The impacts of energy and financial crisis along with climate change have generated the necessity of cheap sustainable green energy. Against this background EU set targets for reducing greenhouse gas emissions, increasing the share of renewables in final energy consumption and increase in energy efficiency for the next years. Upgrading the otherwise lost waste heat, which is estimated to be over 60% of the globally released energy, to electrical energy is a promising strategy for sustainable energy. The use of thermoelectric devices which convert directly the waste heat to electrical energy, is a desirable technology for future power generation. Despite the big effort of the last years their conversion efficiency is quite low and the thermoelectric materials that are currently used are based on Tellurium, which is very rare on the earth surface. In this proposal we suggest the use thermoelectric materials based on Silicides and Oxides, which are abundant on the earth surface and relatively cheap. The aim is the optimization of synthesis and processing conditions using the state of the art panoscopic approach in combination, for first time, with tunable porosity which is expected to further enhance their efficiency. The fabricated nanostructured bulk thermoelectric materials will be characterized with several experimental techniques and studied through theoretical calculations. Technical improvement of some techniques will be performed for better characterization of the fabricated materials. This proposal also involves applied research in the form of construction and characterization of a prototype thermoelectric device using the fabricated materials.