Thermoelectric Micro-Scale Generation by Carbonaceous Devices

The paper reports on research focused on the use of largely available carbonaceous materials, such as graphite, carbon black and chars, as thermoelectric materials for micro-generation at high temperature. The key feature is the possibility to ignite the thermoelectric device to self-sustain electric generation. The results of the tests performed with such materials, under both cold and hot conditions, showed that a significant change of the electromotive force, with absolute increase up to three orders of magnitude, occurred under hot conditions with flame irradiation, achieving measured values of electromotive force up to 55 mV, in the best case. Monoliths based on biomass chars and covered with a layer of gunpowder gave rise to similar variation of the Seebeck coefficient, as the case of the flame exposed samples. This result confirms the basic idea of the investigation and the possibility of generating an electrical peak in a self-sufficient combustion thermoelectric device with power up to 1.0 W. A theoretical assessment has been proposed to provide an interpretation of the observed phenomenology, which is related to the non-linear dependence of the material properties on temperature, in particular the Seebeck coefficient and thermal conductivity.