4 ms·

The article goes on about the idea of collecting hydrogen from the atmosphere using a graphene filter. There is no appreciable amount of hydrogen in the atmosph

The article goes on about the idea of collecting hydrogen from the atmosphere using a graphene filter. There is no appreciable amount of hydrogen in the atmosphere.

mnw21cam 12y ago
And the fact that hydrogen molecules don't pass through graphene. Only hydrogen ions.
TylerJay 12y ago
I'm confused too. Is this just bad reporting or am I missing something?
Gravityloss 12y ago
Using air humidity? Say we have 10 grams of water per cubic meter of air (so about 1% of the total air mass), so about 1 gram of hydrogen. At about 140 kJ/kg, and assuming a 10% reduction efficiency, and 100 watts per square meter solar panel, it should be able to reduce 0,071 grams per second or 260 grams per hour. Assuming 10% of air moisture can be extracted, the wind passing through the system to keep the water flow would need to be about 0,7 m/s. It's almost always as windy as that. The rough numbers are frighteningly good. All we need is the system to be cheap.
- danieltillett 12y ago
  ... and some way to store and transport hydrogen. We can make hydrogen quite cheaply right now (it is kindergarten technology), but once you try to store and/or transport it then this is where things get really, really difficult [1]. 1. http://en.wikipedia.org/wiki/Hydrogen_storage http://en.wikipedia.org/wiki/Hydrogen_storage
  - Gravityloss 12y ago
    No, I assumed (in hindsight could have mentioned it) that you could use the hydrogen locally to generate electricity. The thing is connected to the the electricity network. But I realized that is roughly the momentary day power of the panel. The real yearly average production is maybe 15% of that. Forgot the panel efficiency with this http://en.wikipedia.org/wiki/Photovoltaic_system#mediaviewer/File:SolarGIS-Solar-map-World-map-en.png http://en.wikipedia.org/wiki/Photovoltaic_system#mediaviewer...
marcosdumay 12y ago
Don't graphene oxidate in the presence of hydroxyl ions? Separating hydrogen from water will creating tons of them.

The article goes on about the idea of collecting hydrogen from the atmosphere using a graphene filter. There is no appreciable amount of hydrogen in the atmosphere.

mnw21cam 12y ago

And the fact that hydrogen molecules don't pass through graphene. Only hydrogen ions.

TylerJay 12y ago

I'm confused too. Is this just bad reporting or am I missing something?

Gravityloss 12y ago

Using air humidity? Say we have 10 grams of water per cubic meter of air (so about 1% of the total air mass), so about 1 gram of hydrogen. At about 140 kJ/kg, and assuming a 10% reduction efficiency, and 100 watts per square meter solar panel, it should be able to reduce 0,071 grams per second or 260 grams per hour. Assuming 10% of air moisture can be extracted, the wind passing through the system to keep the water flow would need to be about 0,7 m/s. It's almost always as windy as that. The rough numbers are frighteningly good. All we need is the system to be cheap.

danieltillett 12y ago
... and some way to store and transport hydrogen. We can make hydrogen quite cheaply right now (it is kindergarten technology), but once you try to store and/or transport it then this is where things get really, really difficult [1]. 1. http://en.wikipedia.org/wiki/Hydrogen_storage http://en.wikipedia.org/wiki/Hydrogen_storage
- Gravityloss 12y ago
  No, I assumed (in hindsight could have mentioned it) that you could use the hydrogen locally to generate electricity. The thing is connected to the the electricity network. But I realized that is roughly the momentary day power of the panel. The real yearly average production is maybe 15% of that. Forgot the panel efficiency with this http://en.wikipedia.org/wiki/Photovoltaic_system#mediaviewer/File:SolarGIS-Solar-map-World-map-en.png http://en.wikipedia.org/wiki/Photovoltaic_system#mediaviewer...

marcosdumay 12y ago

Don't graphene oxidate in the presence of hydroxyl ions? Separating hydrogen from water will creating tons of them.