Green Building Forum - Harvesting energy from thin air - Graphene will make it possible.

Harvesting energy from thin air - Graphene will make it possible.

Chris P Bacon — Thu, 27 Nov 2014 07:46:27 +0000

http://www.independent.co.uk/news/science/scientists-predict-green-energy-revolution-after-incredible-new-graphene-discoveries-9885425.html

Story on the front page of today's Independent reporting on a study published in Nature that states that:

"Researchers have discovered that graphene allows positively charged hydrogen atoms or protons to pass through it despite being completely impermeable to all other gases, including hydrogen itself.

The implications of the discovery are immense as it could dramatically increase the efficiency of fuel cells, which generate electricity directly from hydrogen, the scientists said.

The breakthrough raises the prospect of extracting hydrogen fuel from air and burning it as a carbon-free source of energy in a fuel cell to produce electricity and water with no damaging waste products.

â€œIn the atmosphere there is a certain amount of hydrogen and this hydrogen will end up on the other side [of graphene] in a reservoir. Then you can use this hydrogen-collected reservoir to burn it in the same fuel cell and make electricity,â€ said Professor Sir Andrei Geim of Manchester Univeristy."

Still only small scale and probably many years work involved in realising this on a commercial scale but it looks very positive.

Harvesting energy from thin air - Graphene will make it possible.

Ed Davies — Thu, 27 Nov 2014 08:48:42 +0000

http://www.independent.co.uk/news/science/scientists-predict-green-energy-revolution-after-incredible-new-graphene-discoveries-9885425.html#77104af25d2743b6b879f06148bbb576

Harvesting energy from thin air - Graphene will make it possible.

rhamdu — Thu, 27 Nov 2014 08:55:29 +0000

Here is the Nature paper http://www.nature.com/nature/journal/vaop/ncurrent/full/nature14015.html

Yes, graphene turns out to be permeable to H+ ions, and this might eventually lead to a new kind of fuel cell.

We have hydrogen fuel cells already. Graphene might make them lighter or safer or more reliable. Cool.

But the Indy piece implies that elemental hydrogen (H2) is abundant in the air. It ain't. Just lots of water (H2O). You can use wind energy to split water, and if you insist, that water could be extracted from the air by a big dehumidifier, though I think most engineers would just wait for it to rain.

Geim is a smart cookie, I think he has been misquoted by idiots.

Harvesting energy from thin air - Graphene will make it possible.

Chris P Bacon — Thu, 27 Nov 2014 09:35:57 +0000

Posted By: rhamduBut the Indy piece implies that elemental hydrogen (H2) is abundant in the air. It ain't. Just lots of water (H2O). You can use wind energy to split water, and if you insist, that water could be extracted from the air by a big dehumidifier, though I think most engineers would just wait for it to rain.

But there is some hydrogen in fresh air is there not? 1 part in 2 million if the interweb is correct. So presumably if you force enough air through your graphene filter you will harvest enough hydrogen?

No idea how much hydrogen a fuel cell car consumes but presumably some of the mathematicians around here can calculate how big a scoop you will need on your speeding car to keep it going....

What happens if we start consuming hydrogen from air, does the concentration of 1 part in 2 million come back into balance naturally or will we end up depleting the available hydrogen?

Harvesting energy from thin air - Graphene will make it possible.

tony — Thu, 27 Nov 2014 09:44:34 +0000

how do stop the proton combining with oxygen before it passes through the membrane?

Harvesting energy from thin air - Graphene will make it possible.

rhamdu — Thu, 27 Nov 2014 09:58:15 +0000

Posted By: Chris P Bacon
But there is some hydrogen in fresh air is there not? 1 part in 2 million if the interweb is correct. So presumably if you force enough air through your graphene filter you will harvest enough hydrogen?

No graphene filter is in prospect. Graphene is permeable to H+ ions, not the (very few) H2 molecules in the atmosphere. The Indy doesn't seem to understand the difference.

In any case, as you say, you'd have to force huge amounts of air into the filter. There's a theoretical minimum energy required to separate gases, and energy payback seems unlikely.

Harvesting energy from thin air - Graphene will make it possible.

rhamdu — Thu, 27 Nov 2014 10:03:13 +0000

Posted By: tonyhow do stop the proton combining with oxygen before it passes through the membrane?

You make sure there is no oxygen on that side!

Harvesting energy from thin air - Graphene will make it possible.

tony — Thu, 27 Nov 2014 10:04:11 +0000

expensive

Harvesting energy from thin air - Graphene will make it possible.

fostertom — Thu, 27 Nov 2014 10:39:39 +0000

Posted By: Chris P BaconWhat happens if we start consuming hydrogen from air, does the concentration of 1 part in 2 million come back into balance naturally or will we end up depleting the available hydrogen?

That was my thought - yet another assumption that we can dump into or extract from the carefully balanced biosphere, which appears infinitely large, without unforseen consequences.

Harvesting energy from thin air - Graphene will make it possible.

SteamyTea — Thu, 27 Nov 2014 10:44:15 +0000

Not going to hold my breath for this technology

But on a more serious note, if you burn hydrogen in air, as opposed to oxygen only, you create oxides of nitrogen, which is not a good thing.

Harvesting energy from thin air - Graphene will make it possible.

Ed Davies — Thu, 27 Nov 2014 10:49:05 +0000

Second guessing the comment I linked above:

QJRMS: â€œThe hydrogen content of atmospheric air at ground levelâ€

http://onlinelibrary.wiley.com/doi/10.1002/qj.49708335808/abstract

0.6 parts per million. I assume that's of Hâ‚‚.

I calculate that if you burned all the hydrogen in the atmosphere in a year you'd be able to produce 244 GW. That might cover a couple of European countries, I suppose, but hardly a panacea. Dunno how fast the hydrogen would be replaced - there must be some sort of replacement process going on as hydrogen is lost to space being light enough to reach escape velocity from the upper atmosphere just due to thermal speeds.

But that's if you can get at all the molecular hydrogen (Hâ‚‚). I can't imagine there's much atomic ionised hydrogen around and what little there is must get reacted pretty quickly, I'd think.

Harvesting energy from thin air - Graphene will make it possible.

rhamdu — Thu, 27 Nov 2014 10:51:53 +0000

If we are going to scrub the whole atmosphere for hydrogen (and we are not, for so many reasons) we might as well take out the excess CO2 and methane while we are about it.

Harvesting energy from thin air - Graphene will make it possible.

ringi — Thu, 27 Nov 2014 11:27:55 +0000

What about just scrubbing mains gas at the point you wish to use a fuel cell, with the rest of the mains gas mix being put back into the pipe for other customers to use....

Harvesting energy from thin air - Graphene will make it possible.

fostertom — Thu, 27 Nov 2014 12:08:44 +0000

Posted By: SteamyTeaif you burn hydrogen in air, as opposed to oxygen only, you create oxides of nitrogen

Really? So much for hydrogen as the ultimate 'clean' fuel.

Harvesting energy from thin air - Graphene will make it possible.

fostertom — Thu, 27 Nov 2014 12:12:46 +0000

Posted By: Ed Daviesif you burned all the hydrogen in the atmosphere in a year you'd be able to produce 244 GW

So this 'harvesting energy from thin air' is a complete non starter. So what is the process good for - filtering pure hydrogen out of a hydrogen-rich mixed gas? Like natural gas - is that what ringi's suggesting?

Harvesting energy from thin air - Graphene will make it possible.

Viking House — Thu, 27 Nov 2014 12:30:38 +0000

There's sufficient Hydrogen produced everyday in the form of Methane, you just have to scrub out the Carbon.
Does putting Hydrogen through a fuel cell instead of burning it prevent the creation of oxides of nitrogen?

Harvesting energy from thin air - Graphene will make it possible.

fostertom — Thu, 27 Nov 2014 13:01:54 +0000

Extracting hydrogen from methane, just like extracting it from water, takes big energy input to 'crack' the chemical bonds - in case of extracting from water, exactly same energy as is usefully released by subsequently burning it. Exactly zero nett energy gain - in fact considerable nett loss, due to the inefficiencies in the transactions.

So cracking methane or water to get hydrogen is totally negative as an energy source - unless the energy input is 'free' in some way, like solar, but even then that solar energy could have been used much more fruitfully. Or hydrogen as a waste by product of some other process - unlikely.

Hydrogen at best is only a tranformed form of some already existing energy. It is only justified, despite the energy-downgrade waste in its production by transformation, when the need for 'portable' fuel is paramount, in vehicles - when the only alternative is liquid fossil. Then, even worse in that use, powering a heat engine, the latter are inherently wasteful, converting at very best 50% (usually about 35%) of the fuel's energy to useful mechanical energy, the rest as heat, which goes to waste as it's hard to find useful use for that much un-storable lo-grade heat on board a vehicle.

Harvesting energy from thin air - Graphene will make it possible.

ringi — Thu, 27 Nov 2014 13:29:21 +0000

In a CHP setup you can crack the mathane with little energy lose, as the free Cs combine to give you CO2 and lots of heat.

Then the hydrogen can feed a cell that tracks the elec usage of the house in real time.

Even if you don't use the excess heat, it still only uses about the same amount of gas as centralized generation due to transmission loses etc.

The problem is that the setup is too expensive at present!

Harvesting energy from thin air - Graphene will make it possible.

fostertom — Thu, 27 Nov 2014 13:41:36 +0000

Posted By: ringithe free Os

do you mean the free Cs? Is there a simple to understand energy flow diagram of this end to end process?

Harvesting energy from thin air - Graphene will make it possible.

Viking House — Thu, 27 Nov 2014 13:47:45 +0000

This Devon guy I've met scrubs Methane through the waste water of his Thermophylic Anaerobic Digesters, the Carbon is taken up by the water, he's left with Carbolic Acid and pure Hydrogen, its Passive so doesn't use any energy.
His Hydrogen fuel cell is running at 78% efficiency and produces 20% heat, he's confident of getting it to 85% with cleaner water.

Harvesting energy from thin air - Graphene will make it possible.

SteamyTea — Thu, 27 Nov 2014 14:38:47 +0000

Posted By: Viking HouseDoes putting Hydrogen through a fuel cell instead of burning it prevent the creation of oxides of nitrogen?

As far as I know yes it does. Fuel cells are better than combustion in that respect.

Harvesting energy from thin air - Graphene will make it possible.

tony — Thu, 27 Nov 2014 15:02:51 +0000

sparks produce oxides of oxygen (O3) and nitrogen (NOx) without any fuel present. explosions do too.

Harvesting energy from thin air - Graphene will make it possible.

SteamyTea — Thu, 27 Nov 2014 15:15:31 +0000

Here is the E&T bit about it, probably a bit more realistic:
http://eandt.theiet.org/news/2014/nov/graohene-membrane-fuel-cell.cfm

Harvesting energy from thin air - Graphene will make it possible.

bot de paille — Thu, 27 Nov 2014 15:42:46 +0000

Graphene is going to kick ass and save the world!

Harvesting energy from thin air - Graphene will make it possible.

ringi — Thu, 27 Nov 2014 16:31:50 +0000

Sorry fostertom , I did mean the fee Cs.

Methane is CH4,
So 2* CH4 is split in 4*H2 + 2C using steam and a catalyst
Add a O from the air to give 4*H2 + C2O + a little heat
Then add more 0 to give 2*H20 + electric output + more heat in the form of lots of stream
Some of the stream is fed back into the first step; hence this can work for CHP, but does not work well for producing H2 to store.

There is very long tern research into fuel cells that can run on methane or methanol directly, I donâ€™t think hydrogen is a good option for transport as it is so hard to store.

Harvesting energy from thin air - Graphene will make it possible.

Ebeneezer — Thu, 27 Nov 2014 22:24:26 +0000

Posted By: Chris P Bacon
What happens if we start consuming hydrogen from air, does the concentration of 1 part in 2 million come back into balance naturally or will we end up depleting the available hydrogen?

Other have explained why it is not a good idea but I haven't seen a direct answer to the above question.

I was pretty sure* I read that naturally the % of hydrogen is continually decreasing within the atmosphere, because it (a) can escape the atmosphere into space and (b) reacts with other elements to form other compounds (which don't naturally split again).

*I have been searching for the original source but can't find it, so maybe I am wrong - surely someone will let me know if I am ;)

Harvesting energy from thin air - Graphene will make it possible.

bot de paille — Fri, 28 Nov 2014 07:41:25 +0000

Are you thinking about helium?

Harvesting energy from thin air - Graphene will make it possible.

SteamyTea — Fri, 28 Nov 2014 07:55:20 +0000

Yes helium is running out.
http://scienceblogs.com/startswithabang/2012/12/12/why-the-world-will-run-out-of-helium/

Harvesting energy from thin air - Graphene will make it possible.

CWatters — Fri, 28 Nov 2014 12:17:55 +0000

http://www.sciencedaily.com/releases/2014/03/140304094839.htm

"around four-fifths of all hydrogen released into the air is rapidly removed through soil activity,"

but where does that hydrogen come from? Is it created by radioactive rocks?

Harvesting energy from thin air - Graphene will make it possible.

CWatters — Fri, 28 Nov 2014 12:31:07 +0000

Bit more googling found this paper...

http://www.atmos.washington.edu/~jaegle/group/Pub_Trop_files/J%20Geophys%20Res-Atmos%202007%20Price.pdf

Table 1 appears to suggest that the biggest sources of hydrogen in the atmosphere are VOCs and the incomplete burning of fossil fuels and biomass. eg mostly man made sources.