Hydrogen efficiency by electrolysis (electrode distance)

[@chrislannion]

Salut l’ami. Vidéo intéressante. Il faudrait peut être tester avec d’autres métaux pour la cathode/anode. J’ai lu qqpart que l’utilisation d’un générateur de signaux continus (impulsions carrées notamment) permettrait d’augmenter l’efficacité du processus en réduisant l’énergie consommée. J’ai qqs doutes mais cela mériterait expérimentation (notamment en faisant varier la fréquence et la durée des impulsions). Si tu as l’occasion de faire la manip et de présenter les résultats… merci pour la vidéo en tout cas.

[@foxtizzo]

Ah intéressant! Par contre il faut alors un dispositif pour mesurer l'énergie consommée, qui va être variable... Je m'étais fabriqué un appareil en 12 v qui sort une onde carrée et dont on peut modifier les longueurs d'impulsions, je pourrais utiliser celui-ci (C'était pour faire des étincelles à la base...).

[@chrislannion]

@@foxtizzo si sur une tension fixe de U tu mesures une intensité fixe I (donc une énergie U.I.t), tu peux considérer qu’avec un signal carré tu auras une consommation par seconde de U.I.delta et delta=d/f avec d=durée du signal à U en secondes et f=fréquence du signal carré. Et donc si tu fais tourner ton expérimentation pendant t (en secondes) l’énergie totale consommée sera de U.I.delta.t, a moins qu’on observe un décalage de l’intensité par rapport à la tension et une différence entre le décalage quand U passe de 0 a U et le decalage quand U passe de U a 0 (sorte d’effet capacitif). Ça par contre ça se mesure avec l’oscilloscope électronique.

[@foxtizzo]

@@chrislannion Merci, je vais voir ce que je peux faire!

[@holgerkirschbaum6911]

I just stumbled over your video. Not sure what you wanna show or what is the conclusion. No matter what you’ll do, energy in will be always energy out (in one way or another). At least your video is showing partly that hydrogen is one of the worst energy storage and production option…..

[@foxtizzo]

Thank-you for the comment. I'm interested in the E-out in form of hydrogen, not heat or something else. My conclusion is that you can put the electrodes far apart without affecting the efficiency, and thus separate the Hydrogen from the oxygen very well without any membrane. I would say that the efficiencies that I get are not that bad compared to other methods when it comes to storage. I don't know what you are thinking about? Batteries? Pumped storage power plant (water)? They indeed have very high efficiencies but also some drawbacks...

[@holgerkirschbaum6911]

@@foxtizzo the effect that the distance of the electrodes doesn’t impact the efficiency is explained by the thermodynamic laws. However, separating the two gases takes a bit more than just to increase the distance. Even if you think they are far apart and it easy to “funnel” them you still have oxygen produced in the cathode double layer (Helmholtz double layer, secondary conductor). Aside from that stainless steel can’t be used (yes, to prove the mechanics and chemistry SS is good enough). What I meant “with storage” is that is so unbelievable expensive to compress and store hydrogen - it is simply not economical

[@foxtizzo]

​@@holgerkirschbaum6911 Thank you for this information... This seems to be very important and nobody speaks about it when they experiment with electrolysis to make hydrogen. I thought the efficiency would be lower by putting the electrodes further apart because ther would be more resistance for the ions to travel across the longer distance, so more heat losses... I've seen that ruthenium plated stainless-steel is sometimes used for this purpose. Yes, compressing this gas isn't cost effective at all, the best would be low pressure and big storage. But that's the case for almost every gas you would compress. I've tried compressing wood gas, it's really not worth it, better use it directly. I've done the calculations for methane (from a biodigester) to run a car . To travel 250 km you need 15kwh electricity to remove the CO2 by scrubbing and 10kwh to compress the gas at 200bar. That's 25kwh electricity for 250km, about the same as you would need for an electric car...

[@holgerkirschbaum6911]

@@foxtizzo for professional electrolysers usually coated/plated titanium expanded metal meshes are used, wherein the coating can be MMO (mixed metal oxides), platinum or carbon. Methan is also not a good gas to compress as the critical temperature is low at -162C. Good gasses which are easy to compress are butane or propane as they can be easily liquified by relatively low energy and normal temperatures. Unfortunately they are still fossil fuels and therefor carbon based. However, you must have made a wrong calculation with the 15kwh for 250km. It is average 15kwh for 100km (BEV) and about 40kwh for a fuel diesel car for 100km. I don’t understand why so many people trying to utilise hydrogen? Only because you can simply make it at home? Hydrogen is and will never be an alternative energy source (I know investors will tell otherwise)

[@foxtizzo]

​@@holgerkirschbaum6911 Thank you! I was talking about an order of magnitude for the electric car. I meant the 25kwh electricity to fillup for a 250km ride (with methane from biogas) are near to the 37.5kwh you need to recharge the battery of your electric car for the same distance. Although there are probably more than 25kwh of energy in the full methane tank, but the thermic engine has such a low efficiency... "I don’t understand why so many people trying to utilise hydrogen?" Well that's easy to answer: you can make it easily out of electricity and water. Methane is interesting because you can make it easily out of organic waste (and heat eventually). Even if it's very uneffective, if you have too much solar power and don't know what to do out of it, it's better to store it that way! Find a way to make butane or propane or a liquid fuel out of theese two gases with a better efficiency than it needs to compress hydrogen or methane, and you'll be the king. Fisher-Tropsch seems to be cost ineffective compared to fossil-fuels...