motivation for new energy technology l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Motivation for New Energy Technology PowerPoint Presentation
Download Presentation
Motivation for New Energy Technology

Loading in 2 Seconds...

play fullscreen
1 / 24

Motivation for New Energy Technology - PowerPoint PPT Presentation


  • 81 Views
  • Uploaded on

Motivation for New Energy Technology. Reduction of localized pollution in heavily populated areas Improved fuel efficiency Reduction in CO 2 emissions Conservation of energy resources PNGV - 3X improvement in fuel economy for automobiles between 1994 and 2004. Some Background on Fuel Cells.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Motivation for New Energy Technology' - tatum


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
motivation for new energy technology
Motivation for New Energy Technology
  • Reduction of localized pollution in heavily populated areas
  • Improved fuel efficiency
    • Reduction in CO2 emissions
    • Conservation of energy resources
      • PNGV - 3X improvement in fuel economy for automobiles between 1994 and 2004
some background on fuel cells
Some Background on Fuel Cells
  • First fuel cell - William Groves, 1839
  • Convert chemical energy to electrical energy
  • Can be thought of as a battery to which the energetic reactants are continuously supplied
  • Have potential to revolutionize global energy production
established applications of pem fuel cells
Established Applications of PEM Fuel Cells

Power source for spacecraft applications

Small scale terrestrial electric power generation

Photo of Apollo 11, taken from Kennedy Space Center web site:

http://images.jsc.nasa.gov/images/pao/AS11/10075233.jpg

potential applications of pem fuel cells
Potential Applications of PEM Fuel Cells
  • Fuel-cell-powered automobiles
    • High efficiency (45-65%)
    • Low tail-pipe emissions
  • Stationary power generation systems
    • Conserve fossil fuels
    • Reduce SOx emissions
  • Battery replacement devices
  • Fuel-cell-powered submarines

Photo obtained from International Fuel Cells web site:

http://www.internationalfuelcells.com/solution/trans/index.shtml

schematic of a pem fuel cell
Schematic of a PEM Fuel Cell

Gottesfeld, S. Adv. Electrochem. Sci. Eng. (1997), 5, 198.

pem fuel cell components
PEM Fuel Cell Components
  • Bipolar gas flow plates
    • Gas distribution to electrodes
    • Current collection from MEA
  • Membrane Electrode Assembly (MEA)
the membrane electrode assembly mea
The Membrane Electrode Assembly (MEA)
  • MEA composition
    • Two electrodes
      • Carbon-fiber paper
      • Coated with catalyst
    • Polymer membrane electrolyte
      • conducts protons
      • electrical insulator
      • separates gases

Gray et. al. Energy & Fuels (1998), 12, 1125.

the polymer electrolyte membrane
The Polymer Electrolyte Membrane
  • Perfluorocarbon sulfonic acid ionomer
    • Ex.: Nafion
      • + High protonic conductivity
      • + Excellent long-term chemical stability
      • - Temp < 100° C
      • - Cost
basic electrochemistry of hydrogen fuel cell
Basic Electrochemistry of Hydrogen Fuel Cell
  • Anode: H2 2H+ + 2e-
  • Cathode: O2 +4H+ + 4e- 2H2O
  • Theoretical cell potential: 1.22 V
voltage loss processes
Voltage Loss Processes
  • Actual voltage for H2 fuel cell is typically 0.6-0.7 V (compared to 1.22 V theoretical)
    • Cathode activation
    • Cell resistance
    • Anode activation
    • Mass transport resistance
hydrogen fuel cell catalyst
Hydrogen Fuel Cell Catalyst
  • Nature of catalyst
    • Historically- Pt catalyst used
    • Last 6 years - reduced Pt loading has substantially reduced the cost without lessening performance
  • Activity of catalyst
    • Anode: Dissociative adsorption of H2
    • Cathode: O2 oxygen anions
fuel storage
Fuel Storage
  • The figure depicts storage volume and weight in comparison to 55 L of gasoline.
  • Attractive candidates for autos
    • Methanol
    • Hydrocarbons

Schmidt et. al. Journal of Power Sources (1994), 49, 302.

reforming of methanol
Reforming of Methanol
  • Reaction: CH3OH + H2O CO2 + 3H2
  • Side reactions:
    • CH3OH CO + 2H2
    • CO + H2O CO2 + H2
  • These three reactions are the origin of the CO and CO2 contaminants in hydrogen fuel cells
anode catalyst poisoning
Anode Catalyst Poisoning
  • CO
    • Produced in fuel reformation process
    • Strongly adsorbs to active sites on catalyst
  • CO2
    • May generate CO via CO2 + H2 CO + H2O
    • Could form COH-type residues with adsorbed hydrogen
anode poisoning by co
Anode Poisoning by CO

Chalk et. al. Journal of Power Sources (1998), 71, 31.

improving fuel cell performance
Improving Fuel Cell Performance
  • Use a platinum alloy as the anode catalyst
    • Improves anode CO and CO2 tolerance
    • Reduces the overvoltage associated with the cell reaction
  • Platinum-ruthenium alloys have been found to be effective catalysts.
slide17

Weight Percent Ruthenium

80

90

100

20

40

60

70

0

10

30

50

2400

2334 C

2200

L

2000

70

79

1800

1769 °C

Temperature °C

1600

Pt

+

Ru

Pt (fcc)

Ru (hcp)

1400

1200

62

80

1000

100

50

60

80

90

20

10

30

40

0

70

Atomic Percent Ruthenium

The Platinum-Ruthenium Phase Diagram

direct methanol pem fuel cells
Direct Methanol PEM Fuel Cells
  • Major advantage: hydrogen reformation is bypassed
  • In the past, DMFC’s shunned for low power density (orders of magnitude less than that of hydrogen fuel cell)
  • Recent improvements have been immense
    • Currently under intense study
dmfc redox reactions
DMFC Redox Reactions
  • Reactions
    • Anode: CH3OH + H2O CO2 + 6H+ + 6e-
    • Cathode: 3O2 + 6H+ +6e- 3H2O
  • Catalysts
    • Anode: Pt-Ru nanoparticles
    • Cathode: Pt
fuel cell stack
Fuel Cell Stack
  • Fuel cells must be combined to increase power capability
  • Combination: voltages additive
pem fuel cell membrane electrode assembly mea and stack
PEM Fuel Cell Membrane Electrode Assembly (MEA) and Stack

Gray et. al. Energy & Fuels (1998), 12, 1127.

economics of fuel cells
Economics of fuel cells
  • In parentheses is the max cost for which fuel cells would be cost effective in that application
  • Note reduction in Pt utilization with time
  • PEM fuel cells can not yet compete with gas-powered cars
  • PEMFC’s could be competitive in buses and stationary systems
advantages of pem fuel cells
Advantages of PEM Fuel Cells
  • High power density (~6kW/m2)
  • High efficiency
  • Reliable
  • Materials are durable and benign
  • No emissions (from the fuel cell)
conclusions
Conclusions

PEM fuel cells are very promising

Tremendous advances have been made in the past 6 years

Appear to be close to large-scale commercialization

Much development still needed