Design and implementation of a measurement system for automatically measurement of electrical parameters of thermoelectr
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Design and implementation of a measurement system for automatically measurement of electrical parameters of thermoelectric generators
Dmitry Petrov, Fabian Assion and Ulrich Hilleringmann Department of Sensor Technology, University of Paderborn, 33098 Paderborn, Germany ABSTRACT The continues development of thermoelectric generators causes a permanent improvement of their characteristics. New types of thermoelectric generators can work at temperatures up to 1000 K. With this, special measurement equipment is needed to control the electrical parameters of the new developed specimens. The devices must be tested over the whole range of operating temperatures. For each temperature value a series of electrical measurements has to be performed. To establish the maximal output power of the thermoelectric generators, a load resistor with variable resistance has to be connected to the output of thermoelectric generator. The measurement system should measure the electrical current through the load resistor and the voltage over this resistor to determine the device parameters. A large amount of measurement data have to be collected and processed to evaluate the electrical characteristics of the specimen and to present them in graphical form, suitable for the comparison with others specimens. INTRODUCTION The importance of regenerative energy systems has increased during the last years. The conversation between different energy forms, in electrical or combustion engines used in industry or transportation, will always cause some energy losses, mostly as thermal energy. Depending of the efficiency factor of the motor, this can be a considerable part of converted energy [1]. The efficiency of engines is theoretically limited by some fundamental laws, and practically by economical and technical reasons and cannot be improved much more. The other way to reduce the energy losses is to convert the dissipated power back into electrical energy by using thermoelectric generators. In the past the upper limit of operating temperature of thermoelectric generators was limited to 150-200 ºC [2,3]. The new generation of thermoelectric generators (TEG) with interconnects of titanium disilicide (TiSi2) can operate at temperatures up to 1150 K [4]. To improve the efficiency of a TEG, it is essential to check their electrical parameters such as output current and voltage with different electrical load values over the whole range of operation temperatures. This allows to determine the maximal power point (MPP) of the TEG and thereby the maximal efficiency factor and the maximal electrical output power during the device operation. The measurement equipment, used for the electrical tests of TEG, should allow measuring all above-mentioned electrical parameters over the specified range of operating temperatures.
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MEASUREMENT PRINCIPLE Thermoelectric modules are formed by serial connection of p- and n- type semiconductors forming thermocouples, whereas the heat flow is in parallel through all thermocouples. The sides of TEG are called hot and col
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