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.
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:
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
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