You are correct on both counts. Water vapor is a greenhouse gas and storing hydrogen in useful amounts is difficult.
However, I'm not sure visualizing the problem as you described is totally accurate. Hydrogen has more energy per weight but less per volume than gasoline. You don't need to store the same weight of hydrogen as you do of gasoline to get the same operating range. You'll need a larger tank, but how large depends on the pressure designs of the tank.
I doubt the auto industry and suppliers like GE would be spending the kind of money they are on hydrogen if the solutions were not technologically feasible.
The hydrogennow organization has some information on the subject:
The amount of water put into the air from hydrogen combustion won't even be detected by your local meteorologist, when checking the moisture content of the air. Consider that all internal combustion engines that burn fossil fuels, such as gasoline, diesel or natural gas, produce water vapor that vents into the air. Changing engines to pure hydrogen will produce about the same amount of water vapor, while eliminating all of the carbon and sulfur emissions.
When hydrogen is burned in an engine, or used in a fuel cell, the end product is water. The net result of the complete circle is that there is no more or no less water in the environment than at the beginning of the cycle.
Since hydrogen is so light, it is difficult to store a lot of it in a small tank. However, Dynetek Industries (among other companies) is currently testing a 12,500 psi tank for gaseous hydrogen. Both Ford and GM are working with 10,000 psi tanks in their prototypes (Ford's Model U and GM's Hy-Wire).
Hydrogen does occupy more space than any other fuel, whether it be in gaseous or liquid state. However, new tanks are providing for more storage of compressed hydrogen gas. The U.S. government recently certified 5,000 psi hydrogen tanks for use in automobiles. The German government has certified 10,000 psi tanks; and the U.S. is soon to follow. Dynetek Industries has also developed a 12,500 psi tank that should be certified within the next two years. BMW uses liquid hydrogen, which provides more hydrogen per volume than gaseous hydrogen, but is more expensive to produce. Liquid hydrogen tanks also require venting of the gas as it warms in the tank. BMW claims that their tanks will not require any venting for up to one week.
Hydrogen tanks do require more space than gasoline tanks. However, they are much safer. Similar tanks have been used in natural gas vehicles for years. They can withstand armor-piercing bullets and dynamite, with no explosion or leaks. A hydrogen tank behind the passenger compartment actually makes the entire car safer from rear-end collisions. So, I would say it is much more practical than a gasoline tank, which will rupture, causing the gasoline to ignite, and frequently, explode. A gasoline fire in an automobile can engulf the passenger compartment, burning passengers to death. Gasoline wicks to the skin when spilled on a person. If hydrogen is spilled, it disperses quickly into the atmosphere. There is no radiant heat from burning hydrogen, so a hydrogen flame will not burn skin unless the body is put directly into the middle of the flame.
hydrogennow.org |
