5 ms·

Scientists predict green energy revolution after new graphene discoveries

40 points by 3eto 12y ago

upofadown 12y ago
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.
trishume 12y ago
This may well be a very important and interesting discovery but I cringed a few times at the poor explanation of some of the science. Example: "a million times thinner than human hair, yet more than 200 times stronger than steel" the word "yet" suggests that it is very strong in an absolute sense despite being so thin. Yet in reality the comparison is to an atom-thick sheet of steel, which is not very strong at all. This strength doesn't easily scale, as evidenced by the fact that graphite (lots of graphene layers) is not 200 times stronger that steel. (note that my explanation of the science may not be perfect but it is better than this article)
- saosebastiao 12y ago
  > This strength doesn't easily scale, as evidenced by the fact that graphite (lots of graphene layers) is not 200 times stronger that steel. This is an even worse explanation of the science. On the level of saying that the strength of steel doesn't scale because I can bend pig iron with my hands.
Animats 12y ago
Materials-science articles about a modest advance in surface chemistry (which is usually called "nanotechnology") are regularly being hyped into "big commercial breakthrough real soon now" articles. Nature and MIT Technology Review (which, despite the name, is a commercial company) are the big offenders. Super-battery or fuel cell articles appear frequently, but never seem to result in actual products. Hydrogen isn't an "energy source", anyway. You have to crack it out of water or pull it out of hydrocarbons. Those processes are uphill energetically. At best, hydrogen is a storage medium.
- ChuckMcM 12y ago
  I agree with your assessment of the materials science articles but in this case I think you missed the 'breakthrough' part. Graphene allows positively charged hydrogen to pass through it. The thought experiment is you create a vessel with an inner porous core, you wrap it in graphene, and then you apply a vacuum. That device will pull any positively charged hydrogen out of the atmosphere (which frankly isn't much except during thunderstorms) This behavior with graphene isn't unknown, the first example was noting that graphene made for an exceptional water filter [1]. [1] http://www.manchester.ac.uk/discover/news/article/?id=11561 http://www.manchester.ac.uk/discover/news/article/?id=11561
  - Animats 12y ago
    Even if that works, it may be subject to all the usual problems, such as filter clog. This is a big problem with hydrogen fuel cells, which require extremely pure hydrogen. It's a general problem with materials whose carefully constructed surface structure has some unusual property. The surface structure may be fragile. A good example is NeverWet, the ultrahydrophobic coating. It repels water because the surface is composed of tiny spikes, and water's surface tension keeps the water supported on the surface of the spikes. This works so well that mud will run off of shoes treated with it. The effect, though, doesn't last long; even slight wear on the surface damages the micro-spikes. Reviews of the product on Amazon agree: great at first, useless within hours to days of use: (http://www.amazon.com/Oleum-274232-Never-Multi-Purpose/product-reviews/B00DNQBFAW http://www.amazon.com/Oleum-274232-Never-Multi-Purpose/produ...).
SixSigma 12y ago
No surprise there, they always hook it onto the cause de jour
andretti1977 12y ago
Oops the site says "you've been hacked by the sirian electronic army (sea)"
thret 12y ago
A bit OT but this reminded me of Maxwell's demon: http://en.wikipedia.org/wiki/Maxwell's_demon http://en.wikipedia.org/wiki/Maxwell's_demon

40 points by 3eto 12y ago

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.

trishume 12y ago

This may well be a very important and interesting discovery but I cringed a few times at the poor explanation of some of the science. Example: "a million times thinner than human hair, yet more than 200 times stronger than steel" the word "yet" suggests that it is very strong in an absolute sense despite being so thin. Yet in reality the comparison is to an atom-thick sheet of steel, which is not very strong at all. This strength doesn't easily scale, as evidenced by the fact that graphite (lots of graphene layers) is not 200 times stronger that steel. (note that my explanation of the science may not be perfect but it is better than this article)

saosebastiao 12y ago
> This strength doesn't easily scale, as evidenced by the fact that graphite (lots of graphene layers) is not 200 times stronger that steel. This is an even worse explanation of the science. On the level of saying that the strength of steel doesn't scale because I can bend pig iron with my hands.

Animats 12y ago

Materials-science articles about a modest advance in surface chemistry (which is usually called "nanotechnology") are regularly being hyped into "big commercial breakthrough real soon now" articles. Nature and MIT Technology Review (which, despite the name, is a commercial company) are the big offenders. Super-battery or fuel cell articles appear frequently, but never seem to result in actual products. Hydrogen isn't an "energy source", anyway. You have to crack it out of water or pull it out of hydrocarbons. Those processes are uphill energetically. At best, hydrogen is a storage medium.

ChuckMcM 12y ago
I agree with your assessment of the materials science articles but in this case I think you missed the 'breakthrough' part. Graphene allows positively charged hydrogen to pass through it. The thought experiment is you create a vessel with an inner porous core, you wrap it in graphene, and then you apply a vacuum. That device will pull any positively charged hydrogen out of the atmosphere (which frankly isn't much except during thunderstorms) This behavior with graphene isn't unknown, the first example was noting that graphene made for an exceptional water filter [1]. [1] http://www.manchester.ac.uk/discover/news/article/?id=11561 http://www.manchester.ac.uk/discover/news/article/?id=11561
- Animats 12y ago
  Even if that works, it may be subject to all the usual problems, such as filter clog. This is a big problem with hydrogen fuel cells, which require extremely pure hydrogen. It's a general problem with materials whose carefully constructed surface structure has some unusual property. The surface structure may be fragile. A good example is NeverWet, the ultrahydrophobic coating. It repels water because the surface is composed of tiny spikes, and water's surface tension keeps the water supported on the surface of the spikes. This works so well that mud will run off of shoes treated with it. The effect, though, doesn't last long; even slight wear on the surface damages the micro-spikes. Reviews of the product on Amazon agree: great at first, useless within hours to days of use: (http://www.amazon.com/Oleum-274232-Never-Multi-Purpose/product-reviews/B00DNQBFAW http://www.amazon.com/Oleum-274232-Never-Multi-Purpose/produ...).

SixSigma 12y ago

No surprise there, they always hook it onto the cause de jour

andretti1977 12y ago

Oops the site says "you've been hacked by the sirian electronic army (sea)"

thret 12y ago

A bit OT but this reminded me of Maxwell's demon: http://en.wikipedia.org/wiki/Maxwell's_demon http://en.wikipedia.org/wiki/Maxwell's_demon