Monthly Archives: February 2017

The hydrogen jerrycan

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Here’s a simple invention, one I’ve worked on off-and-on for years, but never quite built. I plan to work on it more this summer, and may finally build a prototype: it’s a hydrogen Jerry can. The need to me is terrifically obvious, but the product does not exist yet.

To get a view of the need, imagine that it’s 5-10 years in the future and you own a hydrogen, fuel cell car. You’ve run out of gas on a road somewhere, per haps a mile or two from the nearest filling station, perhaps more. You make a call to the AAA road-side service and they show up with enough hydrogen to get you to the next filling station. Tell me, how much hydrogen did they bring? 1 kg, 2 kg, 5 kg? What did the container look like? Is there one like it in your garage?

The original, German "Jerry" can. It was designed at the beginning of WWII to help the Germans to overrun Europe.

The original, German “Jerry” can. It was designed at the beginning of WWII to help the Germans to overrun Europe. I imagine the hydrogen version will be red and roughly these dimensions, though not quite this shape.

I figure that, in 5-10 years these hydrogen containers will be so common that everyone with a fuel cell car will have one, somewhere. I’m pretty confident too that hydrogen cars are coming soon. Hydrogen is not a total replacement for gasoline, but hydrogen energy provides big advantages in combination with batteries. It really adds to automotive range at minimal cost. Perhaps, of course this is wishful thinking as my company makes hydrogen generators. Still it seems worthwhile to design this important component of the hydrogen economy.

I have a mental picture of what the hydrogen delivery container might look like based on the “Jerry can” that the Germans (Jerrys) developed to hold gasoline –part of their planning for WWII. The story of our reverse engineering of it is worth reading. While the original can was green for camouflage, modern versions are red to indicate flammable, and I imagine the hydrogen Jerry will be red too. It must be reasonably cheap, but not too cheap, as safety will be a key issue. A can that costs $100 or so does not seem excessive. I imagine the hydrogen Jerry can will be roughly rectangular like the original so it doesn’t roll about in the trunk of a car, and so you can stack a few in your garage, or carry them conveniently. Some folks will want to carry an extra supply if they go on a long camping trip. As high-pressure tanks are cylindrical, I imagine the hydrogen-jerry to be composed of two cylinders, 6 1/2″ in diameter about. To make the rectangular shape, I imagine the cylinders attached like the double pack of a scuba diver. To match the dimensions of the original, the cylinders will be 14″ to 20″ tall.

I imagine that the hydrogen Jerry can will have at least two spouts. One spout so it can be filled from a standard hydrogen dispenser, and one so it can be used to fill your car. I suspect there may be an over-pressure relief port as well, for safety. The can can’t be too heavy, no more than 33 lbs, 15 kg when full so one person can handle it. To keep the cost and weight down, I imagine the product will be made of marangeing steel wrapped in kevlar or carbon fiber. A 20 kg container made of these materials will hold 1.5 to 2 kg of hydrogen, the equivalent of 2 gallons of gasoline.

I imagine that the can will have at least one handle, likely two. The original can had three handles, but this seems excessive to me. The connection tube between two short cylinders could be designed to serve as one of the handles. For safety, the Jerrycan should have a secure over-seal on both of the fill-ports, ideally with a safety pin latch minimize trouble in a crash. All the parts, including the over- seal and pin, should be attached to the can so that they are not easily lost. Do you agree? What else, if anything, do you imagine?

Robert Buxbaum, February 26, 2017. My company, REB Research, makes hydrogen generators and purifiers.

A very clever hydrogen pump

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I’d like to describe a most clever hydrogen pump. I didn’t invent it, but it’s awfully cool. I did try to buy one from “H2 Pump,” a company that is now defunct, and I tried to make one. Perhaps I’ll try again. Here is a diagram.

Electrolytic membrane H2 pump

Electrolytic membrane H2 pump

This pump works as the reverse of of a PEM fuel cell. Hydrogen gas is on both sides of a platinum-coated, proton-conducting membrane — a fuel cell membrane. As in a PEM fuel cell, the platinum splits the hydrogen molecules into H atoms. An electrode removes electrons to form H+ ions on one side of the membrane; the electrons are on the other side of the membrane (the membrane itself is chosen to not conduct electricity). The difference from the fuel cell is that, for the pump you apply a energy (voltage) to drive hydrogen across the membrane, to a higher pressure side; in a fuel cell, the hydrogen goes on its own to form water, and you extract electric energy.

As shown, the design is amazingly simple and efficient. There are no moving parts except for the hydrogen itself. Not only do you pump hydrogen, but you can purify it as well, as most impurities (nitrogen, CO2) will not go through the membrane. Water does permeate the membrane, but for many applications, this isn’t a major impurity. The amount of hydrogen transferred per plate, per Amp-second of current is given by Faraday’s law, an equation that also shows up in my discussion of electrolysis, and of electroplating,

C= zFn.

Here, C is the current in Amp-seconds, z is the number or electrons transferred per molecule, in this case 2, F is Faraday’s constant, 96,800, n is the number of mols transferred.  If only one plate is used, you need 96,800 Amp-seconds per gram of hydrogen, 53.8 Amp hours per mol. Most membranes can operate at well at 1.5 Amp per cm2, suggesting that a 1.1 square-foot membrane (1000 cm2) will move about 1 mol per minute, 22.4 slpm. To reduce the current requirement, though not the membrane area requirement, one typically stacks the membranes. A 100 membrane stack would take 16.1 Amps to pump 22.4 slpm — a very manageable current.

The amount of energy needed per mol is related to the pressure difference via the difference in Gibbs energy, ∆G, at the relevant temperature.

Energy needed per mol is, ideally = ∆G = RT ln Pu/Pd.

where R is the gas constant, 8.34 Joules per mol, T is the absolute temperature, Kelvins (298 for a room temperature process), ln is the natural log, and Pu/Pd is the ratio of the upstream and downstream pressure. We find that, to compress 2 grams of hydrogen (one mol or 22.4 liters) to 100 atm (1500 psi) from 1 atm you need only 11400 Watt seconds of energy (8.34 x 298 x 4.61= 11,400). This is .00317 kW-hrs. This energy costs only 0.03¢ at current electric prices, by far the cheapest power requirement to pump this much hydrogen that I know of. The pump is surprisingly compact and simple, and you get purification of the hydrogen too. What could possibly go wrong? How could the H2 pump company fail?

One thing that I noticed went wrong when I tried building one of these was leakage at the seals. I found it uncommonly hard to make seals that held even 20 psi. I was using 4″ x 4″ membranes so 20 psi was the equivalent of 320 pounds of force. If I were to get 200 psi, there would have been 3200 lbs of force. I could never get the seals to stay put at anything more than 20 psi.

Another problem was the membranes themselves. The membranes I bought were not very strong. I used a wire-mesh backing, and a layer of steel behind that. I figured I could reach maybe 200 psi with this design, but didn’t get there. These low pressures limit the range of pump applications. For many applications,  you’d want 150-200 psi. Still, it’s an awfully cool pump,

Robert E. Buxbaum, February 17, 2017. My company, REB Research, makes hydrogen generators and purifiers. I’ve previously pointed out that hydrogen fuel cell cars have some dramatic advantages over pure battery cars.

Edward Elric’s Flamel

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Edward Elric, the main character of a wonderful Japanese manga, Full Metal Alchemist, wears an odd symbol on his bright-red cloak. It’s called a Flamel, a snake on a cross with a crown and wings above. This is the symbol of a famous French author and alchemist of the 1300s, Nicholas Flamel who appears also, tangentially, in Harry Potter for having made a philosopher’s stone. But where does the symbol come from?

Edward Elrich with Flammel on back.

Edward Elric wears a snake-cross, “Flamel” on his back.

s03_ama

Current symbol of the AMA

A first thought of a source is that this is a version of the Asclepius, the symbol of the American Medical Association. Asclepius was an ancient Greek doctor who, in 85 BC distinguished between chronic and acute disease, developed theories on diet and exercise, and cured parasitic snakes under the skin by wrapping them around a stick. In mythology, he was chosen to be ship’s doctor on Jason’s voyage, and was so good at curing that Hades told Zeus he revived the dead. Zeus then killed him and set him among the stars as a constellation (the snake-handler, visible in the winter sky between Scorpius and Hercules). Though the story shows some similarities to Full Metal Alchemist, the Asclepius symbol don’t look like Elric’s Flamel. Asclepius had two daughters, Hygeia (hygiene), and Panacea (drugs?); the cup of Hygeia, below, is similar to the Asclepius but not to Ed’s Flamel.

The cup of Hygia, the symbol of pharmacy.

The cup of Hygeia, the symbol of pharmacy.

Staff of Hermes, symbol of the AMA till 2005

Staff of Hermes, symbol of the AMA till 2005

Another somewhat-similar symbol is the Caduceus, symbol of Hermes/ Mercury, left. It was the symbol of the AMA until 2005, and it has wings, but there are two snakes, not one, and no cross or crown. The AMA switched from the Caduceus when they realized that Hermes was not a god of healing, but of merchants, liars, and thieves. Two snakes fighting each other is how the Greeks viewed business. The wings are a symbol of speed. The AMA, it seems, made a Freudian mistake picking this symbol, but it seems unlikely that Flamel made the same mistake.

The true source of the Flamel, I think, is the Bible. In Numbers 21:8-9, the Jews complain about the manna in the desert, and God sends fiery serpents to bite them. Moses prays and is told to put a bronze snake on staff as a cure – look upon it and you are healed. While one might assume the staff was a plain stick like the Asclepius, it might have been a cross. This opinion appears on a German, coin below. The symbol lacks wings and a crown. Still, it’s close to the Flamel. To get the crown and wings, we can turn to the New Testament, John 3:16-17. “Just as Moses lifted up the snake in the wilderness, so the Son of man must be lifted up … “that everyone who believes in Him may have eternal life.” The quote seems to suggest that the snake itself was being lifted up, to holiness perhaps or to Devine service. In either case, this quote would explain the crown and wings as an allusion to Jesus.

German coin, 1500s showing Jesus, a snake and cross on one side. Christ on the other. Suggests two sides of the same.

German “taller” coin, 1500s showing Jesus on the cross on one side, a snake on the cross on the other. Suggests two sides of the same holiness.

I should mention that Flamel’s house is the oldest still standing in Paris, and that it contains a restaurant — one that would be nice to visit. Flamel died in 1418. His tomb has this symbol but was found to be empty. A couple of other odds and ends: the snake on the cross also appears in a horror story, the curse of the white worm, by Bram Stoker. In the story (and movie), it seems there are serpent-worshipers who believe it was the serpent who died for our sins. If you re-read the lines from John, and take the word “Him” to refer to the serpent, you’d get backing for this view. Edward might have adopted this, either as part of his mission, or just for the hell of it. The following exchange might back up Ed’s desire to be controversial.

Roy: I thought you didn’t believe in gods, Full metal.

Edward: I don’t. That’s the thing. I think they can tell, and it pisses them off.

salvation-army

As for the color red, the color may allude to blood and or fire. In this direction, the Salvation Army symbol includes a red “S” on a cross with a crown and the words “Blood and Fire.” In the manga, life-blood and fire appear to be the ingredients for making a philosopher’s stone. Alternately, the red color could relate to a nonvolatile mercury compound, red mercury or mercuric oxide, a compound that can be made by oxidation of volatile mercury. Flamel claimed the symbol related to “fixing the volatile.” Either that’s making oxide of mercury, or putting a stop in death.

Robert E. Buxbaum, February 9, 2017. I’ve also opined on the Holy Grail, and on Jack Kelly of Newsies, and on the humor of The Devine comedy. If you have not read “Full Metal Alchemist,” do.