Thermoelectric Energy Conversion Roberto Dimaliwat, Galena Park High School Galena Park ISD Professor/mentor Choongho Yu, PH.D Mechanical Engineering Dept. Texas A & M University Liang Yin, Graduate Research Assistant

ZT= S² σT/k Thermoelectric Energy Conversion Thermoelectric devices use “bulk materials” with low figure of merit, ZT (efficiency) ZT= S² σT/k Study of the electrical and thermal characteristics of nanowires, The objective is to find out whether the nanowires can replace bulk materials, to produce devices with high ZT. The higher the ZT, the higher the efficiency T = average temperature σ= electrical conductivity S= Seebeck coefficient k= thermal conductivity

Results SiGe nanowires have lower thermal conductivity than bulk materials. As the nanowires get smaller, the thermal conductivity lessens. electrical conductance tends to be constant with temperature change, thus the possible efficiency improvement ZT= S² σT/k Results

Physics and Chemistry TEKS/TAKS Physics TEKS 7B – methods of heat energy transfer. Physics TEKS 5D – conservation of energy &momentum. Physics TEKS 6E – design and analyze electrical circuits Physics TEKS 7A – laws of thermodynamics. Chemistry TEKS 5A – changes in matter, the nature of charge, and the forms of energy. Chemistry TEKS 6A – properties of subatomic particles TAKS Objectives 4 & 5 http://www.tea.state.tx.us/index3.aspx?id=3839&menu_id=793

Hook

The Class Project: Energy Conversion and Conservation Day 1: 1. Hook: Get responses and write on board 2. Do the Pre Test. 3. A short PPT on energy, the different kinds, conservation and transformation using mechanical energy as an example. 4. Discuss the experiment and do parts A (see attached). Days 2and 3. 1. Do Part B and C and students to finalize data and graphs and write the report. 2. Answer Part D. (Questions) See attached. Days 4 and 5. 1. Discuss the lab results. 2. Problem Solving WS 3. Discuss Liang’s slide 4. Post Test

Experiment Set up http://www.youtube.com/watch?v=h570lWTq XOU&feature=related

The experiment (10 groups of 2 to 3 students per group) Objective: To measure how the difference in temperature varies with the voltage generated in a thermoelectric module. Materials (per group) 1 Peltier module 1 clip 2 aluminum plates 1 motor with fan blade 2 transparent plastic containers Hot plate Ice cold water Voltmeter 2 Thermometers  

Part A   1. Place the module between the 2 aluminum plates and secure it with the clip. 2. Connect the wires of the module to the wires of the motor. 3. Place the motor on top of the assembly and attach the fan blade 4. Pour hot water on one of the plastic containers and ice cold water on the other one. 5. Place the containers side by side and dip the aluminum plates, with one side on the cold water and the other side on the hot water. 6. Rotate the fan and observe what happens. Record your observation

1. Turn on the hot plate and heat about 500ml of water Part B   1. Turn on the hot plate and heat about 500ml of water 2. Remove the assembly from the water. 3. Remove the motor/fan connection. 4. Replace the connection with a voltmeter. 5. Empty the plastic containers and place the assembly in the containers just like in Part 1. 6. Put ice cold water in one container and hot in the other. 7. Measure the temperatures on both and record. 8. Measure the voltage on the voltmeter and record. 9. Replace the hot water with hotter water from the hot plate . 10. Measure the temperature and the voltage 11. Repeat the process with different temperatures for about 5 times. 12. Record and graph your data.

Part C. Is the process reversible?   1. Using the same materials, design an experiment to check whether the process is reversible. 2. What other materials do you need? List them down and justify why you need them for. 3. Present the experiment setup and procedures to your teacher for approval. Include the list of additional materials you would need. 4. When you get approval, perform the experiment and gather your data. 5. Analyze your data and write out your report. 6. What are some possible uses of the module and what possible applications can the concept of thermoelectric energy conversion have in your life?

Answer the following questions: Part D. Post Lab Assessment Answer the following questions: What did you observe on the fan when the assembly is placed in the water bath? __________________________________________________________ Explain in terms of energy, what is happening?_________________________ ________________________________________________________________ 3. Explain your data for Part 2. ________________________________________ 4. Explain the graph. ________________________________________________ 5. Compute for the slope of the graph ___________________________________ 6. Is the process reversible? Explain your answer. ________________________________________________________________

Assessment (Pre and Post) Sample Questions: 1. In thermoelectric energy conversion, as the temperature difference increases, the voltage a) stays the same b) decreases c) increases d) decreases exponentially 2. The conservation of energy states that a) energy cannot be created nor destroyed b) can be transformed from one kind to another c) total energy in a closed system is constant d) all of the above

Acknowledgements E3 Team Choongho Yu, Ph.D Mechanical Engineering Dept ,TAMU Liang Yin, Graduate Assistant National Science Foundation Nuclear Power Institute Texas Workforce Commission Chevron