, 05:48PM

And what about the electrolyzer? why are they so expensive ?

Re: PEM Fuel Cells and Thier Cost.
Carbon_Rod, Wed Jun 01 2016, 06:43PM

Many Electrolysis set-ups use around 15g-20g Sodium Hydroxide per 1L of deionized water.
Deionized water is important as things like this can happen:
2(NaCl)(aq) + 2(H2O)(l) → (H2)(g) + (Cl2)(g) + 2(NaOH)(aq)

In general, electrolysis plate materials must each deal with the oxidation or reduction states without contamination of the generated gas.
I suspect the manufacturers are not using graphite, and likely wanted something that would function for at least 1 year of daily use.
There is also the issue of putting the gas into storage bottles....