ME3264: LAB 4 Fuel Cell

Transcription

1 ME3264: LAB 4 Fuel Cell Professor Chih-Jen Sung - Revised tjm Spring 2017 OBJECTIVE The objectives of this laboratory are as follows. (a) Become familiar with the operation of a Proton Exchange Membrane (PEM) H 2 /O 2 fuel cell. (b) Measure and report actual voltage and current outputs of a system. (c) Build a DAQ VI to display and record data at pre-set intervals. (d) Estimate the efficiency of producing energy for PEM fuel cell. PREPARATION 1. Review textbook materials on fuel cell. Understand the working principle of PEM H 2 /O 2 fuel cell and the typical voltage and current relationship in a fuel cell. 2. Review materials on LabVIEW. 3. Homework: Following the derivations in the lecture slides, determine the equilibrium potential and the ideal fuel cell efficiency, if the product water is in (1) liquid form and (2) vapor form. EQUIPMENT LIST AND DESCRIPTION Heliocentris Hydro-Genius TM Professional Model Fuel Cell Stopwatch or phone with a stopwatch app 5 red, 5 black test leads Distilled water Amprobe Am-20 handheld voltmeter for testing battery voltage & acquiring amperage. National Instruments Data Acquisition System (DAQ), file available on MENAS server. Equipment specification sheets (see Appendix) NOTE: Fuel membranes are easily rendered inoperable by contaminated water. USE ONLY DISTILLED WATER supplied in the lab. Advise your TA if you need additional distilled water. M.J. Moran and H.N. Shapiro, Fundamentals of Engineering Thermodynamics, Chapter 13. Prof. Chih-Jen Sung Page 1 of 5 Rev. Spring 2013

2 EXPERIMENTAL AND REQUIREMENTS I. Electrolyzing Water into Hydrogen and Oxygen Note starting levels of each gas. If water level is below 10 ml have the TAs re-fill. Insure that the hose clamps leading to the fuel cell are closed. For operation of the fuel cell and motor circuitry it is more efficient time wise to generate oxygen and hydrogen by applying a power source directly to the electrolyzer instead of using a the solar panel. 1. See that the water levels in the tubes are within 0-5ml, if not have your TA fill the columns. Make sure the tubes from the columns to the fuel cells are clamped off. 2. A double D battery pack (Fig. 1) is wired directly to the electrolyzer. Check the batteries with a voltmeter for at least 1.4 volts. If below 1.4V ask your TA for fresh batteries. 3. Insert the batteries into the pack insuring you get the polarity correct. You should see the gases starting to form within 1 minute, (Fig. 2) if not, check the connections or ask your TA to inspect the set up. 4. Generate about 50-60ml of hydrogen, remove the batteries and you may proceed to part III. You may generate more gases as needed while doing the experiments in part III. DO NOT LET THE ELECTROLYZER RUN DRY. Fig. 1 Fig. 2 II. Producing Electricity in the Fuel Cell Prof. Chih-Jen Sung Page 2 of 5 Rev. Spring 2013

3 1. The small jumper tube connecting the bottom hose barbs of the lower fuel cell should be disconnected from the hydrogen at this point. 2. Release the hose clamps and allow approximately 5 10 ml of each gas to travel to the fuel cell. This purges the lines and introduces fresh gases to the cell. **The gas will travel up to the fuel cell quickly! Be careful not to let all of your gases escape.** 3. Re-clamp and connect the jumper across the two lower hose barbs. This seals the system. 4. Connect the DAQ leads to the propeller positive and negative connections. See Fig. 3. Fig. 3 Single fuel cell connections. 5. Connect leads from the top fuel cell only to the propeller connections. The propeller should start. If not, check all connections. 6. Start the DAQ to record voltage over time and the stop watch (or use your phone) to record time until the propeller stops. Report start, end, and mean voltage, and total propeller run time. Your DAQ will have a real-time display or table on the front panel and be able to save the data to be opened in a spreadsheet program. 7. When the propeller stops, disconnect the negative lead from the fuel cell to the propeller. Repeat steps 1 6 at least 3 times to report overall average voltages and run times. 8. You should continue to produce gases (no data taking required) since you will now be making dual cell runs in series and in parallel. III. Compare Series and Parallel Output 1. Insure you have 40 50ml of H 2 again. 2. Connect two fuel cells in PARALLEL (see Fig. 5) and repeat steps 1 7 in Part II (Step 5 ignored) to run the propeller. Make at least 3 runs in parallel. Prof. Chih-Jen Sung Page 3 of 5 Rev. Spring 2013

4 Fig. 4 Parallel connections. 3. Connect two fuel cells in SERIES (see Fig. 3) and repeat steps 1 7 in Part II (Step 5 ignored) to run the propeller. Make at least 3 runs in series. Fig. 5 Series connections. 4. Compare the results obtained and report what differences you saw between the single cell, parallel and series outputs. In your discussion of the results, consider why these are indeed labeled parallel and series and what the benefits of each would be in application. 5. Determine and compare energy efficiencies. How do you find an optimum operating condition, namely maximum efficiency at as high an output as possible? 6. In the fuel cell, the reverse of electrolysis takes place, namely the gases stored during electrolysis are converted back into water. Altogether such a cycle involves energy losses, determine the overall efficiency. Is the fuel cell an efficient energy device? Prof. Chih-Jen Sung Page 4 of 5 Rev. Spring 2013

5 Appendix: Technical Data Prof. Chih-Jen Sung Page 5 of 5 Rev. Spring 2013