PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

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PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

Post by russssellcrow »

The Fusor Group at the Dallas Makerspace has repurposed a Heidelberg PrimeSetter air chiller dryer to become a PEM Electrolyzer Dryer for our Fusor.

We began by getting a PEM cell from a Horizon solar car toy. The instructions show you how the cell works, and claim it can really make the car go, we didn't test that part.
Horizon_PEM_Cell.jpg
We connected the PEM cell into the chiller dryer, added an extra stack of Peltiers between the Heat Sink and the Chiller block, and built a controller using Heltec's WiFi 32 Kit, (a 32 bit 200Mhz microcontroller). If you try this with an Arduino UNO, you might have a very hard time. The device looks like this, with the major components labelled, these are front and rear views.
PEM_Electrolyzer_Dryer_front.jpg
PEM_Electrolyzer_Dryer_rear.jpg
The Electronics Schematic is old school, because this is a one-off device. After debugging on a Protoboard, we made a working model which fits in a small Hamamatsu Laser container.
PEM_Electrolyzer_Dryer_Schematic.jpg
Heltec_PEM_breadboard.jpeg
After adding the WiFi "Network Name" and "password" to the code, compiling and uploading, the Heltec Wifi 32 Kit will reboot and attempt to attach to the Wifi Network. If it connects, you will see the IP Address which your WiFi Router has assigned to the Heltec. Then you can bring up the Web page which controlls the device in almost any browser (we use Chrome or Firefox) by entering the IP Address, i.e.
//192.168.137.159

Here is functional Block Diagram of PEM Electrolyzer Dryer, which shows the connections of WiFi to the Heltec, Heltec to the Power Electronics, Power Electronics to the Peltiers and PEM cell. Next we will include the Thermocouple for temperature feedback, and augment the Arduino code with a PID block, but the device you see is functioning as is.
PEM_Electronics_BlockDiagram.jpg
During operation, we proceed with the following steps:
1. Start the Fusor vacuum and let it pump down.
2. Fill the PEM with Heavy Water, allowing a little extra to come out of the H2 and O2 ports. These will become water walls to seperate the Deuterium Gas from the air in the lines, and to show us how fast the gasses are being made. Not to worry, the Filters will trap the few drops which make it through (which reminds me that I need to add a trap for the O2 line which vents in the Heat Sink fan!)
3. Turn on the Mass Flow Controller (another Heltec WiFi 32 Kit and controller we will post soon), and open the MFC to allow the vacuuming down of the line to the PEM Electrolyzer Dryer (there is a valve between the two to prevent the vacuum from emptying the PEM cell).
4. Close the MFC, and slowly open the PEM valve. You can watch that D2O bubble pick up speed if the valve is opened too fast.
5. Once the Fusor is <5 microns, we re-open the MFC to balance the Fusor chamber pressure to about 30 microns. The usual value is around 25% on the MFC Webpage.
6. Fire up the CO2 Laser Supply and strike a plasma.

The following file is the Arduino code, and an object file for the Heltec WiFi 32 Kit. If you have already converted your Arduino IDE to program the Heltec you won't need the .h file. If you haven't, then follow the procedure here:
https://heltec-automation-docs.readthed ... start.html
Fusor_Electrolyzer_Gas_Dryer_v51_shared.zip
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Re: PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

Post by Dennis P Brown »

Excellent post - very good explanations and photo's. I was curious how you deal with the air in those two large 'filter' system holders before adding the deuterium? Are they first vacuum evacuated? Also, where did you get that chiller cube or was that in the original device you salvaged?
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Re: PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

Post by Rich Feldman »

Nice report.
I wonder about the effectiveness of drying gas by chilling/condensation.
Depends a lot on the amount of coldness.

Have never seen a quantitative measurement of moisture in H2 or D2 from PEM electrolyzers; we know there's a little.
Someone here reported neutron assays with and without some kind of dryer; was it conclusively different?

With traditional wet (bubbly) electrolysis, we can figure the gas comes out saturated with water vapor.
I did the exercise when filling balloons in summer of 2018.
At 20 degrees C, water is 17 g/m^3; about 10% by weight in deuterium.
At 0 degrees C, water is 5 g/m^3; 2.7% by weight in deuterium.

If there's less water than that to begin with, none will condense on the "dryer" surfaces.
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Re: PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

Post by russssellcrow »

Thanks for the kudos, Dennis.

Yes, you are correct, we vacuum down the filters and Chiller cube (these parts are rated at 10 Bar, so vacuum doesn't bother them). I neglected to put the valve in the Functional Block diagram which isolates the PEM cell, good catch. After evacuation comes the tricky part, we close the Mass Flow Controller, then open the isolation valve to allow the PEM cell to bring the high side up to atmospheric pressure with generated Deuterium Gas. If the valve is opened too fast (which is very easy), it sucks Heavy Water down the line into the Trap Filter (25um). I've toyed with the idea of using an earlier Needle Valve in this position. We originally used this Needle Valve to regulate the chamber pressure, but upgraded to the Mass Flow Controller when Josh Melnick loaned it (and a Bayard Alpert gauge) to our project.

The Chiller Cube was original equipment in the Chiller/Dryer Unit which came out of a Heidelberg PrimeSetter. This was a Laser filmaker for the printing industry, and the Chiller/Dryer kept their air bearing Laser spinner from self-destructing (at 54,000 RPM) from corrosion, by cleaning the compressed air of dust and water. They also used magnetic levitating mirror spinners, like the Pfeiffer turbopumps, but they were never as fast or stable.

Here is a Heidelberg Laser spinner.
ProSetter_Spinner.jpg

Under the aluminum safety cap (right side) is a Wollaston Prism, which reflects the incoming Laser beam by 90' onto the surrounding drum where photosensitive material (film or plate) is exposed. Inside the all brass housing is an air bearing axle, with a mechanical clearance of about 0.00015 inches. If the axle or bearing surface corrodes, it's curtains for the Laser spinner (this explains why the air chiller/filter was so ellaborate). On the side is a Laser Diode, which reflects off the shaft and sends timing clock pulses to the imaging computer which feeds the picture data to the Laser at about 125MHz. This was pretty cool tech in the 1990s.
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Re: PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

Post by Rich Feldman »

The rotating-mirror scanner unit is also very cool; thanks for sharing.
Reminds me of Gerber flatbed photoplotters used in the printed circuit industry when tooling involved big sheets of film. The Gerber file format for art files is still standard today.

My words about air-drying effectiveness were poorly chosen; sorry about that.
Of course the unit can keep dew point below 0 degrees, to protect metal parts against corrosion in an industrial setting that might generally be humid, without ever needing to replace or regenerate desiccant material.

I just meant, it might not make a difference if D2 from the PEM cell is already dryer than the Chiller Cube's limit.

[edit] Reading more of your posts, I see where you added another stage of Peltier cooling.
And reported recovery of 3% of your heavy water. Yay! I was surprised that so much water comes through the PEM.

[\edit]

You still get the benefit of filtration. If and when my own PEM cells get into service, I want to investigate the moisture by trying to frost up a cold finger that's progressively chilled by, say, ice - boiling freon or propane - dry ice - LN2.
Resized_20211207_125230.jpeg
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Re: PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

Post by russssellcrow »

Hey Rich,

Yes PEM cells come with some surprises, but we probably need to get used to this technology. While Tesla, Ford, and GM rush headlong into Lithium powered cars, those clever Japanese at Toyota aren't letting go of the Hydrogen power cycle. They have over 6,000 H2 powered cars on the road, and if they develop safe Hydrogen sequestering in Graphitic Carbon Nitride cells (another subject for another thread), that number could balloon easily.

Back to PEM...the next step is to upgrade the PEM cell we are using. The D2 gas is coming out with impurities, we think because this is such a cheap cell with a bargain basement membrane. I see there are Plug Power parts for sale on Ebay, but their cells are generally outrageously priced.

As to how the PEM membrane has evolved, this looks like a pretty good wrap up in Wiki:

https://en.wikipedia.org/wiki/Proton-exchange_membrane
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Re: PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

Post by Dennis P Brown »

This is really good work - keep up the posts!
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Re: PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

Post by Matt_Gibson »

How cold does a cold trap need to be in order to be effective at drying the deuterium from the electrolyzer? There’s no way I can use dry ice, so I’m looking at a TEC and an aluminum water block.

A quick and dirty test got me down to -10F with a single TEC on a large heatsink with fan. Is this good or nowhere near enough?

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Re: PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

Post by Rich Feldman »

>> How cold does a cold trap need to be in order to be effective at drying the deuterium from the electrolyzer?

How wet are PEM cell output streams?
How much water is tolerable in fusor D2 streams, before it significantly reduces fusion? I can't find the old presentation at fusor.net that compared neutron counts, with moisture being the variable.

Dew point temperature could be a handy way to express moisture contents here.
I find it hard to believe that -10 °F isn't plenty cold, by a large margin.

At 0 degrees C, vapor pressure of water (and presumably D2O) is 4.9 torr.
Let's say the cold trap operates at atmospheric pressure.
After condensation, the gas stream would be 0.6% moisture, 99.4% D2 plus DH. (The amount of DH depends on isotopic purity of the heavy water put into the electrolyzer.) Those are percentages by volume, or by molecule count. In an earlier post to this thread I gave percentage by weight, which was meaningful for floating balloons but not for fusing.
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Re: PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

Post by Frank Sanns »

Dry ice traps are the typical lab way to remove most water. That is around -78C.

Assuming the PEM cell is running at room temperature, the maximum water content is around 20g per m3. Using a salt/water ice bath gets that number down to around 2g/m3.

Passing that stream over a desiccant will remove most of the water.

You may or may not have seen a previous post of mine and Jim Kovalchick and the impact of D2O vs H2O. Huge difference in the impact of the two. The D2O is only a small fraction of the problem with normal H2O.
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Re: PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

Post by Matt_Gibson »

Thank for the replies and the charts. From the looks of things, there doesn’t seem to be a huge difference going below -10F. There’s already a drastic drop from room temperature to -10F?

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Re: PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

Post by Rich Feldman »

Frank, can you help us find the experimental data by you and/or Jim K about the effect of water or D20 in fusor gas?

We agree about moisture carrying capacity values, as found for example at engineeringtoolbox. Here I've added a column giving partial pressure of water vapor, at saturation, in atmospheres.
vapor.gif
vapor.gif (5.91 KiB) Viewed 4768 times
So at room temperature, a PEM cell output stream saturated with water would carry 17.3 g/m^3. Table says that's 2.3% of the gas molecules. Percentage would be slightly lower with D2O, because its vapor pressure is slightly lower.

Do fusor tests show neutron count to be reduced by more than 2.3% ? Or perhaps twice that, if reaction rate follows the square of deuterium fraction in the plasma? Do heavy molecules poison the reaction or disproportionally consume electric energy?

We could reduce the water or D2O fraction to 0.6% at 0 °C, less than 0.1% at -10 °F, and much lower still with dry ice. And/or reduce it by using desiccant.

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Re: PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

Post by Frank Sanns »

As a chemist I offered the stoichometry and fusion data for H2O and D20.

The big distinction is between fusible hydrogen (deuterium) and non fusible hydrogen (protium). In the case of protium hydrogen, all of the atoms dilute the deuterium fusion fuel.

For one atom of water, there are 2 hydrogens for each oxygen. Using the numbers (gram atoms) from the periodic chart, oxygen is 16 and protium is 1. A molecule of protium water is then 18 gram atoms.

This means that 18 grams of protium will ionize to give 2 x 6.02^23 atoms of protium and 1 x 6.02^23 atoms of oxygen. (6.02 x 10^23 being Avogadro's number of atoms per mole).

In the case of D20, a molecule of will weigh 20 gram atoms. It is higher than protium because of the presence of a neutron in each deuterium atom. A molecule of deuterium is oxygen 16 plus two deuterium atoms of 2 each. The total being 20 gram atoms.

At this point, the same weight of water will have 18/20 as much deuterium oxide as normal protium water. That is 10% less contaminates from the stoichiometry alone.

Now for the big contributor and that is the total number of contaminate atoms. In the case of the same 18g of weight of deuterium oxide, there are 10% fewer molecules of deuterium water. The 90% (0.9)will be added to the same equation for the protium at the beginning of this post. Ionization of this deuterium water will yield 0.9(2 x 6.02^23) atoms of deuterium and 0.9(1 x 6.02^23) atoms of oxygen.

Doing the final calculations shows that 18g of "water" will ionize to give 12.04 x 10^23 (protium) plus 6.02 x 10^23 (oxygen) for a total of 18.06 x 10^23 contaminating atoms.

The same 18g of deuterium oxide will ionize to make only the oxygen contaminating (non fusible species) since the deuterium that is liberated is fusion fuel. Thus only 90% of the protium oxygen will be produced or 5.4 x 10^23 contaminating atoms.

in conclusion, it is 18.06/5.4 or 3.34 times worse using protium water than deuterium oxide. It is actually most likely much worse with protium water because oxygen can easily be scavenged up by hot ion guns and central grids and all metal internal surfaces of the fusor that are exposed to the plasma. Protium thought will persist as a contaminate.

Lastly the acceleration of protium and deuterium. Protium being half of the mass of deuterium will have a different velocity profile in the fusor and a will ionize neutrals differently. I have not run those numbers to determine the ions formed from each of those species but it will be minor compared to what is calculated above.

The link to the original post can be found at: viewtopic.php?p=100007#p100007
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Re: PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

Post by Rich Feldman »

Thank you for pointing to the thread with assays by neutron count, Frank. I read that and learned a lot. Concur with your long explanation posted today.

I think the conclusion for Matt, as demonstrated by Jim and Rich et al, is that drying between PEM and fusor inlet makes a measurable difference but not a huge one.
Residual protium water on chamber surfaces is bad.
We need to keep our heavy water dry, minding its hygroscopic nature when exposed to air.

Don't we expect that PEM cell loaded with good heavy water will have only D2 and incidental D2O in outlet stream? You explained why the latter isn't so bad. Maybe the benefit of drying is mostly from reducing the protium in the form of HDO that got in there from not so heavy water; it won't help with the fraction of HD in the gas. Be nice if we could inexpensively analyze the HD fraction and the D2O fraction (I bet many humidity sensors would work in a deuterium atmosphere).

I'm puzzled if introducing one molecule of D2O for every 43 molecules of D2 is a problematic amount of dilution. D2 at atmospheric pressure, upstream of the flow-limiting restriction, can't hold any more than that at room temperature.

Consider accepted claims of fusion in chambers where ultimate vacuum from pump is 4 microns, and pressure with D2 flowing is about 20 microns. I think that means 20% of the molecules are ones that would be there anyway if there were no intentional inflow. 4 microns is the equilibrium between pump speed and unintentional gas load. The latter isn't reduced when we start admitting D2.

Please correct me if that's wrong. Don't want to mislead the newcomers. I like to talk, but my electricity in vacuum play was long ago and never involved D2.
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Re: PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

Post by Matt_Gibson »

Best performance from the deuterium is one goal, but my main concern is the condensation that I see making its way into my MFC. It was enough to create some rust on one of the openings.

From what I gather, a TEC cooler with waterblock is likely to stop this condensation and make a decent impact on the overall quality of the deuterium.

Dry ice or liquid nitrogen performance seems only necessary for lab conditions?

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Re: PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

Post by Frank Sanns »

Then it is only the dew point that you need to control. Assuming the PEM cell is 100% RH at its operating temperature, then everything downstream must be held at that temperature or above to prevent condensation.

Saturated water vapor will condense at the coldest spot in the entire system. To control condensation alone, a trap only needs to be literally only a fraction of a degree colder than the rest of the system. The vapor pressure is determined by the coldest point anywhere in a system. In reality, flow rate and flow conduction and thermal conduction are factors since nothing is ideal. So a trap that is 10 degrees colder than the rest of your system is probably plenty cold to stop the condensation.
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Re: PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

Post by Matt_Gibson »

Sounds like I don’t need to go all out stacking Peltiers trying to get to dry ice temperatures then :-)

I should be able to eliminate the condensation and achieve reasonably dry deuterium with what I’ve got on hand.

Now to cobble something up…

-Matt
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Re: PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

Post by Richard Hull »

Sounds like a submerged 1/8-inch diameter, coiled copper gas line from the PEM to the inlet flow to the fusor will do the trick even using common ice water in the tank with the coiled line.

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Re: PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

Post by Rich Feldman »

Any cold trap solution needs periodic draining of condensate.
Might it be just as easy, logistically, to periodically replace the media in a desiccant column?

Attached picture shows how I dried hydrogen for filling a balloon in 2018. Coming from a very warm zinc-and-acid reaction, gas was bubbled through ice water (in this case to condense most of the moisture!), then sent through silica gel desiccant. The blue indicator beads at inlet end had just begun color change toward pink.
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Re: PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

Post by Frank Sanns »

The problem with using molecular sieves or any drying media is that the heavy water is lost. Condensing it allows for recovery and reuse. It is not an issue for a small fusor run as the quantity of liquid is nearly insignificant. On a larger scale though you don't want to be tossing out multi dollar per gram material unnecessarily.
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Re: PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

Post by Daniel Harrer »

Why is it truly lost? Just heat the molecular sieves in a closed environment, let the created "heavy" steam go into a place where it condenses and collect. The very same setup used to distil chemicals should work.

To avoid overpressure and danger this must have some way to keep the pressure low. An opening is probably fine as wet air from outside should not flow much against the pressure. But if this is a concern then a one-way valve is a simple solution.

In essence this replaces a somewhat complex cooling setup (this must happen before the gas gets to low pressures; my setup has the cathode of the PEM cell at 0.5 bar or whatever I set it to, which is already a bit low for cooling) by some recovery that probably has to be done once in a blue moon.
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Re: PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

Post by Frank Sanns »

It is always more efficient to reclaim at the source. Just like in thermodynamics, the more steps, the more losses.

Have you ever tried to distill a gram or two and recover it? The losses on the surfaces can be quite large. There is also a fact of condensation that the more non-condensible gasses in the system, the lower the recovery quantity. Every time you open a sealed chamber you introduce another gas be it air, nitrogen, argon, or some other gas that is inert to your product.

It is much easier to have a sealed system with a small drain at the low point in the condenser and bleed off liquid periodically. There should be zero losses after the the system is first operated. No follow up steps needed.
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Re: PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

Post by Daniel Harrer »

Distilling just a gram is obviously not worth it. At maybe $3/g I wouldn't even consider it if I expect less than 10, better 30 grams before losses.
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Re: PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

Post by Richard Hull »

Yes, you have to be doing a lot of wet PEM work doing fusion to recover multi-gram quantities which means you are probably doing something wrong or have a bad pem cell, I would think. I am so glad I use tanked Deuterium gas! sure it is way more expensive per gram atom, but it arrives pure into my fusor.

I also note a lot of folks here using the PEM system have done very good fusion and continue to do so with no real drying arrangements. I feel for those getting wet delivery lines out of their pem cells. I wonder about too much current or poor maintenance causing issues.

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Re: PEM Electrolyzer Dryer on Heltec ESP32 w/ Webpage

Post by Bob Reite »

I just ran my D2 from a pem cell through a one stage silica jel dryer and it seemed to work fine. One thing that I should do is compare pem cell vs tanked D2, since I have access to both now.
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