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PEM fuel cell deuterium generator

Posted: Sun May 11, 2014 1:05 am
by Tucker Sandbakken
This is a chapter of our research paper about the deuterium gas generator we are showing off at ISEF. The vent valve isn’t really needed if you purge the air out of the system using the vacuum chamber. The dual chamber system allows under and overpressure protection… if you fail to include these, you WILL burst the fuel cell! You have to get the oil amounts right.. too much and you can suck oil into your dryer. Too little and it is inefficient to purge the air out of the system.

Another tip: This eats batteries! We switched to a 1 amp 5 volt power supply with two diodes to drop the voltage to about 3 volts.

Costs; About $20 for an eBay HydroCar kit and another $20 for heavy water from United Nuclear.


Deuterium gas generator system


A. PEM fuel cell
Normally, deuterium gas used in nuclear experiments is delivered via compressed gas cylinders. To reduce cost, deuterium oxide and a proton exchange membrane (PEM) fuel cell was used. This was much simpler than traditional electrolysis.
The PEM fuel cell is part of an educational toy, the HydroCar made by Horizon Fuel Cell Technologies. It is powered by two AA batteries.
PEM fuel cells normally generate electricity from combining hydrogen and oxygen which results in water; however, they are reversible and when a low voltage DC current is passed through the cell, hydrogen is generated on one side of the cell and oxygen on the other.

B. Drying
The generated deuterium gas is “wet” (100% humidity) which will inhibit nuclear fusion. The gas is dried by passing it through a column of Drierite, which is a desiccant. A needle valve admits the dried deuterium gas into the vacuum chamber.

C. Over and under pressure protection
A possibility exists that gas demand exceeds supply and the PEM fuel cell may be exposed to a vacuum and destroyed, so a vacuum relief bleeds air into the D2 reservoir if the pressure exceeds about 0.6 PSI. The deuterium gas is vented if the pressure is exceeded.

D. Only small amounts of heavy water are needed
Given that one mole (M) of heavy water weighs 20 grams, electrolysis of 1 g of D2O generates 1/20 M of D2 gas. The ideal gas law states that 1 M of gas occupies 22.4 L at STP. Therefore, one gram of D2O generates 22.4/20 L or about a liter of D2 gas.

E. Deuterium Gas Generator procedure
1. Fill the oil reservoirs full with vacuum pump oil.
2. Open the flow valve with vacuum in the chamber. This flushes air out of the D2 reservoir. The oil will displace the air in the D2 reservoir.
3. Close the flow valve when the oil has transferred to the D2 reservoir.
4. Switch on the battery to the PEM fuel cell. Observe the gas displacing the oil in the D2 reservoir back into the oil reservoir.
5. When the oil is all but displaced, switch off the battery..
6. Repeat steps 1-5 until all the air is purged from the system.

Re: PEM fuel cell deuterium generator

Posted: Sun May 11, 2014 1:24 pm
by Richard Hull
This is an excellent report on the PEM cell system you have devised for a D2 generator and might serve as a superb model of a D2 source for future fusioneers. A very complete exposition on this valuable and necessary component. I especially like the oil displacement by the generated D2.

Thank you for this clear idea of how this is assembled and operated to achieve the desired effect.

Richard Hull

Re: PEM fuel cell deuterium generator

Posted: Mon May 12, 2014 12:50 am
by Dave Xanatos
This is PERFECT, exactly what I was looking for, as I will be using D20. Thanks very much for making this available.

Re: PEM fuel cell deuterium generator

Posted: Mon Jun 23, 2014 1:56 am
by Dave Xanatos
I now have two PEM cell electrolyzers and I'm custom machining some polycarbonate reservoirs and dryer tube... I have one remaining question, since I've not played with PEM cells before: how does one feed the D2O into the cells? From the D side or the O side? And, I'm guessing just by looking at the orifice diameter that gravity feed is probably not sufficient- that the D2O should be fed into the cell under some minimal pressure. I see online some pictures of people using a syringe to feed the cell. Is this the recommended method? And if so, how do I know when I've fed in a sufficient quantity of D2O, and how do I ensure I don't overpressure the cell?

Thanks for the guidance,

Dave

Re: PEM fuel cell deuterium generator

Posted: Mon Jun 23, 2014 11:09 pm
by Bob Reite
According to the instructions that came with the toy car kit:

"In order to humidify the fuel cell, complete the following points:
Use the syringe (A) to suck distilled water [in our case D2O] (not included in this kit) into the syringe. Once the syringe is filled with water, place the syringe into the top nozzle on the oxygen side of the fuel cell (D) and
proceed to push water into the oxygen side of the fuel cell (marked O2) until you see water passing through the chamber in front of the screen and out the lower nozzle. Leave the fuel cell for 5 to 10 minutes to fully hydrate."

The manual also warns you not to hydrate the cell through the hydrogen side.

The set up is shown in the .pdf files attached to this topic, but it is not quite clear how the D2O is being introduced.

Re: PEM fuel cell deuterium generator

Posted: Tue Jun 24, 2014 2:04 am
by Dave Xanatos
Thanks very much - those few lines of text were exactly what I was missing. I have the full setup but I was afraid to put water in the wrong side, or too much, or... :)

I ordered the PEM cells from some guy in Germany through ebay, and didn't have any manuals, etc. Google also turned up no useful details... you've been a great help.

Dave

PS., Adding just one keyword, syringe, to my search would have made all the difference, but... http://letsmakerobots.com/content/using ... -fuel-cell

This link says just the opposite regarding where to put the water: Insert the syringe into the lower hose attachment on the HYDROGEN-side, and push the water into the cell until all the air is expelled and the water starts coming out of the top hose.

So which is right? Perhaps it's oxygen side only for electrolyzing, ... :)

Re: PEM fuel cell deuterium generator

Posted: Tue Jun 24, 2014 3:49 am
by John Futter
Hi all
From inspection and knowing that Nafion only lets protons through it is obvious that you apply the water /D2O to the oxygen side of the fuel cell.
It is the proton exchange through the membrane that makes this work.

Re: PEM fuel cell deuterium generator

Posted: Wed Jun 25, 2014 4:02 pm
by Calmarius
What's the advantage of using a PEM cell for electrolysis over using simply to metal electrodes and a battery/solar cell?

Re: PEM fuel cell deuterium generator

Posted: Thu Jun 26, 2014 2:18 am
by Bob Reite
The main advantage that I can think of is you don't have to add an acid or a base to the D2O to get enough ions to make it work.

Re: PEM fuel cell deuterium generator

Posted: Wed Aug 20, 2014 7:41 pm
by Deiter Hanbicki
Great idea, the only question I have is where did you find 3-hole stoppers? I've only ever seen 2, and can't find any on the internets.