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Have reworded quite a bit: Removed this bit "which will be used in the future to produce hydrogen for cars through HTE of water." as it's a bit too speculative. Would be nice to get some theoretical hydrogen economy in there if anyone has any ideas on how to word something so far-reaching? Have also removed the 20% conversion efficiency too, as it's really quite variable depending on temperature, process, etc. A nice link to it would help, so long as that first para doesn't get too unwieldy 82.69.54.182 05:01, 18 Jun 2005 (UTC)
The reference to pyrolysis should be removed. just looking at the respective pages for pyrolysis and hydrogen shows that pyrolysis is not used currently to generate hydrogen gas. — Preceding unsigned comment added by 124.168.56.180 ( talk) 10:22, 14 July 2015 (UTC)
I'm looking at the DOE page referenced from this one, and I'm confused.
If a process requires 225 megajoules (thermal) to produce 145 megajoules (1 kg) of hydrogen, where is the other 80 megajoules? I presume it has to show up as heat at the electrolyzer output, which is at 850 degrees C. The graph on page 2 shows that the process has "thermal energy input", which suggests the reaction is endothermic. So if 850 C requires 40 MJ/kg thermal energy input, does that mean it's actually 120 MJ/(kg output) at the input, at some temperature higher than 850 C, and rejecting 80 MJ/(kg output) at the output at 850 C? If so, how hot is the input?
The DOE page suggests 1 kg of hydrogen produced comes out as 3 kg hydrogen, 8 kg oxygen, and 18 kg steam, and enters as 2 kg hydrogen and 27 kg steam. To carry in 40 MJ of thermal energy, that mix would have to be 690 K hotter, or 1540 C! You'd think the DOE page would mention a scary fact like that.
Iain McClatchie 06:42, 17 October 2005 (UTC)
the externel link to the DOE is not working— Preceding unsigned comment added by 62.68.29.247 ( talk) 13:46, 7 November 2006 (UTC)
The battery symbol of the first figure is the reverse of convention where the (+) terminal is shown as the longer line segment. I'm nit picking here but inconsistency can cause confusion in certain contexts { Spyglasses ( talk) 02:26, 25 April 2021 (UTC)}
"At current hydrocarbon prices, HTE can not compete with pyrolysis of hydrocarbons as an economical source of hydrogen, which produces carbon dioxide as a by-product."
Current (written in past) hydrocarbon prices, does not reflect geopolicially inflated natural gas prices that may be current at time of reading. Needs a specific benchmark price. Pyrolysis is not the 20th century economic production method for hydrogen. Steam reforming is. Pyrolysis creates graphite (solid) and hydrogen. No CO2 byproduct. — Preceding unsigned comment added by 2607:FEA8:2260:E00:49E1:4FAC:68F0:6397 ( talk) 23:38, 3 December 2022 (UTC)
This article is rated Start-class on Wikipedia's
content assessment scale. It is of interest to the following WikiProjects: | |||||||||||||||||||||||||||||||
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Have reworded quite a bit: Removed this bit "which will be used in the future to produce hydrogen for cars through HTE of water." as it's a bit too speculative. Would be nice to get some theoretical hydrogen economy in there if anyone has any ideas on how to word something so far-reaching? Have also removed the 20% conversion efficiency too, as it's really quite variable depending on temperature, process, etc. A nice link to it would help, so long as that first para doesn't get too unwieldy 82.69.54.182 05:01, 18 Jun 2005 (UTC)
The reference to pyrolysis should be removed. just looking at the respective pages for pyrolysis and hydrogen shows that pyrolysis is not used currently to generate hydrogen gas. — Preceding unsigned comment added by 124.168.56.180 ( talk) 10:22, 14 July 2015 (UTC)
I'm looking at the DOE page referenced from this one, and I'm confused.
If a process requires 225 megajoules (thermal) to produce 145 megajoules (1 kg) of hydrogen, where is the other 80 megajoules? I presume it has to show up as heat at the electrolyzer output, which is at 850 degrees C. The graph on page 2 shows that the process has "thermal energy input", which suggests the reaction is endothermic. So if 850 C requires 40 MJ/kg thermal energy input, does that mean it's actually 120 MJ/(kg output) at the input, at some temperature higher than 850 C, and rejecting 80 MJ/(kg output) at the output at 850 C? If so, how hot is the input?
The DOE page suggests 1 kg of hydrogen produced comes out as 3 kg hydrogen, 8 kg oxygen, and 18 kg steam, and enters as 2 kg hydrogen and 27 kg steam. To carry in 40 MJ of thermal energy, that mix would have to be 690 K hotter, or 1540 C! You'd think the DOE page would mention a scary fact like that.
Iain McClatchie 06:42, 17 October 2005 (UTC)
the externel link to the DOE is not working— Preceding unsigned comment added by 62.68.29.247 ( talk) 13:46, 7 November 2006 (UTC)
The battery symbol of the first figure is the reverse of convention where the (+) terminal is shown as the longer line segment. I'm nit picking here but inconsistency can cause confusion in certain contexts { Spyglasses ( talk) 02:26, 25 April 2021 (UTC)}
"At current hydrocarbon prices, HTE can not compete with pyrolysis of hydrocarbons as an economical source of hydrogen, which produces carbon dioxide as a by-product."
Current (written in past) hydrocarbon prices, does not reflect geopolicially inflated natural gas prices that may be current at time of reading. Needs a specific benchmark price. Pyrolysis is not the 20th century economic production method for hydrogen. Steam reforming is. Pyrolysis creates graphite (solid) and hydrogen. No CO2 byproduct. — Preceding unsigned comment added by 2607:FEA8:2260:E00:49E1:4FAC:68F0:6397 ( talk) 23:38, 3 December 2022 (UTC)