Somewhere in the last quarter of yesterday’s 20-hour drive, we found ourselves in the dismal valley that runs down the middle of California. My friend tried channel hopping on the radio at frequent intervals, but as we are not fans of religious programming, Mexican music, country music, most oldies, etc., we were out of luck. So we tried AM.
We found ourselves listening to the Art Bell show, which was being hosted by some guy named George. Someone called in saying something about how we should take advantage of the alien technology that provides free energy, blahblahblah. “George” said he’d like to see hydrogen power technology be developed faster. But then he wondered about its byproduct: water. He wondered how the water that is generated by power generation by hydrogen will affect the environment. He imagined Phoenix in the summertime, full of cars dripping water all over the place. Would the dry-heat summers become steambaths? If everyone used hydrogen power, would there be more and larger rainstorms? Could hydrogen power cause enormous environmental problems?
So I wondered:
[ul]
[li]What are the methods of using hydrogen for power? Just burning? A non-burning chemical reaction?[/li][li]How much water is created as a byproduct of using hydrogen vs. the amount of water created (or released, or whatever) by burning gasoline and diesel?[/li][li]Given that it’s a big planet, would the amount of water put into the environment if “everyone” used hydrogen fuel cause any problems? (And as a layman I’m assuming that any problems would be less than burning gasoline.)[/li][/ul]
Whatever water comes out of the tailpipe is just a drop in the bucket (heh). Evaporation of water in and around a city is much, much greater than any water vapor cars could produce. After a major rainstorm, literally millions of gallons of water will evaporate back into the atmosphere.
From [url=http://www.marinwater.org/poolevaporation.html]this cite[/url we find that an uncovered swimming pool 20’ x 40’ can lose 4300 gallons a MONTH to evaporation. When people are in the pool splashing around the evaporation is even faster. The cite above (The Marin Municipal Water District) estimates that including ‘splash out’, a 20 x 40’ swimming pool may lose 35,000 gallons of water a year to evaporation.
Now think about how much water evaporation happens when people water their lawns on hot days.
So let’s say that you had a car that produced 1 gallon of water per every 20 miles you drove. If the average commute in a city is 20 miles, it would take about 150 cars to release as much water vapor in a day as a single swimming pool loses in a day.
Olympic swimming pools are 50 meters long by 25 wide. Going by the above numbers, a single outdoor olympic-size swimming pool could lose over 500,000 gallons of water in a single year. My city has four of these, and it’s in frigid Canada. I’m guessing there must be many more of them in warmer places.
But forget swimming pools - how about lakes? Most cities have dozens of stormwater lakes and natural lakes. My house is on the shore of a large lake inside the city. These things lose hundreds of millions of gallons per year in evaporation.
Some radio hosts are just incapable of critical thinking.
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.