Thermoelectric energy conversion is a direct method of generating electrical energy through a temperature difference. The source of heat in this case can be any source (e.g. the heat of the human body or the heat of nuclear decay). That makes the thermoelectric generator a unique source of electrical energy. The low efficiency of such a conversion and the high cost of the device restricts its applications to narrow specific field. Now worldwide research is carried out for searching for new cheap non-toxic materials to create effective thermoelectric converters that make it possible to reduce the cost of production. Therefore, the harvesting of waste heat from combusted engines, industrial furnaces and other sources of thermal energy will be more efficient. Silicide based thermoelectric seems to be prospective candidate. Silicon is the fourth abundant element in Earth’s crust. And a couple of silicon compounds based on manganese silicides and magnesium silicide has a high thermoelectric figure of merit that exceed unity. Besides that, with the exception of organic compounds, these materials are the cheapest thermoelectric materials. And the last decades of studies of their thermoelectric properties have shown that their thermoelectric figure of merit can be improved.
The thermoelectric generator consists of thermoelectric modules. The thermoelectric module itself consists of two legs made from semiconductors with a different type of conductivity. The mentioned above most efficient silicide thermoelectrics are magnesium silicide has n-type conductivity and manganese silicide has p-type conductivity. Both these materials fine fit together to be a silicide thermoelectric module. Unfortunately, the difference in coefficient of thermal expansion (CTE) of these materials makes it hard to use in the TE module under high temperature. In this work, the processes occurring in a thermoelectric generator operated in a temperature gradient from 100 to 600C are modeled by the means of finite elements method. The computer model of a medium-temperature thermoelectric generator module, based on thermoelements consisting of magnesium silicide as an n-type leg and higher manganese silicide as a p-type leg was built. The efficiency and performance, have been evaluated. To describe the thermoelectric properties of materials, we use our own experimental data and data published in other papers. Computation of the optimal leg configuration for maximum efficiency has been carried out. Resulting mechanical stresses that arose due to mismatched thermal expansion coefficients have been considered. The obtained results are compared with existing commercial thermoelectric generators.
|Publication||International journal «Resource-Efficient Technologies»|
|Affiliation of speaker||ITMO University|
|Position of speaker||Магистр|