At the moment about 12% of the world’s energy supply is based on biomass. Biomass is used for cooking in developing countries. Traditionally, biomass is burned on open fires, which are characterized by low efficiency. To achieve a complete combustion an electric fan is used that blows air through the combustion chamber to increase the ratio air to fuel. Such an energy- efficient stove based on traditional stove design is developed by a NGO. A thermoelectric generator produces the electric energy for the fan. The generator does not need additional biomass because the thermoelectric modules convert heat directly into electric power. The first part of this thesis is an introduction to thermoelectricity with an economic view of new opportunities for using the thermoelectric generator. In the second part the prototypes are presented. The last section describes the optimization of the TEGBioS III to improve the electric performance. Also the differences between using one or more thermoelectric modules are described. The influence of insulation and the position of the flame are studied. A study for using aluminum blocks between the heat sink and the TE module is simulated and tested.