SvennoJ said:
happydolphin said:
Guys, this may seem like a dumb question, but:
If
"warming due to CO2 leads to more evaporation of water and more water vapor in general in the atmosphere, Water is a much stronger greenhouse gas than CO2 and can cause even more warming."
and we use hydrogen cars,
then wouldn't that pose a problem?
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Actually hydrogen fuel cars would emit less water vapor then the cars we drive now. And it is a negligable amount anyway.
For stoichiometry calculations, Gasoline is often considered as Octane (C8H18)
So the combustion of C8H18 is:
C8H18 + 12.5O2 --> 8CO2 + 9H2O
So the stoichiometry gives (118lb of C8H18 reacts with 400lb of Oxygen to give 353 lb of CO2 and 162 lbs of water). So per pound of gasoline burnt you get 1.42 lbs of water. Density of gasoline is around 6 lbs / gal and that of water is 8.3 lbs/gal. Plugging in those numbers you get 1.03 gallons of water are produced per gallons of gasoline burnt. Now to be able to compare apple to apple, I convert the water produced per mile of travel. Assuming 25 miles to a gallon average of a US Car that works out to be : 0.04 gal of water produced per mile
2> Water Production in a Hydrogen Powered Fuel Cell Car
The earliest (not the best) hydrogen powered fuel cell car gives 220 miles with a hydrogen storage tank (5,000 psi) of 156.6 liters volume. Density of Hydrogen at 300k and 5000psi (300K) is 0.023 g/ml ( NIST - isothermal properties of hydrogen). So a 156.6l tank holds 3.6 kg of hydrogen. And 3.6 kg of hydrogen will give 32.4 kg (14.7 lb) of water. 14.7 lb of water is 1.77 gal of water. Now 1.77 gallons of water is distributed over 220 miles. So that works out to be : 0.008 gal of water produced per mile
So hydrogen powered fuel cell cars will produce 5 times lesser water than gasoline cars.
It would be nice if hydrogen fusion started to pay off so we would have the energy needed to create a hydrogen fuel economy.
The USA would need about 7 trillion kilowatt hours of electricity per year to produce enough hydrogen to replace current gasoline usage.
(50 kilowatt hours to produce hydrogen to the equivalent of 1 gallon of gasoline)
http://www.americanenergyindependence.com/hydrogen.aspx
This can be produced by a 100x100 mile solar farm in the Californian desert.
http://www.americanenergyindependence.com/solarenergy.aspx
Quite a big area, nevermind the amount of materials needed to produce 100 sq miles of solar panels. Hydrogen fusion plants should be more efficient I would think.
The 7 trillion is on top of the 4 trillion kilowatt hours that are used now each year of which 42% is produced by burning coal, 25% by natural gas, 19% nuclear, 8% hydropower, 3% wind, biomass 1%, geothermal and solar less then 1%
http://205.254.135.7/energyexplained/index.cfm?page=electricity_in_the_united_states
Nuclear seems the only option in the near future to keep the lights and the airconditioning on. Hopefully we'll get a breakthrough in hydrogen fusion technology before we get ships running on nuclear reactors to replace oil. Imagine those illegaly dumping waste in international waters :/
http://www.atomicengines.com/ships.html
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So what's stopping us from making it happen?
Also, can commercial airplanes run off hydrogen cells with today's technology?
