AirBreathing Proton Exchange Membrane Fuel Cell Analysis

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Air-Breathing Proton Exchange Membrane Fuel Cell
Analysis Paul Landrum Jane Sun Advisor Dr. Trung
Van Nguyen

• What is a proton exchange membrane fuel cell
  (PEMFC)?
• An electrochemical device that converts chemical
  energy to electrical power
• Uses hydrogen as a source of fuel
• Fuel Cells Whats the big deal?
• Fuel cells are up to 80 efficient, compared to a
  15-30 efficiency for heat engines used in
  todays cars
• Generates water as its main byproduct, compared
  to numerous harmful pollutants created by fossil
  fuels
• Offers a long lasting alternative to a limited
  fossil fuel supply
• Hydrogen can be obtained from hydrocarbon fuels
  and solar energy, which is an unlimited resource
  oxygen is abundant in the atmosphere
• Can be constructed to various sizes to power a
  wide range of electrical devices (e.g. household
  appliances, automobiles)
• Theory
• A PEMFC consists of two ends at which two
  different reactions occur. Hydrogen gas enters
  the fuel cell at the anode side and undergoes the
  following reaction
• 2H2 ? 4H 4e-
• Oxygen gas enters the fuel cell on the cathode
  side and undergoes the reaction

• One run was performed to see whether hydrating
  the inlet hydrogen stream would affect the stack
  (See Figure 5). Contrary to expectations,
  hydration did not help. This implies that the
  original stack was sufficiently hydrated and
  adding water caused flooding.
• FIGURE 5

• Experiments were run under various conditions for
  a four-cell stack
• No Fan to test the effect of orientation on
  stack performance
• Horizontal 4 runs
• Vertical 3 runs
• Fan to find the optimal fan speed at which
  maximum current is reached
• Unsealed 3 runs
• air was funneled via a Styrofoam cup
• Sealed 9 runs
• Ziploc bag used to seal the air between the
  fan and the fuel cell stack to
• ensure oxygen flow through channels
• Results
• After each experiment, the raw data was analyzed
  to produce a series of plots that are indicative
  of the stacks performance. One of these plots
  shows the relationship between overall stack
  potential and absolute current density. In this
  type of graph, three parts are examined
• Open Circuit Voltage (OCV) This is the initial
  and highest potential the stack can achieve
  before the voltage step-down process. High OCVs
  are desired.

The electrons are led to power an external source
and eventually return to the cathode side while
the protons continue to diffuse through the
membrane to the cathode. On the cathode side,
the electrons and protons reunite and react with
oxygen to form water. The entire procedure is
illustrated in Figure 2.

• Experimentation
• For all experiments, a testing system
  manufactured by Arbin Instruments was employed to
  control and record relevant variables, including
  voltage, current, and temperature.
• Each experiment began with recording the open
  circuit voltage of the fuel cell stack, followed
  by a step-down procedure where current was
  measured while voltage was held constant. The
  voltage was decreased until mass transfer
  limitation was reached due to the slow diffusion
  of oxygen. A fan was used in later trials in
  order to increase oxygen flow to the cells in an
  effort to achieve higher current and thus greater
  power.