Wednesday, September 13, 2006

Hydrogen Storage Breakthrough?

Good job Science Cat!

This could be big...

Really Big...

Via Space Transport News comes this story on a ROOM TEMPERATURE hydrogen storage system that contains 30% more H2 than liquid hydrogen of equal volume!

More info here.

The down side would seem to be the use of Ruthenium as a catalyst, as it is not terribly common. Note however, that it is a bit more common than platinum and found in the same ores. Platinum is a big component of fuel cells anyway and is occasionally considered a deal breaker regards the technology.

It is possible that a cheaper catalyst might be developed, and platinum group metals are believed to be in abundace on the moon and in certain asteroids.

Regardless, the storage of hydrogen at room temperature and in this density is, it seems to me a HUGE story!

Wow! :)


Steven Den Beste said...

No, it's not big. The "deal breaker" for hydrogen is: where are you getting it from? There's no natural source of pure hydrogen, so it can only be made by using energy from some other source. What source? And how do you convert enough energy from that source to produce enough hydrogen to be used as a fuel?

Also, the energy density you're talking about is still not very great. The density of liquid hydrogen is 0.07 kilograms per liter. That's 1/12th the density of gasoline. So if this gives you 30% better density than liquid hydrogen it means that it is about 1/9th the density in terms of weight.

Per unit weight, hydrogen has about three times the energy of gasoline, which means that to achieve energy parity you need three times as big a fuel tank.

Moreover, I think you read the report wrong. It says "A 30% solution of borohydride in water actually contains one-third more hydrogen than the same volume of liquid hydrogen."

Are they counting the hydrogen that's part of the water? I bet they are, and that can't be released for use as a fuel because it's already burned.

The claim is "2200 watt-hours per liter". On the other side of the scale we have gasoline at 20,000 BTU/pound with a density of 0.85, so we have a lot of unit conversion to do. Pardon me for a moment while I do some math. (Jezus; why can't America switch to the Metric System like normal people?)

Steven Den Beste said...

Back again. Here's the numbers:

claimed density for this new approach: 2200 watt-hours/liter

* 3600 joules/watt-hour
=7.9 megajoules/liter

Gasoline energy density is 20,000 BTU/pound.

* 0.85 pounds/pint
* 2.11 pints/liter
* 1055 joules/BTU
=37.8 megajoules/liter

In other words, gasoline has 4.8 times as much energy per volume as this new approach is claimed to have. And since the new approach requires carrying a heck of a lot of water around (for the boro-hydride solution) it's also going to weigh a lot more.

To equal the energy of a 12 gallon fuel tank of gasoline, this new approach requires a tank that carries 57.6 gallons -- or just shy of a quarter of a ton of water.

And there's still the problem of where the hydrogen comes from in the first place.

No, this isn't big. It's pretty much meaningless for vehicles. Sorry.

Ken said...

Thanks for commenting!

Your point regards Hydrogen wells nonexistance is perfectly sound.

However, like most alti-fuels this is predicated on a huge influx of cheap electrical power (likely nukes...GO NUKES) to make it viable.

Given large enough energy reserves even biodiesel can be viable.

H2 is notoriously hard to store, this is room temperature and stores at 30% better density than liquid hydrogen. This does seem like a big deal. It is as you astutely point out, very inferior in energy density to gasoline. But it is, at least as easy to handle which makes quick fill-ups possible, thereby compensating for the shorter range.

My metro, running off an H2 engine would get ~10mpg. A diesel H2 engine might increase that by 50%. and fuel cells are advertised as being 50% more effiecent than diesels, so figure equivalent to 22mpg. That is annoying indeed compared to my 40mpg but perfectly in line with cars from a few decades ago. A bigger car would get less milage, but could carry a bigger tank, though of course with diminishing returns.

Note that the idea here is energy independance and nearly everything in it is renewable (save the uranium or thorium that powered the electrolysis).

This it seems to me is a step up from an electric car or a huge H2 pressurised tank.

It could also become utter vaporware if the only catalyst ends up being as precious as platinum......

Steven Den Beste said...

It may be one step up, but it's the first step on a thousand mile climb.

There is no "huge influx of cheap electricity", not even from nukes. Until you tell me where all that marvelous cheap electricity is coming from, I won't take this seriously.

By the way, there are other problems with this. The car has to have two tanks. One begins full of borohydride solution. The other begins empty. As the solution is processed with the catalyst to release the hydrogen, the waste water and boron (whatever chemically it becomes) get dumped into the other tank.

At the service station, you unload the waste tank, load the fuel tank, and go on your merry way. And the waste fluid has to be trucked back to the original processing plant so the boron can be recharged with hydrogen, from whatever source it comes from.

This is a non-trivial added expense compared to current fuels which only need to take a one-way trip to the consumer.

I'm a little worried about the ruthenium supply, but I'm a whole lot more worried about the boron supply. Are there really adequate quantities of it out of there for it to become the foundation of the vehicle fuel cycle? Because you need a gram or two of ruthenium per vehicle, but each tank of fuel will contain many kilos of boron. The assumption is that the fuel is a saturated solution, since it's the boron which binds the hydrogen.

Can we really come up with a few hundred thousand tons of boron? It's not expensive now but that's because it's not in huge demand now.

And even if the hydrogen being fed to the fuel processing plant is free, how much expense would the fuel cost, including the amortized cost of the processing plant and the cost of the boron in it?

Steven Den Beste said...

By the way, the numbers don't make sense if you assume that this yields 30% more burnable hydrogen per unit volume than liquid hydrogen. If that were the case, the energy per liter would be higher than the energy per liter of LH2, and the quoted energy density isn't remotely that high.

Either there was confusion in the report (not uncommon) or hyperbole (also not uncommon) and that the quoted "30% more hydrogen per volume" includes the hydrogen bound to oxygen in the water for the solution. That hydrogen is useless for our purposes because it's in a low energy state.

Ken said...

Actually the energy density at 30% + sounds about right.

H2 has a very good WEIGHT to energy ratio. Its density sucks.

Your points about the 2 tank solution is of course on target, but the ability to store H2 at room temperature takes the big problem out of the game.

Gas and diesel are superb fuels, H2 cannot match them in density and convinience (it is the least dense thing in the universe afterall:) but gas and diesel are not going to be viable forever.

The issue is energy independance and dealing with a finite fossil fuel supply. That will require something else. Either biofuels, which have their own issues, or something like this. They will NOT be as good as petroleum, but this is more practical than a battery car. And they can be made pretty darn convienient. (the fuel truck that fills a station would simultaneously load itself with the waste borax for instance.

Regards the power issues, there will be nukes or we're screwed.

I'm betting that sooner or later we will start building them (nuke plants) again. Without non-fossil fuel sources of power, all futurism is dystopic and Malthusian.