30 Oilfield Review

Hydrogen: A Future Energy Carrier?

Kamel BennaceurGatwick, England

Brian ClarkSugar Land, Texas, USA

Franklin M. Orr, Jr.Global Climate and Energy Project (GCEP)Stanford UniversityStanford, California, USA

T. S. RamakrishnanRidgefield, Connecticut, USA

Claude RouletHouston, Texas

Ellen StoutAir LiquideHouston, Texas

For help in preparation of this article, thanks to Chris deKoning, 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.

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.

The world has a voracious appetite for energy.Abundant, inexpensive resources have fueledtechnological advances from the IndustrialRevolution to the present. Continued growth willrequire a continued supply of inexpensive energythat is not sustainable with current resources. Inaddition, concerns about greenhouse-gas emis-sions from fossil-fuel sources are generating anew set of technological requirements.

In the ideal, albeit distant, future is a world ofrenewable, pollution-free energy sources foreverything from electrical power grids to personalvehicles. The path to that future is, techno-logically speaking, a steep uphill climb.

Hydrogen is likely to be a part of thisidealistic future, and possibly an important part.A hydrogen molecule [H2] in the presence ofoxygen can be converted to water with a releaseof heat and work. It is difficult to imagine acleaner source of energy.

However, there are challenges. To begin with,molecular hydrogen does not occur naturally inhigh concentrations; it is only 0.00005% of theair.1 Hydrogen is normally bound in othermolecules, water and hydrocarbons being themost common. Unlike natural gas, molecularhydrogen is not found in large accumulations ingeologic strata, either.

This means that hydrogen is not a primaryfuel source. Like electricity, it is a means fortransmitting energy from primary fuel sources tousers. Like electrical power, hydrogen must be

produced and transported, although hydrogenhas an additional attribute that makes it moreattractive for some applications than electricity:it can be stored for later use.2 This feature makesit useful for powering vehicles and otherportable devices.

Current production of hydrogen is about50 Mt/yr [55 million US tons/yr], mostly forindustrial purposes in chemical and petro-chemical applications. A world economy usinghydrogen as a major energy carrier will require atremendous increase in that volume, as well as acomplex new infrastructure for transporting anddelivering hydrogen to end users.

This article discusses the global transition toa hydrogen economy and the roles oil and gasindustry sectors might play over the nextdecades. Also described are some of the majortechnological barriers that must be overcome.

What Is the Hydrogen Economy?The hydrogen economy is a system that useshydrogen as a major carrier in the energy supplycycle. The term evokes a vision of energy usage inthe future that is sustainable and environ-mentally friendly.

That vision follows the historic trend towardusing energy sources that produce less and lesscarbon as a by-product.3 Wood was a primaryenergy source for millennia, but its primacy wassupplanted by coal in the late 1800s because coalhas a greater energy density. Use of oil as a fuel

Spring 2005 31

increased during the 1900s, surpassing coal as aglobal energy source in the 1960s. Natural gasuse is now increasing in importance.4

This progression of energy sources has beenaccompanied by a decrease in the amount ofcarbon dioxide [CO2] produced to release a givenquantity of energy as work or heat (right). Onereason this proportion has decreased is thedecreasing carbon-to-hydrogen (C/H) atomic ratioin the predominant fuel source.5 The ratio for coalis about 1.6 Oil has a ratio of about 0.5, andmethane C/H ratio is exactly 0.25.

Although this progression of fuel sourcesresults in less CO2 per unit of energy released,the world consumption of energy has increasedeven more rapidly. As a result, the undesirableproduction of greenhouse-gas CO2 is expected torise, contributing to global warming.7 Theamount of CO2 generated annually is unlikely todecrease over the next few decades, becausehydrocarbons will remain the prevalent fuelsources. To control atmospheric accumulation,the CO2 generated must be captured and stored.8

> Decarbonization of energy sources. The carbon intensity in our majorenergy supplies has declined as the world moved from wood (gold) to coal(black) to oil (green) and now toward natural gas (red) as the predominantenergy source. The amount of carbon produced (dashed black) declined witheach change in primary energy source. The inset shows the amount ofcarbon produced per unit energy for these fuel sources. Nuclear energy is asmall contributor to the energy supply. (Data from Nakicenovic, reference 3.)

100

Shar

e of

glo

bal e

nerg

y, %

Carb

on in

tens

ity, g

/MJ

80

60

40

20

01850 1900

Year1950

Wood Oil

Gas

Nuclear

Coal

Carbon intensity

2000

35

30

25

20

15

10

Wood

Coal

Oil

Gas

29.9

25.8

20.1

15.3

Source Carbon intensity, g/MJ

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 gravitationalpotential in a pumped-water system or as hydrogen. Acapacitor, which can store electrical potential, is impractical for widespread societal needs.

3. Nakicenovic N: “Global Prospects and Opportunities forMethane in the 21st Century,” in Seven Decades withIGU. International Gas Union Publications, publishedjointly by International Systems and CommunicationsLimited and International Gas Union (2003): 118–125.

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 ofabout 0.67 is less than coal, but its energy content is alsoless. The net result is that the production of CO2 per unitof energy is higher for wood than for the other fuelsources discussed here.

6. Killops SD and Killops VJ: “Long-Term Fate of OrganicMatter in the Geosphere,” in An Introduction to OrganicGeochemistry, 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.

More importantly, fossil fuel resources are finite,and will eventually become prohibitivelyexpensive to recover. As gasoline becomes moreand more expensive in that distant future, someother portable energy source, such as hydrogenor batteries, will be needed.9

The apparent next step is to eliminate carbonfrom the energy source. Several green, orenvironmentally friendly, energy sources areavailable today, but their usage is not a majorpart of energy consumption. In 2001, fossil fuelsprovided 85.5% of world energy consumption,nuclear reactors provided about 6.5%, with othersources combined providing only 8%.10 USgovernment projections indicate little produc-tion from sources other than fossil fuels andnuclear power in the USA through 2025 (below).11

Attention around the world has focused onthe promise of the hydrogen molecule as theultimate green fuel. With no carbon, its C/H ratiois zero: the end of the trend to less carbon infuels. H2 can be burned to generate only water,heat and mechanical work, or it can be convertedto water, heat and electrical work using a fuelcell (see “Fuel Cells: A Quiet Revolution,”page 34). One kilogram of H2 provides about thesame power as 3.8 L [1 gal] of gasoline.

Although its promise is great, technologicallimits currently make hydrogen uneconomic andimpractical as an energy carrier.12 The hydrogenvehicles on the road today are for demonstrationand testing projects; they are not commercially

available. The cost for hydrogen production anddelivery will have to improve by about a factor offour. Storage capacity on-board vehicles will haveto improve by a factor of two to three. Inaddition, fuel cells to replace the internalcombustion engine will have to improve by afactor of 4 to 5, with an improvement in servicelife by a factor of 2 to 3.13 The challenges includecost, durability, efficiency improvements andmaterial embrittlement. International efforts infundamental science aim to bridge these gaps.

International CommitmentMany nations are funding projects to move theworld toward an environmentally friendly energysystem. Two major thrusts are of particularinterest to the oil and gas industry. Carboncapture and storage (CCS) seeks to mitigate theimpact of fossil fuels on the environment.Second, efforts to make hydrogen a major energycarrier could radically change the energyindustry, although its impact is probably decadesin the future.

There are initiatives to make other greenenergy sources more economical and practical.For example, wind farms and geothermal sourcesprovide primary energy now, but their potentialto provide a significant proportion of our energyneeds in the near future is limited. Sources suchas wind and solar radiation are intermittent.Hydrogen could provide a means for storingexcess power from these sources for use in calmor cloudy weather.

The fossil fuels, oil, natural gas and coal, willremain important primary sources of energy formuch of the coming century. Currently, the mosteconomic means for producing hydrogen isthrough a process known as steam reforming,which produces hydrogen from natural gas. Thevast reserves of coal make it the likely nextsource for producing hydrogen throughtechniques of gasification, partial oxidation orautothermal reforming.

Converting these fuels to hydrogen atcentralized plants will allow carbon capture andstorage (CCS), sometimes referred to as carbonsequestration. CCS will be more economical ifdone from large, centralized facilities, whetherfor generating electricity, producing hydrogen orother uses.

The US government has a US$ 1 billiondemonstration project called FutureGen with a10-year goal to build a coal-based power plantthat successfully generates electricity andhydrogen without undesirable emissions.14 In theEuropean Union (EU), the similar 10-yearHYPOGEN project commits (euro) =C1.3 billionfor developing a zero-emissions power plantusing fossil fuel as a large-scale test facility forproducing hydrogen and electricity.15

Geologic storage of carbon dioxide in depletedoil or gas reservoirs, in unminable coal seams orin deep saline reservoirs is the most likely short-term solution for CCS. Both FutureGen andHYPOGEN require an economical transport bothof the fuel such as coal to the plant and of the CO2

by-product to a storage reservoir, possiblyrestricting locations of the plants.

The EU also has a large-scale demonstrationprogram to build an entire community with ahydrogen-based infrastructure. HYCOM is a 10-year, =C1.5 billion project running in parallel tothe HYPOGEN project.16

The US Hydrogen Fuels Initiative has a goal tomake fuel cell vehicles practical and cost-effective for large numbers of Americans by2020.17 The project provides US$ 1.2 billion tofund development of hydrogen, fuel-cell andinfrastructure technologies needed to achievethis target.

These huge projects are not the onlyinitiatives. Many countries around the world areinvesting funds toward similar goals. In fact, thenumber of projects underway is so large, and it isincreasing so rapidly, it is difficult to enumeratethem all.

32 Oilfield Review

> US energy consumption by source. Most of the US energy consumptionover 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 atabout the same levels as today. Other energy sources, particularly renewablesources, will remain small fractions of the total supply. (Data from “AnnualEnergy Outlook 2005,” reference 11.)

100

Ener

gy c

onsu

mpt

ion,

1015

Btu

/yr

10

1

0.1

0.01

0.001

Petroleum liquidsNatural gas

CoalNuclear power

HydroelectricWood and biomass

Geothermal

WindSolar thermal

Other

Solar photovoltaic

Municipal solid waste

2002 2005 2010 2015 2020 2025Year

Spring 2005 33

Several organizations provide clearinghousesfor information among the various groups. Twoexamples are the Carbon SequestrationLeadership Forum (CSLF) and the InternationalPartnership for the Hydrogen Economy (IPHE).The CSLF is an international organizationfocused on developing improved cost-effectivetechnologies for CCS, including separating,capturing and transporting carbon dioxide forlong-term safe storage.18 The IPHE serves as amechanism to organize and implement effective,efficient and focused international research,development, demonstration and commercialutilization activities related to hydrogen and fuelcell technologies.19

Iceland provides an interesting laboratory fordeveloping green energy. The country has nofossil energy resources, but has an abundance ofgeothermal energy and also has significanthydroelectric generating capacity. Since theenergy crisis of the 1970s, Iceland has created analmost pollution-free infrastructure forstationary energy, such as industrial use andlarge power plants. For transport and for itsfishing fleet, the government of Iceland envisionsreplacing fossil fuels with hydrogen and otheralternative fuels.20 From 2001 through 2005, theEuropean community funded ECTOS, a

=C7 million demonstration program of three H2

fuel cell buses and the related infrastructure inIceland’s capital, Reykjavik.

Many countries have committed to decades-long plans, or roadmaps, to develop a hydrogen-oriented economy. A complete infrastructure hasto be developed, including hydrogen production,delivery and storage. More efficient means forusing hydrogen in fuel cells are in development.

The transition is potentially disruptive to society,so public education and outreach are importantparts of these roadmaps.

Roadmaps provide an integrated, systematicand systemic approach, to ensure coordination ofchanges throughout the infrastructure. The EUroadmap provides a rough time line for actions tomove ahead (above). It foresees that, in the nextdecade, existing localized distribution networks

> European Union roadmap for implementing the hydrogen economy, including fuel cell development.

Fossil fuel-based economy 2000

Increasing decarbonization of H2 production; renewable sources,fossil fuels with CCS, new nuclear power plants

Widespread H2 pipeline infrastructure

Interconnection of local H2 distribution grids; significant H2 productionfrom renewable sources, including biomass gasification

H2 production from fossil fuels with CCS

Local clusters of H2 distribution grids

Local clusters of H2 filling stations

H2 transport by road, and local H2production at refueling stations byreforming natural gas and byelectrolysis

H2 production byreforming natural gasand by electrolysis

Direct H2 production from renewable sources; decarbonized H2 economy

Stationary low-temperature FC systems for commercial niches (<50 kW)

Stationary high-temperature fuel cell systems (MCFC and SOFC) (<500 kW); H2 internal combustion enginedeveloped; demonstration fleets of FC buses

Stationary low-temperature fuel cell systems (PEMFC) (<300 kW)

Series production of FC vehicles for fleets (with direct H2 and on-board reforming) and othertransport (such as boats); FC for auxiliary power units

First H2 fleets; first-generation H2 storage

Atmospheric pressure hybrid SOFC systems commercial (<10 MW)

FC vehicles competitive for passenger cars

Low-cost, high-temperature FC systems; FCs commercial in microapplications

Second-generation on-board storage (long range)

Significant growth in distributed power generation withsubstantial penetration of FCs

H2 becomes primary fuel choice for FC vehicles

H2 use in aviation

Fuel cells become dominanttechnology in transport, indistributed power generation,and in microapplications

2000

2010

2020

2030

2040

H2 production and distribution

Fuel cell (FC) and H2 systems: development and deployment

2040

2030

2020

2010

2050

2050Hydrogen-

oriented economy

Public incentives and priv

ate efforts

Fundamental research

, applied research and demonstra

tion

- Fuel ce

lls for ve

hicles a

nd electrical generation

- Hydrogen productio

n, transporta

tion, distribution and use

Public re

wards and private benefits

Large-scale hydrogen and fuel ce

ll commercia

lization

- H 2 p

roduction

- FC mobile applica

tions

- H 2 t

ransport

- FC sta

tionary applica

tions

- H 2 s

torage

Research, te

sting and development; fi

eld tests; nich

e fleets

Increasin

g market penetration

9. Conversion of natural gas to liquids may be an interimstep. For more on gas-to-liquid conversion: “TurningNatural Gas to Liquid,” Oilfield Review 15, no. 3 (Autumn 2003): 32–37.

10. “International Energy Outlook 2004,” Table A2. EnergyInformation Administration of the US Department ofEnergy (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 Departmentof Energy (2005). Available at www.eia.doe.gov/oiaf/aeo(accessed April 18, 2005).

12. “The Hydrogen Initiative.” American Physical SocietyPanel on Public Affairs. Available at www.aps.org/public_affairs/popa/reports/index.cfm (accessedApril 18, 2005).“Basic Research Needs for the Hydrogen Economy,”Report of the Basic Energy Sciences Workshop onHydrogen 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 ResearchCentre and Institute for Prospective Technological Studies (2005). Available at www.jrc.nl (accessedApril 18, 2005).

16. For information on HYCOM: Peteves SD, Shaw S andSoria A: “HYCOM Pre-Feasibility Study, Final Report,”document EUR 21575 EN, Joint Research Centre andInstitute 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 (accessedApril 18, 2005).

(continued on page 36)

Efforts to move the world toward a hydrogeneconomy include a reexamination of themeans for converting hydrogen into energy.Hydrogen combusts, so it can be used as a fuelin an internal combustion engine, either aloneor mixed with gasoline. It can also be used asa fuel in a turbine engine. However, consider-able research and development now focus ona different mechanism, the fuel cell.

A fuel cell, like a battery, uses electrochem-ical means to create electricity.1 Both types ofdevices can provide more power by stacking multiple cells. However, a battery stores a lim-ited amount of energy in its chemicals, andonce that energy is spent, the battery is dead.2

A fuel cell uses an external reservoir to con-tinuously replenish the fuel.

A fuel cell has two advantages over an inter-nal combustion engine. Fuel cells have thepotential to be significantly more efficient thanconventional combustion engines. Some fuelcells can achieve 60% efficiency, much betterthan the 20% to 35% efficiency of a gasolineinternal combustion engine. A fuel cell has nomoving parts, although there are externalpumps to supply the fuel.

The second advantage is decreased pollu-tion. An internal combustion engine run onhydrogen will not produce CO2. However, if airis used, the process can still produce oxides ofnitrogen [NOx] in a high-temperature systemor a combined-cycle system, which uses a fuelcell in combination with a turbine. A hydrogen-powered fuel cell normally produces onlywater, 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 ofelectrolytes are available to separate the electrodes (below).

The anode contains a catalyst, which splitshydrogen molecules and ionizes the atomsinto electrons and protons [H+]. The liberatedelectrons provide the electrical output of afuel cell. In some cells, the protons passthrough the electrolyte to recombine with oxygen and electrons on the cathode side,forming water (next page, right). This is thereverse of water electrolysis, which is used togenerate hydrogen from water and electricity.In other types of cells, negatively charged ions

pass through the electrolyte from the cathodeto the anode, forming water at the anode andcompleting the circuit.

The catalyst in low-temperature cells usu-ally contains platinum, which is an expensive material. Replacing platinum with a lowercost material in the catalyst is an activeresearch subject. High-temperature fuel cellscan use lower cost catalysts, such as nickel.

The polymer electrolyte membrane—alsocalled a proton exchange membrane—fuelcell (PEMFC), is the leading contender foruse in passenger vehicles.3 It is lightweight,operates at low temperature, has a quickstartup and uses a solid membrane, all ofwhich are considered advantages for massconsumer operation. However, the platinumcatalyst is expensive and makes the cell sus-ceptible to small amounts of carbon monoxide[CO] in the fuel stream. The proton paththrough the electrolyte has to remainhydrated, so the temperature in the cell mustremain below about 100°C [212°F], and tem-peratures below freezing can be a problem.

34 Oilfield Review

Fuel Cells: A Quiet Revolution

> Comparison of fuel cell types.

Name Conductingion

Operatingtemperature, °C

Powerdensity

Disadvantages Advantages Applications

PEMFC

PAFC

DMFC

AFC

MCFC

SOFC

Polymer electrolytemembrane fuel cell

Phosphoric acidfuel cell

Direct methanolfuel cell

Alkaline fuelcell

Molten carbonatefuel cell

Solid oxidefuel cell

H+

H+

H+

OH –

CO32 –

O2 –

60 to 80

200

60 to 120

100 to 250

Greater than650

600 to 1,000

High

Medium

Medium

High

Low

Mediumto high

Platinum catalyst; sensitiveto CO poisoning; cannot runabove dehydration temperature;slow reaction kinetics; not durable

High cost; large and heavycells; low efficiency (37 to 42%);platinum catalyst

Generates carbon; low efficiency;platinum catalyst

Cannot tolerate CO2

Not durable; high temperatureand corrosive electrolyte; needsCO2 to recycle

Slow startup; requires thermalshielding; not durable

Fast startup; favorablepower-to-weight ratio; lowtemperature; reduced corrosionand management problems

Mature technology; 200 unitsin use; tolerant of impurities in H2 fuel

Powered by methanol; fewstorage problems

Mature technology; stable operationfor more than 8,000 operating hours; high efficiency (60%)

Variety of catalysts (precious metals not needed); resistant toimpurities; high efficiency (60%);external reformer not needed

Precious metals not needed;variety of catalysts; high efficiency(50 to 60%); external reformer notneeded; resistant to poisoning; mostsulfur-resistant fuel cell; fuel flexibility(including CO); solid electrolyte reducescorrosion and management problems

Transportation, electric utility

Electric utility,transportation

Small portableapplications

Military, spaceand underseaapplications

Natural gasand coal-basedpower plants

Electric utility

Spring 2005 35

For large-scale, stationary applications suchas power plants, the solid oxide fuel cell(SOFC) is the most promising technology.4

The electrolyte is a nonporous ceramic thatpasses charged oxygen ions [O2-] from cath-ode to anode, generating water in the fueldischarge stream. The solid electrolyte allowsmore configurations than other cells: tubularor honeycomb in addition to the typical paral-lel-plate stack. Its high-temperatureoperation—about 600 to 1,000°C [1,112 to1,832°F]—allows use of less expensive cata-lysts. Fuels other than pure hydrogen,including CO, also can be used at these hightemperatures without externally reforming

the fuels into hydrogen. It has high efficiency,about 60%, that can be boosted to 80% or morethrough effective use of heat generated duringthe process.5

The phosphoric acid fuel cell (PAFC) is oneof the most mature technologies. Over 200units are in use, mostly for stationary powergeneration, but some have been used to powercity buses.6

Newer than the other types of fuel cell, thedirect methanol fuel cell (DMFC) is a type ofPEMFC that uses methanol rather than hydro-gen as a fuel. Although the energy content ofmethanol is lower than hydrogen, dealing witha substance that is a liquid at room tempera-ture is attractive from a storage and handlingperspective. The release of carbon into theatmosphere is a drawback to this technology.

Long-term durability is an issue for all fuelcells. The SOFC has the longest demonstratedlifetime, 20,000 hours, but that is half thedesired lifetime for a stationary application,such as electric generation.7 A PEMFC fortransportation application has achieved2,200 hours.8 Replacing stacks containing theanode and cathode will be an expensive main-tenance issue.

The cost of fuel cells has kept them in nicheapplications (above). However, as hydrogenbecomes more readily available to the general

public, these niches will expand. DMFC tech-nology is most likely for small-scale consumerappliances, such as laptop computers and cel-lular phones. Portable generators, such as theAxane system, which uses a PEMFC, arealready on the market.

> Fuel cells. A polymer electrolyte membranefuel cell (PEMFC) is a low-temperature devicethat passes protons [H+] through a membrane,forming water on the cathode side (top). Asolid oxide fuel cell (SOFC) passes oxygen ions[O2-] through a ceramic membrane, formingwater on the anode side (bottom). To increasethe power output of a given type of cell,multiple units are combined in a stack.

Water andwaste heat(H2O)

Excessfuel

Anode

Hydrogenfuel (H2)

Air supply(O2)

Polymer electrolyte membrane

H+

LoadElectron flow

Cathode

Unusedgas

Excess fueland water

Anode

Hydrogenfuel (H2)

Air supply(O2)

Solid oxide electrolyte

O2–

LoadElectron flow

Cathode

e-

e-

Anode reaction:2H+ + 2e-

Cathode reaction:2H2OH2 O2 + 4H+ + 4e-

Anode reaction:H2O + 2e-

Cathode reaction:2O2–H2 + O2– O2 + 4e-

> Current use of hydrogen. Fuel cells, such as the Axane Roller Pac portablefuel cell (inset), use a very small proportion of the current hydrogenproduction. The predominant uses are for basic chemical production and formaking fuels such as gasoline less polluting. Uses near the bottom of thischart are most likely to be supplied by tube trailers and cylinders. Those atthe top are most likely to have a pipeline supply, and those in the middle arelikely to have onsite generation.

Space

Glass

Heat treatment,steel

Fuelcells

Laboratoryanalysis

Glass polishing

Heat treatment,stainless steel Food, fat and oils

Optical glassfiber

Basicchemicals

Refining forclean fuelsFood,

sorbitol

Electronics Specialtychemicals

10 100 1,000m3/hr

10,000 100,000

1. For a comparison of oilfield batteries to fuel cells: Hensley D, Milewits M and Zhang W: “The Evolution ofOilfield Batteries,” Oilfield Review 10, no. 3 (Autumn1998): 42–57.

2. Some batteries use the reverse of the electrochemicalprocess to recharge, but the amount of energy avail-able without recharging is limited by the capacity ofthe 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).

will expand, with clusters of H2 stations nearthese networks. Fuel cell technologies willimprove power delivery for both stationary use,such as power plants, and mobile use in vehicles.

The EU roadmap predicts that mobile use willexpand slowly from fleet transportation topersonal vehicles. Meanwhile, localized networksof hydrogen delivery systems will expand, with awidespread pipeline infrastructure developed inthe next 20 to 30 years.

Fossil fuels will be used, but with CCS,according to the roadmap. Later still, renewablesources and a new generation of nuclear reactorsthat generate electricity and hydrogen willassume greater importance. Ultimately, about50 years from now, the roadmaps predict aneconomy based on renewable primary energysources with hydrogen as a major component ofthe energy delivery system.

The push from governments does notguarantee that a hydrogen economy will develop,but it provides an important impetus towardtheir goals. Several industries will be impacteddirectly by the transition to a hydrogen economy,and businesses in these industries are takingsteps in the same direction. Improved fuel cellsare under development in many companies andin universities and research institutions. Severalautomobile manufacturers have small fleets ofdemonstration vehicles on the road. Some usefuel cells; others operate using a hydrogeninternal combustion engine.

The Pierre Elliot Trudeau Airport in Montreal,Quebec, Canada, has initiated a hydrogen projectwith Air Liquide as one of the participants. Theairport authority plans to convert all its utilityand service vehicles to fuel cells or internalcombustion engines that run on hydrogen.

Gas companies and utility companies areresearching ways to store hydrogen. Hydrogenstorage tanks capable of withstanding highpressure must be developed for mobile appli-cations, 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 Toyotacommitted US$ 225 million to the Global Climateand Energy Project (GCEP), which is operated byStanford University.21 The 10-year program isbuilding a diverse portfolio of technologyprojects aimed at reduction of greenhouse-gasemissions. It focuses on high-risk projects withhigh potential to fundamentally change thetechnology, as well as systemic analysis of ways toimprove the environment. The program gotunder way in 2002. Some of the current projectsat Stanford and elsewhere include developingtechnologies for lower temperature fuel cells,studying microbes for producing H2, investigatingthe fundamentals of catalyst-doped nanotubesand working on geologic storage of CO2.

Shell and other companies that marketgasoline directly to consumers have opened a fewhydrogen-refueling stations in conjunction withdemonstration-vehicle fleets. The explorationand production (E&P) sector of our industry hasan important role to play in moving toward ahydrogen economy.

The E&P Business and the Transition to HydrogenThe HYPOGEN and FutureGen programsenvision the next stage of hydrogen productionas coming from centralized plants that use fossilfuels, including coal or gas. CCS is a major part ofthese plans.22

Several carbon storage options have beenproposed. Chemically binding the carbon, eitherusing limestone ponds or by mineralization, isunproven on a large scale, and it is likely to beexpensive. Storage in the ocean, either bydissolution or as a liquid or hydrate at depth, isan established technology, but laboratory testsindicate it causes trauma to marine life.23 Little isknown about the long-term impact of increased

CO2 concentration on the ecosystem.24 Currently,the most practical option is geologic storage indepleted oil and gas reservoirs, unminable coalseams and deep saline aquifers (below left).25

Any method of CO2 storage must be a long-term solution that avoids leakage of CO2 backinto the atmosphere. The E&P and oilfieldservices industries, and research laboratoriescan provide considerable experience to the CCSeffort through their understanding of geologicformations and fluid flow in them. The industryhas the technology to identify structures, accessformations and operate the surface andsubsurface facilities to inject CO2. Monitoringthe operation and the migration of CO2 is also apart of this expertise.

CO2 can be injected into depleted oil and gasreservoirs. Generally, the original reservoir sealwill also contain the CO2 gas, up to the originalpressure of the reservoir. In addition, CO2 mayhave a benefit as an enhanced recovery sweep gas.

Enhanced oil recovery (EOR) projects withCO2 have been under way since 1972, starting inthe Permian basin, USA.26 Injected CO2 displacesoil to producing wells. In addition, undermiscible conditions some CO2 goes into solutionwith the oil and some oil fractions go into the CO2

phase.27 These mixtures displace oil efficiently,increasing recovery. In either case, a portion ofthe CO2 remains in the formation. Now, the desireto decrease greenhouse-gas emissions encouragesa reexamination of CO2 EOR to both improve oilrecovery and to store CO2 underground.

A cross-border EOR project between the USAand Canada is the first designed specifically forCO2 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 DakotaGasification Company operates the synfuels plant,and EnCana Corporation now operates Weyburnfield. About 3 million m3 [106 million ft3] of gas—96% CO2 with traces of hydrogen sulfide, nitrogenand hydrocarbons—are transported and injecteddaily. CO2 migration has been modeled usingECLIPSE 300 reservoir simulation software, andthe results match time-lapse seismic surveys.29

Passive seismic monitoring has also detectedmicroseismic events that are associated with CO2

injection, providing another monitoring method.30

Enhanced recovery from natural gasreservoirs has been proposed and modeled, butto date, there have been no field projects.31 CO2

in both liquid and gaseous states is denser thanmethane, so a gravity-stabilized injection schemecould be used.

36 Oilfield Review

> Estimates of worldwide CO2 storage potential. (Data on CO2 injection forEOR from Gielen, reference 24; other data from McKee, reference 25.)

Worldwide CO2 Storage Potential

Option

For comparison:

Worldwide capacity,Gt carbon

Depleted oil and gas reservoirs

Unminable coal seams

Deep saline reservoirs

100s

10s to 100s

100s to 1,000s

Worldwide anthropogenic CO2 emissions (McKee)

CO2 injection for EOR (Gielen)

7 Gt/yr carbon

12 Mt/yr carbon

Spring 2005 37

CO2 has been used to improve recovery fromcoalbed methane reservoirs. Because CO2 has agreater affinity for adsorption by coal than doesmethane, it will displace methane; in addition,coal can adsorb at least twice as much CO2 asmethane.32 Enhanced coalbed methane recoveryis limited to coal seams that will not be mined, toavoid future safety concerns.

The greatest potential for geologic CO2

storage is in deep saline aquifers. While coalseams and gas and oil reservoirs are not presenteverywhere in the world, saline aquifers arecommon in most sedimentary basins (right). Theamount of aquifer volume that can be filled withCO2 is not yet established, but estimates are thatsufficient volume exists to hold hundreds of yearsof CO2 emissions.33

In 1996, Statoil began a project to store CO2

that is produced with natural gas from theSleipner field.34 The CO2 is injected into theUtsira formation, which lies above the productiveHeimdal formation. The Saline Aquifer CO2

Storage (SACS) project and a subsequent SACS2project, both funded by the EuropeanCommission’s Thermie Program, developed bestpractices in the research, monitoring andsimulation of CO2 migration in subsurfacestorage aquifers using the Sleipner injection as abasis. This work continues in an EU project,CO2STORE. Since its inception, this operationhas 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 thepotential exists for the E&P industry to move itsproduction of these carriers closer to thewellhead. Particularly in places where a naturalgas network does not exist, wellhead conversionof natural gas into electricity using a fuel cellmight be economic. CCS also could beimplemented locally.

Steps toward a hydrogen economy are justbeginning, and the final form of a hydrogen-based future is yet to be determined. E&Pcompanies and the service industry are in uniquepositions to help craft that future.

Technological Marathon The advances necessary to achieve a hydrogeneconomy are enormous, particularly to replacecurrent gasoline or diesel internal combustionengines for personal transportation. Theroadmaps prepared by the USA, the EU, Japanand other countries recognize the challenges,and have extended time lines of about 50 yearsfor implementation of a hydrogen economy.35

Scientists do not see this as a sprint, but as a

marathon with a long series of hurdles requiringfundamental breakthroughs along the way.Extensive progress in fundamental materialsscience is essential. The focuses for technologydevelopment are production, transport anddistribution, storage and safety, and cost-effective and reliable fuel cells.

Production—Hydrogen, like electricity, mustbe generated. Almost all of the hydrogen nowproduced is for industrial use: ammonia plantsuse about 57.5%, refineries use 27.4% andmethanol producers use 9.7%.36

A dramatic increase in production will benecessary to meet the goals of governmentprograms to create a hydrogen economy.Production in the USA will have to increase fromabout 11 Mt/yr [12 million US ton/yr] to 265 Mt/yr[292 million US ton/yr] to satisfy the projectedtransportation needs in the USA in 2020.37 Arecent study assumes that there will be morethan 6,000,000 hydrogen-powered cars in Europeby 2020.38 Japan’s goal is to have 5,000,000 fuelcell vehicles on the road by 2020, along with astationary 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 ofCO2 Ocean Sequestration on Marine Animals,” paper C2-3, presented at the 7th International Conference onGreenhouse Gas Control Technology, Vancouver, BritishColumbia, Canada (September 5–9, 2004). Available atwww.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 atwww.iea.org/dbtw-wpd/textbase/papers/2003/eet04.pdf(accessed April 18, 2005).

25. McKee B: “Solutions for the 21st Century—Zero EmissionsTechnologies for Fossil Fuels,” Technology Status Report,International Energy Agency, Committee on EnergyResearch 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.co2captureandstorage.info/project_summaries/23.htm (accessed April 18, 2005).

27. Jarrell PM, Fox CE, Stein MH and Webb SL: PracticalAspects 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 Insightsfrom 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 CandidateSites 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 NationalR&D Programs,” Paris: International Energy Agency and Organization for Economic Co-operation and Development, 2004.

36. Suresh B, Schlag S and Inoguchi Y: “CEH MarketingResearch Report—Hydrogen.” Chemical EngineeringHandbook 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).

> Major onshore (green) and offshore (blue) sedimentary basins. The brown line indicates the 1,000-m[3,280-ft] water-depth contour.

10 GW of capacity.39 Shell Hydrogen estimates anetwork of hydrogen filling stations would costabout US$ 20 billion each for the USA and Europe,and about US$ 6 billion for Japan. The companyindicates that necessary renewal of the currentretail network over the same period of time alsowill be a major investment.

Currently, the most cost-effective means ofproducing hydrogen is steam reforming ofmethane. However, hydrogen production throughsteam reforming neither eliminates carbondioxide production nor addresses the finiteresource of hydrocarbon fuels. Production fromcoal is considered the next step, but like

production from methane, CCS must be includedto achieve reductions in greenhouse gases.

Hydrogen can be generated from water andelectricity through electrolysis, the reverse of theprocess 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 atnight when electricity usage is lower, isinexpensive enough to make hydrogengeneration potentially cost-effective in someareas.41 Other primary sources of power includewind farms and solar power.

Biomass can also be used for hydrogengeneration. Although carbon is part of theprocess, this is considered a carbon-neutraloption, since the CO2 is taken up in the nextgeneration of biomaterials. If combined with CCSat the generation plant, this option couldengender a net decrease in atmospheric CO2. Ofcourse, this option also dedicates a large surfacearea somewhere for growth of the biomaterial.

It is unclear whether conversion fromelectricity generated by nonpolluting sources tohydrogen is an efficient path for society. Theenergy loss through electrolysis is not regained inother efficiencies from hydrogen usage. It is

38 Oilfield Review

> 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 than100,000 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 anddiesel fuel.

TEXAS

LOUISIANA

BatonRouge

Corpus Christi

Freeport

Houston

Bayport

G u l f o f M e x i c o

THE NETHERLANDS

FRANCE

BELGIUM

Isbergues

Waziers

Charleroi

Feluy

AntwerpTerneuzen

Rozenburg

Bergen-op-Zoon

Hydrogen plantPipeline Hydrogen/CO plant

0

0 150 300 450 km

100 200 300 miles

0

0 50 100 km

25 50 miles

Spring 2005 39

arguably more efficient to use electricity directlyor for charging batteries that power automobiles,rather than generating hydrogen.42 This wouldrequire significant improvements in batterytechnology, including decreasing rechargingtimes, decreasing battery weight and disposing ofold batteries.

Of greater interest are hydrogen productionmethods that are in the laboratory stage ofdevelopment. Direct conversion of sunlight tohydrogen, without an intermediate step ofgenerating electricity, is being investigatedthrough new nanoscale and biological processes.Water can also be split into hydrogen and oxygenat very high temperatures, termed thermolysis,which may become possible in solar collectorsoperating above 500°C [932°F], or in the nextgeneration of high-temperature nuclear reactors.43

Such reactor technology is still a few decadesaway, and its implementation must overcomepublic reluctance to build nuclear plants.

Transport and distribution—Hydrogen canbe generated at or near the point of use, or it canbe generated at a centralized location andtransported. Today, as much as 96% of hydrogenproduction is used locally. The USA has the mostdeveloped market for merchant hydrogen—thatwhich is transported for sale—with just over 15%of the production transported to another site.44

Depending on the method of production, thehydrogen may contain impurities, such as carbonmonoxide [CO] or CO2. For some end uses, thehydrogen may need to be conditioned to removesuch impurities.

Although small amounts of hydrogen aretransported by cylinder or in bulk, mostmerchant hydrogen moves through pipelines.Localized clusters of hydrogen pipelines havebeen 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 hydrogenpipelines today is about US$ 0.5 million to US$ 1.5 million, which is roughly the same asequivalent natural gas pipelines. Hydrogenpipelines with large diameter, such as 30 in., maybe necessary to service an extensive transpor-tation infrastructure. Such pipelines areexpected to cost more than equivalent naturalgas pipelines: about 50% more for materials thatresist hydrogen embrittlement and 25% more forlabor due to hydrogen-specific welding.46

Cost will be a major factor in extending thisdistribution network from existing facilities andbuilding new pipeline networks. Taking just two

parts of the world as examples, about 180,000filling stations will need to be converted tohydrogen in the USA and about 135,000 inEurope. Some of these will be on a pipelinenetwork, but others, perhaps many others, willgenerate hydrogen locally.

A safe and acceptable means for dispensinghydrogen into vehicles or for personal use mustbe developed. It has to be inexpensive,convenient, and above all, safe. Air Liquide hasdeveloped technology to rapidly transfer largequantities of hydrogen at 5,000 psi [35 MPa]. Thetechnology is used in the Clean Urban Transit inEurope (CUTE) program and other places. Thebuses in Iceland, made by DaimlerChrysler, havecompressed 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 acompressed gas, as a liquid, or as a metal orchemical hydride. Of these, liquid hydrogen hasthe highest energy density.48 However, it is still about one-third of the volumetric valuecompared to gasoline and one-quarter ofgasoline’s gravimetric energy density.49 Aboutone-third of the energy content is lost inliquefaction.50 For safety reasons and to avoidpressure buildup, the hydrogen gas must beallowed to bleed off, so liquid hydrogen is not a viable solution for long-term storage inmobile applications.

Several metal or chemical hydrides are underinvestigation for storing hydrogen. Theadvantage of this method is its safety andstability in comparison with liquid or compressedgas storage. However, getting hydrogen into thehydride in a timely way—such as a three- to five-minute fillup at a filling station—is not yetpossible, and getting it out currently requires

heating the hydride to a high temperature. Theweight of current hydride substrates and theircontainer is much greater than the weight ofstored hydrogen.

Developing means for localized storage is thegreatest hurdle to overcome for mobile uses inpersonal vehicles.

Safety—Today, trained personnel usehydrogen safely in industrial settings. Expandinginto use by the general public will involve risksthat must be mitigated. However, handlingmethane, propane or gasoline also involves risksthat have been mitigated and are nowunderstood 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 EnergyFuture—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 paperNREL/SR–540–32525 (July 2002): 21.

46. Parker N: “Using Natural Gas Transmission PipelineCosts 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-FreeEconomy,” 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 heatof 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).

> Selected physical properties of hydrogen, methane, propane and gasoline.

Molecular weight (u)

Density (kg/m3) at normal conditions

Buoyancy (density with respect to air)

Diffusion coefficient (cm2/s)

Lean flammability limit in air (% by volume)

Rich flammability limit in air (% by volume)

Minimum ignition energy (mJ)

Minimum self-ignition energy (K)

Lean detonability limit in air (% by volume)

Rich detonability limit in air (% by volume)

Explosion energy (kg equivalent TNT per m3 of vapor)

2.02

0.084

0.07

0.61

4.1

75

0.02

858

18

59

2.02

16.04

0.651

0.55

0.16

5.3

15

0.29

813

6.3

13.5

7.02

44.06

1.87

1.52

0.12

2.1

10

0.26

760

3.1

7.0

20.2

~107

4.4

3.4 to 4.0

0.05

1.0

7.8

0.24

501 to 744

1.1

3.3

44.2

Property Hydrogen Methane Propane Gasoline

Hydrogen is considerably less dense than air.In addition, it diffuses in air more rapidly thanthe fuels discussed here. From a safetyperspective, these facts mean that leakedhydrogen rises rapidly and disperses, as long as itis not in an enclosed space. However, a car withwindows and doors closed is an enclosed space,so the passenger compartment of a vehicle willhave to be protected from leaks. Hydrogen isodorless, making leak detection difficult, but solong as sufficient oxygen is available, it isnontoxic. The effects of significant quantities ofhydrogen leaked into the atmosphere over thelong term are unknown, but the effects on

climate, air pollution and the ozone layer areunder study by a GCEP-funded group.

Compared with methane, propane andgasoline, the concentration range forflammability of hydrogen in air is broader. Thelower limit of concentration for ignition is 20%less than methane’s limit, that is, less hydrogenis required in an air mix to ignite. In addition, theminimum energy required for ignition is 15 timesless than that of methane. As an added safetyconcern, a hydrogen flame is practicallyinvisible. Hydrogen sensors are needed toprovide warning of hazardous situations.

The explosive limits for hydrogen are alsodifferent from methane, propane and gasoline.These fuels detonate with much leaner mixtures:at least triple the amount of hydrogen is requiredto detonate. However, hydrogen can detonate atmuch richer mixes than the other fuels.Mitigating this risk is the fact that considerablylower energy is involved in a hydrogen explosion:a gasoline vapor explosion carries 22 times more energy.

There is an additional risk associated withstoring hydrogen as a compressed gas. Hydrogen-powered cars on the road use tanks at 5,000 or10,000 psi [35 or 70 MPa]. The hydrogen tank and

40 Oilfield Review

> Shell hydrogen station and fuel cell car. This station in Washington, DC, has both gasoline pumps and a hydrogen pump (top). The General Motorsdemonstration 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 arange of about 270 km [168 miles]. (Photographs courtesy of Shell Hydrogen BV.)

Spring 2005 41

all high-pressure fittings must be reliable andfailure-proof to avoid a potentially explosiverelease of pressure. Proper maintenance andverification of the storage system are critical.This is particularly significant in personalvehicles, which generally are not operated andmaintained by trained professionals. Bothtechnological improvements and a massivepublic education program are needed to achievethe level of safety that will be required for large-scale, nonindustrial uses of hydrogen.

Hydrogen embrittlement is a different kind ofrisk than the flammability and explosive riskscommon to fossil fuels. Because the molecule isso small, it migrates easily along microcracks invessels. This expands and extends the cracks,weakening the material. With enough damage,the vessel can fail below its yield stress. Specificalloys, plating or coating processes are employedto avoid hydrogen embrittlement, as well ascontrolling the amount of residual hydrogen insteel and the amount picked up in processing.

The challenge is to achieve these goals as thenumber of hydrogen containers increases and asthey are used by untrained people. All fuels arepotentially hazardous, and hydrogen is noexception. Making a transition from hydrogenhandled only by trained experts to handling bythe general population will require publicacceptance and time to become familiar withthis new fuel, just as has been done for other newfuels, such as liquefied petroleum gas (LPG).

Safety underpins all other issues. Makinghydrogen production, distribution and use safefor widespread public use through continualdevelopment is only the first part. Governmentswill need to set codes and standards for handlinghydrogen in nonindustrial settings. Governmentsand companies will also have to educate the public about the proper use and handling of hydrogen.

Driving Toward Greener PasturesHydrogen-powered vehicles are the dream ofthose advocating a hydrogen economy. Smalldemonstration fleets, including both buses andpassenger vehicles, are on the road in severalplaces around the world. In operation, theyproduce only a trail of water vapor.

These vehicles are not yet ready for purchaseby average motorists. General Motors Corporationrecently announced a US$ 88 million shared-costproject with the US Department of Energy todevelop, build and deploy 40 hydrogen fuel cellvehicles.51 Other demonstration cars havereportedly cost US$ 3 to 4 million to build. TheDaimlerChrysler demonstration buses in Icelandthat run on hydrogen cost about =C1.25 million,which is about three to four times the cost of adiesel-powered bus.52 Improvements in technologyand mass production are required to bring thesecosts down.

These demonstration vehicles are fueled atspecially built hydrogen filling stations. A Shellstation in Washington, DC, added one hydrogenpump to a gasoline filling station at a reportedcost of US$ 2 million.53 The costs of bothhydrogen-powered automobiles and the pumpingstations to fill them are expected to decline overtime. This will result from both technologicalimprovements and economies of scale asproduction moves from building individual itemsto mass production. The cost of hydrogen shouldeventually reach the current equivalent of US$ 2/kg to US$ 4/kg.

Shell is taking a step-by-step approachtoward a commercial hydrogen mass market. Thefirst step was stand-alone projects withrestricted access. Only trained personnel haveaccess to the equipment, and industrialstandards of safety are applied. Projects in thiscategory include depots for small fleets ofhydrogen-fueled buses.

The second-generation sites have publicaccess that is separate from existing gasolinestations. Shell opened a station in 2003 thatgenerates hydrogen from water for the three citybuses operating in Reykjavik as part of theECTOS project.

Current projects, such as the one inWashington, DC, are in the third step, which fullyintegrates hydrogen with traditional fueling atone station (previous page). Shell is initiatingthe fourth step, mininetworks of stationsinvolving partnerships among multiple energycompanies and governments. These networkswill service fleets of 100 or more vehicles. In thefifth step, occurring in the time period of 2010 to2020, the mininetworks will be connected withcorridors of hydrogen fueling stations, andservice will be added to areas lacking stations.

Several highway corridors have beendesignated for hydrogen demonstrations bygovernment and private entities, for example, inCalifornia and Florida, USA, British Columbia,Canada, and Germany.

Despite these activities, a world based on ahydrogen economy is not a foregone conclusion.Companies involved in developing these tech-nologies and bringing them to market recognizethe hurdles ahead. A different technologicalsolution to controlling greenhouse-gas emissionsand the eventual decline of fossil fuel reservesmay develop.

The future energy supply is likely to be amixture of many sources, including fossil fuels,nuclear and green energy, with hydrogen andelectricity as carriers. Eventually, perhaps after20 or 30 years, the free market will decide basedon economics and quality of life issues, such ascontrol of greenhouse gases. As the world movestoward the next stage, companies will continueto advance the technologies, and they willcontinue to evaluate the economics.

Comparing alternatives requires that they beviewed in a systemic fashion. Within the dis-cussion of a hydrogen economy, this hassometimes been referred to as a well-to-wheelframework. What is the cost of delivering acertain amount of energy, starting with the costof infrastructure for its acquisition and addingmaterial costs, conditioning, transport, storage,delivery, usage and finally disposition ofunwanted by-products? Thus, if society requireszero emissions of CO2 or other pollutants, thosecosts should be figured into all scenarios. Newinfrastructure must be included in the appro-priate scenarios, perhaps a hydrogen deliverysystem in some scenarios or CCS in others.

Eventually, dominance by oil as the primarysource of energy will be supplanted by somethingelse. Its first replacement will probably benatural gas. The next one may be coal with CCS,nuclear power or some combination of renewablesources. While hydrogen is not and will not be an energy source, its use with fuel cells maymake it an important energy carrier in synergywith electricity. —MAA

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 (accessedApril 18, 2005).

52. Doyle, reference 47.53. “Washington Station Offers Gas, Snacks and Hydrogen,”

The New York Times, November 11, 2004: C6.