Transcript 第一章 緒論

Chapter 5 Fuel Cell
Introduction
 Historical Notes
 Types of Fuel Cells
 Fuel Cell Electrochemistry
 Advantages of Fuel Cells
 Applications of Fuel Cells
 Advanced Hydrogen Production
Technologies
 Advanced Hydrogen Transport and Storage
Technologies

5-1 Introduction
What is a Fuel Cell

A fuel cell → an electrochemical device that
combines hydrogen and oxygen to produce
electricity, with water and heat as its by-product.
5-2 Historical Notes
Finally Coming of Age

In 1839, Sir William Grove reasoned that it
should be possible to react hydrogen with
oxygen to generate electricity.

In 1889, fuel cell was coined by Ludwig Mond
and Charles Langer, who attempted to build the
first practical device using air and coal gas.
5-2 Historical Notes
Finally Coming of Age

1.
2.
3.
In early 20th Century, fuel cells were forgot
A lack of understanding of materials and
electrode kinetics.
Internal combustion engine was developed.
Petroleum was discovered and rapidly exploited.
5-2 Historical Notes
Finally of Coming Age


In 1932, the first successful fuel cell device was
built by engineer Francis Bacon.
He improved on the expensive platinum catalysts
employed by Mond and Langer with a hydrogenoxygen cell using a less corrosive alkaline
electrolyte and inexpensive nickel electrodes.
5-2 Historical Notes
Finally of Coming Age


Until 1959, Bacon and his coworkers were able
to demonstrate a practical five-kilowatt system
capable of powering a welding machine.
In October of that same year, Harry Karl Ihrig of
Allis-Chalmers Manufacturing Company
demonstrated his famous 20-horsepower fuel
cell-powered tractor.
5-2 Historical Notes
Finally of Coming Age

1.
2.
In the late of 1950s, fuel cells were noticed
NASA began to search some electricity
generator for space mission.
Nuclear reactors as too risky, batteries as too
heavy and short live, and solar power as
cumbersome, NASA turned to fuel cells.
5-2 Historical Notes
Finally of Coming Age


In 1960s, fuel cells would be the panacea to the
world energy problem. The some qualities that
make fuel cells idea for space exploration were
considered. (ex. Small size, high efficiency, low
emission.)
Nearly 30 years US$1 billion in research have
been devote to address the barriers to the use of
fuel cells for stationary application.
5-2 Historical Notes
Finally of Coming Age

1.
2.
3.
Fortunately
A number of manufacturers have supported numerous
demonstration initiatives and ongoing research and
development into stationary application.
Phosphoric acid fuel cells is being offered
commercially, and more advanced designs, such as
carbonate fuel cells and solid oxide fuel cells, are the
focus of major electric technologies.
Full-sized (commercial) cells and full-height stacks
have been successfully demonstrated for the
carbonate fuel cell design.
5-2 Historical Notes
Finally of Coming Age

It has taken more than 150 years to develop
the basic science and to realize the
necessary materials improvement for fuel
cells to become a commercial reality.
The fuel cell is finally coming of age!!
5-2 Historical Notes
Finally of Coming Age
5-2 Historical Notes
Finally of Coming Age
5-3 Types of Fuel Cells
Overview of Fuel Cells


Fuel Cells generate electricity through an
electrochemical process in which the energy
stored in a fuel is converted directly into DC
electricity.
Electrical energy is generated without
combusting fuel, so fuel cells are extremely
attractive from an environmental stand point.
5-3 Types of Fuel Cells
Overview of Fuel Cells

1.
2.
3.
4.
5.
6.
Attractive fuel cell characteristic
High energy conversion efficiency
Modular design
Very low chemical and acoustical pollution
Fuel flexible
Cogeneration capability
Rapid load response
5-3 Types of Fuel Cells
Overview of Fuel Cells

1.
2.
3.
4.
Basic operating principle of fuel cells
An input fuel is catalytically reacted in fuel
cell to create an electric current.
The input fuel passed over the anode where it
catalytically splits into ions and electrons.
The electrons go through an external circuit to
serve an electric load while the ions move
through the electrolyte toward the oppositely
charge electrode.
At electrode, ions combine to create byproducts, primarily water and CO2.
5-3 Types of Fuel Cells
Overview of Fuel Cells

The figure of basic operating principle
5-3 Types of Fuel Cells
Overview of Fuel Cells

Fuel Cell Characteristics
5-3 Types of Fuel Cells
Overview of Fuel Cells
5-3 Types of Fuel Cells
Overview of Fuel Cells

1.
2.
3.
4.
Four primary types of fuel cells which are
based on electrolyte employed
Phosphoric Acid Fuel Cell
Molten Carbonate Fuel Cell
Solid Oxide Fuel Cell
Proton Exchange Membrane Fuel Cell
5-3 Types of Fuel Cells
Overview of Fuel Cells

A comparison of the fuel cell types
5-3 Types of Fuel Cells
Overview of Fuel Cells

Fuel cells are typical grouped three section
5-3 Types of Fuel Cells
Phosphoric Acid Fuel Cells

1.
2.
The most mature fuel cell technology
Among low temperature fuel cell, it was
showed relative tolerance for reformed
hydrocarbon fuels.
It could have widespread applicability in the
near term.
5-3 Types of Fuel Cells
PAFC Design an Operation

The sketch of PAFC operation
5-3 Types of Fuel Cells
PAFC Design an Operation

1.
2.
3.
4.
5.
The components of PAFC
Electrolyte : liquid of acid
Electrolyte carriers : Teflon bonded silicone
carbide matrix (pore structure→capillary
action to keep liquid electrolyte in place)
Anode : platinum catalyzed, porous carbon
Cathode : platinum catalyzed, porous carbon
Bipolar plate : complex carbon plate
5-3 Types of Fuel Cells
PAFC Design an Operation

1.
The most designs of PAFC
The plates are “bi-polar” in that they have
grooves on both side –
one side supplies fuel to anode of one cell, and
the other side supplies air or oxygen to the
cathode of the adjacent cell.
5-3 Types of Fuel Cells
PAFC Design an Operation
The PAFC reactions
Anode : H2 → 2H+ + 2e
Cathode : ½ O2 + 2H+ +2e- → H2O
5-3 Types of Fuel Cells
PAFC Design an Operation

The characteristics of PAFC operation
1.
Some acid may be entrained in fuel or oxidant
streams and addition of acid may be after
many hours of operation.
The water removed as steam on the cathode by
flowing excess oxidant past the back of
electrodes.
2.
5-3 Types of Fuel Cells
PAFC Design an Operation

1.
2.
The temperature effect to PAFC
The product water removal procedure required
that the system operated at temperature around
375°F (~190°C).
At lower temperature : the water will dissolve
in the electrolyte and not be removed as steam.
At high temperature (approximately 410°F~
(~210°C) : the phosphoric acid begins to
decompose.
5-3 Types of Fuel Cells
PAFC Design an Operation

1.
2.
How does excess heat be removed
Proved carbon plates containing cooling
channels.
Air or liquid coolant, can be passed
through these channels to remove heat.
5-3 Types of Fuel Cells
PAFC Design an Operation

1.
2.
3.
a.
b.
PAFC performance characteristics
Power density : 160 to 175 watts/ft2
Thermal energy supplied at : ~ 150°F (only a
portion at 250°F to 300°F)
Efficiency :
With pressurized reactants : 36% to 42%
(HHV)
Supply usable thermal energy : 31% to 37%
(HHV)
5-3 Types of Fuel Cells
Proton Exchange Membrane Fuel Cells
(PEMFC)

1.
2.
3.
4.
The introduction of PEMFC
PEMFC has higher power density than any
other fuel cell system.
PEMFC has comparable performance with the
advanced aerospace AFC.
PEMFC can operate on reformed hydrocarbon
fuels.
PEMFC uses a solid polymer electrolyte
eliminates the corrosion.
5-3 Types of Fuel Cells
Proton Exchange Membrane Fuel Cells
The introduction of PEMFC
5. Its low operating temperature (70-85 oC):
a. provides instant start up: 50 % maximum
power immediately at room T & full operating
power within 3 min.
b. require no thermal shielding to protect
personnel.
6. Advances in performance and designs offer the
possibility of lower cost.

5-3 Types of Fuel Cells
PEMFC Designs and Operation

The sketch of PEMFC operation
5-3 Types of Fuel Cells
PEMFC Designs and Operation

The sketch of PEMFC operation
5-3 Types of Fuel Cells
PEMFC Designs and Operation

1.
2.
3.
4.
The components of PEMFC
Electrolyte : polymer membrane.
Anode : thin sheet of porous, graphitized paper.
(water-proofed with PTFE or Teflon, with one
surface being applied with a small amount of
Pt-black)
Cathode : (the same as above).
Bipolar plate : graphite.
5-3 Types of Fuel Cells
PEMFC Designs and Operation

1.
2.
3.
4.
The features of the electrolyte
Electronic insulator, but an excellent
conductor of hydrogen ions.
The acid molecules are fixed to the polymer,
but the protons on these acid groups are free to
migrate through the membrane.
Solid polymer electrolyte→electrolyte loss is
not an issue with regard to stack life.
Be handled easily and safely.
5-3 Types of Fuel Cells
PEMFC Designs and Operation

The heart of PEMFC
The electrolyte is sandwiched between the anode
and cathode, and the three components are
sealed together under heat and pressure to
product a single “membrane/electrode assembly”
(MEA, < 1mm thick).
5-3 Types of Fuel Cells
PEMFC Designs and Operation

1.
2.
3.
The features of the bipolar plates
The bipolar plates are called “flow field
plates”.
They make electrical contact with the back of
the electrodes and conduct the current to the
external circle.
They supply fuel to the anode and oxidant to
the cathode.
5-3 Types of Fuel Cells
PEMFC Designs and Operation

1.
2.
a.
b.
Useable fuel for PEMFC
Pure hydrogen
Reformed Hydrocarbon fuels:
Without removal or recirculation of byproduct CO2.
The traces of CO produced during the
reforming process must be converted to CO2 (a
simple catalytic process).
5-3 Types of Fuel Cells
PEMFC Designs and Operation
The PEMFC reactions
Anode : H2 → 2H+ + 2e
Cathode : O2 → 4H+ + 4e- → 2H2O
5-3 Types of Fuel Cells
PEMFC Designs and Operation

1.
2.
3.
4.
The characteristics of PEMFC operation
The electrode reactions are analogous to those
in PAFC.
The PEMFC operates at about 175°F (80℃).
The water is produced as liquid water and is
carried out the fuel cell by excess oxidant flow.
Fully operating power is available within
about 3 minute under normal condition.
5-3 Types of Fuel Cells
PEMFC Designs and Operation
5-3 Types of Fuel Cells
PEMFC Designs and Operation

1.
2.
The performance of PEMFC recently
At 0.7V/cell on hydrogen and oxygen, 65psia :
850A/ft2 (~0.91 A/cm2)
At 0.7V/cell on hydrogen and air, 65psia :
500A/ft2 (~0.54 A/cm2)
5-3 Types of Fuel Cells
PEMFC Designs and Operation

1.
2.
1.
The performance of Ballard/Dow PEMFC
At 0.7V/cell:
At 65psia, hydrogen/oxygen : 2000A/ft2
At 65psia, hydrogen/air : 1000A/ft2
At 0.5V/cell, :
At 65psia, hydrogen/oxygen : 4000A/ft2
↓
2000 W/ft2
5-3 Types of Fuel Cells
PEMFC Designs and Operation

1.
2.
3.
4.
The power density of PEMFC
a factor of 10 greater than other FC systems → a
significant reduction in stack size and cost.
In 5kW production fuel cell stacks, 0.7V at 650 A/ft2
on hydrogen/air at 45psi, stack dimensions 9.8 * 9.8
* 16.7 in: stack-only power density of over 5.4
kW/ft3
1.25 kW/ft3 on hydrogen/air at 45psi, if including
fuel/oxidant controls, cooling, product water removal
Approaching 14.2 kW/ft3 are certainly feasible.
5-3 Types of Fuel Cells
PEMFC Designs and Operation

When HC/air are to be used, higer T FC, the
MCFC, SOFC, and to some extent, PAFC,
have an efficiency advantage over PEMFC.
↑
waste heat can be used to drive air
compressors, reforming of HC fuels, electric
generation or other thermal load
5-3 Types of Fuel Cells
PEMFC Designs and Operation
Using either air or liquid cooling
↓
a compact power generator
and the excess heat of PEMFC is be used for
1. space heating or residential hot water
2. utility cogeneration applications

5-3 Types of Fuel Cells
PEMFC Designs and Operation

1.
2.
3.
4.
The pressure effects to all fuel cells
Performance is improve by pressuring the air.
Find an balance about the energy and financial
cost associated with compressing air and the
improved performance.
Rule of thumb: < 45 psia
∵PEMFC uses a solid electrolyte
∴ a significant pressure differential can be
maintained across the electrolyte→low P fuel
& higher P air
5-3 Types of Fuel Cells
PEMFC Designs and Operation

1.
2.
3.
4.
A very significant cost penalty of PEMFC as
compared with PAFC
The PEMFC uses platinum at both the anode
and cathode.
presently, 0.001 oz/in2 ~0.6 oz/kW for H2/air
Los Alamos National Lab & Texas A &M
Univ., 0.00007 oz/in2 ~0.042 oz/kW for H2/air
or ~0.021 oz/kW for H2/ O2
Be expected to reduce platinum requirement to
0.035 oz/kW (1 g/kW) or about $2/kW.
5-3 Types of Fuel Cells
Molten Carbonate Fuel Cells

1.
2.
The goals of developing MCFC
Operating directly on coal, but that seems less.
Operation on coal-derived fuel gas or natural
gas is viable.
5-3 Types of Fuel Cells
MCFC Design and Operation

The sketch of MCFC operation
5-3 Types of Fuel Cells
MCFC Design and Operation

1.
2.
3.
4.
The component of MCFC
Electrolyte : a molten carbonate salt mixture,
consist of lithium carbonate and potassium
carbonate.
Anode : a highly porous sintered nickel
powder, alloyed with chromium.
Cathode : a porous nickel oxide material
doped with lithium.
Electrolyte carriers : a porous, insulating and
chemically ceramic matrix.
5-3 Types of Fuel Cells
MCFC Design and Operation
The MCFC reactions
Anode : H2 + CO3-2 → H2O + CO2 + 2eCO + CO3-2 → 2CO2 + 2e
Cathode : O2 + 2CO2 + 4e- → 2CO3-2
* require a system for collecting CO2
5-3 Types of Fuel Cells
MCFC Design and Operation

1.
a.
b.
The MCFC compares with PAFC
As the operating temperature increases, the
theoretical operating voltage for a fuel cell
decrease and with it the maximum theoretical
fuel efficiency.
The operating voltage of the MCFC is higher
than the PAFC at the same current density.
As size and cost scale roughly with electrode
area, a MCFC should be smaller and less
expansive than a “comparable” PAFC.
5-3 Types of Fuel Cells
MCFC Design and Operation

1.
2.
3.
The relations of high operating temperature
and MCFC
Operating at between 1110°F(600℃) and
1200°F(650℃).
In combined cycle operation, electrical
efficiencies are in excess of 60%(HHV).
At the high operating temperature, the gaseous
hydrocarbon fuel such as natural gas would be
reformed to produce hydrogen within the fuel
cell itself.
5-3 Types of Fuel Cells
MCFC Design and Operation
The relations of high operating temperature
and MCFC
4. At high operating temperature(1200°F), noble
metal catalysts are not required.
5. At high operating temperature(1200°F), the salt
mixture is liquid and is a good conductor.
6. The cell performance is sensitive to operating
temperature.
a. A change in cell temperature from 1200°F to
1110°F results in drop in voltage 15%.

5-3 Types of Fuel Cells
MCFC Design and Operation

1.
2.
How does excess heat reuse and remove
The temperature of excess heat is high enough
to yield high pressure steam, which may be
fed to turbine to generate additional electricity.
To achieve sufficient of conductivity of the
electrolyte, a higher volume of air is passed
through the cathode for cooling purpode.
5-3 Types of Fuel Cells
Solid Oxide fuel cells

1.
2.
3.
The introductions of the SOFC
The SOFC uses a ceramic, solid-phase electrolyte
which reduces corrosion considerations and
eliminates the electrolyte management problems
associated with the liquid electrolyte fuel cells.
To achieve adequate ionic conductivity in such a
ceramic, however, the system must operate at about
1830 °F (1000 °C).
At that temperature, internal reforming of
carbonaceous fuels should be possible, and the waste
heat from such a device would be easily utilized by
conventional thermal electricity generating plants to
yield excellent fuel efficiency.
5-3 Types of Fuel Cells
SOFC Design and Operation

The sketch of SOFC operation
5-3 Types of Fuel Cells
SOFC Design and Operation
The SOFC reactions
Anode : H2 + O-2 → H2O + 2eCO + O-2 → CO2 + 2eCH4 + 4O-2 → 2H2O + CO2 + 8e
Cathode : O2 + 4e- → 2O2-2
 It is significant that the SOFC can use CO as its
direct fuel.
5-3 Types of Fuel Cells
SOFC Design and Operation

1.
a.
b.
2.
3.
The components of the SOFC
Electrolyte : solid ceramic.
Materials : dense yttria-stabilized zirconia
It is an excellent conductor at high
temperatures.
Anode : a porous nickel/zirconia cermet
Cathode : magnesium-dope lanthaum
manganate
5-3 Types of Fuel Cells
SOFC Design and Operation

1.
2.
3.
4.
5.
SOFC performance Characteristics
It development cells and small stacks :
0.6V/cell at about 232 A/ft2
Lifetimes are over 30000(hr).
The efficiencies of unpressurized SOFCs :
45% (HHV)
The efficiencies of pressurized SOFCs :
60% (HHV)
Using the waste heat, could add fuel efficiency
of the SOFC system.
5-3 Types of Fuel Cells
SOFC Design and Operation

1.
How does manage temperature
Maintain proper volume of the air stream into
the cell.
5-3 Types of Fuel Cells
SOFC Design and Operation

1.
2.
3.
4.
The relations of high operating temperature
and SOFC
The SOFC operates at approximately 1830°F
(1000°C).
The high operating temperature offers the
possibility of internal reforming.
The SOFC can tolerant several orders of
magnitude more sulfur than order fuel cells.
The SOFC requires a significant start-up time.
5-3 Types of Fuel Cells
SOFC Design and Operation
The relations of high operating temperature
and SOFC
5. The cell performance is very sensitive to
operating temperature.
a. A 10% drop in temperature → 12% drop in
cell performance
6. The high temperature also demands that the
system include significant thermal shielding to
protect personnel and to retain heat.

5-4 Fuel Cell Electrochemistry
internal reformer
In a conventional fuel cell system, a
carbonaceous fed to a fuel processor where it is
steam reformed to produce H2.
 Methane and steam reforming reaction :
CH4 + H2O → CO + 3H2

5-4 Fuel Cell Electrochemistry
MCFC

1.
2.
3.
4.
The electrochemical reactions occurring in
MCFCs
Anode : H2 + CO3-2 → H2O + CO2 + 2eCathode : ½ O2 + CO2 + 2e- → CO3-2
Overall : H2 + ½ O2 + CO2 (cathode) → H2O +
CO2 (anode)
The reversible potential equation :
E = E° + RT/2F ln(PH2/PH2O) +
RT/2F ln(PCO2,c/PCO2,a)
5-4 Fuel Cell Electrochemistry
SOFC

1.
2.
3.
4.
The electrochemical reactions occurring in
SOFCs
Anode : H2 + O2-2 → H2O + 2eCathode : ½ O2 + 2e- → O2-2
Overall : H2 + ½ O2 → H2O
The corresponding Nernst equation
E = E° + RT/2F ln(PH2PO21/2 /PH2O)
5-5Advantages of Fuel Cells
Environmental Acceptability


1.
2.
Because fuel cells are so efficient, CO2
emissions are reduced for a given power
output.
Example :
By 2000, decrease CO2 emissions by 0.6
MMT of carbon equivalent.
Emissions of SOx and NOx are 0.003 and
0.0004 pounds/megawatt-hour.
5-5Advantages of Fuel Cells
Efficiency


1.
2.
3.
4.
Dependent on type and design, the fuel cells direct
electric energy efficiency ranges form 40 to 60
percent (LHV).
Characteristics :
Operates at near constant efficiency.
Efficiency is not limited by the Carnot Cycle.
For the fuel cells/gas turbine system, the efficiency
achieves 70 percent (LHV).
When by-product heat is utilized, the efficiency of
the fuel cell systems approach 85 percent.
5-5Advantages of Fuel Cells
Distributed Capacity

1.

Distributed generation reduces the capital
investment and improves the overall
conversion efficiency of fuel to end use
electricity by reducing transmission losses.
Losses : presently 8-10 percent
Many smaller units are statistically reliable.
5-5Advantages of Fuel Cells
Permitting

Permitting and licensing schedules are short due
to the ease in siting.
5-5Advantages of Fuel Cells
Modularity

1.
The fuel cell is inherently modular.
Be configured in wide range of electrical
output, form nominal 0.025 to greater than 50megawatt (MW) for a natural gas fuel cell to
greater than 100-MW for the coal gas fuel cell.
5-5Advantages of Fuel Cells
Fuel Flexibility

1.
2.
3.
4.
5.

1.
The primary fuel source for the fuel cell is
hydrogen, which can be obtained from :
Natural gas
Coal gas
Methanol
Landfill gas
Other fuels containing hydrocarbons.
Advantage of fuel flexibility
The power generation can be assured even
when a primary fuel source unavailable.
5-5Advantages of Fuel Cells
Cogeneration Capability
High-quality heat is available for cogeneration,
heating, and cooling.
 Fuel cell exhaust heat is suitable for use in
residential, commercial, and industrial
cogeneration application.

5-6Applications of Fuel Cells
Introduction

In theory, a fuel cell can power anything that
runs on electricity. The following applications
can take particular advantage of a fuel cell's
attributes.
5-6Applications of Fuel Cells
Cars, Trucks, and Buses


1.
2.
Most vehicles today rely on an internal
combustion engine (ICE).
Electric motors are much more suitable
They deliver their maximum torque at low rpm,
just when a vehicle needs it most.
A driver heads downhill or puts on the brakes,
an electric motor can double as a generator to
recapture that energy and covert it back to
electricity for subsequent use.
5-6Applications of Fuel Cells
Cars, Trucks, and Buses

1.

1.
2.
The choke point of electric motor
The short range and tedious recharging of the
1st generation
A fuel cell powers the vehicle's electric motor
These problems can be overcome. A hydrogen
tank can be refueled in about five minutes.
It has a similar range to a conventional
automobile.
5-6Applications of Fuel Cells
Businesses and Homes

1.
2.
a.

The reasons of fuel cells are attractive in stationary
applications
They deliver unparalleled fuel efficiencies, especially
in Combined Heat & Power (CHP) applications.
Fuel cells offer a new level of reliability :
If a blackout occurs, they will keep essential
mechanical components and external landmark
signage online.
Fuel cells offer highly reliable, high-quality
electricity.
5-6Applications of Fuel Cells
Laptops, Cell Phones, and other Electronics

1.
2.
Fuel cells will find their first widespread use in
portable electronics
These "micro fuel cells" offer far higher energy
densities than those of comparably sized
batteries. The typical laptop can operate
unplugged for ten hours or more.
Micro fuel cells also offer the added appeal of
eliminating the need for battery chargers and
AC adapters, as they require refueling instead
of recharging.
5-7 Advanced Hydrogen Production
Technologies

1.
2.
3.
4.
Introduction
Hydrogen is a clean, sustainable resource with
many potential application.
Hydrogen is now produced primary by steam
reforming of natural gas.
This is relatively expensive process that uses
electric current to dissociate water.
Three process of producing hydrogen :
photobiological, photoelectrochemical,
thermochemical.
5-7 Advanced Hydrogen Production
Technologies

1.
2.
a.
b.
PHOTOBIOLOGICAL PRODUCTION
Most photobiological system use the natural
activity of bacteria and green algae to produce
hydrogen.
Two significant limitation :
Low solar converting efficiencies.(5~6% of
sun’s energy to hydrogen energy)
Nearly all enzymes are inhibited in their
hydrogen production by presence of oxygen.
5-7 Advanced Hydrogen Production
Technologies
PHOTOBIOLOGICAL PRODUCTION
3. The way to overcome oxygen intolerance and
increase conversion efficiencies :
a. A green algae : the Chlamydomonas strain →
product hydrogen and oxygen simultaneously.
b. Cell free process : theoretical efficiency
approach 25%

5-7 Advanced Hydrogen Production
Technologies

1.
2.
a.
b.
PRODUTION BY PHOTOELECTROCHEMICAL (PEC) TECHNOLOGY
PEC production uses semiconductor
technology in one-step process of splitting
water directly upon sunlight illumination.
A PEC system :
a photovoltaic cell → produce electric current
when exposed to light
Electrolyzer
5-7 Advanced Hydrogen Production
Technologies

3.
4.
a.
b.
PRODUTION BY PHOTOELECTROCHEMICAL (PEC) TECHNOLOGY
Advantage : producing low-cost renewable
hydrogen.
The two limited factor of an efficient and costeffective PEC system :
The high voltage required to dissociate water.
The corrosiveness of aqueous electrolytes.
5-7 Advanced Hydrogen Production
Technologies

PRODUTION BY PHOTOELECTROCHEMICAL (PEC) TECHNOLOGY
5.
The way to overcome limits :
The structure → the multijunction device
Material :
Gallium based (GalnP2, GaAs) → efficiency is
more than 25 % , but is expensive.
Amorphous silicon → efficiency is more than
13 % , but cost is low.
a.
b.
1.
2.
5-7 Advanced Hydrogen Production
Technologies
PRODUTION BY PHOTOELECTROCHEMICAL (PEC) TECHNOLOGY
4. The sketch of a multijunction device

5-7 Advanced Hydrogen Production
Technologies

1.
2.
a.
THERMOCHEMICAL PRODUCTION
Gasification and pyrolysis : using heat to
produce a vapor from which hydrogen can be
derived use a conventional steam reforming
process.
Pyrolysis :
Biomass is break into highly reactive vapors
and carbonaceous resident, or char.
The vapors, when condensed into pyrolysis oil,
can be steam reformed to produce hydrogen.
5-7 Advanced Hydrogen Production
Technologies

b.
c.
d.
THERMOCHEMICAL PRODUCTION
The char is burn to provide the required heat
for the pyrolysis reaction.
The fast way to produce hydrogen is directly
linked to a steam reformer.(12%~17%
hydrogen by weight of dry biomass)
Advantage : the lowest cost production
methods, but it needs catalysts.
5-7 Advanced Hydrogen Production
Technologies

3.
a.
b.
c.
THERMOCHEMICAL PRODUCTION
Gasification of municipal solid waste (MSW) :
It is low-cost, sustainable source of hydrogen
production.
MSW, on average, consist about 70% by
weight of biomass material.
Gasification result in an clean fuel gas from
which hydrogen can be reformed.
5-7 Advanced Hydrogen Production
Technologies

4.
a.
THERMOCHEMICAL PRODUCTION
The Texaco’s high-temperature gasification :
Result in a high yield of hydrogen and
produces a non-hazardous, glass-like ash
byproduct.