Pacific Northwest National Laboratory, a U.S. Department of Energy research lab, has come up with a new formula for hydrogen pellets that looks like it holds a lot of energy, per gram.
The PNNL pellet is made out of ammonia borane, or AB, compressed into small pellets. A milliliter of AB weighs about 0.75 grams and can hold up to 1.8 liters of hydrogen. Researchers speculated that a fuel system powered by AB pellets will occupy less space and be lighter in weight than systems using pressurized hydrogen gas. That's one of the pellets (and not a half-dissolved Jawbreaker) in the photo.
A number of companies are working on solid hydrogen storage. Storing hydrogen in pipelines and tanks is problematic. Because it's a tiny molecule, hydrogen in its gas form can leak out of containers. It also corrodes many materials. A solid material, however, can fix hydrogen with chemical bonds until it needs to be released. It also prevents explosions (although the Hindenburg zeppelin fire was caused by the aircraft's paint.)
Ecotality has created a system that stores hydrogen in magnesium oxide. Add water and you get hydrogen. SignaChem has one that revolves around sodium. Trulite is working on a portable hydrogen storage system that stores the gas in sodium borohydride.
Hydrogen, of course, has many critics. Hydrogen can be expensive to make and manufacturing it can release more pollutants in some circumstances than burning gasoline. But proponents note that it's plentiful in the universe. It can also come in handy in various applications. Some have theorized that hydrogen factories, powered by ocean-wave plants, could be built far out at sea. The hydrogen could then be brought to shore in ships stocked with solid-state storage.
In other words, hydrogen may not take over the world, but it could make sense in a lot of places. Toyota and others are still working on hydrogen cars. (See video of me driving a hydrogen car . That thing romped.)
Some of the difficulties involve devising ways to get the hydrogen to release from its carrier at a steady, predictable rate, the cost of the solid-state carriers, and their weight.