Driving to a Hydrogen Future

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es - which isn't a very high pressure.

but you wouldn't need to up the pressure much to compensate - if you were a llowed to compensate that way, which seems very improbable.

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natural gas, but the economics of the transition are likely to be messy.

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That actually doesn't make sense to me. What is important is the specific energy of the reaction. While total combustion of 2 CH4 + 4 O2 >> 2 CO2 +

4 H2O may use more oxygen, it likely produces a lot more energy than does 2 H2 + O2 >> 2 H2O. But you can't say for sure until you find the data for each reaction.

Rick C.

lol

It seems to be about one third that of methane. Am I looking at the wrong figures? perhaps it competes better in liquid form?

--
  When I tried casting out nines I made a hash of it.

Oops.

Enthalpy for two moles of hydrogen plus one of oxygen is 483.64 kjoules

Free energy released is a bit less 457.18 kjoule (presumably at STP)

Enthalpy released for one mole of methane plus tw moles of oxygen 890.32 kjoule.

Free energy released is 817.92 kjoule.

So the free energy ratio per mole is 3.58:1 in methane's favour.

That's an appreciably lower calorific value for hydrogen versus methane.

Sorry about that. I've clearly been listening to too much pro-hydrogen propaganda.

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Bill Sloman, Sydney

That is because the vapour pressure of benzene at room temperature is about 4mBar basically a vacuum. Not comparing like with like.

Indeed. The simple explanation of atomic size and from that the mean free path doesn't quite cut it.

He 31 Ne 38 Ar 71 Kr 88 Xe 108 Rn 120

Having complete outer shells makes them bigger and fluffier than any of the other elements (but also they are spherically symmetric).

Kaye & Laby / NPL have some tables of what they "should" do if they followed the first order corrected non-ideal gas laws. A better one would be the L-J potential or one of the more recent models.

I confess I am at a loss as to why exactly Neon is such an outlier.

I presume there must be something about it's radius and the scale length of the Van der Waals interactions that makes it unusually sticky.

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Regards, 
Martin Brown

Up to a point. As you add electron shells, the p-, d-, and f-shells aren't spherically symmetric. The p-shell is the lumpiest.

It's the first of the noble gases to have p-orbital electrons, and their probability density distribution is going to be lumpier than you get with d-orbital and f-orbital electrons, but this is mere handwaving.

The Leonard-Jones potential is pretty much handwaving too, but it is dignified by history, since it has been around since 1924.

Apparently the Stockmayer potential (which I'd never heard of) adds a point dipole. To represent a filled set of p-orbitals you'd have to add a hexapole (which I've never heard of either, though google has, if not in this context).

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Bill Sloman, Sydney

That's with equal gas volumes; with equal mass, it's 3.58 *2 : 1*16, so 1:2.2 in Hydrogen's favor. The other half of the moving-volumes-of-gas picture, though, is that natural gas HAS to be piped in from wells, hundreds of miles away,. Hydrogen can be produced near any point-of-use. It's dubious that a trans-Canada pipeline for hydrogen will ever be needed.

How?

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

I was thinking that too, also there's no reason to convert hydrogen into electricity with static plant. just "pipe" electricity in instead.

--
  When I tried casting out nines I made a hash of it.

Isn't the topic piping hydrogen so it can be used in autos directly? Why do you say convert hydrogen into electricity?

Rick C.

John hasn't been reading the thread. The answer is by electrolysing water.

The power required to do that can be generated by solar farms or windmill arrays.

Since you can store a lot of hydrogen (particularly if you liquify it first) this deals with the fact that solar and wind power are intermittent.

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Bill Sloman, Sydney

The preferred method of using hydrogen in cars is by burning it in a fuel cell in the car to generate electricity, avoiding the power waste implicit in the Carnot cycle.

It's even better to use the electricity to charge a battery, but a big tank of liquid hydrogen can store a lot more energy much more cheaply than a comparable heap of batteries.

It's been known for a least a decade that if we all went over to electric cars, the heap of batteries doing nothing in parked cars would be big enough to hold at least half a days worth of national energy consumption/production.

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Bill Sloman, Sydney

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2 kjoule. 1:2.2 in Hydrogen's favor.

Sadly, it's moles, not mass, that define gas volume, and the effort require d to pile it from one palce to another.

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A high voltage direct current power link, possibly build with high temperat ure superconductors immersed in liquid hydrogen, would make more sense, tho ugh perhaps not all the way across Canada.

The hydrogen gas economy is all about putting solar farms to generate elect ricity where there's lots of sun and no cloud, and shipping the energy capt ured out by electrolysing water to hydrogen and putting that into pipes, ta nkers or big tanks, depending on whether you want to ship the energy locall y or overseas, or store it until the sun isn't shining and the wind isn't b lowing.

--
Bill Sloman, Sydney

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890.32 kjoule.

6, so 1:2.2 in Hydrogen's favor. t

Hydrogen can be

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hy do you say convert hydrogen into electricity?

cell in the car to generate electricity, avoiding the power waste implicit in the Carnot cycle.

nk of liquid hydrogen can store a lot more energy much more cheaply than a comparable heap of batteries.

cars, the heap of batteries doing nothing in parked cars would be big enou gh to hold at least half a days worth of national energy consumption/produc tion.

We've had this discussion before. This is a bit like borrowing from Peter to pay Paul. The whole point of the battery in a car is to power the car. Not many cars are sitting around waiting for the odd chance they are neede d. Most people drive their cars two or more times a day. On top of that, they don't want to have to worry about an unplanned use being prevented by the car having insufficient charge.

Storing charge in a car for the few hours it is at work is pointless. If i t is charged up by solar during the day it will then be driven home and wil l only be available for part of the afternoon peak usage time. Here those hours are 3 to 7 pm in the summer and 6 to 9 am and 5 to 8 pm in the winter . The commute will take the car offline for much of these peak times. Mea nwhile the car will need to retain enough charge to complete the drive back to work the next day and any lunch trips required, planned or unplanned.

There may be some potential for storing electricity in car batteries, but t he obstacles are numerous and the likely outcome is that only a rather smal l fraction of the total automotive battery capacity will be available for s torage use.

Rick C.

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.32 kjoule.

o 1:2.2 in Hydrogen's favor.

red to pile it from one palce to another.

I think everyone in this part of the conversation is talking through their hats. Not one person has indicated they actually understand what is import ant regarding a hydrogen pipeline. We can talk about this aspect or that, but we don't know what determines the utility of piping hydrogen.

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ature superconductors immersed in liquid hydrogen, would make more sense, t hough perhaps not all the way across Canada.

ctricity where there's lots of sun and no cloud, and shipping the energy ca ptured out by electrolysing water to hydrogen and putting that into pipes, tankers or big tanks, depending on whether you want to ship the energy loca lly or overseas, or store it until the sun isn't shining and the wind isn't blowing.

It's also about developing cars that can practically convert hydrogen into transportation. All in all there are a lot of hurdles to leap and we are a pretty long way from having that working on a useful scale.

BEVs on the other hand, are here now and require *much* less change to the infrastructure. For the time being the only change required is to provide charging for trips. Tesla was all about that although now they seem to be working on adding more charging capacity in urban areas to help support sal es. I think this is as much a PR issue as anything, but I don't know that for sure. My use case is to charge at home, but there are those for whom t hat is not as practical. I guess going out once or twice a week to park at the charger and having dinner nearby isn't such a terrible thing. I wonde r if this will lead to a business model for shopping areas to attract busin ess by promoting charging.

Rick C.

There's less reason to convert electricity to hydrogen.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics

Fess up, you're just so satisfied with those bumpercars at the amusement park,, you don't want to drive a real road vehicle any more!

My Audi has an ungoverned top speed of 156 MPH.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics

This is why I don't quit reading newsgroups. This guy is just so bizarre he'e entertaining in a sad way.

It's also funny that he is so proud of his car's top speed which he will never use, but he shuns the Teslas which will blow his car away in pretty much any performance measure he will actually encounter.

Rick C.