OT They myth of the hydrogen economy
- From: "s_knight8" <s_knight8nospam@xxxxxxxxxxx>
- Date: 07 Jan 2006 13:40:25 EST
http://www.321energy.com/editorials/pfeiffer/pfeiffer010506.html
The Myth of the Hydrogen Economy
Dale Allen Pfeiffer in Dale Allen Pfeiffer's Blog
http://www.lulu.com/allenadale
January 5th, 2006
There is a lot of talk about the hydrogen economy. It is at best naïve, and
at worst it is dishonest. A hydrogen economy would be a pitiful,
impoverished thing indeed.
China, the most heavily populated nation in the world, is undergoing one of
the greatest economic expansions in modern times. The rate of economic
growth over recent years has been astounding in itself, but what is truly
surprising to some observers is the manner in which China's industrial
revolution has evolved.
There are a number of problems with hydrogen fuel cells. Many of these are
engineering problems which could probably be worked out in time. But there
is one basic flaw which will never be overcome. Free hydrogen is not an
energy source; it is rather an energy carrier. Free hydrogen does not exist
on this planet, so to derive free hydrogen we must break the hydrogen bond
in molecules. Basic chemistry tells us that it requires more energy to break
a hydrogen bond than to form one. This is due to the Second Law of
Thermodynamics, and there is no getting around it. We are working on
catalysts which will help to lower the energy necessary to generate free
hydrogen, but there will always be an energy loss, and the catalysts
themselves will become terribly expensive if manufactured on a scale to
match current transportation energy requirements.
All free hydrogen generated today is derived from natural gas. So right off
the bat we have not managed to escape our dependency on nonrenewable
hydrocarbons. This feedstock is steam-treated to strip the hydrogen from the
methane molecules. And the steam is produced by boiling water with natural
gas. Overall, there is about a 60% energy loss in this process. And, as it
is dependent on the availability of natural gas, the price of hydrogen
generated in this method will always be a multiple of the price of natural
gas.
Ah, but there is an inexhaustible supply of water from which we could derive
our hydrogen. However, splitting hydrogen from water requires an even higher
energy investment per unit of water (286kJ per mole). All processes of
splitting water molecules, including foremost electrolysis and thermal
decomposition, require major energy investments, rendering them
unprofitable.
Hydrogen advocates like to point out that the development of solar cells or
wind farms would provide renewable energy that could be used to derive
hydrogen. The energy required to produce 1 billion kWh (kilowatt hours) of
hydrogen is 1.3 billion kWh of electricity. Even with recent advances in
photovoltaic technology, the solar cell arrays would be enormous, and would
have to be placed in areas with adequate sunlight.
We must also consider the water from which we derive this hydrogen. To meet
our present transportation needs, we would have to divert 5% of the flow of
the Mississippi River. This would require yet more energy, further reducing
the profits of hydrogen. This water would then have to be delivered to a
photovoltaic array the size of the Great Plains. So much for agriculture.
The only way that hydrogen production even approaches practicality is
through the use of nuclear plants. To generate the amount of energy used
presently by the United States, we would require an additional 900 nuclear
reactors, at a cost of roughly $1 billion per reactor. Currently, there are
only 440 nuclear reactors operating worldwide. Unless we perfect fast
breeder reactors very quickly, we will have a shortage of uranium long
before we have finished our reactor building program.
Even hydrogen fuel derived from nuclear power would be expensive. To fill a
car up with enough hydrogen to be equivalent to a 15 gallon gas tank could
cost as much as $400. If the hydrogen was in gaseous form, this tank would
have to be big enough to accommodate 178,500 liters. Compressed hydrogen
would reduce the storage tank to one tenth of this size. And liquefied
hydrogen would require a fuel tank of only four times the size of a gasoline
tank. In other words, a 15 gallon tank of gasoline would be equivalent to a
60 gallon tank of hydrogen. And, oh yes, to transport an equivalent energy
amount of hydrogen to the fueling station would require 21 times more trucks
than for gasoline.
Compressed and liquefied hydrogen present problems of their own. Both
techniques require energy and so further reduce the net energy ratio of the
hydrogen. Liquid hydrogen is cold enough to freeze air, leading to problems
with pressure build-ups due to clogged valves. Both forms of hydrogen
storage are prone to leaks. In fact, all forms of pure hydrogen are
difficult to store.
Hydrogen is the smallest element and, as such, it can leak from any
container, no matter how well sealed it is. Hydrogen in storage will
evaporate at a rate of at least 1.7% per day. We will not be able to store
hydrogen vehicles in buildings. Nor can we allow them to sit in the sun. And
as hydrogen passes through metal, it causes a chemical reaction that makes
the metal brittle. Leaking hydrogen could also have an adverse effect on
both global warming and the ozone layer.
Free hydrogen is extremely reactive. It is ten times more flammable than
gasoline, and twenty times more explosive. And the flame of a hydrogen fire
is invisible. This makes it very dangerous to work with, particularly in
fueling stations and transportation vehicles. Traffic accidents would have a
tendency to be catastrophic. And there is the possibility that aging
vehicles could explode even without a collision.
On top of this, we must consider the terrific expense of converting from
gasoline to hydrogen. The infrastructure would have to be built virtually
from scratch, at a cost of billions. Our oil and natural gas based
infrastructure evolved over the course of the past century, but this
transition must be pulled off in twenty years or less.
Automobile engineers and others within the industry do not believe we will
ever have a hydrogen economy. Daimler-Chrysler has admitted as much. Rather
than developing a hydrogen economy, it makes more sense-and will always make
more sense-to buy a more efficient car, ride public transport, bicycle or
walk.
.
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