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Gwen Groover

Table of Contents

Fuel Cells

Questions from the first presentation

  1. What is the proposed source for the hydrogen used in hydrogen fuel cells? Also, how large can fuel cells get (as in power output)?
  2. How do ethanol fuel cells work and what kind of efficiency do they get?
  3. More pictures and big-text bullet points, please – I have bad eye-sight. Also I had trouble hearing. . . Anyway, you described what fuel cells are, but what practical considerations are there when making fuel cells? How well do they perform and how does might this fit into larger social concerns, specifically?
  4. How do fuel cells work? Maybe you meant to explain this, but just didn't get to it. I feel like I didn't learn much about fuel cells from your presentation.
  5. I still don't feel I have a very good understanding of the chemistry behind the operation of fuel cells... How do they work, and what are the challenges preventing us from being able to scale up fuel cell production (particularly of hydrogen fuel cells) in an economically-viable fashion?
  6. What significant current technologies rely on fuel cells for energy?  Also:  What happens to the cells once they are spent?
  7. Can you teach us the chemistry underlying fuels cells?  Maybe batteries as well so we understand the difference...?
  8. What is the difference between a rechargeable battery and fuel cell?
  9. Is there any degradation associated with repeated refueling of fuel cells?
  10. What’s the energy density of the cells—you mentioned putting them in cars; can a fuel cell with enough power to drive a car fit in a car?
  11. How stable and safe are they? I saw the most recent James Bond movie..…
  12. Is there an economic advantage over rechargeable batteries?
  13. What are fuel cells used for?
  14. What is the history of fuel cell development?
  15. What does the future of fuel cells look like?
  16. What is the price of a fuel cell? the efficiency?
  17. What considerations are there in catalyst poisoning?

First Presentation

  • What’s the difference between a fuel cell and a battery?
    • Fuel cells use reactant from external source, which must be refilled periodically, while batteries are closed systems.
  • How do they work?
    • Fuel cells work by catalysis, separating the protons and electrons of the reactant and forcing the electrons through a circuit to obtain useable electrical energy; the catalyst is frequently something like platinum group metal or alloy. Another catalytic process puts the electrons back in, combining them with the protons and oxidant to form waste products (often simply something like water or CO2).
    • A typical fuel cell produces voltage of 0.6 V to 0.7 V at full rated load; voltage decreases as current increases. They can be combined in series and parallel to deliver desired energy - in series yields higher voltage, while in parallel, higher current; this is called a fuel cell stack.
  • What sorts are common? How well do they work? What’s the catch on each?
    • Proton exchange fuel cells
      • Hydrogen-oxygen proton exchange membrane fuel cell (PEMFC): “archetypal hydrogen fuel cell”; probably one of the most practical to implement on a mass-consumer scale, as hydrogen isn’t enormously difficult to produce.
    • Fuels can include hydrogen, hydrocarbons, and “chemical hybrides”; oxidants include oxygen (often from air), chlorine, and chlorine dioxide
    • US Department of Energy (DoE) reported in 2009 that on mass-production scale, 80-kW automotive fuel cell systems cost about $61 per kilowatt; goal is $35 per kilowatt. (per Wiki, with no source cited)
  • What are the advantages of fuel cells over other methods of power generation?
    • No moving parts and no combustion, so in ideal situations can achieve ridiculously high efficiency - one source claims 99.9999% efficiency is possible in ideal situation, equivalent to 1 minute of downtime over a period of several years. This also makes them ideal for use as power sources in remote locations
    • Minimal hazardous emissions, especially with hydrogen-oxygen fuel cells, where the only byproduct is water.
    • They can be extremely practical for energy storage, for example as a way to store solar energy, as shown by a pilot program in Washington. (Their site's a bit unclear on some things, so details might not be exact.) Solar panels power an electrolyzer to produce hydrogen, which is then stored. When possible, power is generated from solar or wind energy; when not, the stored hydrogen is used as fuel for a fuel cell, which acts as a backup generator. The group in question is on a tiny island off the coast with no large-scale power grid, so this is a small-scale setup for power generation, but it should scale up reasonably well.

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References

United States. Department of Energy. Energy Efficiency & Renewable Energy. Fuel Cells Technologies Program. Fuel Cells. Fuel Cells Technologies Program, 23 Jun 2009. Web. 3 Apr 2010. <http://www1.eere.energy.gov/hydrogenandfuelcells/fuelcells/index.html>

United States. Department of Defense. Fuel Cell Test and Evaluation Center. FCTec. Fuel Cell Test and Evaluation Center, 2010. Web. 4 Apr 2010. <http://www.fctec.com/index.asp>

Zhang, Jiujung, ed. PEM Fuel Cell Electrocatalysts and Catalyst Layers: Fundamentals and Applications. London: Springer-Verlag, 2008. SpringerLink. Web. 4 Apr 2010. <http://www.springerlink.com/content/mk263n/>