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Thermoelectric (Peltier--Seebeck) Effect Demonstration

Thermoelectric Generator Background: Unlike traditional dynamic heat engines, thermoelectric generators contain no moving parts and are completely silent. Such generators have been used reliably for over 30 years of maintenance-free operation in deep space probes such as the Voyager missions of NASA. Compared to large, traditional heat engines, thermoelectric generators have lower efficiency. But for small applications, thermoelectrics can become competitive because they are compact, simple (inexpensive) and scalable. Thermoelectric systems can be easily designed to operate with small heat sources and small temperature differences. Such small generators could be mass produced for use in automotive waste heat recovery or home co-generation of heat and electricity. Thermoelectrics have even been miniaturized to harvest body heat for powering a wristwatch. In this video you will see my demonstration of a thermoelectric generator model I bought through Amazon or you can buy it from http://www.xump.com/Science/Thermoele.... I filled the left plastic cup with hot water and the right plastic cup with cold water with ice cubes. This device operates at temperature differentials of at least 20 Deg. F. and it takes about 30 seconds for this differential to appear at the thermoelectric module near the top of the aluminum fins (strips or legs or whatever you want to call them) and the motor to begin to spin. It takes time for the heat/cold to make its way up the aluminum conductors. Note that just one cup can be cooled or heated in order for this device to operate. After a sufficient temperature gradient has been established between the 2 cups of water, place one aluminum conductor or "fin" into each of the included plastic cups. The motor will continue to spin long after the aluminum fins are removed from the cups of hot and cold water because the temperature difference between the fins take time to reach equilibrium temperature and the current stops flowing. Applying an ice cube directly to what was the hot side of the thermoelectric module will reduce the time for the motor to start spinning and it will spin in the reverse direction because the cold side was the hot side in the earlier part of the video. Reversing hot and cold sides reverses the current flow direction through the motor. This device can be connected to a battery up to 12VDC to demonstrate the heating I cooling of the thermocouple sandwiched in the neck of the device. Operate the device only briefly with a battery, as overheating of the thermocouple may result without the use of a proper heat sink. Warning: Surface will become hot! (depends upon input voltage -try using a single 1.5V battery). After the thermocouple is allowed to heat for a few seconds, try switching the switch on top to demonstrate the fan spinning from the energy supplied by the battery. Sample Questions: 1. What happens when the temperature gradient between the 2 cups of water is increased/decreased? Why? 2. What direction is the fan blade spinning? Is it possible to reverse the direction of the fan? How? 3. How are temperature gradient and voltage related? 4. What is the minimum voltage required for the fan to operate (requires voltage meter and connecting wires)? 5. How could this technology be applied to other systems?