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Lawrence Livermore Prototype LH2 Tank Maintains Extended Thermal Endurance

5 June 2008

Llnllh2
H2 is often stored as a compressed gas, GH2 (red dot) at ambient temperature (horizontal axis), very high pressure (dotted lines), and relatively low density (vertical axis). Liquid hydrogen (LH2) is stored at much higher density, (blue dot) with higher energetic cost to densify hydrogen. Insulated pressure vessels have flexibility to operate across a broad region (shaded) of the phase diagram, and can be fueled with GH2 at a low energetic cost when energy or fuel cost savings is important or with LH2 when long driving range is a higher priority. Click to enlarge.

An insulated cryogenic pressure vessel developed and installed in an experimental hybrid vehicle—a Prius converted by Quantum for hydrogen use—by a Lawrence Livermore National Laboratory (LLNL) research team can hold liquid hydrogen (LH2) for six days without venting any of the fuel.

The LLNL development has significantly increased the amount of time it takes to start releasing hydrogen during periods of long-term parking, as compared to today’s liquid hydrogen tanks capable of holding hydrogen for merely two to four days.

LH2 tanks hold super-cold liquid hydrogen at around -420°F (-251°C); pressure builds as heat from the environment eventually warms the hydrogen inside. Current automotive LH2 tanks must vent evaporated hydrogen vapor after being parked three to four days, even when using the best thermal insulation available (200 times less conductive than Styrofoam insulation).

In recent testing of its prototype hydrogen tank onboard the liquid hydrogen (LH2) powered Prius, LLNL’s tank demonstrated a thermal endurance of six days and the potential for as much as 15 days, helping resolve a key challenge facing LH2 automobiles.

Today’s automotive LH2 tanks operate at low pressure (2-10 atmospheres; 0.2 to 1.0 MPa). The LLNL cryogenic capable pressure vessel is much stronger, and can operate at hydrogen pressures of up to 34.5 MPa (5,000 psi), holding the hydrogen even as the pressure increases due to heat transfer from the environment. This high-pressure capability also means that a vehicle’s thermal endurance improves as the tank is emptied, and is able to hold hydrogen fuel indefinitely when it is about one-third full.

Hydrogen_car_rear_big
Prototype LLNL LH2 tank mounted in a Prius.

Last year, the LLNL experimental hybrid vehicle demonstrated the longest driving distance on a single tank of hydrogen (650 miles). The recent thermal endurance experiments validate the key benefit of cryogenic pressure vessels: They deliver the high density of liquid hydrogen storage without the evaporative losses.

The LLNL prototype LH2 tanks represent the third generation of insulated pressure tanks built by the lab. The 151-liter tank stores more fuel (10.7 kg LH2) than the previous generation, in a total package that is considerably more compact. This design meets the DOE 2007 volume target (1.2 kWh/liter) and the 2010 DOE weight target (2 kWh/kg).

The Livermore work, sponsored by the Department of Energy’s (DOE’s) Office of Energy Efficiency and Renewable Energy, is part of DOE’s National Hydrogen Storage Project to demonstrate advanced hydrogen-storage materials and designs.

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June 5, 2008 in Hydrogen Storage | Permalink | Comments (21) | TrackBack (0)

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The pressure increases due to heat transfer from the environment. It's basic physics. Increasing the temperature causes gas molecules to move faster.

Today’s liquid hydrogen tanks capable of holding hydrogen for merely two to four days.

LLNL’s tank demonstrated a thermal endurance of six days and the potential for as much as 15 days, helping resolve a key challenge facing LH2 automobiles.

Why the limit? It's because they use evaporation of the tank's hydrogen to cool the tank and reduce the pressure.

This is sort of like planning a car with a leaky gas tank that empties in 2 days ... then improving the situation by slowing the leak so the gas tank will only empty in 6 days.
It's a good thing the Prius has batteries to get them to the hydrogen station for a fill up each week.

This concept is still a long way from commercialization.
1) Where does my luggage go? The picture shows that combining cryogenic LH2 with a pressure tank is very bulky. However, that may be possible to solve.
2) The pressure tank is expensive and this will be really expensive.
3) Liquid hydrogen is not available at any gas stations and it will cost a fortune to make it available.

For fuel cells vehicles to have a future they should be able to do what existing technology can do and in addition they must have at least one important feature they do better. Two examples could be.

1) Make a fuel cell car with an on board electrolyzer and a pressure tank. This car may? be able to get as long a range as a gasoline car and it would never need to be filled at a central gas station because all it needs is electricity and water which is available everywhere. That would really be something if they could make them affordable. It is probably not possible to obtain affordability and feasibility in this case unless they can get the necessary H2 pressure (for adequate vehicle range) directly from the electrolyzer without the need to use an expensive and heavy on board compressor as well.

2) Make a compact and inexpensive direct ethanol fuel cell. At the time this will be available there should also be an ethanol fueling infrastructure in place in many countries and the car would be better than an ICE car because it is more efficient and noise free.

There are a lot of applications for this technology other than cars (air travel construction equipment etc.).

I find it funny that certain posters will tell us repeatedly that hydrogen will be necessary for storing excess seasonal energy for use in seasons with deficient energy production, when in fact, hydrogen is even less effective as a long term energy storage medium than battery storage.

Bob, you beat me to it.

Its hard to say where this H2 teck will go, or how it will be used, but high temp super conductors should/will be in the mix in the end. That might make it worthwhile.

Its better then it looks.. it doesnt leak all the fuel in 6 days it just needs to be USED and thus drain the tank SOME every 6 days.
This also isnt a fuel cell car but a h2 ice car they are talking about as the volt only needs 4 kg to go 300 miles and would go 750 miles on 10.

Liquid h2 is mostly a german obsession as they need it to run thier v12 v16 and v24 h2 ice engines. As for the us market it MIGHT pop up in supercars and high high end cars and trucks where fuel costs.. liquid h2 is spendy as apposed to gas h2 wich is now CHEAPER then gas and deisel many places... is not the issue but CAFE is.

Its far more likely more a military item. 5000kg of h2 is light yet packs 100 Mwh of power if run through a fair eff fc.. enough power to run a freight train all day ay full throttle...
As for seasonal power flux.. what h2 does is CONSUME the flux so you can build more wind then you need at ALL times and convert all the extra to h2 to fuel things better fueled by it.

In the end we will likely have 70% nuke 40 wind 10 solar 25 wave and so on so at NO time do we burn coal or nat gas instead using those for plastics.\ and chemicals.

Wintermane, just in case you didn't realize it, your numbers add up to 145%.

Thats the point of h2 and wind/solar.. you overbuild a solid capacity in excess of what you ever need for most things and fling the extra into h2. So h2 is an overflow system.

Why not use wind and solar to compress air for energy storage (see recent Sci Am article on same). It's not as sexy (or problematic) as H2, but adheres to KISS principle.

" thermal endurance improves as the tank is emptied, and is able to hold hydrogen fuel indefinitely when it is about one-third full."
As there is no perfect thermal insulation, regardless of the tank strenght, I do not believe this tank is able to hold about 1/3 of its volume in liquid H2 indefinitely.
By "one-third full" I presume they mean 1/3 volume of the tank in liquid phase H2.

Hi Bob ...
There is a reason I think hydrogen will be used as I suggest. Physics.

Hydrogen is not ideal at transport just because the tanks need to be heavy, insulated, cooled, and hold high pressure. The result is a wasteful system as demonstrated in this article. The alternate green choice, batteries, are improving in cost, capacity, lifetime and weight. They have very low energy losses.

In stationary power plant situations where bulk energy is shifted from night to day, batteries are not ideal because of high cost and short lifetimes. Here a tank lifetime is extensive and it can be filled and emptied as often as necessary without degrading. Stationary tanks can be bulky, heavy, and cheaply insulated. They can also be cheaply cooled, but when under low pressure cooling is not such an issue. The Hydrogen fuel can also be run through a turbine and produce almost instant power on demand, then the waste heat used in a conventional steam plant.

For these reasons, I would expect the future role of hydrogen to be primarily in stationary "peaking" and energy shifting power plants, but not so much for cars.

Jorge got most of it, but I think the take-home lesson is this:

[the tank] is able to hold hydrogen fuel indefinitely when it is about one-third full.
What you get for your 20% hit on the fuel value of the H2 for the liquefaction is a mere tripling of the density over compressed gas at 5000 PSI.

Personally, I think that hydrogen won't compete with battery electric, but rather biofuels. Batteries seem to be the pretty obvious choice for the principle source of power for future light vehicles. Hydrogen will compete with cellulosic ethanol and biodiesel (hopefully algae biodiesel) as the energy source for PHEV generators, locomotives, ships, and construction/farm equipment.

With 2kwh/kg gravimetric energy density and 6-day-full-tank holding capacity, what is there not to like about this cryogenic Liquid H2 storage? By contrast, current battery averaged about 0.10kwh/kg, or twenty times heavier.

You worry about wasting H2 by venting it after 6 days? Well, then, just park your car close to an electrical receptacle and plug it out, and run up your engine-alternator or fuelcell to consume the H2 about to be vented out, and sell the kwh of electricity produced to the grid utility. Look, ma, no H2 wasted!

When you're down to 1/3 of tank capacity, the tank volume at 5000 psi will be able to hold that much H2 in gaseous form at room temperature, so no more H2 will need venting, and you will be able to drive the car to fill her up again.

Alternatively, don't fill up the whole Liquid H2 tank if you are about to park the car for over 6 days...but hey, are you unemployed or what? Or, may they'll let you sell back the excess Liquid H2 from your tank to the pump, if you should unexpectedly got fired from your job! :(

@Bob Bastard,

Low-cost indefinitely long-term storage of H2 can be easily done by using very large volume and lower pressure, whereby you will have very high volume to surface area ratio, hence much lower material cost and very little leakage or, in the case of Liquid H2 storage, very little heat gain, hence very little venting, due to the very low surface to volume ratio. Again, no waste of Liquid H2 should happen, since H2 will be steadily consumed to produce electricity at a rate just as fast as evaporation of the LH2 from ambient heat gain.

It's just a matter of physics, my friends.

Quoth Dan A:

Personally, I think that hydrogen won't compete with battery electric, but rather biofuels.
You can say that, but the sheer size of that LH2 tank makes me wonder if a practical personal vehicle can accomodate both a tank and a serious battery pack.  You need to get into the pickup/SUV class before there's enough room beneath beds and such to squeeze such bulk without changing much else.

The beauty of biofuels is that they are both compatible with existing systems (also a liability) and also quite dense.  Squeezing 3 gallons of gas somewhere in an Aptera gives you 390 miles of sustainer range; even if it was only 260 miles on ethanol, most people would be okay with it.  But adding 3 kg of hydrogen would require a ground-up redesign and constrain many of the other elements.

Long-term storage of H2 can not be easily done by using very large volume and lower pressure because you will have a very large surface area. Use of (compressed) gaseous hydrogen at ambient temperature is very bulky. Surface to mass ratio is what matters not surface to volume ratio.

I don’t think that a little leakage after 6 days matters. But is the tank that provides some leakage after even 2 days affordable?
I still find it hard to believe that we will make hydrogen a viable way to store and transport power in the near future.

Biofuels, PV cells, CTL and batteries are maturing – we need them NOW - we are hemorrhaging.

The claim that the tank can hold the H2 indefinitely when it's one third full raised my eyebrows. Doesn't any tank loose H2 through diffusion of the H2 molecules through the tank walls?

@Bob, Roger, ToppaTom

Storage of hydrogen can also take place in nanomaterials. I believe there is no leakage in that case. That would be perfect as an off season storage. Plus its much more compact and safe than gaseous H2 at low pressure. Weight is not an issue for static applications. I don't know about the price of these wonder materials though.

Lets take a hypothetical drive to the cottage in a "new tech" car.

Our BEV does not have sufficient range to get there. With an infrastructure, we travel part way, stop for a nice leisurely supper while recharging, and arrive well rested. Now the car charges on cottage power for the return trip.

Lets try the HYDROGEN car, with the new improved tank. This has plenty of range to zip up to the cottage in one go, but we arrive cramped and tired. At the end of the week's holiday, our tank is near empty despite us buying lots of hydrogen and we are lucky to make it back out to a hydrogen filling station.

For me, the BEV choice is obvious.

No the battery car would be cramped as hell the h2 car would be a 2 seat sports car owned by a ricj annoyinh jerk and we all would be driving something far more annoying and cheap than either of em... And our cottage in the woods would be motel 6 and 2 cans of lysol and fabreeze... firest scent..

H2 will in most cars be GAS no liquid and they can store gas h2 quite well now so it MIGHT make your trunk a tad bigger but it wont be insane.

I expect OUR h2 car will be a cheap indutrial tank connected to a cheap industrial fuel cell.. giving us a cheap industrial car that goes very very far on little money.. but is as exciting as a brick and as peppy as one too.

The attempts to use hydrogen as an energy storage medium just aren't sensible. So much energy/water is wasted in its production,transportation and storage due to its very low density. It makes far more sense to use the electricity directly where possible (commuter vehicles) and use a higher molecular weight molecule (of which there are plenty of good candidates) for trucks/trains/planes etc. If you want to use fuel cells, use SOFC that can utilize hydrocarbons rather than PEM which require H2.

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