Energy Density of Some Materials (KHW/kg)
So potentially, Hydrogen wins big but the main problem is that there are no naturally occurring sources of hydrogen so it must be made and that has an energy cost associated with it.
Note: the actual fire on the Hindenburg was the result of a spark that ignited the outer skin and not the spontaneous explosion of hydrogen
Hydrogen as a Secondary Fuel:
Hydrogen can be easily separated from Oxygen in water via Electrolysis. This process is about 67% efficient
Burning hydrogen combines with oxygen to form water --> no other combustion products (except for small amounts of nitrogen oxides formed around high temperature combustion zone)
For use as a secondary fuel, Hydrogen needs to be stored as a liquid. (20 K; -253 C).
As a liquid its energy density per unit volume is 1000 times higher.
For a given stored energy requirment, a cryogenic hydrogen facility is much less expensive than a pumped hydro facility
But overall efficiency is 25% cryogenic storage is energy intensive
But, one can make a hydgrogen-oxygen fuel cell Using a catalyst, hydrogen combines with oxygen to make water plus electricity. In the lab, such cells can acheive 85% efficiency but large scale value is unknown and untested although there have been some recent breakthroughs:
This animation shows the process that goes on inside an individual fuel cell. The red Hs represent hydrogen molecules (H2) from a hydrogen storage tank. The orange H+ represents a hydrogen ion after it's electron is removed. The yellow e- represents an electron moving through a circut to do work (like lighting a light bulb or powering a car). The green Os represent an oxygen molecule (O2) from the air, and the blue drops at the end are for pure water--the only byproduct of hydrogen power.
Advantages of Hydrogen technology and fuel cells
Good overview of different kinds of Fuel Cells
Basic Chemisty of a Fuel Cell:
What about fuel cell yield? This information is hard to find, but GM announced in October 2001 the following specifications:
Hydrogen is already produced mainly to form ammonia to be used in fertilizer. Hydrogen is extracted from methane and steam to make Carbon Dioxide.
Problems with the use of Hydrogen:
Transport of Hydrogen Gas:
Because of the inefficiency in producing it, hydrogen will always be more expensive than the electricity that produced it, if you do the price comparison at the production site
But, for situations where customers are 1000 miles away from the production site - it is cheaper to deliver hydrogen through a pipeline system than electricity through the power grid.
A possible strategy is to build large, sturdy windmills in the Aleutian Island Chain (one of the windiest places on the Earth), for the purposes of producing electricity to make hydrogen from Sea Water. The hydrogen would then be shipped over the pipeline network to customers thousands of miles away.
The use of liquid hydrogen as a fuel source has potential (particularly on jet airplanes) but technical problems associated with storage and delivery have not yet been overcome
Best hope Hydrogen fuel cell technology will continue to improve and soon (3-5 years) individual vehicles will use this as a main fuel source.