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New Hydrogen Storage Technique
pwp writes to mention that researchers at the University of New Brunswick are reporting they have found a new method of storing hydrogen gas. The new method is able to condense hydrogen gas into a usable solid under mild conditions. "Hydrogen gas is typically stored under pressure in large metal cylinders, approximately four feet high. These cylinders are heavy and expensive to transport. Since they are under pressure, they also pose a safety hazard. 'We've reached a milestone with our ability to condense hydrogen into a usable solid,' said Dr. McGrady. 'The next step is to produce a safe, compact storage system for the compound that is both lightweight and affordable.' The research is expected to produce reversible hydrogen storage materials that can be processed into a powder for use in limitless commercial applications."
Nitpick: 9% is approximately 1/11. That means that 10/11 parts is 'packaging,' so there's ten times as much non-hydrogen stuff as there is hydrogen.
There is no "I disagree" mod for a reason. Flamebait, Troll, and Overrated are not substitutes.
http://meetings.aps.org/Meeting/MAR07/Event/59811
extracted:
Investigation of the Direct Hydrogenation of Aluminum to Alane in Supercritical Fluids
Alane, AlH$_{3}$ has many of the properties that are requisite for materials to be considered viable for onboard hydrogen storage applications. Most notibly, it contains 10.1 wt{\%} hydrogen and undergoes dehydrogenation at appreciable rates at temperatures below 100$^{\circ}$C. However, the very low, $\ge $ 6 kJ/mol, enthalpy of dehydrogenation of AlH$_{3}$ prohibits subsequent re-hydrogenation through standard gas-solid techniques except at very high pressures or very low temperatures. The extremely low solubility of gaseous H$_{2}$ in conventional organic solvents also vitiates a solution-based approach. Re-hydrogenation of Al using a supercritical fluid potentially offers a workable approach since the fluid can act as a solvent, at the same time remaining completely miscible with permanent gases like hydrogen. Recently, it has been found that mixtures of NaH and Al can be hydrogenated to sodium alanate, NaAlH$_{4}$ under modest pressures and temperatures in supercritical fluids. We have now extended these studies to the hydrogenation of Al to AlH$_{3}$. The results of these studies and experimental details will be reported.
(The important question is now the energetic cost of preparing alane by this method, which
impacts the efficiency of using alane-derived hydrogen as a fuel.
Whoah, seriously? They're making alane (stabilized aluminum hydride, AlH3)? Yep, a quick search revealed this to be the case. This would interest the rocketry industry as well, since alane offers great Isp. Let me check those weight numbers. Aluminum's atomic mass is about 27, while hydrogen's is about 1. AlH3 would thus be about 10% hydrogen by weight, so 9% would be essentially saturated, and 6% over half saturated. If correct, this would be incredible.
HOWEVER...
As many people seem to forget on energy and rocketry threads, breakthroughs like this are sadly a dime a dozen. The vast majority never reach the market or reach it in a greatly diminished form. Thus, take press-release style reports of breakthroughs with a heavy grain of salt.
Assuming ethanol comes from murdered children and the hydrogen from magic, hydrogen saves 132% more lives than ethanol.
http://www.biofuels.fsnet.co.uk/sustain.htm .0092 ratio... that's uh, less than 1/100th or 100 times as much packing material....
Typically, a 1460 x 230 mm K size industrial gas cylinder weighs 65kg and holds 7.2 cubic metres of hydrogen, which has to be compressed at 175 bar (c. 2500 psi) - a convenient size and weight (same as a 50 litre fuel tank) for one cylinder to fit into a car, but the actual weight of the hydrogen is only 0.6kg.
hmmm... 65kg/.6kg
every day http://en.wikipedia.org/wiki/Special:Random
Ye Gods!
... Errr, OK; you mean ICE?
TFA is *very* short on details but, as far as I can determine, they have nothing more than a (slightly) more efficient gas/metal adsorbtion method.
To illustrate *how* short on detail it is, take the quote "The way to do this is to turn hydrogen into a compound -- a solid -- so you can use it when you want, safely, in the amount you want."
Hydrogen aDsorbtion (which means sticking to the surface of, rather than being pulled into the structure of (aBsorbtion) onto metals) has been known about for a very long time. Using these techniques does do away with the classical problems of storing hydrogen cryogenically (cold, volatility and risk of explosion) but for a *huge* cost of energy-density/weight ratio. So much so that it isn't really worth the effort. Even if they have achieved a ten-fold improvement over traditional (titanium) adsorbtion methods, it wouldn't be nearly enough to be viable consumer level energy requirements.
- Molecular hydrogen (H2) physically sticking to a porous storage medium, such as a metal organic framework, without chemically reacting.
- Chemically storing atomic hydrogen in a compounds, such as metal hydrides, where it can reversibly react to form H2.
The challenge is trying to do the above reversibly in non-extreme temperature and pressure conditions and in a method that won't break down with hundreds and thousands of empty/full cycles.The reason the weight percent numbers seem small is that H2 has a molecular weight of ~2 AMU and any material with the capacity to adsorb lots of hydrogen or store it chemically is going to be made of much heavier atoms. In this way, mass percentage is deceiving but it is the most common measure of storage capacity. My wild guess is that the 6.5% cutoff is in the ballpark of the energy output to mass ratio of gasoline. Luckily, neither fuel requires the automobile to haul around all the oxygen necessary to for the reactions.
If people aren't happy with single digit weight percentages, they could suggest using a heavier hydrogen isotopes to double or triple the numbers!
I started laughing when the article stated that burning hydrogen produced zero pollution. Sure, if you live in a pure oxygen environment. Unfortunately, cars have to operate with a supply that's mostly nitrogen and significant portion of the resulting pollution is nitrogen compounds. Besides, the energy density per weight still sucks worse than decent battery technology which really does have zero emissions at the point of use.
I believe the relevant slashdot article is here. The link has moved since (and lost relevance, as, judging by the wording of slashdot summary, TFA just announced a presentation), but the guys behind it still have their website (here). But what matters is that the method is not the same. The new method (for suitable values of new) uses an aluminum compound, the one the DTU guys (or whoever) have demonstrated uses ammonia.
The issue with H20 in this instance is that it's terribly difficult to get the Hydrogen atoms away from the Oxygen atom. The bonds are quite strong.
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Absolutely true - I was going to mention the bond energy of water (460 kJ/mol, if anyone cares - or is still reading this). Other than that, yes, the hydrogen storage density of water is quite high. Trouble is, the instant you remove a single hydrogen atom, you get hydroxide, which generally doesn't do nice things to fluid systems. The trick is removing both H atoms. It gets easier for the second one, which is nice.
However (and I don't remember exactly how), there are catalysis effects that promote water dissociation without high temperatures, for example, or other non-ideal processing steps. Gotta achieve the bond energy, though; that's still thermodynamics. But platinum, palladium, and others can be used (I think) to selectively sweep the hydrogen from the feedstock. You can do "photo-dissociation" too, IIRC.
While we're on the subject, how about some passive solar power, doing nothing but cracking water 24/7? I mean, we're going to have to get all this hydrogen from someplace...yeah, I know - takes a LOT of panel area.
-joe.