hydrogen power science fact of science fiction
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7/23/2019 HYDROGEN POWER Science Fact of Science Fiction
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H YDROGEN is the lightest and most abundant element in
the universe as well as the source of all energy. Deep within the
sun and stars, nuclear fusion converts hydrogen into helium. The
energy that is released when four hydrogen atoms become a
helium atom is the energy which fuels all life. Evidence of the
incredible amount of energy contained within a hydrogen atom is
the thermonuclear or hydrogen bomb, which exploits nuclear
fusion to release its destructive power.
In our natural environment, hydrogen exists primarily incombination with other elements. In order for hydrogen to be
useful as a fuel, it must exist as H2 or free hydrogen.! H2 must
therefore be produced, unli"e fossil fuels such as natural gas, coal
and oil which can be directly mined or extracted. In this sense,
hydrogen is a secondary source of energy, analogous to electricity.
The energy used to produce H2 is stored, with some losses, within
the H2 molecule. This energy can then be "ept in storage, used on#
site, or transported to a remote location for energy conversion.
The fact that hydrogen must be produced is a ma$or consideration
when examining its effectiveness as an energy carrier, and is the
biggest stumbling#bloc" to widespread use in commercial
applications.
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%ree hydrogen exists at normal atmospheric conditions as
an odorless, colorless gas. It is stable and will co#exist harmlessly
with free oxygen &'2( until an input of energy drives the
exothermic &heat#releasing( reaction which forms water. Thisreaction from a higher energy state to a lower one generates a
positive output of energy. %or over a century it has been predicted
that a system will be developed in which hydrogen, extracted from
pure water using energy derived from the sun, is used as a fuel or
as an energy#carrier,! and will serve to provide the demands for
all of society)s power re*uirements. The beauty of the system
being that solar energy and water, the sources, are practically
limitless and that the resulting energy conversion is relatively pollution#free with the only waste product being pure water. +
seemingly perfect cycle, beginning and ending with energy and
water.
In -/, 0ules 1erne predicted with impressive foresight the
use of hydrogen fuel in his ci#%i classic 3ysterious Island. 1erne
describes a process whereby, 4water will one day be employed as
fuel, that hydrogen and oxygen which constitute it, used singly or
together, will furnish an inexhaustible source of heat and light, of
an intensity of which coal is not capable. 45ater will be the coal
of our future.! 5here is this technology that has had // years to
come to fruition6 +n examination of the history of hydrogen
research as well as a loo" at today)s research and development
helps to provide some answers.
History
7robably the first recorded event of the production of
hydrogen in the laboratory is contained within 8th century
alchemical texts. The alchemists dealt extensively with the
transmutation of metals, a procedure which re*uired the
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dissolution of metals in salts or acids. +t the time, the existence of
the element hydrogen was un"nown to the alchemists, although
they were aware of the presence of something different in these
metal9acid reactions. Theophrastus :ombastus 7aracelsus!&;<=#8;( was purported to have said, when he dissolved iron in
spirit of vitriol, +ir arises and brea"s forth li"e the wind.! He was
most probably referring to the production of hydrogen. till, little
was understood of the gas) properties. Its burnability was not
noted until the th century by Tur*uet de 3ayerne. >;?
It was the common belief in th century Europe that air
itself was a basic element. ome perceptive individuals suspectedthat there existed a property of air which was re*uired for the
combustion and the sustenance of life. ome important figures
involved in this *uest were the Dutch physician Herman
:oerhaave &@@-#=-(, the English scientist Aobert :oyle &@2#
@<( &who developed :oyle)s Baw( and the English physician
0ohn 3ayow &@;8#@<( all of which were outspo"en in their
belief in a life#giving! substance within air.
It was also believed that there existed a substance called
phlogiston which imparts burnability in matter and that
combustion was the release of phlogiston. This theory was first
published in @< by the Cerman scientist Ceorg Ernst tahl
&@@/#=;(. Henry avendish &=#-/(, believing in the
existence of phlogiston, attempted to describe some of its
properties. He succeeded in isolating carbon dioxide &' 2( and
hydrogen gas &H2( and dubbed them fixed air! and flammable
air! respectively. He was able to obtain precise measures of
hydrogen)s specific weight and density, although he thought he
was studying >;?a pure state of phlogiston. avendish also
discovered that igniting a mixture of flammable air and oxygen
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&air( produced water. These were to be pivotal investigations into
the properties of hydrogen.
The %rench chemist +ntoine Baurent Bavoisier &;=#<;(
continued the study of flammable air, repeating avendish)sexperiments, and eventually produced hydrogen and oxygen in the
laboratory via the dissolution of metals in acid. He was also able to
split water molecules using a heated copper tube. In another
experiment he combined hydrogen and oxygen and produced
water. These experiments, in -8, were to prove definitively that
H2 and '2 are the basic constituents of water. It was his important
publication, The 3ethod of hemical omenclature, in which
Bavoisier named the flammable air! hydrogen, and the life#sustaining air! oxygen. Bavoisier was eventually executed after the
%rench Aevolution in <; because of his associations with the
pre#Aevolution %rench government, a loss heavily mourned by the
international scientific community of the day.
The discovery that flammable air! was fourteen times
lighter than air led to the use of hydrogen as a bouyant in
aeronautical balloons. + %rench physicist 0ac*ues +lexandre esar
harles &;@#-2=( was the first to use hydrogen in a balloon
"nown as a harliere,! in which he was able to fly to an altitude of
="m in -= &use of hydrogen continued on into the 2/th century,
eventually being replaced by helium due to its inert properties,
thus reducing chance of explosion(.
oon after +lessandro 1olta built his first electric cell near
the turn of the century, two English scientists, 5illiam icholson
and ir +nthony arlisle, discovered that by passing an electric
current through water, hydrogen and oxygen could be produced.
This process, called electrolysis, was to become an important
method for the production of hydrogen. In -=<, ir 5illiam
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Croves was able to reverse the process, combining hydrogen and
oxygen with platinum electrodes and a sulfuric acid &H2';(
electrolyte to produce electricity and water, inventing the first fuel
cell.
Early in the <th century, the Aeverend 5illiam ecil
presented a paper to the ambridge 7hilosophical ociety entitled,
'n the +pplication of Hydrogen Cas to 7roduce 3oving 7ower in
3achinery.! :asically, the paper described a hydrogen#powered
engine in which hydrogen and oxygen were combined and ignited.
The ensuing vacuum generated a moving force via the air that
rushed in to fill the void. +lthough there is no record that theengine was actually built, ecil)s proposal pioneered the study of
hydrogen)s use as a fuel.
'n into the 2/th century, hydrogen)s development as a fuel
source had achieved little progress until the cottish geneticist
0.:.. Haldane presented a paper to ambridge Fniversity in
which he proposed that :ritain could meet it)s increasing demand
for energy by using wind energy to electrolyGe water into hydrogenand oxygen. The gases, first li*uefied, can be stored in
underground reservoirs until needed. They can then be
recombined in combustion motors or oxidation cells.! This paper,
presented in <2=, offered a glimpse into the potential of a solar#
hydrogen fuel system. +t a time when the use of fossil fuels,
especially coal, was prevalent, Haldane emphasiGed the scarcity of
fossil fuels and the eventual necessity of an alternative source of
energy.
Haldane also pointed out that li*uid hydrogen has three
times as much heat per pound of hydrocarbon fuel. This is an
important factor when developing hydrogen fuel for use in air and
space travel, where weight is of a prime design criteria. However,
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the lightness of hydrogen allows for only about one#third of the
energy per unit volume. +n aircraft using hydrogen will be able to
fly higher and farther due to the lighter fuel load than an aircraft
using the energy#e*uivalent amount of $et fuel.
>;?>=?
The tan"s,however, must be much larger and ta"e up to one#third of the
fuselage in current designs for commercial aircraft. >;?
In the <=/s, interest in hydrogen as a fuel reached a new
height. In Cermany, two men were extremely influential in
hydrogen research %ranG BawacGec" and Audolph Erren.
BawacGec", a Cerman turbine designer, was s"etching designs for
hydrogen powered cars as early as <<. >;? His wor", in
collaboration with the Cerman#+merican 0.E. oeggerath, and theCerman inventor Hermann 'berth, led to ideas for developments
in efficient pressuriGed electrolyGers, li*uid hydrogen use as a
roc"et fuel, and the transportation of hydrogen in pipelines for use
as an energy#carrier.
The most influential pioneer of the <=/s would
undoubtedly be Audolf Erren. +n expert in the combustion
process, Erren began developing hydrogen engines in the late
<2/s. He advanced the concept of in$ecting hydrogen into the air#
fuel mixture of combustion engines, serving to heighten the
output of the combustion process. Erren, wor"ing in cooperation
with the Cerman, +ustralian, and :ritish governments, converted
buses, vans, rail cars, and even submarines to be powered by
hydrogen or any combination of hydrogen#fuel mixtures. >;?
>? However, a conflict of interests brought about by 5orld 5ar II,
made it impossible for Erren to wor" with both the :ritish andCerman governments and Erren)s efforts to expand the technology
were fruitless. Eventually the government research money was
cutoff and Erren)s research fell into a period of dis*uiet.
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'ther important developments of the <=/s included the
wor" of the Cerman engineer Hermann Honnef, who designed
huge wind#power generators which could theoretically produce up
to // megawatts of power, stored as hydrogen. +lthough they never went beyond the drawing board, Honnef)s ideas were
predecessors to much of the wind#turbine technology used
effectively today.
Hydrogen was also being used to supplement fuel in large
dirigibles in both Cermany and England. In the <2/s and <=/s,
before switching to helium, hydrogen was the primary bouyant
used in large passenger balloons. These Jeppelins! were able tofly to altitudes of 2;// feet at 8 mph. The fuel used to drive the
motors was typically a benGol#gasoline mixture. In order to
maintain proper bouyancy, the captain was re*uired to blow off
hydrogen as fuel was consumed. +n innovative solution was
to >;-?combine the blow#off hydrogen with the main fuel in the
internal#combustion engines. In this way they were able to
decrease fuel consumption. >;? England also used this strategy in
their A/ airships, and were also able to reduce the re*uirements
for hydrocarbon fuel.
Jeppelins are still what people most associate with
hydrogen, and the Hindenburg disaster is probably the most well#
"nown event involving hydrogen. The Hindenburg)s association to
hydrogen has created a negative public image of the gas, and has
perpetuated the myth that hydrogen is extremely dangerous. The
Hindenburg was actually designed to use helium as the bouyant.
+t the time of the ill#fated $ourney to ew 0ersey, helium was
extremely hard to come by due to F.. trade embargoes. They used
hydrogen, the next best thing, but the ship was not e*uipped with
the necessary safety features re*uired to deal with the flammable
gas. The explosion was well covered by the media at the time.
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Bittle "nown is the fact that most of the deaths &there were thirty
six casualties( were not attributed to the actual explosion, but
occured when many tried to $ump to safety and died on landing. It
is now established that hydrogen is, in fact, less dangerous thanmost fuels used today. >/?
In the Fnited tates, I.I. i"ors"i, who developed the first
wor"ing helicopter, was loo"ing into the use of hydrogen as an
aircraft fuel. In <=-, he presented his ideas to the +merican
Institute of Electrical Engineers, suggesting that the use of li*uid
hydrogen would permit, 4 a great change, particularly with
respect to long#range aircraft4! This would ma"e possible thecircumnavigation of the earth along the e*uator in a nonstop flight
without refueling. It would also enable an increase in the
performance of nearly every type of aircraft.! His statement would
prove prophetic in the years to follow.
The next decade saw little in the way of forward progress in
hydrogen research and development, presumably due to the
distractions of 5orld 5ar II. +ny existing collaborations betweenCerman and English scientists disintegrated, and funding went
elsewhere. The only significant events were the redistribution of
fossil#fuel resources, which led many countries to start loo"ing for
sources of domestic energy. This factor contributed directly to the
wor" of 0.. 0ust in +ustralia, who found that hydrogen, produced
via off#pea" electricity, cost roughly the same per mile as gasoline
in truc"s. >? 7lans were made to develop commercial#siGed
electrolysis plants, but were scrapped after the +llied victory in
<;8 made oil available and cheap once again.
'ne +ustralian who continued hydrogen research was A.'.
King, who relocated to the Fniversity of Toronto in anada to
further the cause. %rom <;- to <88, King led his team of
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scientists at the Fniversity of Toronto to conduct numerous
studies into the use of hydrogen as an alternative to gasoline in
ordinary internal combustion engines. They were able to show
that hydrogen was indeed feasible in this capacity, the primary constraint being that the compression ratio in the engines had to
be "ept below seven to one. >=?These studies in Toronto showed
that combustion engines can be converted to run on hydrogen
simply and cheaply.
During the same period, the :ritish scientist %rancis T.
:acon began development of the hydrogen#air fuel cell. This fuel
cell, called the :acon ell, substituted an al"ali &potassiumhydroxide &K'H(( for the acid as the electrolyte, eliminating the
problem of corrosion of the electrodes. The :acon ell was used as
the model fuel cell which was to become an integral part of
++)s space program.
In the <8/s, the F.. +ir %orce was using hydrogen fuel in
experimental high#altitude, long#range reconnaissance aircraft.
:ased at the ++ Bewis Aesearch enter in 'hio, the +ir %orceconverted a :#8 to run on li*uid hydrogen. The pilot had the
option to switch from the conventional "erosene fuel source to
hydrogen. This was fed under pressure from the wing#tip fuel tan"
to a heat#exchanger where the cryogenic li*uid was heated to a gas
and burned normally in one of the two $et engines. +lthough the
program was a success, the use of other fuels proved to be more
cost#efficient, and the use of hydrogen as an aircraft fuel was
discontinued.
+t the same time, Boc"heed, in con$unction with 7ratt L
5hitney, was developing a high#altitude, supersonic spy plane to
run on li*uid hydrogen fuel. This plane, the B#;//, got as far as
wind#tunnel testing before the program was discontinued for
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technical and logistical reasons. + large amount of drag was
introduced due to the larger volume re*uirements of li*uid
hydrogen storage. This re*uired more power to "eep the plane in
flight. 'ne positive outcome was the determination that li*uidhydrogen did not re*uire more safety precautions than that which
were re*uired for hydrocarbon fuels. This is an important step in
helping to dispel the Hindenburg 3yth.!
Boc"heed and ++ have since continued development of
an advanced supersonic transport &+T( using li*uid hydrogen
fuel &Bi*H2(. tudies in the tradeoff of reduced fuel consumption
with Bi*H2 versus increased drag have shown that the Bi*H 2 +T would still be ;=M more efficient &environmental advantages also
play a part in the consideration, with reduced carbon emissions,
less noise, and lower 'Nemissions(. >;? till, the final
considerations are economic, and hydrocarbon fuels are still
cheaper than hydrogen, when production, storage, and
transportation are accounted for. Fntil the scarcity of fossil fuels
ma"es their price increase to a higher level, government support
of Bi*H2 aircraft will be lac"ing.
In the <@/s ++ developed the use of the hydrogen fuel
cell for use in the +pollo missions to the moon. The fuel cells,
utiliGing expensive platinum electrodes, provided electrical power
on#board, as well as generating drin"ing water for the crew)s
consumption. It proved to be a highly reliable system and is still
used today in the pace huttle missions.
+lso, during the <@/s, an +ustralian electrochemist 0ohn
')3. :oc"ris, while wor"ing as a consultant with Ceneral 3otors,
began advancing the idea of a hydrogen economy.! In this
ambitious energy concept, the cities of the Fnited tates could be
supplied with energy derived from the sun, and the energy stored
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using hydrogen. C3 studied the use of hydrogen for a time, yet
did not pursue the technology to any significant >;<?degree. :oc"ris
continued his crusade, and the phrase hydrogen economy,! which
has nothing to do with economics, has become an importantconcept.
In <@@, @ year old Aoger :illings modified a model#+ %ord
to run on hydrogen. :illings went on to convert many late model
automobiles to run on hydrogen using their internal combustion
engines. In <2, he won the anti#pollution category of the Frban
1ehicle Design ompetition with a hydrogen#fueled 1ol"swagen.
:illings soon teamed up with other interested parties to form oneof the most influential advocates and developers of hydrogen#
fueled automobiles, the :illings Energy orporation of 7rovo. He
has demonstrated the feasibility of hydrogen use in buses and mail
truc"s. Aoger :illings is still in the forefront of hydrogen
technology, spea"ing out and demonstrating the advantages of
hydrogen use in transportation and home appliances. ince that
time, literally hundreds of automobiles have been converted to run
on hydrogen.
The energy crisis! of <= produced a ma$or impetus for a
renewed interest in alternative fuel sources. The '7E situation
and the realiGation that fossil fuels were not only running out but
environmentally undesirable, led to a shift in public opinion. The
renewed public interest was so strong that it generated an
incredible amount of publicity. 3ost of the ma$or publications
printed stories about hydrogen. +rticles appeared in Business
Week, Readers Digest , Time, Scientific American, and Fortune.
Hydrogen had become a popular solution to the prevailing
urgency to find a source of domestic energy.
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The upsurge in interest led to the formation of advocate
groups. The Hindenburg ociety, formed on the =8th anniversary
of the Hindenburg disaster, was dedicated to the safe utiliGation
of hydrogen as a fuel.! The purpose was to educate and dispelmany of the myths which deemed hydrogen to be a dangerous,
useless substance. 'riginally an informal group, popular interest
led to the necessity for the formation of the International
+ssociation for Hydrogen Energy in <;. +nother important
group, the Institute of Cas Technology, also played an important
role in generating public awareness and support for hydrogen
research. 'ther associations that have sprouted up since then
include the +merican Hydrogen +ssociation and the ationalHydrogen +ssociation.
Creat gains were made in the research of hydrogen in the
</s, but interest waned in the decade to follow. The reason was
once again economics. Hydrogen was still too expensive. +lthough
the environmental aspects were appealing, they could not
outweigh the fact that natural gas, oil, and coal were much
cheaper and easier to use. +lso, the crisis! in the 3iddle East
dissipated when '7E loosened its grip, and the price of oil
leveled off.
3ost advances since the </s have been made using
hydrogen in motor#driven vehicles, either in con$unction with
other fuels, or used in electric vehicles. ince <-2, Ceorgetown
Fniversity has been developing a fuel#cell9battery#operated bus.
The buses have been used in alifornia, 5ashington D.., and
hicago with favorable results. anada)s :allard 7ower ystems
developed a 2/#passenger bus to run on a hydrogen fuel#cell.
Daimler :enG, in Europe has also developed vehicles which run on
metal hydride storage systems. + press release dated 3ay ;,
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<<@, gave details of a newly unveiled fuel cell vehicle available to
the public. The E+A II fuel cell vehicle has room for six people.
The fuel cells produce an output of 8/ "5 and enable a top speed
of / "m9h. The range of the vehicle, on full hydrogen tan"s, ismore than 28/ "ilometers. >?
Daimler#:enG has also mentioned development of an
automobile that will produce hydrogen on#board, using methanol.
+ successful method of producing hydrogen on the go! would be
a ma$or step in hydrogen evolution, and would create a revolution
in transportation, even if hydrocarbon fuels are still used.
'ther automobile manufacturers, such as 3aGda and
Aenault, have developed hydrogen powered vehicles, although
none have been slated for public availability as of yet. ome F..
companies, pushed by stiffer environmental legislature, and
deadlines to produce Gero#emission! automobiles by the year
2///, have increased the push to ma"e available a hydrogen#
powered passenger vehicle. There is little evidence that the
+merican automobile manufacturers are able to meet any of theenvironmental goals set by tate and %ederal legislatures.
5hether this is technical inability or a conflict of interests is
unclear.
In the Fnited tates, recent legislation has paved the way for
hydrogen programs. In <</, the par" 3. 3atsunaga Hydrogen,
Aesearch, Development and Demonstration +ct &7B /#8@@( led
to the enactment of a 8#year management and implementationplan for hydrogen research and development. The Hydrogen
Technical +dvisory 7anel was established for coordination and
consultation.
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The Energy 7olicy +ct of <<2 &7B /2#;-@( authoriGed the
Department of Energy to administer the five year ALD program.
In accordance with the 3atsunaga +ct, the program would include
investigation into renewable production of hydrogen,transportation of hydrogen via existing natural gas pipeline
systems, hydrogen storage for vehicle use, and fuel cells for
hydrogen powered vehicles.
The Hydrogen Energy Aesearch 7rogram was introduced in
the Hydrogen, %usion and High Energy and uclear 7hysics
Aesearch +ct of <<;. The bill authoriGed O=; million over four
years. The main goal is the demonstration of the practicability of using hydrogen in transportation, industrial, residential, and
utility applications by the year 2///. The bill passed the House
but did not pass the enate. The Hydrogen %uture +ct of <<8 was
a toned down version of the original bill which reduced the
emphasis on demonstration pro$ects, and instead focussed more
on ALD. The bill passed congress and is now in effect with much
funding going into ALD.
Today, interest in hydrogen seems to be on an upswing once
again. Aecognition of the benefits of hydrogen has reached a
global scale. The continued demonstration of the attainability of a
renewable, clean#burning fuel has captured public awareness, and
has won the support of those governments which aid in funding
research and creating infrastructure webs.
>8/?
Present Technologies
There are four processes which must be considered when
developing a hydrogen#fuel system. These processes areP
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. 7roduction
2. torage
=. Transportation
;. Energy conversion
There are many alternatives from which to choose when
developing a hydrogen system. The factors in which each
alternative is considered, involve efficiency, economic feasibility,
and environmental impacts. How these factors are weighted
against each other is open for debate. urrently the prevailing
trend is to consider cost#effectiveness above all else. Aecent trends
in legislature and public concern are shifting emphasis more
towards renewable and pollution#free considerations as a priority
for development of hydrogen technology.
Hydrogen is a secondary source of energy, not a primary
source li"e oil or natural gas. Therefore, in order to be utiliGed
hydrogen must first be produced. There are many ways in which
hydrogen can be produced. 3ethods of production include
chemical, electrochemical, photochemical, biological, and
thermochemical processes.
The simplest method to produce hydrogen is to dissolve
metals in acid. %or example, when Ginc &Jn( is placed in a solution
of hydrochloric acid, it reacts to produce Ginc chloride and
hydrogen.
Jn Q 2H R Jn2 Q H2
This reaction can be reproduced simply in the laboratory,
although the amount of hydrogen produced is minimal. till, this
method was used to a large extent during 5orld 5ar II when
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scrap aluminum was dissolved in sodium hydroxide &lye( in order
to generate hydrogen. The hydrogen was then used to inflate
unmanned balloons for weather observation and raising radio
antennas.
>=?
This method is relatively expensive, and is notconsidereda method for mass production &today, research is being
done with scrap iron to produce hydrogen, for use in
transportation as a method of producing hydrogen onboard(.
mall amounts of hydrogen can then be economically produced to
provide the needs of a small hydrogen#fuel system.
The cheapest, and by far the most widely used method for
producing hydrogen is steam reformation. team, and a carbon#
based feedstoc" &usually methane or natural gas(, are combinedunder high temperature and high pressure to produce carbon
dioxide and hydrogen. It is estimated that <8M of hydrogen
produced in the F is by the steam methane reformation
method. >-? 3ost of this hydrogen is used in industrial applications.
+lthough hydrogen can be produced in this manner for about
O/.@8 per "ilogram, the environmental conse*uences of the use of
hydrocarbons are still a concern. The production of carbon
dioxide, a greenhouse gas,! as well as nitrogen oxides &'N(
contribute to the pollution of the Earth)s atmosphere. +lso, the
limited resources can only ma"e the cost increase as the supplies
of fossil fuel sources decrease. + newly developing renewable
option is the use of biomass, or recycled carbonaceous material, as
the feedstoc" in the steam reformation process. The air pollution
problems still exist, but it will be an intelligent use of a waste
product. +nother method for producing hydrogen is electrolysis.
Electrolysis involves the application of a small voltage &approx. 21
D( to pure water. The electrical energy decomposes the water
molecule into its constituent elements, hydrogen and oxygen. This
techni*ue has the advantage of producing hydrogen directly from
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water, with none of the environmental drawbac"s which
accompany processes using fossil#fuels. till, the relatively low#
efficiency ¤tly @/#@8M with a theoretical maximum of -8M(
of the process, and the high cost of electricity ma"e this anexpensive option. >/? The cost of producing hydrogen via
electrolysis is about O=.// per "g. >-?
The method of electrolysis is the most attractive for those
interested in a completely clean, renewable process using solar
energy to produce the electricity. 7hotovoltaic cells, hydropower,
and wind turbines are currently being used to generate the
electricity re*uired to electrolyGe water for hydrogen production.8,@ 'ther renewable options include geothermal, tidal, wave action,
and thermal gradients in the ocean. +lthough most of these
processes do not produce sufficient amounts of energy to provide
hydrogen on a large scale, on#site electricity production coupled
with a small on#site electrolyGer can produce enough energy to
provide for the energy needs of a household along with fuel for the
family automobile. This allows hydrogen to be produced easily
without having to wait for an infrastructure to develop.
'ther attempts at water#splitting have involved super#
heating water to temperatures high enough to liberate the
hydrogen from the water molecule &thermochemical(. The
temperatures re*uired are in the range of 8///S#@///S %. +dding
chemicals such as sulfuric acid can lower the re*uired
temperature but the bottom line is that the only feasible way of
generating the heat re*uired is by way of a nuclear reaction.
uclear power generation, needless to say, has severe safety
implications. There is still research being done in the
thermochemical production of hydrogen which doesn)t re*uire
nuclear power plants. +n example would be solar power plants in
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which the heat of the un is focused into a tiny point where the
heat accumulates, much li"e a magnifying glass. et there are still
environmental concerns due to the chemicals involved, and the
nitrogen oxides which are formed from a heat reaction in air&which has a high concentration of nitrogen(.
7hotoprocesses involve the use of light energy for the
production of hydrogen. These methods in one way or another,
attempt to mimic the natural phenomena of photosynthesis. In
plants, chlorophyll captures light energy and uses it to produce
complex sugar#phosphate compounds. The most astonishing fact
is that this chemical reaction, basically ' 2 Q H2' Q light energy R >8?sugars Q '2 occurs at room temperatureU 3uch research has
been done to reproduce this feat. 7hotobiological techni*ues
which coax photosynthetic plants, algae, and bacteria into
respiring hydrogen, photochemical techni*ues which synthetically
duplicate the photosynthetic process, and photoelectrochemical
techni*ues which use layers of semiconductors separated by water
are being researched today. >;?>-? These are promising technologies,
but are still in the experimental stage. If efficiency improves, then
photoprocesses may play a part in the future of hydrogen.
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Storage and Transportation
Hydrogen is typically stored as a li*uid, or as a gas. There
are advantages and disadvantages to each of these storage options,
the choice of which depends upon the ultimate use.
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Hydrogen becomes a li*uid at temperatures below #;2=.=S
% Ě.<S (. Bi*uefication of hydrogen is very energy#intensive,
with one#third of the energy content of the hydrogen used in the
li*uefication process./ This is offset by a reduction of volumere*uirements for hydrogen storage, with much less storage space
re*uired for a li*uid than a gas. Bess volume needed for storage,
ma"es li*uid hydrogen the preferred form of hydrogen used in the
+erospace industry with ++ being one of the largest consumers
of li*uid hydrogen in the world. >;?>2?
'nce in li*uid form, hydrogen can be transported in
pressuriGed tan"s by truc", barge, or rail. Due to the very low
boiling temperature of hydrogen, losses due to boil#off can beconsiderable. Insulation of the tan"s is of utmost importance to
reduce these losses. If insulated properly, hydrogen can be stored
for as much as five years without significant losses. ><?>/?
Hydrogen can also be stored as a pressuriGed gas. +s a gas it
can be transported via pipelines, using existing natural gas
distribution lines. + concern would be possible embrittlement of
the lines due to absorption by the metal fittings. torage of
hydrogen as a gas is the most economical method, but due to the
necessity for larger tan"s, weight and space re*uirements can be a
problem. It is estimated that the mass of a pressure tan" is //
times the mass of the hydrogen stored within it./ Higher
pressure means less volume re*uired, but the walls need to be
reinforced to withstand the greater pressure. +lthough hydrogen
is extremely light, the containers necessary to store gaseous
hydrogen can be heavy and bul"y.
+nother method of storing gaseous hydrogen involves metal
hydrides. ertain metals such as magnesium, titanium, or iron,
have an affinity for hydrogen. Fnder certain conditions, these
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metals will absorb gaseous hydrogen, and store it within its
molecular structure. 5hen the hydride is heated, the hydrogen is
released. +lthough energy is re*uired to store and to release the
hydrogen, this option has proved attractive for use as a storagemedium onboard automobiles. The main reason is that it is much
less energy#intensive than the li*uefication process, although heat
energy is re*uired to release the hydrogen. >;? +lso, safety and space
concerns are reduced when metal hydride storage is used in
automobiles.
There are a variety of other methods being developed for
hydrogen storage. These include carbon adsorption, glassmicrospheres, onboard partial oxidation reactors, and recyclable
li*uid carriers. ome of these options appear promising, but they
will still ta"e some time to develop.
Power Conversion
There are two ways of using hydrogen to generate power.
'ne is simple combustion. The use of hydrogen in internalcombustion engines has been used extensively. The other is the
conversion of hydrogen into electricity in a fuel cell, which is
essentially electrolysis in reverse. :oth of these have their
advantages and disadvantages.
Internal combustion engines can be easily converted to run
on hydrogen, or a hydrogen#fuel mixture. >?>/? The noxious
emissions are greatly reduced, with water being the only by#product if pure hydrogen and oxygen are used. itrogen oxides
are still formed from the high heat of combustion, and are still a
source of air pollution.
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'ver the past two decades, most research has gone into the
development of the fuel cell. The operation of a fuel cell involves
the combination of hydrogen &anode( and oxygen &cathode( in the
presence of an electrolyte. 'utput voltages range from /. to .2 1./ The type of fuel cell varies depending on the electrolyte used.
%uel cell types include the 7hosphoric acid fuel cell, the al"aline
fuel cell, and the solid oxide fuel cell. The most common type, the
al"aline fuel cell, is still used by ++ on board spacecraft.
+nother type of electrolyte being developed is the proton#
exchange membrane which uses a solid polymer to facilitate the
reverse electrolysis process. This solid polymer, which is much li"e
plastic "itchen wrap, conducts protons, and is very conducive tothe purpose of an electrolyte. +lthough membrane costs are high,
this type of fuel cell appears very promising, and is currently being
used in advanced research &chatG Bab, Humboldt tate
Fniversity, alifornia(.
The use of hydrogen is at an all#time high. It is possible to
convert any car sitting in the driveway to run on hydrogen. It is
being proven every day that hydrogen can be used as a
replacement not only for gasoline, but natural gas in heaters and
stoves in the home. Hydrogen could some day replace electricity
as the primary energy#carrier via high#voltage power lines, being
transported in pipelines and converted to electricity on#site.
7roduction of hydrogen is also becoming easy to do for
anyone with access to about 21 of D electricity. 3any
homesteads generate enough electricity using windmills and solar
panels to supply the household)s needs. + small electrolyGer added
to this system could easily produce enough hydrogen to fuel a
vehicle. It is clearly possible that anyone with a little ingenuity and
s"ill can convert the household to use hydrogen, convert the car to
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run on hydrogen, and generate the electricity for hydrogen
production using only solar energy, all for about the cost of a mid#
siGed +merican sedan.
+ny in depth study of hydrogen reveals the vast array of
system configurations for hydrogen power. The bottom line is that
any system which utiliGes hydrogen in any capacity is going to be
better off for it. Harmful emissions are reduced, efficiency is
increased and water&the original source(, is produced. 'n a larger
level, it would seem possible that use of hydrogen alone or in
con$unction with other fuels would be a ma$or step in the right
direction, and bring us a little closer to a more harmonic cycle of energy use.
References
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