Fabrication of High Temperature Thermoelectric Energy Harvesters for Wireless Sensors

Examensarbete för masterexamen
Master Thesis
Nanotechnology (MPNAT), MSc
Köhler, Elof
Implementing energy harvesters and wireless sensors in turbofan jet engines could simplify development procedure and decrease costs. Some of the more difficult areas to measure with wired sensors due to cable wiring, can with wireless sensors and energy harvesters be easily accessed from the cooling channels where the temperature is between 500-900C. This thesis covers the design, analytic modeling, power calculations, synthesis and fabrication of a suitable thermoelectric energy harvester. Known high temperature solutions are based on materials with peak efficiency in lower or higher temperature regions. The modules in this paper are optimized for the temperature range between 600-800C. Chosen materials are n-type Ba8Ga16Ge30 and p-type La-doped Yb14MnSb11, having the highest measured zT value in this region. The use of these materials is uncommon and commercial modules based on these two materials do not exist yet. The total module area was set to 1cm2 and the design goal was to be able to maintain a temperature gradient of at least 200C with as high specific power as possible. The material choices and other design variables like the number of couples, thickness of electrodes, area and height of thermoelectric legs were selected using a model created in MATLAB. The La-doped Yb14MnSb11 was synthesized and identified from x-ray scattering. A measurement of properties was not possible due to insufficient size of the crystals. Ba8Ga16Ge30 was synthesized and resulted in an approximated zT value of 0.83 at 700C. Calculations based on 17 couples and 1mm height of the thermoelectric legs gives a power output of 1100mW/g or 600mW/cm2 with a temperature gradient of 200C. The calculated power from one module yields more than the required power for a single wireless sensor, connecting several modules in series would be preferable, reducing the losses from DC-DC conversion and makes it possible to power entire sensor networks.
Elektrofysik , Övrig elektroteknik, elektronik och fotonik , Energi , Materialteknik , Övrig teknisk fysik , Materialvetenskap , Nanovetenskap och nanoteknik , Produktion , Transport , Electrophysics , Other electrical engineering, electronics and photonics , Energy , Materials Engineering , Other engineering physics , Materials Science , Nanoscience & Nanotechnology , Production , Transport
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