hydrogen as a fuel
Hydrogen is believed by many to be an
ideal fuel. It is a combustible gas that can be used both for
home heating, cooking and as a source of fuel for automotive
transportation. Hydrogen does not exist in pockets under the
ground like natural gas. Instead it must be manufactured either by
stripping it out of other conventional fuels such as gasoline or
natural gas, or by the process of electrolysis. Electrolysis is
a process of separating chemical bonds by running an electric current
through it. The one chemical formula nearly all of us remember
is H20 where the H stands for Hydrogen. By running an
electrical current through water it can be broken into its constituent
components one of which is hydrogen.
Hydrogen is a secondary fuel source. It takes energy to strip
it out of stored hydrocarbons such as natural gas and oil, or to
produce it through the process of electrolysis which requires an
electric current. About 96% of the commercial hydrogen used today was
created by stripping it from natural gas or oil. Hydrogen is
usually only made by electrolysis when it needs to be extremely pure.
Because so much of the hydrogen we use today is made from fossil fuels
it really does not currently constitute much of an alternative to
The main argument for hydrogen as a fuel source is that it is
pretty much pollution free (assuming the energy source used to make it
was pollution free). For example, when used as part of a
hydrogen fuel cell the primary waste result is water.
Unfortunately though, despite this worthy characteristic, hydrogen
has many other attributes that make it questionable as a long-term
fuel source. To begin with hydrogen is one of the least energy
dense materials to be found anywhere. At room temperature and pressure, hydrogen takes up three thousand more times space than gasoline containing an equivalent amount of energy. Estimates on the energy
efficiency of hydrogen vary depending on the source. Most
estimates put it at around 20-30% efficient meaning that it takes
about 4 units of energy to create 1 unit of hydrogen energy.
However, the biggest problem with hydrogen is not its energy
efficiency but the challenge of storing it and transporting.
Hydrogen is a lighter than air gas and given the opportunity it will
dissipate into the atmosphere. To store it and use it you must
put it under extreme pressure to the point that it becomes a liquid.
In this process about 30-40% of its original energy potential is lost.
Putting the gas under extreme pressure also makes the container
holding it extremely cold (as much as -432 degrees Fahrenheit).
This means it must be handled carefully when in a liquid format.
Because containers must use thick metal and be extremely well
constructed to handle the high pressure of liquid hydrogen their cost
is also a consideration. A hydrogen tank for a vehicle costs
about 100 times as much as a standard car gasoline tank.
Because hydrogen is only practical to use when under high pressure
the size and weight of the storage container is not a minimal factor
in using it and transporting it. If used in vehicles the weight
of the storage tank adds significantly to the weight of the vehicle
thus undermining its energy efficiency. There are also
considerable risks should the high pressure container ever be breached
in an automobile accident.
Hydrogen transport is also difficult even if left in a gaseous
state. It is much lighter than natural gas and can easily leak
out of pipes designed for natural gas. If transported in this fashion
it would require a brand new network of pipelines which itself would
represent an enormous expense.
Hydrogen may very well be more of a distraction than a solution
when it comes to developing clean renewable energy systems. The
infrastructure required to make use of it does not exist and even if
it did the cost the source energy used to produce the hydrogen would
probably be far more effective if used directly.