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Albion
2010-Sep-16, 07:26 PM
Has anyone done any research on the consequences of the increased water vapor in the atmosphere from replacing all petroleum burning vehicles with hydrogen burning? I've read some articles about the weather created by water use in Phoenix, AZ and wondered if all cities would show this effect? What would that do for farming on the leeward side of a large city in times of drought?

HenrikOlsen
2010-Sep-16, 09:42 PM
Water vapor has a natural max concentration before it rains out.

cjameshuff
2010-Sep-16, 09:45 PM
Water vapor has a natural max concentration before it rains out.

And the planet's already covered with large amounts of it, freely evaporating.
Also, hydrocarbons have that name because they contain hydrogen as well as carbon. Hydrocarbon-burning vehicles already produce roughly as much water as CO2. Given the low density of hydrogen, hydrogen cars would probably produce less water than petroleum-burning ones do.

Ara Pacis
2010-Sep-17, 07:03 PM
Yeah, look up lake effect precipitation (http://en.wikipedia.org/wiki/Lake-effect_snow).

Albion
2010-Sep-17, 11:11 PM
Yeah, look up lake effect precipitation (http://en.wikipedia.org/wiki/Lake-effect_snow).

No need to look it up, I live on the west side of Lake Michigan. "Lake Effect Snow" is part of the vocabulary here. I thought there would be more water exhaust. I also had no idea that petroleum combustion engines produced water either. But I guess that's what's dripping off the tail pipe. Thanks for that bit of information.

Swift
2010-Sep-19, 03:29 AM
The only way large scale use of hydrogen as a fuel makes sense is if you make it from water, either by a photoelectrochemical process or by something like thermal nuclear. So the net effect is to use energy to separate water into hydrogen and oxygen, and then later to recombine them to get energy. In effect, you are using hydrogen as a energy storage medium, and there is no net addition of water to the atmosphere.

Tuckerfan
2010-Sep-19, 04:03 AM
Years ago, on another message board, I asked basically the same question, since you would be increasing the amount of water vapor in places not exactly known for their high humidity (deserts). One of the engineers on that board actually ran the numbers and calculated that the water vapor released by the swimming pools in Phoenix, AZ, was greater than the amount of water vapor which would be released if every vehicle in that city ran on hydrogen.

Now, it's possible that there could be some problems caused by this (after all, it could cause subtle environmental changes that over long periods of time significantly alter the environment), but it seems unlikely. After all, one of the big issues in many places is the expansion of deserts, so if the hydrogen economy causes deserts to shrink, it will probably be awhile before it becomes a significant concern.

whimsyfree
2010-Sep-19, 09:19 AM
hydrocarbons have that name because they contain hydrogen as well as carbon. Hydrocarbon-burning vehicles already produce roughly as much water as CO2. Given the low density of hydrogen, hydrogen cars would probably produce less water than petroleum-burning ones do.

That would imply they were either much more efficient or much less powerful.

Tuckerfan
2010-Sep-19, 03:21 PM
That would imply they were either much more efficient or much less powerful.

Fuel cell vehicles are much more efficient than conventionally powered vehicles. The problem with fuel cells, however, is that they tend to be incredibly expensive. (Though the costs are starting to come down significantly.)

cjameshuff
2010-Sep-19, 11:35 PM
That would imply they were either much more efficient or much less powerful.

Both, actually. Hydrogen vehicles have power outputs on the low end, and even in an internal combustion engine there are efficiency benefits to hydrogen. And they simply can't burn much hydrogen, because they can't carry it.

The Honda FCX Clarity carries 4.1 kg of H2 in a 5000 psi tank (don't blame me for the weird mix of units). Assuming an average number of carbons of 8, there's 18 hydrogens per carbon. At ~3 kg H2 per 16 kg of gasoline, you get that amount of hydrogen in about 34 liters or 9 gallons of gasoline. With its 280 mile range, that's the H2O output of a gasoline vehicle getting 31 miles/gallon. Most don't carry that much. (Another effect reducing overall H2O production would be the increased number of vehicles stopped at filling stations at any given time...)

Antice
2010-Sep-20, 06:30 AM
Hydrogen as an energy carrier is a bad idea for land based vehicles. It's got a low density, has a tendency towards mixing with air, and combust energetically at the slightest provocation.
Batteries or synfuel made from hydrogen and CO2 is much better. Synfuels can have all the same characteristics we like about the fossil variety without all the emmission drawbacks of fossil fuels. the Co2 emitted is sequestered during the manufacturing of the fuel, so it's carbon neutral.
I've recently read about a third energy carrier option. namely Boron. it's interesting and could be really usefull if it could work out. (http://www.eagle.ca/~gcowan/boron_blast.html#Introduction)

Tuckerfan
2010-Sep-20, 07:04 AM
Hydrogen as an energy carrier is a bad idea for land based vehicles. It's got a low density, has a tendency towards mixing with air, and combust energetically at the slightest provocation.
Batteries or synfuel made from hydrogen and CO2 is much better. Synfuels can have all the same characteristics we like about the fossil variety without all the emmission drawbacks of fossil fuels. the Co2 emitted is sequestered during the manufacturing of the fuel, so it's carbon neutral.
I've recently read about a third energy carrier option. namely Boron. it's interesting and could be really usefull if it could work out. (http://www.eagle.ca/~gcowan/boron_blast.html#Introduction)

The problem with boron is that its so expensive (about $5K or so an ounce, last I checked). Sure, it can be reclaimed and reused, but the initial start up costs are incredibly high because of that. You can do many of the same things with aluminum (in terms of using it as a fuel source) that you can with boron, without the high costs associated with boron.

Ara Pacis
2010-Sep-20, 05:06 PM
I think electricity is where it's at. To retool our automotive infrastructure around Boron or Aluminum fuels would be expensive. For the same price we could install battery swapping stations and perhaps even electric roads.

Swift
2010-Sep-20, 05:15 PM
I think electricity is where it's at. To retool our automotive infrastructure around Boron or Aluminum fuels would be expensive. For the same price we could install battery swapping stations and perhaps even electric roads.
I don't particularly disagree. I suspect it will come down to which improves fasters: hydrogen fuel cells and hydrogen storage, versus battery technology. Both are currently marginal. I also suspect that for specific applications, one might be better than the other, but neither is a universal subsitute for petroleum based fuels.

cjameshuff
2010-Sep-21, 03:28 AM
The problem with boron is that its so expensive (about $5K or so an ounce, last I checked). Sure, it can be reclaimed and reused, but the initial start up costs are incredibly high because of that. You can do many of the same things with aluminum (in terms of using it as a fuel source) that you can with boron, without the high costs associated with boron.

Aluminum and zinc...the latter not giving as good energy density, but perhaps being easier to recycle. Aluminum-air batteries (a type of fuel cell, actually, burning the aluminum electrode itself instead of hydrogen diffusing through the electrode) get rather impressive energy and power densities.

Ronald Brak
2010-Sep-21, 05:15 AM
I don't particularly disagree. I suspect it will come down to which improves fasters: hydrogen fuel cells and hydrogen storage, versus battery technology. Both are currently marginal. I also suspect that for specific applications, one might be better than the other, but neither is a universal subsitute for petroleum based fuels.

Because of lower energy costs per kilometer and lower maintenance costs, electric cars appear to be far from marginal in dollar terms over traditional combustion engine cars for many applications, a notable one appearing to be taxi services using either fast charging or Better Place style battery swapping. For example, an Australian company has made a bid to supply New York with 26,500 electric taxis starting in 2014 and electric cabs are being trialed or considered in many other cities including London. Forty or more electric taxis are being used in Shenzen.

whimsyfree
2010-Sep-21, 09:42 AM
Both, actually. Hydrogen vehicles have power outputs on the low end, and even in an internal combustion engine there are efficiency benefits to hydrogen. And they simply can't burn much hydrogen, because they can't carry it.

The Honda FCX Clarity carries 4.1 kg of H2 in a 5000 psi tank (don't blame me for the weird mix of units). Assuming an average number of carbons of 8, there's 18 hydrogens per carbon.


That can't be right. Octane (a suitable reference) has 18/8=2.25 hydrogens per carbon. Honda FCX Clarity is a fuel cell vehicle, not ICE. It is estimated to cost around USD140,000 to make (Wiki).


At ~3 kg H2 per 16 kg of gasoline,


I make it 2.5 to sig figs, ignoring C-13, deuterium and such.


you get that amount of hydrogen in about 34 liters or 9 gallons of gasoline. With its 280 mile range, that's the H2O output of a gasoline vehicle getting 31 miles/gallon. Most don't carry that much.


Now you've lost me. Carry which much of what?


(Another effect reducing overall H2O production would be the increased number of vehicles stopped at filling stations at any given time...)

Fuel system lossage might be another reason.

whimsyfree
2010-Sep-21, 10:12 AM
Aluminum and zinc...the latter not giving as good energy density, but perhaps being easier to recycle. Aluminum-air batteries (a type of fuel cell, actually, burning the aluminum electrode itself instead of hydrogen diffusing through the electrode) get rather impressive energy and power densities.

The alumin(i)um is produced using a lot of electricity. Wikipedia says the best modern smelters use 12.8 kWh/kg. The same source gives the practical output of aluminium-air batteries as 1.3kWh/kg, so the efficiency is just over 10% (ignoring mechanical losses). That doesn't seem very good.

The most obvious alternatives to liquid hydrocarbons from petroleum are synthetic hydrocarbons from coal and oils from plants. Noone seems to want to talk about these, though.

Swift
2010-Sep-21, 01:15 PM
The most obvious alternatives to liquid hydrocarbons from petroleum are synthetic hydrocarbons from coal and oils from plants. Noone seems to want to talk about these, though.
Actually, there have been past discussions on this on BAUT. And certainly people talk about these in the larger world. I do research on supports for Fischer-Tropsch catalysis, so I'm pretty familar with the literature on GTL (gas-to-liquid), BTL (biomass-to-liquid), and CTL (coal-to-liquid) research, all of which are very active in both research and development.

One problem with CTL is that it is not carbon neutral, and so it is not an attractive option if one is concerned about global warming. GTL is also not carbon neutral, but converting the "waste" methane from oil production to a useable fuel is much more attractive, even for controlling GW, then flaring it off, as is now usually done.

whimsyfree
2010-Sep-23, 10:05 PM
Actually, there have been past discussions on this on BAUT. And certainly people talk about these in the larger world. I do research on supports for Fischer-Tropsch catalysis, so I'm pretty familar with the literature on GTL (gas-to-liquid), BTL (biomass-to-liquid), and CTL (coal-to-liquid) research, all of which are very active in both research and development.

One problem with CTL is that it is not carbon neutral, and so it is not an attractive option if one is concerned about global warming. GTL is also not carbon neutral, but converting the "waste" methane from oil production to a useable fuel is much more attractive, even for controlling GW, then flaring it off, as is now usually done.

Whether or not C-neutrality is important depends on why we want to develop an alternative to gasoline for vehicles. If it's to prevent AGW then I think it's a moot question because it's not going to happen. If it's because we've run out of petroleum then we'll need something that can be used in existing vehicles. The idea of replacing a billion vehicles worldwide in a few years with much more expensive and less capable battery-electric or fuel-cell electric vehicles is absurd. BTL does not produce a fuel usable in current vehicles. Natural gas reserves are quite limited and natural gas is highly sought by the power generation industry already. Biodiesel is a 1-1 replacement for petrodiesel but requires a large growing area and can service only a fraction of the current fleet.

jlhredshift
2010-Sep-23, 10:55 PM
Whether or not C-neutrality is important depends on why we want to develop an alternative to gasoline for vehicles. If it's to prevent AGW then I think it's a moot question because it's not going to happen. If it's because we've run out of petroleum then we'll need something that can be used in existing vehicles. The idea of replacing a billion vehicles worldwide in a few years with much more expensive and less capable battery-electric or fuel-cell electric vehicles is absurd. BTL does not produce a fuel usable in current vehicles. Natural gas reserves are quite limited and natural gas is highly sought by the power generation industry already. Biodiesel is a 1-1 replacement for petrodiesel but requires a large growing area and can service only a fraction of the current fleet.

My bold

I don't know but roughly 6,250 trillion cubic feet world supply should last a few years.

whimsyfree
2010-Sep-23, 11:26 PM
My bold

I don't know but roughly 6,250 trillion cubic feet world supply should last a few years.

World reserves are far greater than that. Peak gas predictions are somewhere around 2030. I don't know how well founded they are but I doubt they allow for the large scale substitution of gas for oil.