Well if we're going to discuss some fantasy molecule that they have no clue how to fabricate, perhaps we should discuss semiconductive nanotube ultracapacitators, or even better, nanotube flywheels!

E = 2 k R e_s [m^2 / kg]

E = energy stored per unit mass
k = configuration factor, about 0.8 (pure rim is 1.0)
R = radius of flywheel
e_s = tensile strength (unit conversion to acceleration), theoretical maximum for carbon nanotubes is 200 GPa, say 50 GPa with a safety factor.

A carbon nanotube flywheel with a 1 m radius could store 90 GJ/kg! It will spin at about 0.005 of the speed of light! It would probably disintegrate and explode if damaged. Still it kicks the crap out of molecular hydrogen at 142 MJ/kg.

Perhaps I should write this up, publish it, and request some government funding... The two concepts are roughly equally likely to come to fruition.

The flywheel's big weakness is handling the acceleration force that automobile parts and passengers experience. These forces happen in all three dimensions so any pothole could overwhelm the magnetic bearings causing a rapid failure.

I think his point was that such flywheels are as practical as the modified molecule. i.e. neither makes a damn bit of sense for cars, nor do we know how to make either.

On the subject of flywheel storage though, someone mentioned that hydrogen is a great fit for intermittant production sources like solar and wind. It should be pointed out that you could just as easily put a high capacity flywheel underground next to those solar/wind power producers and achieve the same effect without the need for generating and burning hydrogen. I'd be curious to see if flywheels are actually more power efficient on the charge/discharge than generating and burning hydrogen.

Some round trip efficiencies of various electricity storage mechanisms:

Hydrogen/PEM fuel cell: 35 %
Pb-Acid battery: 60 %
Ni:MH battery: 65-70 %
Compressed Air: 70 % (powers compressor of natural gas turbine, so not a closed cycle)
Vanadium Redox flow battery: 70 - 75 %
Flywheel: 60 - 80 %
Pumped Hydroelectric: 80 %
Sodium-Sulfur battery: 70 - 85 %
Li-ion battery: 90 %
Ultracapacitator: 95 %

Sid:

You make a good point that flywheels also have the potential to make a good "overnight buffer" to soak up off-peak power generation. A lot of the pro/con comparison will come down to specific design details -- not fundamental limits of physics -- so there is little to really compare, until we have some concrete performance requirements set down and potential designs on the table.

If EVs are an important part of the future, then there is a lot of thinking and innovation we ought to be doing when it comes to running and managing the power grid. I never learned enough about grid-scale electrical engineering, but it appears to be a fascinating subject.

Andrey:

You make an important point about the tendency towards increasingly concentrated and uniform-quality power sources, but as you admit, that "trend" is an oversimplified view of life. We still derive plenty of power from falling water, even though it is a low-density source of energy. We just convert it to electricity before we ship it. We use increasing amounts of natural gas, even though it has lower energy density (on a standard volumetric basis) than coal. We use what is useful, and we have a knack for making a lot of unusual things useful.

And I don't see where your negative attitude comes from regarding storing hydrogen, at least in a moderately dense form, if not dense enough to use in automotive applications. The Germans were filling airships with hydrogen over eighty years ago and flying them for weeks at a time to all sorts of distant places. Given that, I think we can easily fill a couple large, moderate pressure gas bags with a night's worth of off-peak hydrogen made from some wind farm, and burn it off over the next day to provide peak-demand power. You could even build a small network of pipes to send it to nearby industrial users who have a particular need for it: Food manufacturers (partially hydrogenated vegetable oil), oil refiners, chemical companies, what have you. However, I think we both agree that hydrogen has some serious drawbacks in the automotive segment, and that we will not likely see a practical, purely hydrogen powered vehicle for quite some time, the advance in this article notwithstanding.

And I also think that you need to define the "quick charge" problem with a more concrete range of user-end specifications in mind. I think your unspoken standard is whether it is possible, given a five-to-ten minute fueling stop, to charge a two-ton EV with enough electricity to have a range of 300-400 miles. This would give you the same kind of long-range quick-refuel performance a conventional car would get. It would also be a challenge to charge up, as you point out.

However, I think you would need to do some market research to find out if that level of performance capability is an absolute requirement for all (or most) motorists on the American road -- or how much extra they would be willing to spend to have that capability on-call all the time. Because my bet is that most motorists would be willing to trade in that capability for something much more modest, if the incentives were right.

Since most motorists do not engage in coast-to-coast marathon road trips on a daily basis, I'm willing to believe there is some room in the market for a car, with a 200 mile maximum range, that can take aboard 100 or 150 miles of energy in 15 or 20 minutes. Your problem can shrink or grow considerably with a few strokes of the pen: Taking aboard 400 miles of energy in 5 minutes time requires 12 times more power transfer than taking aboard 100 miles of range in 15 minutes, all else being equal. A0nd I think a 200 mile car with a 100 mile quick-charge (15 min.) capability would be very attractive to a lot of users, especially if its lifetime cost of ownership was cheap.

We can blue-sky a bunch of more radical solutions to the range problem, including battery-exchange stations, pantograph/third rail systems on major rural interstates, generator add-ons/trailers, etc. Some have been thought-out before, some have not been tested as much, but they are beyond our scope here.

Some day we might attain a practical hydrogen setup, but as we often repeat here, it looks like the sort of thing for which we should not be holding our breath.

Robert:

While other technologies might have lower losses, low-pressure hydrogen storage might be cheaper to install and maintain than some of the alternatives, and might be more responsive on power upswings as well. Banks of batteries in particular are not that cheap to build; hydrogren storage can be accomplished in little more than a large metal sphere or flexible bag. Loss rate is an important part of the picture, but not the end of the story for all applications.

NBK:
Some comments.
Hydropower, compared with wind and solar, is quite concentrated source of energy and mean to store the energy too – currently way better than hydrogen promise in future.

Range, rate of fast charge, and acceleration numbers presented by EV and battery manufacturers represent best possible trail results. Consider how battery performance will deteriorate on 3-year old battery pack at hot weather (plus extensive use of AC). Add to equation under inflated tires and aggressive driving, and you get the picture.

As you know, there are two major enemies to long battery life: deep discharge and high current (discharge or recharge – does not matter). These limitations are so severe, that Toyota in their Prius Ni-Mh battery pack uses only 1/3 of it capacity (and never charge it to 100% capacity) to prolong it life. Fast charge represents the most stressful strain on battery, and could not be carried out somehow often. Same thing with long travel.

As I said, PHEV seems to me our best real-life option for foreseen future. Pure electric currently could hope to be employed only in niche applications.

Andrey:

Going over some of what's written here, especially on the more specific automotive issues, I actually think our positions are fairly convergent. We both seem to agree that PHEV offers the most flexible drivetrain, and is the technology most capable of matching current conventional operating convenience within a near-term development timeframe.

We might have somewhat differing views on exactly how large the pure-EV niche is likely to be -- both in terms of what customers want, and in terms what technical capabilities are on the horizon. I probably think that the niche is larger than you anticipate. The only thing to do is follow the technical developments, see what they mean in terms of price and performance, and see how that matches up with what customers want/can afford.

I did not imagine that we would get all our hydrogen or methane from biomass, to run all the cars in the U.S. The U.S. consumes some 140 billion gallons of gasoline per year. The more methods we have for getting transportation fuels from other sources, the more options we have to be less dependant on only one solution.

Quick charging high power battery packs:

Most of us seem to overstate the difficulties with quick charging high power battery packs.

Battery packs can easily be split in 2 or 4 or 8 parallel battery banks (of about 10 Kwh each) that can be recharged simultaneouly, like 4 or 8 track/channel anything.

This way, you reduce the current required 4 to 8 times and you dont need super-conductors. If you use higher voltage such as 660 Volts (common with on-board battery packs) you can quick charge your PHEV or EV in 6 tp 8 minutes without using excessive currents.

Multi-channel (4 to 8, to satisfy various battery packs size) 660 volts chargers may be too expensive for your home garage but would quickly become a standard facility at the corner gas/recharge station.

This would NOT be an expansive facility if used 100 + times a day.

NBK:
Yes, it boils down to most currently obvious : PHEV.
I could only imagine that in twenty years on “Green Electric Car Congress” EV purists will press gasoline PHEV owners “to get out of their gas-guzzlers”.

The main family car would be a PHEV with EV's initially filling some niche roles (commuter car, fun car)

Folks,
This is an article on H2-holding Buckyball. It's not about EV or PHEV.
No one is so stupid to produce H2 from electricity, especially electricity from fossil fuel sources. H2 can be produced directly from coal or biomass by gasification with higher efficiency than electrical generation. H2 can also be produced from high-temp electrolysis at twice the electrical efficiency of normal-temp electrolysis. With proper techniques, H2 can have comparable efficiency from well-to-wheel as electricity in BEV, while H2 has much faster fill-up (recharge) time and no worry about battery degradation, nor battery replacement cost.

The best H2 carrier is in the form of CH4 (methane), the compressed form of which in an ICE-hybrid will get you 3-1/2 times as far as compressed H2 at the same pressure. Forget about Buckyball, hydrides, or other expensive contraption. For local driving, use H2 in a 15-20 gallon compressed tank for ~120 mi range. For long-distance driving, fill up the same tank with CH4 and you can drive up to 400 miles. Now, can any BEV get you that far?

oli:

your formula is incorrect.
I have {E= (1/2)*k*e_s/(density)} in your notations.
density ~ 1340 kg/m3. Three orders of magnitude make difference, don't they?

I'm affraid that nanotube flywheel may always be too expansive for average consumer.Current price of nanotubes is 500$ per kilo (or pound,not sure).
I'm not specialist in that area,but think the strongest
material we are tring to get the more energy we must put
in its creation.For example if nanotubes are 3.000 times stroner than steel we must put 3.000 times mor energy in their creation that in steel.I think there is no easier way because it would contradict nature law.
If I'm right perspectives of flywheels seem to be very doutfull...

Sorry,price of nanotubes is 500$ per GRAM not per pound.