The Hydrogen EconomyThe Hydrogen Economy

By John MooreBy John Moore

Physics 335Physics 335

Spring 2004Spring 2004

IntroductionIntroduction

The Hydrogen Economy is The Hydrogen Economy is the concept of using the concept of using hydrogen as the energy hydrogen as the energy carrier rather than fossil carrier rather than fossil fuels.fuels.

There are numerous benefits There are numerous benefits from converting to a from converting to a Hydrogen Economy.Hydrogen Economy.

However, the obstacles and However, the obstacles and the associated Physics are the associated Physics are often not clearly understood.often not clearly understood.

AgendaAgenda

Why the United States needs an Why the United States needs an alternative to fossil fuelsalternative to fossil fuels

The properties of hydrogenThe properties of hydrogen The obstacles for the Hydrogen The obstacles for the Hydrogen

EconomyEconomy What a Fuel Cell isWhat a Fuel Cell is How a Fuel Cell worksHow a Fuel Cell works The future of the Hydrogen EconomyThe future of the Hydrogen Economy

Currently, most the energy in the Currently, most the energy in the U.S. comes from fossil fuelsU.S. comes from fossil fuels

However, there are problems with fossil fuels…However, there are problems with fossil fuels…

Main problems with fossil fuelsMain problems with fossil fuels

They will eventually be depleted.They will eventually be depleted. They cause a variety of They cause a variety of

environmental problems.environmental problems. They force the U.S. to be dependent They force the U.S. to be dependent

on middle eastern countries.on middle eastern countries.

DepletionDepletion

Millions of years ago, like today, plants Millions of years ago, like today, plants used solar energy to power their growthused solar energy to power their growth

Plants decayed into oil, coal and natural Plants decayed into oil, coal and natural gasgas

This left a giant warehouse of fossil fuelsThis left a giant warehouse of fossil fuels This warehouse will eventually run low and This warehouse will eventually run low and

the decay process will not repeat itself in the decay process will not repeat itself in the near to medium term futurethe near to medium term future

Environmental ProblemsEnvironmental Problems

Air pollutionAir pollution Global warmingGlobal warming Effects on earth Effects on earth

from mining or from mining or extracting the fuelextracting the fuel

Effects on the Effects on the earth when earth when something goes something goes wrong – Exxon wrong – Exxon ValdezValdez

DependenceDependence

United States may be forced to United States may be forced to protect foreign sources of oilprotect foreign sources of oil

Persian Gulf WarPersian Gulf War Current War with IraqCurrent War with Iraq Cost of War = Billions of dollars + Cost of War = Billions of dollars +

American livesAmerican lives

The Properties of HydrogenThe Properties of Hydrogen

Hydrogen is the smallest of all atomsHydrogen is the smallest of all atoms High energy content per weightHigh energy content per weight

- 3 times that of gasoline- 3 times that of gasoline Very low energy density per volumeVery low energy density per volume

- Requires large storage tanks- Requires large storage tanks

Higher Heating Value of Different Higher Heating Value of Different Fuel OptionsFuel OptionsHHV per Unit Volume [GJ/m^3]

05

10152025303540

Hydro

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(200

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Hydro

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d Hyd

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Met

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(200

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Met

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(800

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Liqui

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Liqui

d Eth

anol

Liqui

d Pro

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Liqui

d O

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me

[G

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The Obstacles to the Hydrogen The Obstacles to the Hydrogen EconomyEconomy

Electricity RequirementElectricity Requirement

The electricity to produce Hydrogen would The electricity to produce Hydrogen would have to be derived from renewable have to be derived from renewable sources rather than fossil fuelssources rather than fossil fuels

All of the fossil fuel energy used for All of the fossil fuel energy used for transportation now will have to convert to transportation now will have to convert to hydrogen which in turn will have to be hydrogen which in turn will have to be produced by electricityproduced by electricity

Electrical generating capacity of the U.S. Electrical generating capacity of the U.S. will have to doublewill have to double

Production and StorageProduction and Storage

Questions that must be answered:Questions that must be answered:• How will the Hydrogen be produced?How will the Hydrogen be produced?• How will the produced Hydrogen be How will the produced Hydrogen be

transported, distributed and stored?transported, distributed and stored?

How can Hydrogen be produced?How can Hydrogen be produced?

Possible sources of production:Possible sources of production:• Electrolysis of waterElectrolysis of water• Reforming fossil fuelsReforming fossil fuels

Electrolysis of Water• Dissociate water

molecules into (H2) and (O2)

• Can be done anywhere

• One mole of water produces a mole of hydrogen gas and a half-mole of oxygen gas

Reforming Fossil FuelsReforming Fossil Fuels

Oil and natural gas contain Oil and natural gas contain hydrocarbonshydrocarbons

Split the hydrogen from the carbon Split the hydrogen from the carbon using a fuel processor or a reformerusing a fuel processor or a reformer

Discard leftover carbon as carbon Discard leftover carbon as carbon dioxidedioxide

Does the reforming process really Does the reforming process really make sense?make sense?

Reforming fossil fuels does reduce air Reforming fossil fuels does reduce air pollution. pollution.

However, it does not solve the:However, it does not solve the:• Greenhouse gas problemGreenhouse gas problem• Depletion problemDepletion problem• Dependence problemDependence problem

Therefore, it is only a transitional Therefore, it is only a transitional step and not the final solution.step and not the final solution.

Storage OptionsStorage Options

Storing Hydrogen can be done in Storing Hydrogen can be done in three ways:three ways:

- Compressed form- Compressed form

- Liquid form- Liquid form

- Chemical bonding- Chemical bonding

Compressed HydrogenCompressed Hydrogen

Similar to compressing natural gas Similar to compressing natural gas but Hydrogen is less densebut Hydrogen is less dense

Normally compressed between 200 Normally compressed between 200 and 250 bar for cylindrical tanks up and 250 bar for cylindrical tanks up to 50 litersto 50 liters

Currently, not practical for vehicles Currently, not practical for vehicles due to weight and sizedue to weight and size

Liquid HydrogenLiquid Hydrogen

Does not liquefy Does not liquefy until -253°C until -253°C

40% of energy can 40% of energy can be lostbe lost

Liquid hydrogen Liquid hydrogen has a high energy has a high energy to mass ratioto mass ratio

Bonded HydrogenBonded Hydrogen

Certain metal and Certain metal and metal alloys can metal alloys can absorb Hydrogenabsorb Hydrogen

Metal hydride tankMetal hydride tank Hydrogen released Hydrogen released

from metal when from metal when heat is appliedheat is applied

What is a Fuel Cell?What is a Fuel Cell?

Creates electricity Creates electricity through through electrochemical electrochemical processprocess

Emits heat and Emits heat and water onlywater only

Passenger vehiclesPassenger vehicles Most promising Most promising

type - PEMtype - PEM

Parts of a PEMFCParts of a PEMFC

There are four There are four main parts:main parts:• AnodeAnode• CathodeCathode• CatalystCatalyst• Proton Exchange Proton Exchange

MembraneMembrane

The AnodeThe Anode

The anode is the negative post of the The anode is the negative post of the fuel cell. fuel cell.

It conducts the electrons that are It conducts the electrons that are freed from the hydrogen molecules freed from the hydrogen molecules so that they can be used in an so that they can be used in an external circuit. external circuit.

It has channels etched into it that It has channels etched into it that disperse the hydrogen gas equally disperse the hydrogen gas equally over the surface of the catalyst. over the surface of the catalyst.

The CathodeThe Cathode

The cathode is the positive post of the fuel The cathode is the positive post of the fuel cell. cell.

It has channels etched into it that It has channels etched into it that distribute the oxygen to the surface of the distribute the oxygen to the surface of the catalyst. catalyst.

It also conducts the electrons back from It also conducts the electrons back from the external circuit to the catalyst, where the external circuit to the catalyst, where they can recombine with the hydrogen they can recombine with the hydrogen ions and oxygen to form water. ions and oxygen to form water.

The CatalystThe Catalyst

The catalyst is a special material that The catalyst is a special material that facilitates the reaction of oxygen and facilitates the reaction of oxygen and hydrogen. hydrogen.

It is usually made of platinum powder very It is usually made of platinum powder very thinly coated onto carbon paper or cloth. thinly coated onto carbon paper or cloth. The catalyst is rough and porous so that The catalyst is rough and porous so that the maximum surface area of the platinum the maximum surface area of the platinum can be exposed to the hydrogen or can be exposed to the hydrogen or oxygen. oxygen.

The platinum-coated side of the catalyst The platinum-coated side of the catalyst faces the PEM.faces the PEM.

The Proton Exchange MembraneThe Proton Exchange Membrane

The electrolyte is the proton The electrolyte is the proton exchange membrane. exchange membrane.

This is a specially treated material This is a specially treated material that only conducts positively charged that only conducts positively charged ions. ions.

The membrane blocks electrons. The membrane blocks electrons.

The Chemistry of a PEMFCThe Chemistry of a PEMFC Pressurized hydrogen Pressurized hydrogen

gas (H2), enters the gas (H2), enters the fuel cell on the anode fuel cell on the anode side side

Oxygen gas (O2) is Oxygen gas (O2) is forced through the forced through the catalyst on the catalyst on the Cathode sideCathode side

This reaction in a This reaction in a single fuel cell single fuel cell produces about 0.7 produces about 0.7 volts volts

Anode side:2H2 => 4H+ + 4e-

Cathode side:O2 + 4H+ + 4e- => 2H2O

Net reaction:2H2 + O2 => 2H2O

In order to transition to a In order to transition to a Hydrogen Economy…Hydrogen Economy…

Convert energy production to Convert energy production to renewable sourcesrenewable sources

Build Hydrogen production, Build Hydrogen production, transportation, storage and transportation, storage and distribution facilitiesdistribution facilities

Large scale manufacture of fuel cellsLarge scale manufacture of fuel cells

ConclusionConclusion

In general, a transition to a pollution free, In general, a transition to a pollution free, hydrogen economy is possible but the obstacles hydrogen economy is possible but the obstacles are significant. are significant.

The initiative has begun. President Bush has The initiative has begun. President Bush has announced a $1.2 billion dollar initiative to announced a $1.2 billion dollar initiative to reduce U.S. dependence on foreign oil by reduce U.S. dependence on foreign oil by developing hydrogen-powered fuel cells. developing hydrogen-powered fuel cells.

Nevertheless, the complete transition is still a Nevertheless, the complete transition is still a long way off. In the meantime, it is important to long way off. In the meantime, it is important to work to reduce fossil fuel dependence through work to reduce fossil fuel dependence through efficiency and substitution.efficiency and substitution.

SourcesSources

"The Future of the Hydrogen Economy: Bright or Bleak?", Baldur Eliasson and Ulf Bossel, Proceedings, THE FUEL CELL WORLD, Lucerne /Switzerland, July 2002

“How the Hydrogen Economy works” http://www.howstuffworks.com/hydrogen-economy.htm