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Project Summary

Difficulty	7
Time required	Long (a couple of weeks)
Prerequisites	None
Material Availability	Specialty item required. See the Materials and Equipment list for details.
Cost	Very High (over $150)
Safety	Minor injury is possible, so wear safety goggles. To do this science fair project, you will need to electrolyze water into hydrogen and oxygen. Hydrogen is flammable, so keep the fuel cell and hydrogen storage tank away from sparks.

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Abstract

Objective

In this science project, you will learn how a fuel cell works and compare its efficiency to that of an internal combustion engine.

Introduction

A fuel cell is an electrochemical device that converts the energy in chemicals into electricity. A battery is also an electrochemical device that converts chemical energy into electricity, but there is a limited supply of chemicals in a battery, so eventually the chemicals are all consumed and the battery no longer supplies electricity. In a fuel cell, however, the chemicals can be replenished, so the fuel cell can continue to produce electricity.

In a proton exchange membrane fuel cell (PEMFC) the fuel used is hydrogen and the byproduct of the PEMFC is clean water. The standard method of creating electricity is by burning fossil fuels which can be harmful to our environment. A big advantage of fuel cells is that they do not create pollution. In addition, the fuel cell has no moving parts so it doesn't break down like an internal combustion engine can. This means that there could be fewer breakdowns for a car that uses a fuel cell, compared to a car with a standard internal combustion engine.

The fuel cell was first demonstrated by William Grove in 1839. The first thing that Grove did was to pass a current through water and separate water into its components: hydrogen and water. This process is called electrolysis. He then wondered if electrolysis could be reversed. The answer was yes. When the hydrogen and oxygen recombined, an electric current was produced. While William Grove invented an interesting device, the fuel cell remained a lab curiosity for many years due to the expense of making one, as well as other complexities. Finally, in the 1930s, Francis Thomas Bacon developed an alkali electrolyte fuel cell, which was eventually used in NASA's Apollo missions.

The fuel cell is made up of five parts: the anode, a catalyst layer, an electrolyte layer, another catalyst layer, and finally, the cathode. Fuel, such as hydrogen gas in the case of a PEMFC, enters the system at the anode. The hydrogen gas then reacts with the catalyst layer, ionizes, and is separated into hydrogen ions and electrons, as shown here:

In the dissolution reaction above, two hydrogen molecules are ionized into four positively charged hydrogen ions and four negatively charged electrons. As described above, this reaction is called electrolysis. The electrons move externally out of the PEMFC into the cathode. This is because the electrolyte, the layer sandwiched between the anode and the cathode, allows only positive H+ ions to pass through. The electrons that move out of the fuel cell (electricity) are used to power loads such as lights or motors. At the same time, oxygen gas comes into the fuel cell at the cathode. The oxygen, electrons, and hydrogen ions react at the cathode catalyst and create water, as shown in the reaction below:

Figure 1. This is a schematic of a proton exchange membrane fuel cell (PEMFC). The two catalyst layers are between the anode and the electrolyte, and the electrolyte and the cathode. (U.S. Department of Energy, 2007.)

The second reaction shown above is typical of a PEMFC using hydrogen gas as the fuel. There are several different types of fuel cells, each with advantages and disadvantages. Some of the advantages of the PEMFC are that they start up rapidly and are compact and lightweight. One major disadvantage is that the electrolyte is required to be saturated with water for optimal operation.

Fuel cells are used in many industries, including consumer electronics, telecommunications, and transportation. Several cities have buses that are powered by fuel cells instead of by internal combustion engines, which are powered by gasoline.

Figure 2. This is a zero-emission bus. (U.S. Department of Energy, 2007.)

In this science fair project you will accomplish two things. You will help the environment and learn about this area of science by investigating the efficiency of the PEMFC. The thermal efficiency of the standard internal combustion engine is much less than 40%. Which is the more efficient engine?

Terms, Concepts and Questions to Start Background Research

Research the following terms and questions before beginning this science fair project.

• Fuel cell
• Electrolysis
• Anode
• Catalyst
• Electrolyte
• Cathode
• Ionize
• Efficiency
• Ohm's law

Questions

• How many different kinds of fuel cells are available?
• What are the advantages and disadvantages of each of the different kinds of fuel cells?
• How do the different parts of the fuel cell work?
• What is the efficiency of a standard internal combustion engine?

Bibliography

Check out the following sources to learn more about fuel cells.

• Wikipedia Contributors. (2008, April 28). Fuel cell. Wikipedia: The Free Encyclopedia. Retrieved April 28, 2008 from http://en.wikipedia.org/w/index.php?title=Fuel_cell&oldid=208823058
• Bonneville Power Administration. (2004). Investigation 7: Energy Efficiency. Retrieved May 7, 2008 from http://www.bpa.gov/Energy/N/projects/fuel_cell/education/Docs/7-EnergyEfficiency.pdf
• Nice, K. and Strickland, J. (2000). How Fuel Cells Work. Howstuffworks. Retrieved May 9, 2008 from http://www.howstuffworks.com/fuel-cell.htm
• The United States Department of Energy has a lot of information on fuel cells. Here is a link that describes the different fuel cells:
  U.S. Department of Energy. (2007, March 8). Fuel Cells. Retrieved May 16, 2008 from http://www1.eere.energy.gov/hydrogenandfuelcells/fuelcells/fc_types.html
• The following website has some good information on the history of the fuel cell:
  National Museum of American History Smithsonian Institution. (2007, September). Collecting the History of Fuel Cells. Retrieved May 19, 2008 from http://americanhistory.si.edu/fuelcells/

Materials and Equipment

• Science fair fuel cell kit; available at www.fuelcellstore.com, SKU: 7235009
• Distilled water
• Fresh AA batteries (3)
• Resistor (1) less than 0.5 ohms. You can purchase this at http://www.mouser.com , part number 660-CF1/4CT52RR30J. If you can't find a resistor this low you can use 4 or 5 1-ohm resistors in its place.
• Digital multimeter, there are several models available at RadioShack for different prices, such as RadioShack part #22-813, www.radioshack.com/home/index.jsp. Always select a multimeter that fits the requirements of what you are testing. For this science fair project, you will need a multimeter that can test currents from 0–300 mA and can test voltages from 0–10 V.
• Alligator clip cables (3), preferably red and black; RadioShack part #278-1157, www.radioshack.com/home/index.jsp
• Helper
• Timer
• Safety goggles
• Lab notebook

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Experimental Procedure

Fuel Cell Setup

1. Open the fuel cell kit and make sure that you have all of the pieces described in the operating instructions manual. Read through the manual to confirm that you have all of the pieces and to understand how your fuel cell operates.
2. Included in the kit will be an "RFC," which stands for reversible fuel cell. This means that the cell can be used to electrolyze water and as a fuel cell that creates power.
3. The top of the fuel cell has a sticker that shows which side is the hydrogen side and which is the oxygen side. The bottom of the fuel cell has a plastic stand that allows the fuel cell to sit upright.
4. The first step is to hydrate the electrolyte material. Take the syringe and suck water into it by placing the tip of the syringe into the distilled water and pulling the plunger. Suck about 4 milliliters (mL) into the syringe.
5. Take the protective tubing off of the cell. Take an extra piece of short tubing (included in the kit) and push it onto the bottom inlet on the hydrogen side of the fuel cell. The fuel cell is labeled on top with a sticker for convenience.
6. Now push the syringe onto the tubing and slowly inject the distilled water into the fuel cell. After 2-3 seconds you will see water coming out from the top inlet.
7. Take the short tubing off of the bottom inlet on the hydrogen side and connect it to the bottom inlet of the oxygen side. Repeat steps 4 and 6.
8. To obtain the best operation of the fuel cell, the electrolyte needs to be hydrated, but the fuel cell should not be full of water. Remove excess water from the cell. Use the empty syringe to push and pull the excess water from the fuel cell. You can also tap the fuel cell gently.
9. Once the excess water has been removed from the fuel cell, plug the top inlets on both the hydrogen side and the oxygen side. Construct plugs using the short pieces of tubing, along with the included clips. Open one of the clips and then slide the tubing through the clip almost all the way to the end. Close the clip. This squeezes the end of the tubing shut. Plugging the top inlets prevents the electrolyzed gases from escaping. See Figure 3. Once this is completed, the unit is ready for electrolysis.

   Figure 3. Shown are the short tubing and clips for constructing the plugs.

Electrolysis

1. The first step to using this unit as a fuel cell is to electrolyze water. This creates the fuel. Caution: Hydrogen is flammable, so keep the fuel cell and hydrogen storage tank away from sparks.
2. Connect the hydrogen and oxygen storage tanks exactly as described in the operating instructions manual. Fill both outer cylinders with distilled water up to the "0" mark.
3. Connect the long tubing piece to the inlet of the inner cylinder. Make sure that the little notch on the bottom of the inner cylinder of the tank is not blocked by the rim of the outer cylinder of the tank. Also confirm that the inner cylinder is seated tightly inside of the outer cylinder. Write down the water level in your lab notebook in a data table.
4. Connect the hydrogen storage tank, via the tubing, to the bottom inlet on the hydrogen side and the oxygen storage tank to the bottom inlet of the oxygen side. Make sure that the tubing is tightly sealed on both inlets.
5. Insert the 3 AA batteries into the empty battery pack. Make sure to connect the batteries in the correct polarity. There is a diagram on the inside of the pack that you can follow.
6. Now get the timer, digital multimeter, and resistor ready for measurement. Be sure to put on your safety goggles. If you are using more than one resistor, then twist all of the metal leads on one end of the resistors together and the leads on the other end of the resistors together. See Figure 5 for how the resistors should look. Take your multimeter and measure the value of the resistor or combination of resistors. Read the multimeter instruction manual to learn how to measure resistance. Note the resistance down in your lab notebook.
7. Take the black alligator cable and clip one end to the black wire from the battery pack. Clip the other end to the black connection of the fuel cell. Clip the red cable to the red wire from the battery pack and the other end of the alligator cable to the resistor. Use the third alligator cable to clip to the other end of the resistor. Finally, clip the other end of the third alligator cable to the red connection of the fuel cell. The resistor is in series with the battery pack and will allow you to measure the current being supplied to the fuel cell. See Figure 4 for a diagram of the circuit.
8. As soon as you clip the red alligator cable to the red connection of the fuel cell, the distilled water will start to electrolyze into hydrogen and oxygen. Prior to doing this, make sure that the timer is ready. Have your helper be responsible for the timer. Clip the cable onto the fuel cell and start timing the electrolysis. Figure 5 shows the fuel cell in electrolysis mode.
9. You will see evidence of electrolysis when the level of the distilled water in the inner cylinder decreases. Hydrogen gas is pushing the water out. You can see the amount of hydrogen created by reading the change in water level from step 2. Note this down in your lab notebook.
10. Using the multimeter, determine the voltage drop across the fuel cell. This is the input voltage. Measure across the fuel cell's red and black terminals. Read the document Using a Multimeter in the Science Buddies Science Fair Project Guide to learn how to use a digital multimeter to measure voltage. Record the data in your lab notebook. Having your helper help keep track of the time, take a measurement 10 seconds after electrolysis starts. Then take three additional voltage measurements; one after 30 seconds, one after 1 minute and then after 1.5 minutes. Record the data in your lab notebook. Average the voltage measurements to obtain the average input voltage.
11. Using the multimeter, determine the current that is being supplied to the fuel cell. This is the input current. Measure the voltage drop across the resistor. Record the data in your lab notebook. Measure the voltage drop across the resistor each time that you measure the input voltage to the fuel cell. Once you know the voltage drop across the resistor and the value of the resistor you can use Ohm's law to calculate the input current. Simply divide the voltage drop across the resistor (in volts) by the value of the resistor (in ohms). The units of measure for current is amperes. Record the data in your lab notebook. Average the current measurements to obtain the average input current.
12. Time the electrolysis until the hydrogen tank is full. You will know that you have filled the hydrogen tank when all of the water in the inner cylinder has been displaced and you see the water bubbling. Stop the timer and record the time in your lab notebook. Continue electrolyzing oxygen. Once you see the oxygen tank bubbling, wait for an additional 15 seconds. This will clear out any additional water in the fuel cell. The fuel cell operates at its best when there is no extra water in the fuel cell. Disconnect the battery pack from the fuel cell.
13. Calculate the energy to electrolyze hydrogen. Energy is the amount of power expended in an amount of time. Electrical power is defined in Equation 1 and Energy is defined in Equation 2. Equation 3 is derived by substituting 'power' in Equation 2 with the definition of 'power' from Equation 1.
14. Using equation 3, calculate the energy necessary to electrolyze water into hydrogen and oxygen and record the value in your lab notebook. Please notice that in equation 3 you are calculating the input energy using the average current. The accurate way to calculate the input energy is to first integrate the current over the time it took to electrolyze, and then multiply that by the average voltage However, for the purpose of this science fair project, you can estimate the integral by averaging the current.

    Equation 1:

    Power	=	Average Current × Average Voltage
    P	=	(I)(V)

    P is the power in watts (W). I is average current in amperes (A). V is average voltage in volts (V).

    Equation 2:

    Energy	=	Power × Time
    E	=	(P)(t)

    E is energy in watt-seconds or joules (J). P is power in watts (W). t is time in seconds.

    Equation 3:

    Input Energy	=	((Average Input Current) × (Average Input Voltage)) × (Time to Electrolyze)
    E	=	(I)(V)(t)

    E is the energy in joules (J). I is the average current in amperes (A). V is the average voltage in volts (V). t is the time taken in seconds to electrolyze a full storage tank of hydrogen.

Figure 4. This is a diagram of the circuit for this project.

Figure 5. (a) This is the battery connection for electrolysis mode. (b) Several resistors connected together to make a smaller resistance.

Creating Energy

1. Connect a load to the fuel cell. Included in the kit is a small motor. This will be the load.
2. Get the timer and digital multimeter ready.
3. Connect the motor in the same way as the battery pack. Connect the motor to the fuel cell in the correct way, as follows. Take the black alligator cable and clip one end to the black wire from the motor. Clip the other end to the black connector on the fuel cell. Take the red alligator cable and clip one end to the red wire of the motor. Clip the other end to the resistor. Take the third cable and clip it to the other end of the resistor. Finally, clip the free end of the third cable to the red connector on the fuel cell. Immediately start timing the fuel cell mode. The resistor is in series with the motor and will allow you to measure the current the fuel cell is supplying to the motor.
4. As soon as the connection is made from the fuel cell to the motor, the post on the motor will start rotating. It will make a whirring sound. To make the motor action more visible you can attach a propeller or blade onto the motor's post.

   Figure 6. This is the fuel cell supplying voltage to the motor.

5. As the reaction of the fuel cell continues, the hydrogen in the storage tank is being consumed. You will see water re-entering the inner cylinder.
6. Using the multimeter, measure the voltage being supplied by the fuel cell to the motor, after the motor settles down. Have your helper help you keep track of the time. Measure the voltage across the fuel cell terminals. Take three additional measurements after 2 minutes, after 5 minutes, and after 8 minutes, then average the voltage data. This is the output voltage. Record the data in your lab notebook.
7. Using the multimeter, measure the current being supplied by the fuel cell to the motor right after you take the voltage measurement. Measure the voltage across the measurement resistor. Use Ohm's law to calculate the current. Take three additional measurements—after 2 minutes, after 5 minutes, and after 8 minutes—then average the current data. This is the output current. Record the data in your lab notebook.
8. Stop the timer as soon as the motor stops running. You will know when the motor stops running when you stop hearing the whirring sound. Record the time in your lab notebook.
9. Use Equation 4 to calculate the output energy.

   Equation 4:

   Output Energy	=	(Average Current Supplied by FC) × (Average Voltage Supplied by FC) × (Running Time of Motor)
   E	=	(I)(V)(t)

   E is the output energy in joules (J). I is the average current supplied by the fuel cell, in amperes (A). V is the average voltage supplied by the fuel cell, in volts (V). t is the time the motor runs in seconds.

10. With the input energy and the output energy, calculate the efficiency of the fuel cell for every trial with Equation 5. Record this number in your lab notebook.

    Equation 5:

    Efficiency =

    Output Energy Input Energy

11. Repeat this experiment at least two more times, starting from "Fuel Cell Startup" through "Creating Energy." Prior to every trial, gently take the inner cylinder out of the outer cylinder for both the hydrogen and oxygen storage tanks. Disconnect the storage tanks from the fuel cell. Unplug the top inlets on the fuel cell. Gently shake the fuel cell to remove any excess water. Take a short length of tubing and attach it to the bottom inlet of the hydrogen side. Use the syringe to blow air into the fuel cell. This will move any excess gases out of the fuel cell. Stagnant gases in the fuel cell will affect efficiency. Repeat on the oxygen side.
12. Plot the efficiency of the fuel cell. Compare it to the efficiency of a standard internal combustion engine. Label the x-axis Trial and the y-axis Efficiency.

Variations

• How does temperature affect the efficiency of the fuel cell? After electrolyzing water, try placing the fuel cell in the butter compartment of your refrigerator for 30 minutes and then repeating the “Creating Energy” steps of the project. Never freeze the fuel cell. Freezing the fuel cell will damage it. Try placing the fuel cell on a warm window sill or using a hair dryer to heat up the fuel cell.

• For more science project ideas in this area of science, see Energy & Power Project Ideas.

Credits

Michelle Maranowski, PhD, Science Buddies

Last edit date: 2009-03-13 14:50:00