Guide

Main Module | Energy from Mud? Thank a Microbe!
41
Experiment Ideas
exPerimeNt ideaS
end of another), their voltages will be added, and the current will be
averaged between them all.
• When hooking up MudWatts in parallel (i.e. All the (+) ends together and
all of the (-) ends together) their current will be added, and the voltage
will be averaged between them all.
Advanced Level Experiments
Experiment A
Experimental Question: Does the distance between electrodes affect the
amount of voltage, current or power being produced?
Independent Variable: The distance between the electrodes (i.e. the amount
of soil between them)
DependentVariable(s)/Measurables:Voltage, Current, Power
Experiment Notes:
• The amount of soil between the anode and cathode has a couple of
effects. Firstly, the deeper the anode is buried, the less oxygen it will be
exposed to. This is because as oxygen diffuses down through the soil,
it is likely to get consumed by aerobic microbes in the soil. The less
oxygen the anode is exposed to, the lower its redox potential will be.
Since the MudWatt’s voltage is a function of the cathode redox potential
minus the Anode redox potential, burying the anode deeper in the soil
should increase the total voltage created by the MudWatt.
• Secondly, remember that for every electron donated by microbes at
the anode, a positive ion is released into the soil (this is a called a
“proton equivalent” – it can refer to a H+, K+, Na+, or any other positive
ion). Increasing the distance between the anode and cathode will
make it harder for these proton equivalents to diffuse all the way to
the cathode, where they interact with the electron again to form new
compounds, like H2O. So, increasing the distance between anode and
cathode may actually hurt the power generation from the MudWatt
in the long-run, because you may build up proton equivalents at the
anode, which in turn make the environment around the anode more
acidic, which the microbes don’t like.