Pat, the higher the pressure the greater the amount of hydrogen that can be stored in a given volume. So as the pressure is increased the energy density does get better. So "good" is a relative thing. There exists a trade-off between how much fuel and range one has versus how much weight and volume one must carry, and the thing that relates to it is how convenient it is to refill the tanks. The logistics of refueling are what limit hydrogen as a practical fuel.
This is my last post on this blog topics discussion thread, but it's not the end of the discussion, which will be moved to another venue. This is clearly the wrong forum for moving forward technical solutions that advance the state of the art toward the goal of reducing fossil fuel death and illness.
William K writes: "Hydrogen is indeed, at least in theory, an ideal fuel. BUT HYDROGEN LOGISTICS ARE CHALLENGING INDEED!!!"
Agreed, which is why high temperature reactors lend completely different solutions than other choices. Heat input as part of the reaction significantly increases efficiency, which directly affects the bottom line costs of the fuel.
Gasoline and Diesel make wonderful fuels, as both are "relatively" safe from ignition perspectives. Gasoline requires a very narrow vapor density to be really explosive, and diesel is really hard to ignite unless under high temperatures.
Given both fuels have their days numbered with increasing shortages of oil, and both are carbon releasing fuels subject to carbon taxing and CO2 contribution to global warming. Both have high toxic particulates, that are directly linked to health issues and deaths.
SO we know why gas and diesel have been popular for the last 80 years, and there are no other choices that are as nice, that are not CO2 producing.
So, we have to look at 2nd and 3d tier fuels that are not nearly as nice from an engineering solution, but possibly have high marks for improved public health. H2 fuel gas is at the top of that list with no direct emissions if burned at low temps. Direct injection, lean burn, solves most of the NO3 problem
H2 fuel gas, when produced with a PBR and the SI process, are at least economical. We know how to produce relatively safe high pressure cylinders for transportation uses. Both also put H2 fuel gas at the top of the alternative fuel list. There are some that argue that H2 fuel gas isn't a fuel, because it has to be manufactured with some energy input. True ... but the energy costs to extract and refine other fuels is also a net energy investment in the resulting "fuel". PBR combined with SI, or Thorium combined with SI, is near on parity on that basis.
Li-Ion and Li-Polymer batteries are NOT nice either, with a high risk of fire and explosion ... Obama let China have the A123 LiFePO4 patents that are very safe compared to other choices. There are few other relatively cheap and safe battery solutions for EV's storage.
The base line research says that cleaning up a Thorium very high temp reactor to produce H2 with the SI process, will generate transportation fuels very very economically. Fleet retrofits of gas/diesel engines are viable, at reasonable costs. PBR w/SI creates H2 that can be cleaned up for fuel cells at a modest cost too ... which also improves efficiencies for transportation by a factor of 2-3.
Hydrogen is indeed, at least in theory, an ideal fuel.
BUT HYDROGEN LOGISTICS ARE CHALLENGING INDEED!!!
For starters, since hydrogen gas is the smallest moleculre, and hydrogen is the smallest aton, it is difficult to seal. It will flow through a teflon gasket quite rapidly, while the same gasket will completely halt natural gas, and even acetylene gas. This means that hydrogen is a serious challenge to keep captive. Yes, I am aware that it is used in a lot of places, but it takes quite a bit of extra effort just to keep it in the bottle. It would find it's way out of our present natural gas piplines quite easily.
Next, because hydrogen does not liquify without a huge amount of effort, it has to be stored at very high pressures if you need to get an adequate amount in a tank. Those high pressures require a serious compressor, which is expensive and takes lots of power to drive it. In addition, high pressures increase the tendancy toward leakage.
Producing hydrogen gas by any means requires quite a bit of energy, and if that is solar energy it takes a fair amount of area to collect enough to o the job. There may be enough open land around Phoenix to build a plant close by, but not around many other cities of major size.
MY point being that while something may sound like a good idea, a study of all the many details may show otherwise. Also, just wishing something were true does not make it true, no matter what Jim Moore says.
WilliamK writes " I don't see how they will have any effect at all on the transportation"
A PBR doing "high-temperature electrolysis" allows direct conversion of water to commercial quality H2 fuel gas for ICE applications, while also producing steam for generation. That can be combined with "Concentrating solar thermal" (SCT) as a renewable source for a H2 fuel gas transportation economy. To minimize transportation costs that reduce overall efficiency, both PBR and SCT production facilities should be highly distributed around population centers, and augmented with high presure pipeline distribution of H2, possibly reusing existing NG distribution lines.
PBR "high-temperature electrolysis" is important in an H2 transportation economy because it provide a cheap H2 source in areas where solar is just not cost effective.
I'm surprised that your industry view has been so narrow to have missed all the ways to deploy EV's, Hydrogen Fuel Cell EV's, Hydrogen(H2), and H2-EV Hybrid's as an alternative to Oil for all areas of transportation.
Conversion of existing engines can be done several ways, but from several research versions this seems the most practical, and it would not take much to create conversion kits for the most common engine designs.
So ... transportation might be one of the easier applications, with bolt on injections kits and DOT approved tanks.
PBR's are farther along in development for what are several reactor technologies that can be mass produced, and have a passive fail safe basic design. Advantages besides increased safety are relatively small size, easy spent fuel handling, improved efficiency, easily decomissioned, and the high temperature operation is easily integrated into a dual use plant producing both electricity as well as H2 for transportation fuels.
Longer term evolution of research suggests either the molten salt reactor or the liquid flouride thorium reactor are likely to replace PBR's
While atomic power plants may help to eliminat a few of the coal fired power plants I don't see how they will have any effect at all on the transportation or aviation industries. And I don't think that there are a lot of coal fired ships in use now, but I may have missed that informantion.
One more fact is that as more generating capacity comes on line there will be a HUGE effort to sell the additional power, rather than to take any plants off-line, since the more power sold the greater the profits, and the driver for it all is return on investments to maximize shareholders returns. Unused capacity is a non-profit making use of expensive capital and most boards of directors work very hard to avoid that. So building new power plants, while it is a good idea, will probably not deliver the goal that you seek.
Efficiency is usually regarded as desirable but not if the price is excessive. That is just how it is. If gaining an additional 10% of efficiency will double the cost of my new furnace then the payback will take at least ten years, which would prompt me to consider the choice very carefully, because things may change a lot in that time.
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