Figure 15.
Adding
Washer
Spacers.
Figure 14. Parallax BS2 Water
Decomposition Voltage Schematic.
fuel cell’s inability to expel the
hydrogen and oxygen gasses that
form on the metal electrodes below a
certain voltage; in this case, about
1.47 volts as compared
with 1.23 volts. Many
other factors are
involved in this difference of
decomposition voltage; however, the
reasons for these differences are
beyond the scope of this experiment.
So let’s do the experiment to find out
for ourselves.
First, set up
the equipment as
shown in Figure
14. I’ll only show
the Parallax setup
for sake of space,
but the PICAXE
setup is basically
the same. In
effect, we’re
Figure 16.
Determining the
Exact Water
Decomposition
Voltage.
attaching the solar panel to the fuel
cell through a one ohm current sense
resistor to see how much voltage and
current are required to begin
electrolysis. Also, purge any excess
hydrogen that may be left in the
cylinder. Next, slowly rotate the solar
panel into the light and watch the
voltage increase until it “jumps” and
current begins to flow (Figure 15).
This is when electrolysis begins and
the voltage jump is indicative of the
internal resistance of the electrolyzer
going from a near short circuit to
something higher, thus allowing
current to flow. You learned about
this in the Electrolysis Mode
experiment.
Now tilt the solar panel away
from the light to stop the
electrolysis momentarily. Then
“very slowly” adjust it back into the
light until you find the exact
What is a fuel cell?
A fuel cell is a device that converts the chemical energy of a fuel
(hydrogen, natural gas, methanol, gasoline, etc.) and an oxidant (air or
oxygen) into electricity. Fuel cells are classified by their electrolyte material. In
principle, a fuel cell operates like a battery as both batteries and fuel cells are
electrochemical devices. Unlike a battery, however, a fuel cell does not run
down or require recharging. It will produce electricity and heat as long as fuel
and an oxidizer are supplied. As such, both have a positively charged anode,
a negatively charged cathode, and an ion-conducting material called an
electrolyte.
Electrochemical devices generate electricity without combustion of the
fuel and oxidizer, as opposed to what occurs with traditional methods of
electricity generation. Fuel cell construction generally consists of a fuel
electrode (anode) and an oxidant electrode (cathode) separated by an ion-conducting membrane. Oxygen passes
over one electrode and hydrogen over the other, generating electricity, water, and heat. Fuel cells chemically
combine the molecules of a fuel and oxidizer without burning or having to dispense with the inefficiencies and
pollution of traditional combustion (i.e., the Carnot Cycle).
Source - The U.S. Department of Defense (DoD) Fuel Cell Test and Evaluation Center (FCTec) www.fctec.com/fctec_basics.asp
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May 2010