by Learned Nand » Sun Apr 28, 2013 6:03 am
Actually, I'm going to do the math now on how much hydrogen is required to flood a garage. First, let's calculate how much water is needed.
We'll assume that the garage is 4 x 4 x 3 meters. Water has a density of one gram per cubic centimeter. A cubic meter is 1 million cubic centimeters, which means 1 million grams of water, or 1 metric ton of water. That means, to fill the whole garage, we'd need 4 x 4 x 3 metric tons of water, or 48 metric tons.
To find out how much hydrogen is required to create a certain amount of water, let's look at the equation for the combustion of Hydrogen. It's 2H2 + O2 -> 2H2O. That means two hydrogen atoms are required to create one molecule of water. Two hydrogen atoms sum up to about 2 AMU of mass, and 2 AMU of mass in hydrogen produces 18 AMU of mass in water. That means that a certain amount of mass of hydrogen creates 9 times that mass in water.
So, if we have 48 metric tons of water, we need to burn five and a third (5.33333...) metric tons of hydrogen, or about 12,000 pounds of hydrogen. Given that an average car might weigh as much as 4,000 pounds, I find it very unlikely that a fully fueled hydrogen-powered car would carry three times its weight in fuel.
A gasoline-powered car might carry about 16 gallons of gasoline at its fullest, and given gasoline's density of about 6 pounds per gallon (which is about three quarters that of water), this means that a car is only likely to carry about 100 pounds of gas, or about 2.5% of its weight in fuel, not 300% of its weight in fuel. A hydrogen car carrying enough fuel to flood a garage would be carrying 120 times more fuel than a car would carry today.
Terry Pratchett wrote:The trouble with having an open mind, of course, is that people will insist on coming along and trying to put things in it.