| Higher energy density = higher danger of releasing it unintentionally. I totally understand why hydrogen is a great rocket fuel. You need this high energy content and the extreme lightness for high Isp. On land, I suppose, the energy density of 100 tons of hydrogen in one place is unnecessarily high. The fact that hydrogen has no odor, and its flame is entirely infrared, invisible, does not help. By the same token, I think that lithium batteries have excessive energy density for large-scale land applications, like buffer storage for solar / wind power. Even a lead-acid battery, with all its environmental downsides, weight, etc is at least not a major fire hazard. I suppose that large-scale electricity storage will take off when cheaper and safer, while less dense, alternatives to lithium batteries are commercialized. As a power source for a car, a lithium battery at least is not cryogenic. OTOH on the scale of a train this may already be not a big problem. Same possibly for an oceangoing ship, but it would be terrible to start losing fuel and power if a bad storm damages the cryogenic system. An ideal (fantastic) system could use methane and turn it into carbon, only oxidizing the hydrogen. Sadly, similar reactions only work so far with much more complex molecules. |
Converting methane into hydrogen is known as steam reformation. We can easily due this, but we don't want to because it is a fossil fuel.