Horizon Fitness Bio-Energy Kit User Manual page 12

Experiment 3: Ethanol fuel consumption

When the fan begins to run slower or stops running completely, this means the ethanol present in

the fuel cell chamber is mostly consumed. In normal temperature conditions, the majority of the

ethanol inside the fuel cell chamber turns into acetic acid, which is the main component of vinegar.

Let's investigate the consumed fuel (acetic acid) when the fan begins to run slowly.

Step 1. Place a piece of PH paper under the outlet of the purging tube. (see 3A)

Step 2. Open the valve slowly by sliding the switch towards right side, and release a drop of the

solution onto the pH paper, and then close the valve. You can see the paper color changing to a

reddish color quickly. (see 3B)

Step 3. Dip a new pH paper into the solution container. You will notice that the color of the PH

paper changes very little. (see 3C-3E)

The difference in pH paper coloring indicates the change of the acidity level. Ethanol turns into

acetic acid during the reaction taking place at the anode side of the fuel cell, and the pH of the

solution noticeably changes from pH level 6 to pH level 2 (see 3E) showing a red color. The

chemical reactions taking place at the anode and summarized on page 8 show that acetic acid is

formed as hydrogen protons depart from the ethanol molecule and the water molecule. These

hydrogen protons cross the fuel cell membrane, and the liberated electrons form the electricity

that is able to propel the fan.

Conclusion: The Direct Ethanol Fuel Cell creates electricity by chemically converting the ethanol

solution into an acid solution, which is close to common vinegar. In order for the fuel cell to func-

tion continuously, "spent" fuel must be replaced with new fuel regularly.

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