Hydrogen Generator

[sww914]

I've decided to deal with the end of the world right after it happens. I remember Y2K. I just threw out some dried beans that I never used. I still have about 15# of salt.
I love the idea of using hydrogen but the development of the necessary pieces is lagging.

[TheWatchman]

When is the world ending?

What I am preparing for is economic hardship and hyper-inflation. These are becoming obvious to the most casual observer. Myself, about to embark on a life remaining cruise on a fixed income, would like to prepare for limited outside assistance and the most frugal means of extending and enjoying while people who have not prepared will have to terminate their endless vacation because for them it requires $10-20k annually to sustain their lifestyle as 'cruisers'.

Hence the search for alternative means of sustenance.

Fuel will not be affordable in the very near future. Food prices have almost doubled in the last three years. There is political unrest worldwide. Changing weather patterns, etc..

I would rather be prudent and wise as opposed to burying my head in the sand. This is not a religious thread. It is a very serious investigation into alternative methods of sustaining oneself in the cruising environment.

[StringBimini]

Hydrogen will combust, just like propane. However, there are several issues, such as:
1. Safety -- is an asphixiant, burns a colorless flame, can auto-ignite if it leaks from a high pressure source, low ignition temp., requires a classified electrical rating (if used where there are electrical connections and devices).
2. Storage -- 1 kg of hydrogen is (very) roughly equivalent to 1 gallon of gasoline from a heating value standpoint. The problem is storing 1 kg of hydrogen takes a massive amount of volume at low pressures. So, you either need to use it at the exact rate you produce it, or you must store it to provide a surge mass. Storage is accomplished by either (a) highly pressurized gas, (b) liqufied hydrogen, or (c) chemisorption on a metal hydride. On a boat, the only practical one is (c) metal hydrides. Metal hydrides are quite heavy (not such a problem on a boat), but will adsorb on the order of 7 wt% hydrogen at ambient temperature. I have no idea what metal hydrides are available commercially, and at what cost.
3. Generation -- since it is not practical to generate at the exact rate you use it (balancing the consumption/generation is too difficult), you need a surge tank (with metal hydride in it) to take the imbalance. How this might work would be to generate using solar cell electricity for hydrolysis, producing hydrogen, and oxygen(!). Now, hydrolysis is a bit tricky in itself...must have the right anode and cathode, a way to collect the low pressure gas, and I have no idea of the water purity required, but I suspect you can't just use straight sea water (I might be wrong). Never mind how all this might work on a pitching boat, but for this thought experiment, assume we have the hydrolysis down pat, and can dispose of the oxygen (or chlorine gas?) safely. From the metal hydride bed (enclosed in a stainless steel tank), you can release the collected hydrogen by adding heat to the hydride at moderate temp (maybe 180 F). When the gas is released, it will pressurize in the closed tank, and is now useful for whatever purpose (feeding combustion, or fuel cell). Since you will still be making hydrogen, while one metal hydrode tank is degassing/pressurizing, you will need another to continue collecting/adosrbing hydrogen at low pressure. In fact, you may need several tanks, and as you may have noted, you will need a heat source. Open question -- how many cycles can you get on the metal hydride, before it loses adsorption capacity.
4. End use -- can combust it, but need a whole new fuel/air mixer; this will be incompatible with other fuels of course (propane, diesel, etc.). Personally, I would consider a PEM fuel cell. These are not well developed, and are susceptible to poisoning, but again, we are just talking "what if". CO is the main poision for reformer based hydrogen production, but for electrolysis, it shouldn't be an issue. Don't know if there are other impurities from raw water. One side note...metal hydride is excellent at removing CO from hydrogen (if you did use a reformer). Anyway, with pristine electrolsis hydrogen, you might get a decent life from the membrane (I dunno).

In conclusion, I don't think hydrogen on a boat is practical at the present time. With any emerging technology, you have the problem of commercial availability of parts and materials, and there are gaps in industry standards for safe generation, storage, and use (on a boat in particular). Now, you might have better luck trying this at home! (I am kidding, plus the neighborhood organization would never approve). Perhaps in 20 years, this may come to fruition. There is a lot of "free" government research online, if you want to learn more.