Lunch Vietnam seminar-University of MichiganAugust 14, 2008

Fundamentals of Fuel Cells

PresentersDo Ba Thanh & Nguyen Huu Phuoc Nguyen

Outline

Introduction:

+ Energy and Environmental aspects: N

+ Why we need fuel cell? N

+ Hydrogen economy N

+ Fuel cells categories

Operation of fuel cell N- a T

Fuel cell applications a T

Fuel cell problems N-a T

Research direction N- a T

FC in VN- a T

Conclusion

Energy, now and in future• We are relying on fossil fuel [1]

Fig: World energy sources - PercentageFig: World energy demand development

*http://en.wikipedia.org/wiki/World_energy_resources_and_consumption

Energy, now and in future

How long can fossil fuel reserve last? [2] Oil: 1,050 to 1,277 billion barrels (167 to 203 km³) Gas: 6,040 - 6,806 trillion cubic feet (171,000 to 192,700 km³) Coal: 1,081,000 million tons

By the current consumption rate: Oil: 45 years Gas: 72 years Coal: 252 years

* http://en.wikipedia.org/wiki/Fossil_fuel

Energy, now and in future• The actual oil peak curves [3]

Fig: World oil production vs time Fig: Oil production vs time curves for countries, except Middle East and former Soviet Union

Energy, now and in future

• Fossil fuel also create other serious problems

Environmental pollution: one gallon of gas burned releases 2.3 kg of carbon in form of gases!

Global warming

Dependence on oil-rich countries

Therefore, fossil fuel is NOT our future!

http://staffwww.fullcoll.edu/tmorris/elements_of_ecology/images/greenland_icemelt_2002.jpg

Why we need fuel cell?

There for the situation poses two major challenges:

- Find a new source of energy

- Make the new source economically and environmentally viable

To solve overcome these challenges, we are, being predicted that, heading toward the Hydrogen Economy, where fuel cell play a major role.

Hydrogen Economy

Renewable energy sources: Solar, wind, hydropower, biofuel, geothermal Energy carrier: Hydrogen “Green Engine”: Fuel Cell

*http://en.wikipedia.org/wiki/Renewable_energy

Energy Diversity

** F. Barbir, PEM Fuel Cells, theory and practice, Elsevier Academic Press,2005

Type and percentage of renewable energy sources

What is a fuel cellA brief overview *

* PEM Fuel Cells, theory and practice, F. Barbir, Elsevier Academic Press,2005

What is a fuel cell

Fuel cell classification*

- More than 20 types of FC classified according to their electrolyte, fuel, and operating temperature**

- Proton Exchange Membrane FC (PEMFC) is the most promising one from its high power density and low operating temperature (60-80oC)

[*] http://en.wikipedia.org/wiki/Fuel-cell[**] Larminie L., Dicks A., Fuel cell systems explained, Wiley, 2004, 2nd Edition

Fuel Cell Efficiency Tank-to-wheel efficiency:

With pure H2, FC is up to 90% Electrical-mechanical conversion: 80%

Overall: 72%

Ex: Honda’s FCX concept vehicle 60%

Power-plant-to-wheel efficiency: Energy is needed to produce, store, transport H2.

The overall efficiency is around 22% [6]

[6] http://www.efcf.com/reports/E04.pdf

Theoretical : 33%Practical max: 26% [5]

Operations of Fuel Cells and Battery• Similarities:

- No moving parts during operations, so they work quietly and requires minimum maintenance

- Flexible in design (scale, shape and capacity)

- High efficiency (H% is about 90%>> internal combustion engine with H% ~33%)

• Differences

Fuel Cells

- Various fuel sources

- In-situ energy generation

Battery:

- Reactants can be regenerated

- Built-in energy storage

Operation of Fuel Cells

Similar to that of battery: direct conversion of chemical energy into electrical energy

The electrons produced at anode move to cathode to produce electricity.

http://www.esru.strath.ac.uk/EandE/Web_sites/00-01/fuel_cells/fuel%20cell%20operation.html

Anode: 2H2-4x1e = 4H+

Cathode: O2 + 2x2e+4H+ = 2H2OOverall: 2 H2 + O2 = H2O

Reactions inside Fuel Cells

The reaction of H2 to O2 is very difficult at normal condition (10-

4% after 2000 yrs)

What does it make reactions inside FCs occurred?

There are various types of Fuel Cells

Is there any difference in operation between different fuel cell’s types?

Electrode and reactions on its surface

• Electrodes consist of two conductive and porous layers

• Supportive layer is covered by catalyst for the redox reactions

• Catalyst predominantly is Pt nano particles distributed on support’s suface

• Pt catalyzes the redox reactions at normal conditions

* Spiegel C. S.-Designing & Building Fuel Cells, McGraw-Hill Co., 2007

Schematic of electrode structure for fuel cells *

Reactions on PEM fuel cells

Electrolyte is a membrane which is porous and able to exchange proton

Anode: 2H2 -4x1e = 4H+

Cathode: O2 +2x2e + 4H+ = 2H2O

Reaction in total: 2H2 + O2 = 2H2O* Barbir-PEM Fuel Cells: Theory and Practice, Elsevier, 2005

Schematic of PEM fuel cells*

Reactions on PA fuel cells

Electrolyte is the solution of phosphoric acid

Anode: 2H2(g) -4x1e = 4H+(aq)

Cathode: O2(g) + 4H+(aq)+2x2e = 2 H2O(l)

Overall: H2(g) + ½ O2(g) + CO2(g) = H2O(l) + CO2(g)

* Barbir-PEM Fuel Cells: Theory and Practice, Elsevier, 2005

Schematic of PA fuel cells*

Reactions on Alkali fuel cells

Electrolyte is the solution of KOH (Potasium hydroxide)

Anode: 2H2(g) + 2OH-(aq) – 2x1e = 4H2O(l)

Cathode: O2(g) + 2H2O(l) + 2x2e = 4OH-(aq)

Overall: 2H2(g) + O2(g) = 2H2O(l)

Barbir-PEM Fuel Cells: Theory and Practice, Elsevier, 2005

Reactions on Solide Oxide fuel cells

Electrolyte is a non porous solid Y2O3-stabilized ZrO2, melt at 1000oC

Anode: H2(g) + O2-(melt) – 2x1e = H2O (g)

Cathode: ½ O2(g) + 2e = O2- (oxide)

Overall: H2(g) + ½ O2(g) = H2O(g)(a) http://www.sciencemag.org/cgi/content/full/288/5473/2031/F1(b) Barbir-PEM Fuel Cells: Theory and Practice, Elsevier, 2005

Schematic of Solid Oxide electrode (a) Schematics of SOFCs (b)

Reactions on Direct Methanol fuel cells

Similar structure to PEMFCs, but using methanol/ethanol as fuel to generate H+

Anode: CH3OH(l) + H2O(l) = CO2(g) + H+(aq) + 6e

Cathode: 6H+ + 3/2O2(g) + 6e = 3H2O(l)

Overall: CH3OH(l) + 3/2O2(g) = CO2(g) + 2H2O(l)

Schematic of DMFCs *

* Barbir-PEM Fuel Cells: Theory and Practice, Elsevier, 2005

Applications of Fuel Cells

Transportation Vehicles

Power generation stations

AerospaceExploration

HandheldDevices

Fuel Cells for automotives

Toyota FCHV PEM FC fuel cell vehicleA hydrogen fuel cell public bus accelerating at traffic lights in Perth, Western Australia

http://en.wikipedia.org/wiki/Fuel_cell

Some pictures of fuel cells used in bus

H2 cylinders

Fuel cells location

Fuel Cells for automotives

Requirements:

- Size

- Power density: Higher Energy in a volume unit of cell

PEMFCs has been mostly used for this purpose:

- Does not require initial energy supply to initiate the operation of FCs

- Higher power density than other FCs types

- Dry electrolyte

Fuel Cell Problems

Cost: from infrastructure construction and materials.Currently: $110/ kW. To be competitive: $35/kW

Durability of materials, especially at high temperature and severe working conditions of fuel cells

Design and modeling of fuel cells to acquire the humidity, air and hydrogen flow rates, thermal and mass transportation in and out from FCs

The availability of infrastructure and production of hydrogen

FC research areas *

Heat transfer Mass Transfer Water management Membrane material Catalyst Control system

*http://www.fuelcellsworks.com/Supppage8788.html

Futures of FCs

Being considered as a promising and predominant energy source for the future

Research on FCs has been dramatically increased

There are still many obstacles for the wide application of FCs

Challenges for FCs-Hydro infrastructure

Mass production of H2: - Steaming reforming:

C, CH4 + H2O(g) H2 + CO2 (green gas pollution)- Water electrolysis:

H2O --- H2 + ½ O2 (costly)- Bacteria/algae decomposition of water: very slowly H2 Storage- Physically: Compressed or liquidified: dangerous- Chemically: metal hydride (LiH, LiAlH4) or easy

decomposable compounds of H2 (NH3, H2O2): low volume capacity, costly

H2 refill station and safety issues: safety and cost issues

Challenges for FCs-Materials

• Materials to make anode and cathode are not durable enough for long life use purpose

• Research on new material generations just started and requires a lot of efforts

• Catalyst Pt is so expensive and its capacity is limited for mass use• Catalyst Pt is easily poisoned by CO gas or chemicals

J. Power Sources, 158, 1306 (2006)

Cathode

Anode

Membrane

Fresh After 80 cycles

(*) http://www.nature.com/nmat/journal/v1/n4/pdf/nmat782.pdf

(*)

Research and development of FCs in VN

Not any strategic research on FCs is available in VN

VN wants to work on nuclear E-resource than renewable energy resources

Joint-ventured production of C2H5OH is asking for the investment

The opportunity for VEF fellows of UMich unit

We have expertise working on:- Materials synthesis and characterization for the research on

materials- Chemistry and chemistry engineering for the modeling- Mechanical engineering for designing and testing

Can UMich VEF fellows do something for the development of this research field in VN?

Conclusions

We reviewed some fundamentals of fuel cells in the relevance, operations and current research interests of fuel cells

The basics of FCs are simple, but its research and application requires a lot of knowledge on various disciplines

There are still many challenges in infrastructure for the wide application of FCs

VEF fellows in the University of Michigan unit has an opportunity to work together for the initiation and development of this research field in Viet Nam

Thank you