(see also fuel_cell for futher info…)

This design is made of two containers, bridged together with a salt bridge (rope dipped in saturated salted water, wrapped in insulating tape), one with pond sludge, another with clear water.

An airpump feeds clean water with oxygen for the reduction reaction: protons coming from sludge by the salt bridge, together with electrons coming from sludge by the wires, recombine with oxygen to make water. The airpump allows high current to be produced.

Performances: 6V peaks, 200+ mA with airpump, 170 mA without.

This design is made from one container, sludge at the bottom, smart gel proton exchanger on top of it, and clean water on the very top. No air pump, but lower performances. Something like charcoal is used as an electrode material.

• Wiring as electrode.

• Peak voltage at 100mV, drops to 60, stable.
• Voltage changes with oxygenation - + 10 mV.

• Layed down the jar in a crate covered with a plastic bag and filled with water.
• Five times bigger cathode, made of wiring, and then replaced by a flattened aluminium can.

• Augemented cathode surface area & reduced water layer width for oxygen access.

• No improved voltage with bigger wiring cathode.
• Improved voltage (300 mV) with aluminium can cathode.
• When putting directly the multimeter cathode in water, we obtain 600 mV.

• The geometry of the multimeter cathode may be better for voltage than the one made of wiring or aluminium can. However, surface area is necessary to obtain current.

• Flattened aluminium can as electrode.
• Thick paper sheet as PEM.

• Reduced PEM width.
• Augmented electrode (both) surface area.

• Negative voltage when putting a rock on cathode to maintain it in water.
• No improved voltage by the new flat design.
• Still no current measurable, probably very low.
• The addition of coke drops (H+) at the cathode do not help current generation.

• Is paper a good PEM ?

• Two bottles
• Saline bridge made of rope dipped in salt solution & wrapped in tape.
• Hard-drive metal box as electrode material.

• The addition of coke drops (H+) at the cathode do not help current generation.

• Two multimeter electrodes directly in water: about 30 mV.
• One mutimeter electrode on aluminium can dipped in water, one directly in water: about 30 mV.
  • If water is not clean, voltage increases up to 100 mV.
• Two multimeter electrodes in the mud: 10-80 mV depending on location.

• Maybe it needs a longer period to get started - eating up all the oxygen around the anode.
• Maybe our PEMs are not good.

• Is the air pump giving more than what it pumps in terms of energy ?
• Could we make a mechanical airpump coupled with a windmill ?
• Could we improve the cathode design to remove the airpump ?

• Could we use compost tea as a sludge source ? Does it also work with usual soil ?
• How can we keep feeding the sludge, to make the fuel cell operation continuous ?

• Does the efficiency drops if we use flat electrodes from dead batteries ?