Hydrogen: A Future Energy Carrier?
Many see hydrogen as the clean fuel of the future, because its only by-product is
water. Before hydrogen can become a significant part of the energy economy, many
fundamental technological issues must be addressed. Governments, research
institutions and businesses, including the oil and gas industry, must play important
roles in solving problems related to hydrogen production, transport, storage
and distribution.
Kamel Bennaceur
Gatwick, England
Brian Clark
Sugar Land, Texas, USA
Franklin M. Orr, Jr.
Global Climate and Energy Project (GCEP)
Stanford University
Stanford, California, USA
T. S. Ramakrishnan
Ridgefield, Connecticut, USA
Claude Roulet
Houston, Texas
Ellen Stout
Air Liquide
Houston, Texas
For help in preparation of this article, thanks to Chris de
Koning, Shell Hydrogen BV, Amsterdam, The Netherlands;
Chris Edwards and Maxine Lym, GCEP, Stanford, California.
ECLIPSE 300 is a mark of Schlumberger. Roller Pac is a
mark of Axane.
30
The world has a voracious appetite for energy.
Abundant, inexpensive resources have fueled
technological advances from the Industrial
Revolution to the present. Continued growth will
require a continued supply of inexpensive energy
that is not sustainable with current resources. In
addition, concerns about greenhouse-gas emissions from fossil-fuel sources are generating a
new set of technological requirements.
In the ideal, albeit distant, future is a world of
renewable, pollution-free energy sources for
everything from electrical power grids to personal
vehicles. The path to that future is, technologically speaking, a steep uphill climb.
Hydrogen is likely to be a part of this
idealistic future, and possibly an important part.
A hydrogen molecule [H2] in the presence of
oxygen can be converted to water with a release
of heat and work. It is difficult to imagine a
cleaner source of energy.
However, there are challenges. To begin with,
molecular hydrogen does not occur naturally in
high concentrations; it is only 0.00005% of the
air.1 Hydrogen is normally bound in other
molecules, water and hydrocarbons being the
most common. Unlike natural gas, molecular
hydrogen is not found in large accumulations in
geologic strata, either.
This means that hydrogen is not a primary
fuel source. Like electricity, it is a means for
transmitting energy from primary fuel sources to
users. Like electrical power, hydrogen must be
produced and transported, although hydrogen
has an additional attribute that makes it more
attractive for some applications than electricity:
it can be stored for later use.2 This feature makes
it useful for powering vehicles and other
portable devices.
Current production of hydrogen is about
50 Mt/yr [55 million US tons/yr], mostly for
industrial purposes in chemical and petrochemical applications. A world economy using
hydrogen as a major energy carrier will require a
tremendous increase in that volume, as well as a
complex new infrastructure for transporting and
delivering hydrogen to end users.
This article discusses the global transition to
a hydrogen economy and the roles oil and gas
industry sectors might play over the next
decades. Also described are some of the major
technological barriers that must be overcome.
What Is the Hydrogen Economy?
The hydrogen economy is a system that uses
hydrogen as a major carrier in the energy supply
cycle. The term evokes a vision of energy usage in
the future that is sustainable and environmentally friendly.
That vision follows the historic trend toward
using energy sources that produce less and less
carbon as a by-product.3 Wood was a primary
energy source for millennia, but its primacy was
supplanted by coal in the late 1800s because coal
has a greater energy density. Use of oil as a fuel
Oilfield Review
1. See www.uigi.com/air.html (accessed April 18, 2005).
2. Electrical potential must be used as it is generated. To
store this energy, it must be converted to another form,
such as chemical potential in a battery, as gravitational
potential in a pumped-water system or as hydrogen. A
capacitor, which can store electrical potential, is
impractical for widespread societal needs.
3. Nakićenović N: “Global Prospects and Opportunities for
Methane in the 21st Century,” in Seven Decades with
IGU. International Gas Union Publications, published
jointly by International Systems and Communications
Limited and International Gas Union (2003): 118–125.
Spring 2005
80
60
Carbon intensity
Source
Carbon intensity, g/MJ
Wood
29.9
Coal
25.8
Oil
20.1
Gas
15.3
35
30
25
Coal
40
20
Wood
Oil
20
Carbon intensity, g/MJ
100
Share of global energy, %
increased during the 1900s, surpassing coal as a
global energy source in the 1960s. Natural gas
use is now increasing in importance.4
This progression of energy sources has been
accompanied by a decrease in the amount of
carbon dioxide [CO2] produced to release a given
quantity of energy as work or heat (right). One
reason this proportion has decreased is the
decreasing carbon-to-hydrogen (C/H) atomic ratio
in the predominant fuel source.5 The ratio for coal
is about 1.6 Oil has a ratio of about 0.5, and
methane C/H ratio is exactly 0.25.
Although this progression of fuel sources
results in less CO2 per unit of energy released,
the world consumption of energy has increased
even more rapidly. As a result, the undesirable
production of greenhouse-gas CO2 is expected to
rise, contributing to global warming.7 The
amount of CO2 generated annually is unlikely to
decrease over the next few decades, because
hydrocarbons will remain the prevalent fuel
sources. To control atmospheric accumulation,
the CO2 generated must be captured and stored.8
15
Gas
Nuclear
0
1850
1900
1950
10
2000
Year
> Decarbonization of energy sources. The carbon intensity in our major
energy supplies has declined as the world moved from wood (gold) to coal
(black) to oil (green) and now toward natural gas (red) as the predominant
energy source. The amount of carbon produced (dashed black) declined with
each change in primary energy source. The inset shows the amount of
carbon produced per unit energy for these fuel sources. Nuclear energy is a
small contributor to the energy supply. (Data from Nakićenović, reference 3.)
4. “A Dynamic Global Gas Market,” Oilfield Review 15, no. 3
(Autumn 2003): 4–7.
5. Wood does not follow the C/H ratio trend; its value of
about 0.67 is less than coal, but its energy content is also
less. The net result is that the production of CO2 per unit
of energy is higher for wood than for the other fuel
sources discussed here.
6. Killops SD and Killops VJ: “Long-Term Fate of Organic
Matter in the Geosphere,” in An Introduction to Organic
Geochemistry, 2nd edition. Malden, Massachusetts, USA:
Blackwell Publishing (2004): 117–165.
7. For more on global warming: Cannell M, Filas J, Harries J,
Jenkins G, Parry M, Rutter P, Sonneland L and Walker J:
“Global Warming and the E&P Industry,” Oilfield Review 13,
no. 3 (Autumn 2001): 44–59.
8. For more on carbon capture and storage: Bennaceur K,
Gupta N, Sakurai S, Whittaker S, Monea M,
Ramakrishnan TS and Randen T: “CO2 Capture and
Storage—A Solution Within,” Oilfield Review 16, no. 3
(Autumn 2004): 44–61.
31
More importantly, fossil fuel resources are finite,
and will eventually become prohibitively
expensive to recover. As gasoline becomes more
and more expensive in that distant future, some
other portable energy source, such as hydrogen
or batteries, will be needed.9
The apparent next step is to eliminate carbon
from the energy source. Several green, or
environmentally friendly, energy sources are
available today, but their usage is not a major
part of energy consumption. In 2001, fossil fuels
provided 85.5% of world energy consumption,
nuclear reactors provided about 6.5%, with other
sources combined providing only 8%.10 US
government projections indicate little production from sources other than fossil fuels and
nuclear power in the USA through 2025 (below).11
Attention around the world has focused on
the promise of the hydrogen molecule as the
ultimate green fuel. With no carbon, its C/H ratio
is zero: the end of the trend to less carbon in
fuels. H2 can be burned to generate only water,
heat and mechanical work, or it can be converted
to water, heat and electrical work using a fuel
cell (see “Fuel Cells: A Quiet Revolution,”
page 34). One kilogram of H2 provides about the
same power as 3.8 L [1 gal] of gasoline.
Although its promise is great, technological
limits currently make hydrogen uneconomic and
impractical as an energy carrier.12 The hydrogen
vehicles on the road today are for demonstration
and testing projects; they are not commercially
available. The cost for hydrogen production and
delivery will have to improve by about a factor of
four. Storage capacity on-board vehicles will have
to improve by a factor of two to three. In
addition, fuel cells to replace the internal
combustion engine will have to improve by a
factor of 4 to 5, with an improvement in service
life by a factor of 2 to 3.13 The challenges include
cost, durability, efficiency improvements and
material embrittlement. International efforts in
fundamental science aim to bridge these gaps.
International Commitment
Many nations are funding projects to move the
world toward an environmentally friendly energy
system. Two major thrusts are of particular
interest to the oil and gas industry. Carbon
capture and storage (CCS) seeks to mitigate the
impact of fossil fuels on the environment.
Second, efforts to make hydrogen a major energy
carrier could radically change the energy
industry, although its impact is probably decades
in the future.
There are initiatives to make other green
energy sources more economical and practical.
For example, wind farms and geothermal sources
provide primary energy now, but their potential
to provide a significant proportion of our energy
needs in the near future is limited. Sources such
as wind and solar radiation are intermittent.
Hydrogen could provide a means for storing
excess power from these sources for use in calm
or cloudy weather.
100
Energy consumption, 1015 Btu/yr
10
Petroleum liquids
Natural gas
Coal
Nuclear power
Hydroelectric
Wood and biomass
1
Geothermal
Municipal solid waste
Wind
0.1
Solar thermal
Other
0.01
0.001
Solar photovoltaic
2002
2005
2010
Year
2015
2020
2025
> US energy consumption by source. Most of the US energy consumption
over the next 20 years will come from fossil fuels: petroleum liquids (green),
natural gas (red) and coal (black). Nuclear (dark blue), hydroelectric power
(light blue) and wood and biomass sources (gold) are expected to remain at
about the same levels as today. Other energy sources, particularly renewable
sources, will remain small fractions of the total supply. (Data from “Annual
Energy Outlook 2005,” reference 11.)
32
The fossil fuels, oil, natural gas and coal, will
remain important primary sources of energy for
much of the coming century. Currently, the most
economic means for producing hydrogen is
through a process known as steam reforming,
which produces hydrogen from natural gas. The
vast reserves of coal make it the likely next
source for producing hydrogen through
techniques of gasification, partial oxidation or
autothermal reforming.
Converting these fuels to hydrogen at
centralized plants will allow carbon capture and
storage (CCS), sometimes referred to as carbon
sequestration. CCS will be more economical if
done from large, centralized facilities, whether
for generating electricity, producing hydrogen or
other uses.
The US government has a US$ 1 billion
demonstration project called FutureGen with a
10-year goal to build a coal-based power plant
that successfully generates electricity and
hydrogen without undesirable emissions.14 In the
European Union (EU), the similar 10-year
HYPOGEN project commits (euro) =C1.3 billion
for developing a zero-emissions power plant
using fossil fuel as a large-scale test facility for
producing hydrogen and electricity.15
Geologic storage of carbon dioxide in depleted
oil or gas reservoirs, in unminable coal seams or
in deep saline reservoirs is the most likely shortterm solution for CCS. Both FutureGen and
HYPOGEN require an economical transport both
of the fuel such as coal to the plant and of the CO2
by-product to a storage reservoir, possibly
restricting locations of the plants.
The EU also has a large-scale demonstration
program to build an entire community with a
hydrogen-based infrastructure. HYCOM is a
10-year, =C1.5 billion project running in parallel to
the HYPOGEN project.16
The US Hydrogen Fuels Initiative has a goal to
make fuel cell vehicles practical and costeffective for large numbers of Americans by
2020.17 The project provides US$ 1.2 billion to
fund development of hydrogen, fuel-cell and
infrastructure technologies needed to achieve
this target.
These huge projects are not the only
initiatives. Many countries around the world are
investing funds toward similar goals. In fact, the
number of projects underway is so large, and it is
increasing so rapidly, it is difficult to enumerate
them all.
Oilfield Review
H2 production and distribution
Direct H2 production from renewable sources; decarbonized H2 economy
2050
Hydrogenoriented economy
2050
n
tio
iza s s
l
a
Increasing decarbonization of H2 production; renewable sources,
ts rci tion ion
2040
efi me ca at
H2 use in aviation
fossil fuels with CCS, new nuclear power plants
en com appli pplic
b
n
te cell bile ary a
o
i
a
t
iv l
tra
pr fue mo tion
ne
Fuel cells become dominant
2040
nd and - FC C sta
pe
a
t
s n
technology in transport, in
-F
rke
rd roge
a
a
distributed power generation,
gm
ew hyd on
n
r
i
2030
s
and in microapplications
Widespread H2 pipeline infrastructure
lic scale ucti rt
ea
r
b
c
In
Pu rge- prod spo
n
a
e
L - H 2 tra rag
o
Interconnection of local H2 distribution grids; significant H2 production
2030
- H 2 2st
H2 becomes primary fuel choice for FC vehicles
H
from renewable sources, including biomass gasification
n
o
Significant growth in distributed power generation with
ati
H2 production from fossil fuels with CCS
2020
str
e
substantial penetration of FCs
us
on
d
m
Local clusters of H2 distribution grids
de n an
tr s and ratio tion
Second-generation on-board storage (long range)
ts
o
Local clusters of H2 filling stations
lee
eff rch ene ibu
2020
ef
te sea al g distr
Low-cost,
high-temperature FC systems; FCs commercial in microapplications
h
a
c
i
H2 transport by road, and local H2
riv d re tric on,
;n
sts
FC vehicles competitive for passenger cars
d p pplie elec rtati
production at refueling stations by
e
n
t
2010
d o
a a
d
reforming natural gas and by
iel
es h, an nsp
Atmospheric pressure hybrid SOFC systems commercial (<10 MW)
t; f
tiv earc icles , tra
electrolysis
n
n
e
s
e
h n
First H2 fleets; first-generation H2 storage
pm
nc tal re r ve ctio
i
o
l
H2 production by
c n fo u
ve
2010
bli e lls rod
de
Series production of FC vehicles for fleets (with direct H2 and on-board reforming) and other
reforming natural gas
Pu ndamel ce en p
nd
a
g
u
transport (such as boats); FC for auxiliary power units
and by electrolysis
F - Fu dro
g
n
i
t
y
s
2000
-H
Stationary low-temperature fuel cell systems (PEMFC) (<300 kW)
, te
h
arc
se
Stationary high-temperature fuel cell systems (MCFC and SOFC) (<500 kW); H2 internal combustion engine
Re
Fossil fueldeveloped; demonstration fleets of FC buses
2000
based economy
Stationary low-temperature FC systems for commercial niches (<50 kW)
Fuel cell (FC) and H2 systems: development and deployment
> European Union roadmap for implementing the hydrogen economy, including fuel cell development.
Several organizations provide clearinghouses
for information among the various groups. Two
examples are the Carbon Sequestration
Leadership Forum (CSLF) and the International
Partnership for the Hydrogen Economy (IPHE).
The CSLF is an international organization
focused on developing improved cost-effective
technologies for CCS, including separating,
capturing and transporting carbon dioxide for
long-term safe storage.18 The IPHE serves as a
mechanism to organize and implement effective,
efficient and focused international research,
development, demonstration and commercial
utilization activities related to hydrogen and fuel
cell technologies.19
Iceland provides an interesting laboratory for
developing green energy. The country has no
fossil energy resources, but has an abundance of
geothermal energy and also has significant
hydroelectric generating capacity. Since the
energy crisis of the 1970s, Iceland has created an
almost pollution-free infrastructure for
stationary energy, such as industrial use and
large power plants. For transport and for its
fishing fleet, the government of Iceland envisions
replacing fossil fuels with hydrogen and other
alternative fuels.20 From 2001 through 2005, the
European community funded ECTOS, a
Spring 2005
=C7 million demonstration program of three H2
fuel cell buses and the related infrastructure in
Iceland’s capital, Reykjavik.
Many countries have committed to decadeslong plans, or roadmaps, to develop a hydrogenoriented economy. A complete infrastructure has
to be developed, including hydrogen production,
delivery and storage. More efficient means for
using hydrogen in fuel cells are in development.
The transition is potentially disruptive to society,
so public education and outreach are important
parts of these roadmaps.
Roadmaps provide an integrated, systematic
and systemic approach, to ensure coordination of
changes throughout the infrastructure. The EU
roadmap provides a rough time line for actions to
move ahead (above). It foresees that, in the next
decade, existing localized distribution networks
(continued on page 36)
9. Conversion of natural gas to liquids may be an interim
step. For more on gas-to-liquid conversion: “Turning
Natural Gas to Liquid,” Oilfield Review 15, no. 3
(Autumn 2003): 32–37.
10. “International Energy Outlook 2004,” Table A2. Energy
Information Administration of the US Department of
Energy (2004). Available at www.eia.doe.gov/oiaf/ieo
(accessed April 18, 2005).
11. “Annual Energy Outlook 2005,” Tables A1 and A17.
Energy Information Administration of the US Department
of Energy (2005). Available at www.eia.doe.gov/oiaf/aeo
(accessed April 18, 2005).
12. “The Hydrogen Initiative.” American Physical Society
Panel on Public Affairs. Available at www.aps.org/
public_affairs/popa/reports/index.cfm (accessed
April 18, 2005).
“Basic Research Needs for the Hydrogen Economy,”
Report of the Basic Energy Sciences Workshop on
Hydrogen Production, Storage and Use (May 13–15,
2003). Available at www.sc.doe.gov/bes/hydrogen.pdf
(accessed April 18, 2005).
Crabtree GW, Dresselhaus MS and Buchanan MV:
“The Hydrogen Economy,” Physics Today 57, no. 12
(December 2004): 39–44.
13. See www.livepowernews.com/stories05/0331/003.htm
(accessed April 14, 2005).
14. For information on FutureGen: www.fe.doe.gov/
programs/powersystems/futuregen/ (accessed
April 25, 2005).
15. For information on HYPOGEN: Peteves SD, Tzimas E,
Starr F and Soria A: “HYPOGEN Pre-Feasibility Study,
Final Report,” document EUR 21512 EN, Joint Research
Centre and Institute for Prospective Technological
Studies (2005). Available at www.jrc.nl (accessed
April 18, 2005).
16. For information on HYCOM: Peteves SD, Shaw S and
Soria A: “HYCOM Pre-Feasibility Study, Final Report,”
document EUR 21575 EN, Joint Research Centre and
Institute for Energy (2005). Available at www.jrc.nl
(accessed April 18, 2005).
17. For more on the US Hydrogen Fuels Initiative: www.eere.
energy.gov/hydrogenandfuelcells/presidents_
initiative.html (accessed April 18, 2005).
18. For more on CSLF: www.cslforum.org (accessed
April 18, 2005).
19. For more on IPHE: www.iphe.net (accessed
April 18, 2005).
20. For more on the Iceland vision for hydrogen:
eng.umhverfisraduneyti.is/information (accessed
April 18, 2005).
33
Fuel Cells: A Quiet Revolution
Efforts to move the world toward a hydrogen
economy include a reexamination of the
means for converting hydrogen into energy.
Hydrogen combusts, so it can be used as a fuel
in an internal combustion engine, either alone
or mixed with gasoline. It can also be used as
a fuel in a turbine engine. However, considerable research and development now focus on
a different mechanism, the fuel cell.
A fuel cell, like a battery, uses electrochemical means to create electricity.1 Both types of
devices can provide more power by stacking
multiple cells. However, a battery stores a limited amount of energy in its chemicals, and
once that energy is spent, the battery is dead.2
A fuel cell uses an external reservoir to continuously replenish the fuel.
A fuel cell has two advantages over an internal combustion engine. Fuel cells have the
potential to be significantly more efficient than
conventional combustion engines. Some fuel
cells can achieve 60% efficiency, much better
than the 20% to 35% efficiency of a gasoline
internal combustion engine. A fuel cell has no
moving parts, although there are external
pumps to supply the fuel.
Name
Conducting
ion
The second advantage is decreased pollution. An internal combustion engine run on
hydrogen will not produce CO2. However, if air
is used, the process can still produce oxides of
nitrogen [NOx] in a high-temperature system
or a combined-cycle system, which uses a fuel
cell in combination with a turbine. A hydrogenpowered fuel cell normally produces only
water, heat and electricity.
The fuel, typically hydrogen, is supplied to
the anode side of a fuel cell. Oxygen or air is
supplied to the cathode side. Several types of
electrolytes are available to separate the
electrodes (below).
The anode contains a catalyst, which splits
hydrogen molecules and ionizes the atoms
into electrons and protons [H+]. The liberated
electrons provide the electrical output of a
fuel cell. In some cells, the protons pass
through the electrolyte to recombine with
oxygen and electrons on the cathode side,
forming water (next page, right). This is the
reverse of water electrolysis, which is used to
generate hydrogen from water and electricity.
In other types of cells, negatively charged ions
Operating
temperature, °C
Power
density
Disadvantages
pass through the electrolyte from the cathode
to the anode, forming water at the anode and
completing the circuit.
The catalyst in low-temperature cells usually contains platinum, which is an expensive
material. Replacing platinum with a lower
cost material in the catalyst is an active
research subject. High-temperature fuel cells
can use lower cost catalysts, such as nickel.
The polymer electrolyte membrane—also
called a proton exchange membrane—fuel
cell (PEMFC), is the leading contender for
use in passenger vehicles.3 It is lightweight,
operates at low temperature, has a quick
startup and uses a solid membrane, all of
which are considered advantages for mass
consumer operation. However, the platinum
catalyst is expensive and makes the cell susceptible to small amounts of carbon monoxide
[CO] in the fuel stream. The proton path
through the electrolyte has to remain
hydrated, so the temperature in the cell must
remain below about 100°C [212°F], and temperatures below freezing can be a problem.
Advantages
Applications
+
60 to 80
High
Platinum catalyst; sensitive
to CO poisoning; cannot run
above dehydration temperature;
slow reaction kinetics; not durable
Fast startup; favorable
power-to-weight ratio; low
temperature; reduced corrosion
and management problems
Transportation,
electric utility
+
200
Medium
High cost; large and heavy
cells; low efficiency (37 to 42%);
platinum catalyst
Mature technology; 200 units
in use; tolerant of impurities in H2 fuel
Electric utility,
transportation
+
60 to 120
Medium
Generates carbon; low efficiency;
platinum catalyst
Powered by methanol; few
storage problems
Small portable
applications
–
100 to 250
High
Cannot tolerate CO2
Mature technology; stable operation
for more than 8,000 operating hours;
high efficiency (60%)
Military, space
and undersea
applications
2–
Greater than
650
Low
Not durable; high temperature
and corrosive electrolyte; needs
CO2 to recycle
Variety of catalysts (precious
metals not needed); resistant to
impurities; high efficiency (60%);
external reformer not needed
Natural gas
and coal-based
power plants
600 to 1,000
Medium
to high
Slow startup; requires thermal
shielding; not durable
Precious metals not needed;
variety of catalysts; high efficiency
(50 to 60%); external reformer not
needed; resistant to poisoning; most
sulfur-resistant fuel cell; fuel flexibility
(including CO); solid electrolyte reduces
corrosion and management problems
Electric utility
PEMFC Polymer electrolyte
membrane fuel cell
H
PAFC
Phosphoric acid
fuel cell
H
DMFC
Direct methanol
fuel cell
H
AFC
Alkaline fuel
cell
OH
MCFC
Molten carbonate
fuel cell
CO3
SOFC
Solid oxide
fuel cell
O
2–
> Comparison of fuel cell types.
34
Oilfield Review
Electron flow
Space Electronics Specialty
chemicals
Basic
chemicals
e
Load
Water and
waste heat
(H2O)
Excess
fuel
+
H
Glass
Optical glass
Heat treatment,
fiber
steel
Laboratory
Food,
analysis
sorbitol
Heat treatment,
stainless steel Food, fat and oils
Fuel
cells
Glass polishing
10
100
1,000
m3/hr
10,000
Anode
Refining for
clean fuels
100,000
> Current use of hydrogen. Fuel cells, such as the Axane Roller Pac portable
fuel cell (inset), use a very small proportion of the current hydrogen
production. The predominant uses are for basic chemical production and for
making fuels such as gasoline less polluting. Uses near the bottom of this
chart are most likely to be supplied by tube trailers and cylinders. Those at
the top are most likely to have a pipeline supply, and those in the middle are
likely to have onsite generation.
For large-scale, stationary applications such
as power plants, the solid oxide fuel cell
(SOFC) is the most promising technology.4
The electrolyte is a nonporous ceramic that
passes charged oxygen ions [O2-] from cathode to anode, generating water in the fuel
discharge stream. The solid electrolyte allows
more configurations than other cells: tubular
or honeycomb in addition to the typical parallel-plate stack. Its high-temperature
operation—about 600 to 1,000°C [1,112 to
1,832°F]—allows use of less expensive catalysts. Fuels other than pure hydrogen,
including CO, also can be used at these high
temperatures without externally reforming
1. For a comparison of oilfield batteries to fuel cells:
Hensley D, Milewits M and Zhang W: “The Evolution of
Oilfield Batteries,” Oilfield Review 10, no. 3 (Autumn
1998): 42–57.
2. Some batteries use the reverse of the electrochemical
process to recharge, but the amount of energy available without recharging is limited by the capacity of
the battery cells.
3. “Hydrogen and Fuel Cells—Review of National R&D
Programs,” reference 35, main text.
4. “Hydrogen and Fuel Cells—Review of National R&D
Programs,” reference 35, main text.
5. “Hydrogen and Fuel Cells—Review of National R&D
Programs,” reference 35, main text.
6. “Hydrogen and Fuel Cells—Review of National R&D
Programs,” reference 35, main text.
7. “Basic Research Needs for the Hydrogen Economy.”
reference 12, main text.
8. See www.livepowernews.com/stories05/0331/003.htm
(accessed April 14, 2005).
Spring 2005
the fuels into hydrogen. It has high efficiency,
about 60%, that can be boosted to 80% or more
through effective use of heat generated during
the process.5
The phosphoric acid fuel cell (PAFC) is one
of the most mature technologies. Over 200
units are in use, mostly for stationary power
generation, but some have been used to power
city buses.6
Newer than the other types of fuel cell, the
direct methanol fuel cell (DMFC) is a type of
PEMFC that uses methanol rather than hydrogen as a fuel. Although the energy content of
methanol is lower than hydrogen, dealing with
a substance that is a liquid at room temperature is attractive from a storage and handling
perspective. The release of carbon into the
atmosphere is a drawback to this technology.
Long-term durability is an issue for all fuel
cells. The SOFC has the longest demonstrated
lifetime, 20,000 hours, but that is half the
desired lifetime for a stationary application,
such as electric generation.7 A PEMFC for
transportation application has achieved
2,200 hours.8 Replacing stacks containing the
anode and cathode will be an expensive maintenance issue.
The cost of fuel cells has kept them in niche
applications (above). However, as hydrogen
becomes more readily available to the general
Cathode
Hydrogen
fuel (H2)
Air supply
(O2)
Polymer electrolyte membrane
Cathode reaction:
+
O2 + 4H + 4e
2H2O
Anode reaction:
+
H2
2H + 2e
Electron flow
e
Load
-
Excess fuel
and water
Unused
gas
2–
O
Cathode
Anode
Air supply
(O2)
Hydrogen
fuel (H2)
Solid oxide electrolyte
Anode reaction:
2–
H2 + O
H2O + 2e
Cathode reaction:
2–
O2 + 4e
2O
> Fuel cells. A polymer electrolyte membrane
fuel cell (PEMFC) is a low-temperature device
that passes protons [H+] through a membrane,
forming water on the cathode side (top). A
solid oxide fuel cell (SOFC) passes oxygen ions
[O2-] through a ceramic membrane, forming
water on the anode side (bottom). To increase
the power output of a given type of cell,
multiple units are combined in a stack.
public, these niches will expand. DMFC technology is most likely for small-scale consumer
appliances, such as laptop computers and cellular phones. Portable generators, such as the
Axane system, which uses a PEMFC, are
already on the market.
35
will expand, with clusters of H2 stations near
these networks. Fuel cell technologies will
improve power delivery for both stationary use,
such as power plants, and mobile use in vehicles.
The EU roadmap predicts that mobile use will
expand slowly from fleet transportation to
personal vehicles. Meanwhile, localized networks
of hydrogen delivery systems will expand, with a
widespread pipeline infrastructure developed in
the next 20 to 30 years.
Fossil fuels will be used, but with CCS,
according to the roadmap. Later still, renewable
sources and a new generation of nuclear reactors
that generate electricity and hydrogen will
assume greater importance. Ultimately, about
50 years from now, the roadmaps predict an
economy based on renewable primary energy
sources with hydrogen as a major component of
the energy delivery system.
The push from governments does not
guarantee that a hydrogen economy will develop,
but it provides an important impetus toward
their goals. Several industries will be impacted
directly by the transition to a hydrogen economy,
and businesses in these industries are taking
steps in the same direction. Improved fuel cells
are under development in many companies and
in universities and research institutions. Several
automobile manufacturers have small fleets of
demonstration vehicles on the road. Some use
fuel cells; others operate using a hydrogen
internal combustion engine.
The Pierre Elliot Trudeau Airport in Montreal,
Quebec, Canada, has initiated a hydrogen project
with Air Liquide as one of the participants. The
airport authority plans to convert all its utility
and service vehicles to fuel cells or internal
combustion engines that run on hydrogen.
Gas companies and utility companies are
researching ways to store hydrogen. Hydrogen
storage tanks capable of withstanding high
pressure must be developed for mobile applications, such as in automobiles. These companies
and others are also working on niche uses
for hydrogen fuel cells, such as for wheelchairs,
scooters and mobile hydrogen power packs.
Schlumberger, ExxonMobil, GE and Toyota
committed US$ 225 million to the Global Climate
and Energy Project (GCEP), which is operated by
Stanford University.21 The 10-year program is
building a diverse portfolio of technology
projects aimed at reduction of greenhouse-gas
emissions. It focuses on high-risk projects with
high potential to fundamentally change the
technology, as well as systemic analysis of ways to
improve the environment. The program got
under way in 2002. Some of the current projects
at Stanford and elsewhere include developing
technologies for lower temperature fuel cells,
studying microbes for producing H2, investigating
the fundamentals of catalyst-doped nanotubes
and working on geologic storage of CO2.
Shell and other companies that market
gasoline directly to consumers have opened a few
hydrogen-refueling stations in conjunction with
demonstration-vehicle fleets. The exploration
and production (E&P) sector of our industry has
an important role to play in moving toward a
hydrogen economy.
The E&P Business and the
Transition to Hydrogen
The HYPOGEN and FutureGen programs
envision the next stage of hydrogen production
as coming from centralized plants that use fossil
fuels, including coal or gas. CCS is a major part of
these plans.22
Several carbon storage options have been
proposed. Chemically binding the carbon, either
using limestone ponds or by mineralization, is
unproven on a large scale, and it is likely to be
expensive. Storage in the ocean, either by
dissolution or as a liquid or hydrate at depth, is
an established technology, but laboratory tests
indicate it causes trauma to marine life.23 Little is
known about the long-term impact of increased
Worldwide CO2 Storage Potential
Option
Worldwide capacity,
Gt carbon
Depleted oil and gas reservoirs
100s
Unminable coal seams
10s to 100s
Deep saline reservoirs
100s to 1,000s
For comparison:
Worldwide anthropogenic CO2 emissions (McKee)
7 Gt/yr carbon
CO2 injection for EOR (Gielen)
12 Mt/yr carbon
> Estimates of worldwide CO2 storage potential. (Data on CO2 injection for
EOR from Gielen, reference 24; other data from McKee, reference 25.)
36
CO2 concentration on the ecosystem.24 Currently,
the most practical option is geologic storage in
depleted oil and gas reservoirs, unminable coal
seams and deep saline aquifers (below left).25
Any method of CO2 storage must be a longterm solution that avoids leakage of CO2 back
into the atmosphere. The E&P and oilfield
services industries, and research laboratories
can provide considerable experience to the CCS
effort through their understanding of geologic
formations and fluid flow in them. The industry
has the technology to identify structures, access
formations and operate the surface and
subsurface facilities to inject CO2. Monitoring
the operation and the migration of CO2 is also a
part of this expertise.
CO2 can be injected into depleted oil and gas
reservoirs. Generally, the original reservoir seal
will also contain the CO2 gas, up to the original
pressure of the reservoir. In addition, CO2 may
have a benefit as an enhanced recovery sweep gas.
Enhanced oil recovery (EOR) projects with
CO2 have been under way since 1972, starting in
the Permian basin, USA.26 Injected CO2 displaces
oil to producing wells. In addition, under
miscible conditions some CO2 goes into solution
with the oil and some oil fractions go into the CO2
phase.27 These mixtures displace oil efficiently,
increasing recovery. In either case, a portion of
the CO2 remains in the formation. Now, the desire
to decrease greenhouse-gas emissions encourages
a reexamination of CO2 EOR to both improve oil
recovery and to store CO2 underground.
A cross-border EOR project between the USA
and Canada is the first designed specifically for
CO2 storage. Anthropogenic, or man-made, CO2
from a coal gasification plant in North Dakota,
USA, is transported by pipeline for 325 km
[202 miles] and injected into the Weyburn
field in Saskatchewan, Canada.28 The Dakota
Gasification Company operates the synfuels plant,
and EnCana Corporation now operates Weyburn
field. About 3 million m3 [106 million ft3] of gas—
96% CO2 with traces of hydrogen sulfide, nitrogen
and hydrocarbons—are transported and injected
daily. CO2 migration has been modeled using
ECLIPSE 300 reservoir simulation software, and
the results match time-lapse seismic surveys.29
Passive seismic monitoring has also detected
microseismic events that are associated with CO2
injection, providing another monitoring method.30
Enhanced recovery from natural gas
reservoirs has been proposed and modeled, but
to date, there have been no field projects.31 CO2
in both liquid and gaseous states is denser than
methane, so a gravity-stabilized injection scheme
could be used.
Oilfield Review
CO2 has been used to improve recovery from
coalbed methane reservoirs. Because CO2 has a
greater affinity for adsorption by coal than does
methane, it will displace methane; in addition,
coal can adsorb at least twice as much CO2 as
methane.32 Enhanced coalbed methane recovery
is limited to coal seams that will not be mined, to
avoid future safety concerns.
The greatest potential for geologic CO2
storage is in deep saline aquifers. While coal
seams and gas and oil reservoirs are not present
everywhere in the world, saline aquifers are
common in most sedimentary basins (right). The
amount of aquifer volume that can be filled with
CO2 is not yet established, but estimates are that
sufficient volume exists to hold hundreds of years
of CO2 emissions.33
In 1996, Statoil began a project to store CO2
that is produced with natural gas from the
Sleipner field.34 The CO2 is injected into the
Utsira formation, which lies above the productive
Heimdal formation. The Saline Aquifer CO2
Storage (SACS) project and a subsequent SACS2
project, both funded by the European
Commission’s Thermie Program, developed best
practices in the research, monitoring and
simulation of CO2 migration in subsurface
storage aquifers using the Sleipner injection as a
basis. This work continues in an EU project,
CO2STORE. Since its inception, this operation
has injected more than 7 Mt [7.7 million US tons]
of CO2. The project will continue until 2020.
The energy carriers, hydrogen and electricity,
can both be generated from natural gas, and the
potential exists for the E&P industry to move its
production of these carriers closer to the
wellhead. Particularly in places where a natural
gas network does not exist, wellhead conversion
of natural gas into electricity using a fuel cell
might be economic. CCS also could be
implemented locally.
Steps toward a hydrogen economy are just
beginning, and the final form of a hydrogenbased future is yet to be determined. E&P
companies and the service industry are in unique
positions to help craft that future.
Technological Marathon
The advances necessary to achieve a hydrogen
economy are enormous, particularly to replace
current gasoline or diesel internal combustion
engines for personal transportation. The
roadmaps prepared by the USA, the EU, Japan
and other countries recognize the challenges,
and have extended time lines of about 50 years
for implementation of a hydrogen economy.35
Scientists do not see this as a sprint, but as a
Spring 2005
> Major onshore (green) and offshore (blue) sedimentary basins. The brown line indicates the 1,000-m
[3,280-ft] water-depth contour.
marathon with a long series of hurdles requiring
fundamental breakthroughs along the way.
Extensive progress in fundamental materials
science is essential. The focuses for technology
development are production, transport and
distribution, storage and safety, and costeffective and reliable fuel cells.
Production—Hydrogen, like electricity, must
be generated. Almost all of the hydrogen now
produced is for industrial use: ammonia plants
use about 57.5%, refineries use 27.4% and
methanol producers use 9.7%.36
A dramatic increase in production will be
necessary to meet the goals of government
programs to create a hydrogen economy.
Production in the USA will have to increase from
about 11 Mt/yr [12 million US ton/yr] to 265 Mt/yr
[292 million US ton/yr] to satisfy the projected
transportation needs in the USA in 2020.37 A
recent study assumes that there will be more
than 6,000,000 hydrogen-powered cars in Europe
by 2020.38 Japan’s goal is to have 5,000,000 fuel
cell vehicles on the road by 2020, along with a
stationary fuel cell cogeneration system with
21. For more on GCEP: gcep.stanford.edu (accessed
April 18, 2005).
22. Orr FM Jr: “Storage of Carbon Dioxide in Geologic
Formations,” Journal of Petroleum Technology 56, no. 9
(September 2004): 90–97.
23. Ishimatsu A, Kikkawa T, Hayashi M, Lee K-S, Murata K,
Kumagai E and Kita J: “Acute Physiological Impacts of
CO2 Ocean Sequestration on Marine Animals,” paper
C2-3, presented at the 7th International Conference on
Greenhouse Gas Control Technology, Vancouver, British
Columbia, Canada (September 5–9, 2004). Available at
www.ghgt7.ca/papers_posters.php?session_id=C2-3
(accessed April 18, 2005).
24. Gielen D: “The Future Role of CO2 Capture and Storage—
Results of the IEA–ETP Model,” IEA/EET Working
Paper EET/2003/04 (November, 2003). Available at
www.iea.org/dbtw-wpd/textbase/papers/2003/eet04.pdf
(accessed April 18, 2005).
25. McKee B: “Solutions for the 21st Century—Zero Emissions
Technologies for Fossil Fuels,” Technology Status Report,
International Energy Agency, Committee on Energy
Research and Technology, Working Party on Fossil Fuels,
2002. Available at www.iea.org/dbtw-wpd/textbase/
papers/2002/tsr_layout.pdf (accessed April 18, 2005).
26. For more on CO2 EOR projects: www.co2captureand
storage.info/project_summaries/23.htm (accessed
April 18, 2005).
27. Jarrell PM, Fox CE, Stein MH and Webb SL: Practical
Aspects of CO2 Flooding, SPE Monograph Volume 22 (2002).
28. Bennaceur et al, reference 8.
29. Bennaceur et al, reference 8.
For more on time-lapse seismic evaluation: Aronsen HA,
Osdal B, Dahl T, Eiken O, Goto R, Khazanehdari J,
Pickering S and Smith P: “Time Will Tell: New Insights
from Time-Lapse Seismic Data,” Oilfield Review 16, no. 2
(Summer 2004): 6–15.
30. Bennaceur et al, reference 8.
31. Oldenburg CM and Benson SM: “Carbon Sequestration
with Enhanced Gas Recovery: Identifying Candidate
Sites for Pilot Study,” presented at the First National
Conference on Carbon Sequestration, Washington, DC,
May 14–17, 2001. Available at www.netl.doe.gov/
publications/proceedings/01/carbon_seq/2a4.pdf
(accessed April 18, 2005).
32. Peteves et al, reference 15: 55.
33. Gielen, reference 24.
34. Bennaceur et al, reference 8.
35. For an overview of hydrogen economy efforts in different
nations: “Hydrogen and Fuel Cells—Review of National
R&D Programs,” Paris: International Energy Agency
and Organization for Economic Co-operation and
Development, 2004.
36. Suresh B, Schlag S and Inoguchi Y: “CEH Marketing
Research Report—Hydrogen.” Chemical Engineering
Handbook and SRI Consulting, August 2004.
37. “Basic Research Needs for the Hydrogen Economy,”
reference 12: 16.
38. For more on hydrogen stations in Europe: www.msnbc.
msn.com/id/7024047/ (accessed April 14, 2005).
37
Baton
Rouge
LOUISIANA
Houston
TEXAS
Bayport
Freeport
Gul
exico
f of M
0
Corpus Christi
150
0
100
0
Pipeline
Hydrogen plant
Hydrogen/CO plant
0
50
25
300
450 km
200
300 miles
100 km
Rozenburg
50 miles
THE NETHERLANDS
Bergen-op-Zoon
Terneuzen
Antwerp
BELGIUM
Feluy
Isbergues
Charleroi
FRANCE
Waziers
> Hydrogen networks. Air Liquide operates hydrogen pipelines in northern Europe and the US Gulf coast, part of the company’s 1,700-km [1,060-mile]
worldwide network. This is about 10% of all the hydrogen pipelines in the world. Plants in Antwerp, Belgium, and Bayport, Texas, each produce more than
100,000 m3/hr [629,000 bbl/hr] of hydrogen from natural gas. Most hydrogen produced at these plants is used to remove polluting sulfur from gasoline and
diesel fuel.
10 GW of capacity.39 Shell Hydrogen estimates a
network of hydrogen filling stations would cost
about US$ 20 billion each for the USA and Europe,
and about US$ 6 billion for Japan. The company
indicates that necessary renewal of the current
retail network over the same period of time also
will be a major investment.
Currently, the most cost-effective means of
producing hydrogen is steam reforming of
methane. However, hydrogen production through
steam reforming neither eliminates carbon
dioxide production nor addresses the finite
resource of hydrocarbon fuels. Production from
coal is considered the next step, but like
38
production from methane, CCS must be included
to achieve reductions in greenhouse gases.
Hydrogen can be generated from water and
electricity through electrolysis, the reverse of the
process used in a fuel cell. Electrolysis loses
10% to 30% of the input energy.40 If the cost of
the primary power is low enough, this could
be a reasonable means of generating hydrogen.
Off-peak hydroelectric power, for example at
night when electricity usage is lower, is
inexpensive enough to make hydrogen
generation potentially cost-effective in some
areas.41 Other primary sources of power include
wind farms and solar power.
Biomass can also be used for hydrogen
generation. Although carbon is part of the
process, this is considered a carbon-neutral
option, since the CO2 is taken up in the next
generation of biomaterials. If combined with CCS
at the generation plant, this option could
engender a net decrease in atmospheric CO2. Of
course, this option also dedicates a large surface
area somewhere for growth of the biomaterial.
It is unclear whether conversion from
electricity generated by nonpolluting sources to
hydrogen is an efficient path for society. The
energy loss through electrolysis is not regained in
other efficiencies from hydrogen usage. It is
Oilfield Review
arguably more efficient to use electricity directly
or for charging batteries that power automobiles,
rather than generating hydrogen.42 This would
require significant improvements in battery
technology, including decreasing recharging
times, decreasing battery weight and disposing of
old batteries.
Of greater interest are hydrogen production
methods that are in the laboratory stage of
development. Direct conversion of sunlight to
hydrogen, without an intermediate step of
generating electricity, is being investigated
through new nanoscale and biological processes.
Water can also be split into hydrogen and oxygen
at very high temperatures, termed thermolysis,
which may become possible in solar collectors
operating above 500°C [932°F], or in the next
generation of high-temperature nuclear reactors.43
Such reactor technology is still a few decades
away, and its implementation must overcome
public reluctance to build nuclear plants.
Transport and distribution—Hydrogen can
be generated at or near the point of use, or it can
be generated at a centralized location and
transported. Today, as much as 96% of hydrogen
production is used locally. The USA has the most
developed market for merchant hydrogen—that
which is transported for sale—with just over 15%
of the production transported to another site.44
Depending on the method of production, the
hydrogen may contain impurities, such as carbon
monoxide [CO] or CO2. For some end uses, the
hydrogen may need to be conditioned to remove
such impurities.
Although small amounts of hydrogen are
transported by cylinder or in bulk, most
merchant hydrogen moves through pipelines.
Localized clusters of hydrogen pipelines have
been installed in several industrialized areas
(previous page). There are currently 10,000 miles
[16,100 km] of hydrogen pipelines in the world;
the longest one extends over 500 miles [800 km]
in northern Europe.45
The cost of typical, 12-in. diameter hydrogen
pipelines today is about US$ 0.5 million to
US$ 1.5 million, which is roughly the same as
equivalent natural gas pipelines. Hydrogen
pipelines with large diameter, such as 30 in., may
be necessary to service an extensive transportation infrastructure. Such pipelines are
expected to cost more than equivalent natural
gas pipelines: about 50% more for materials that
resist hydrogen embrittlement and 25% more for
labor due to hydrogen-specific welding.46
Cost will be a major factor in extending this
distribution network from existing facilities and
building new pipeline networks. Taking just two
Spring 2005
Hydrogen
Methane
Propane
Molecular weight (u)
Property
2.02
16.04
44.06
~107
Gasoline
Density (kg/m3) at normal conditions
0.084
0.651
1.87
4.4
Buoyancy (density with respect to air)
0.07
0.55
1.52
3.4 to 4.0
Diffusion coefficient (cm2/s)
0.61
0.16
0.12
0.05
Lean flammability limit in air (% by volume)
4.1
5.3
2.1
1.0
Rich flammability limit in air (% by volume)
75
15
10
7.8
Minimum ignition energy (mJ)
0.02
0.29
0.26
0.24
Minimum self-ignition energy (K)
858
813
760
501 to 744
Lean detonability limit in air (% by volume)
18
6.3
3.1
1.1
Rich detonability limit in air (% by volume)
59
13.5
7.0
3.3
Explosion energy (kg equivalent TNT per m3 of vapor)
2.02
7.02
20.2
44.2
> Selected physical properties of hydrogen, methane, propane and gasoline.
parts of the world as examples, about 180,000
filling stations will need to be converted to
hydrogen in the USA and about 135,000 in
Europe. Some of these will be on a pipeline
network, but others, perhaps many others, will
generate hydrogen locally.
A safe and acceptable means for dispensing
hydrogen into vehicles or for personal use must
be developed. It has to be inexpensive,
convenient, and above all, safe. Air Liquide has
developed technology to rapidly transfer large
quantities of hydrogen at 5,000 psi [35 MPa]. The
technology is used in the Clean Urban Transit in
Europe (CUTE) program and other places. The
buses in Iceland, made by DaimlerChrysler, have
compressed hydrogen in cylinders on the roof.
Refilling these tanks takes about 6 to 10 minutes,
giving the buses a range of about 385 km
[240 miles].47
Storage—Hydrogen can be stored as a
compressed gas, as a liquid, or as a metal or
chemical hydride. Of these, liquid hydrogen has
the highest energy density.48 However, it is
still about one-third of the volumetric value
compared to gasoline and one-quarter of
gasoline’s gravimetric energy density.49 About
one-third of the energy content is lost in
liquefaction.50 For safety reasons and to avoid
pressure buildup, the hydrogen gas must be
allowed to bleed off, so liquid hydrogen is
not a viable solution for long-term storage in
mobile applications.
Several metal or chemical hydrides are under
investigation for storing hydrogen. The
advantage of this method is its safety and
stability in comparison with liquid or compressed
gas storage. However, getting hydrogen into the
hydride in a timely way—such as a three- to
five-minute fillup at a filling station—is not yet
possible, and getting it out currently requires
heating the hydride to a high temperature. The
weight of current hydride substrates and their
container is much greater than the weight of
stored hydrogen.
Developing means for localized storage is the
greatest hurdle to overcome for mobile uses in
personal vehicles.
Safety—Today, trained personnel use
hydrogen safely in industrial settings. Expanding
into use by the general public will involve risks
that must be mitigated. However, handling
methane, propane or gasoline also involves risks
that have been mitigated and are now
understood by the public (above).
39. “Hydrogen and Fuel Cells—Review of National R&D
Programs,” reference 35.
40. Mazza P and Hammerschlag R: “Carrying the Energy
Future—Comparing Hydrogen and Electricity for
Transmission, Storage and Transportation,” Institute
for Lifecycle Environmental Assessment, Seattle,
Washington, USA (June 2004).
41. Mazza and Hammerschlag, reference 40.
42. Mazza and Hammerschlag, reference 40.
43. “Basic Research Needs for the Hydrogen Economy,”
reference 12: 16.
44. Suresh et al, reference 36.
45. Simbeck D and Chang E: “Hydrogen Supply: Cost
Estimate for Hydrogen Pathways—Scoping Analysis,”
National Renewable Energy Laboratory paper
NREL/SR–540–32525 (July 2002): 21.
46. Parker N: “Using Natural Gas Transmission Pipeline
Costs to Estimate Hydrogen Pipeline Costs,” Institute
of Transportation Studies paper UCD-ITS-RR-04-35
(December 1, 2004). Available at www.its.ucdavis.edu/
publications/2004/UCD-ITS-RR-04-35.pdf (accessed
April 18, 2005).
47. Doyle A: “Iceland’s Hydrogen Buses Zip Toward Oil-Free
Economy,” The Detroit News (January 14, 2005).
Available at www.detnews.com/2005/autosinsider/
0501/14/autos-60181.htm (accessed April 18, 2005).
48. The energy density referred to here is the standard heat
of combustion per unit mass.
49. Crabtree et al, reference 12.
50. “National Hydrogen Energy Roadmap,” based on the
results of the National Hydrogen Energy Roadmap
Workshop, Washington, DC, US Department of Energy
(April 2–3, 2002). Available at www.eere.energy.gov/
hydrogenandfuelcells/pdfs/national_h2_roadmap.pdf
(accessed April 18, 2005).
39
> Shell hydrogen station and fuel cell car. This station in Washington, DC, has both gasoline pumps and a hydrogen pump (top). The General Motors
demonstration car has a hydrogen fuel cell under the hood (bottom). The version of this car with a 70-MPa [10,000-psi] compressed-hydrogen tank has a
range of about 270 km [168 miles]. (Photographs courtesy of Shell Hydrogen BV.)
Hydrogen is considerably less dense than air.
In addition, it diffuses in air more rapidly than
the fuels discussed here. From a safety
perspective, these facts mean that leaked
hydrogen rises rapidly and disperses, as long as it
is not in an enclosed space. However, a car with
windows and doors closed is an enclosed space,
so the passenger compartment of a vehicle will
have to be protected from leaks. Hydrogen is
odorless, making leak detection difficult, but so
long as sufficient oxygen is available, it is
nontoxic. The effects of significant quantities of
hydrogen leaked into the atmosphere over the
long term are unknown, but the effects on
40
climate, air pollution and the ozone layer are
under study by a GCEP-funded group.
Compared with methane, propane and
gasoline, the concentration range for
flammability of hydrogen in air is broader. The
lower limit of concentration for ignition is 20%
less than methane’s limit, that is, less hydrogen
is required in an air mix to ignite. In addition, the
minimum energy required for ignition is 15 times
less than that of methane. As an added safety
concern, a hydrogen flame is practically
invisible. Hydrogen sensors are needed to
provide warning of hazardous situations.
The explosive limits for hydrogen are also
different from methane, propane and gasoline.
These fuels detonate with much leaner mixtures:
at least triple the amount of hydrogen is required
to detonate. However, hydrogen can detonate at
much richer mixes than the other fuels.
Mitigating this risk is the fact that considerably
lower energy is involved in a hydrogen explosion:
a gasoline vapor explosion carries 22 times
more energy.
There is an additional risk associated with
storing hydrogen as a compressed gas. Hydrogenpowered cars on the road use tanks at 5,000 or
10,000 psi [35 or 70 MPa]. The hydrogen tank and
Oilfield Review
all high-pressure fittings must be reliable and
failure-proof to avoid a potentially explosive
release of pressure. Proper maintenance and
verification of the storage system are critical.
This is particularly significant in personal
vehicles, which generally are not operated and
maintained by trained professionals. Both
technological improvements and a massive
public education program are needed to achieve
the level of safety that will be required for largescale, nonindustrial uses of hydrogen.
Hydrogen embrittlement is a different kind of
risk than the flammability and explosive risks
common to fossil fuels. Because the molecule is
so small, it migrates easily along microcracks in
vessels. This expands and extends the cracks,
weakening the material. With enough damage,
the vessel can fail below its yield stress. Specific
alloys, plating or coating processes are employed
to avoid hydrogen embrittlement, as well as
controlling the amount of residual hydrogen in
steel and the amount picked up in processing.
The challenge is to achieve these goals as the
number of hydrogen containers increases and as
they are used by untrained people. All fuels are
potentially hazardous, and hydrogen is no
exception. Making a transition from hydrogen
handled only by trained experts to handling by
the general population will require public
acceptance and time to become familiar with
this new fuel, just as has been done for other new
fuels, such as liquefied petroleum gas (LPG).
Safety underpins all other issues. Making
hydrogen production, distribution and use safe
for widespread public use through continual
development is only the first part. Governments
will need to set codes and standards for handling
hydrogen in nonindustrial settings. Governments
and companies will also have to educate
the public about the proper use and handling
of hydrogen.
Driving Toward Greener Pastures
Hydrogen-powered vehicles are the dream of
those advocating a hydrogen economy. Small
demonstration fleets, including both buses and
passenger vehicles, are on the road in several
places around the world. In operation, they
produce only a trail of water vapor.
51. “GM in Fuel Cell Deal with Government,” CNNMoney
(March 30, 2005). Available at money.cnn.com/2005/03/30/
news/fortune500/gm_fuelcell.reut/index.htm (accessed
April 18, 2005).
52. Doyle, reference 47.
53. “Washington Station Offers Gas, Snacks and Hydrogen,”
The New York Times, November 11, 2004: C6.
Spring 2005
These vehicles are not yet ready for purchase
by average motorists. General Motors Corporation
recently announced a US$ 88 million shared-cost
project with the US Department of Energy to
develop, build and deploy 40 hydrogen fuel cell
vehicles.51 Other demonstration cars have
reportedly cost US$ 3 to 4 million to build. The
DaimlerChrysler demonstration buses in Iceland
that run on hydrogen cost about =C1.25 million,
which is about three to four times the cost of a
diesel-powered bus.52 Improvements in technology
and mass production are required to bring these
costs down.
These demonstration vehicles are fueled at
specially built hydrogen filling stations. A Shell
station in Washington, DC, added one hydrogen
pump to a gasoline filling station at a reported
cost of US$ 2 million.53 The costs of both
hydrogen-powered automobiles and the pumping
stations to fill them are expected to decline over
time. This will result from both technological
improvements and economies of scale as
production moves from building individual items
to mass production. The cost of hydrogen should
eventually reach the current equivalent of
US$ 2/kg to US$ 4/kg.
Shell is taking a step-by-step approach
toward a commercial hydrogen mass market. The
first step was stand-alone projects with
restricted access. Only trained personnel have
access to the equipment, and industrial
standards of safety are applied. Projects in this
category include depots for small fleets of
hydrogen-fueled buses.
The second-generation sites have public
access that is separate from existing gasoline
stations. Shell opened a station in 2003 that
generates hydrogen from water for the three city
buses operating in Reykjavik as part of the
ECTOS project.
Current projects, such as the one in
Washington, DC, are in the third step, which fully
integrates hydrogen with traditional fueling at
one station (previous page). Shell is initiating
the fourth step, mininetworks of stations
involving partnerships among multiple energy
companies and governments. These networks
will service fleets of 100 or more vehicles. In the
fifth step, occurring in the time period of 2010 to
2020, the mininetworks will be connected with
corridors of hydrogen fueling stations, and
service will be added to areas lacking stations.
Several highway corridors have been
designated for hydrogen demonstrations by
government and private entities, for example, in
California and Florida, USA, British Columbia,
Canada, and Germany.
Despite these activities, a world based on a
hydrogen economy is not a foregone conclusion.
Companies involved in developing these technologies and bringing them to market recognize
the hurdles ahead. A different technological
solution to controlling greenhouse-gas emissions
and the eventual decline of fossil fuel reserves
may develop.
The future energy supply is likely to be a
mixture of many sources, including fossil fuels,
nuclear and green energy, with hydrogen and
electricity as carriers. Eventually, perhaps after
20 or 30 years, the free market will decide based
on economics and quality of life issues, such as
control of greenhouse gases. As the world moves
toward the next stage, companies will continue
to advance the technologies, and they will
continue to evaluate the economics.
Comparing alternatives requires that they be
viewed in a systemic fashion. Within the discussion of a hydrogen economy, this has
sometimes been referred to as a well-to-wheel
framework. What is the cost of delivering a
certain amount of energy, starting with the cost
of infrastructure for its acquisition and adding
material costs, conditioning, transport, storage,
delivery, usage and finally disposition of
unwanted by-products? Thus, if society requires
zero emissions of CO2 or other pollutants, those
costs should be figured into all scenarios. New
infrastructure must be included in the appropriate scenarios, perhaps a hydrogen delivery
system in some scenarios or CCS in others.
Eventually, dominance by oil as the primary
source of energy will be supplanted by something
else. Its first replacement will probably be
natural gas. The next one may be coal with CCS,
nuclear power or some combination of renewable
sources. While hydrogen is not and will not be
an energy source, its use with fuel cells may
make it an important energy carrier in synergy
with electricity.
—MAA
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