Hydrogen Storage
We are consuming more fossil fuels today than ever. As our supply
of nonrenewable energy continues to dwindle with each passing
day, scientists around the world are busy researching ways for
humanity to carry on with their lives when the day finally comes
for the furnace to go out.
The most promising energy source in development seems to be hydrogen,
a fuel that has already been tested and used by NASA on many of
their space shuttles. Hydrogen, a simple molecule with two H atoms,
is the most abundant element in the universe. When used to produce
energy it is completely renewable and produces only water as a
by-product.
In the recent years, the automotive industry has been developing
hydrogen cars that will one day run along the hydrogen highways
and byways of our country. This new innovation has been popular
at automotive trade shows around the world.
The storage of the fuel however, is one factor that remains problematic
in the development and future marketability of hydrogen cars.
Hydrogen possesses a very large volume to mass ratio. Imagine
the empty cardboard box of a newly purchased refrigerator. Although
it takes up a large amount of space, its weight (substance) is
relatively small by comparison. The ability to store hydrogen
efficiently has for years been the main concern of advocates for
hydrogen energy. Below are a few methods that have been proposed
by researchers as possible solutions to the problems of hydrogen
storage.
Compression
For a number of years, scientists have successfully stored compressed
hydrogen in steel and special composite tanks. The problem, when
it comes to practicality, is that these tanks often weigh a considerable
amount and would not realistically fit into a modern consumer
vehicle. However, in recent years, many lighter composite units
have been developed that can hold compressed hydrogen at far greater
pressures than before without sacrificing safety. It is hoped
that these technological advances will continue to make their
way into the consumer market.
Liquid Hydrogen
Hydrogen can also be cooled down to a liquid state. Due to its
compact nature, liquid hydrogen is particularly useful as fuel
for transportation vehicles. NASA frequently uses liquid hydrogen
to fuel their space shuttles, and certain European carmakers,
such as BMW, have long been testing the feasibility of this idea.
The only major downfall with liquid hydrogen storage is that its
cooling mechanism alone would use up to 30-40% of the stored fuel
energy. It is expected however, that a more efficient cooling
system will be developed in the near future that will cut the
maintenance costs of liquid hydrogen in half.
Metal Hydride Tanks
Certain metal alloys can readily absorb and release hydrogen
atoms under particular atmospheric conditions. Tanks containing
these metal alloys are able to absorb hydrogen atoms when the
temperature is low and release them for energy production when
the temperature is at a modestly high level. The benefit of metal
hydride containers is that they are relatively safe in comparison
to highly compressed forms of hydrogen.
In the event of a crash, the metal hydride tank will expose itself
to the atmosphere and correspondingly, its temperature will decrease,
keeping the hydrogen atoms safely situated within the metal alloy.
However, metal hydride does share a common flaw with the above
mentioned solution of compression, namely the issue of weight.
Although light weight metal alloys are currently in development,
most metal hydride tanks today are still too large and cumbersome
for average consumer use. It is hoped that new metal alloys will
be developed in the future that can pack hydrogen atoms more efficiently
within its structure. Other materials such as carbon, silicon
and boron are also being tested for possible use to bond with
the hydrogen atoms.
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