Providing a sustainable supply of energy to the world s population will become a major societal problem for the 21st century. Thermoelectric materials, whose combination of thermal, electrical, and semiconducting properties, allows them to convert waste heat into electricity, are expected to play an increasingly important role in meeting the energy challenge of the future. Recent work on the theory of thermoelectric devices has led to the expectation that their performance could be enhanced if the diameter of the wires could be reduced to a point where quantum confinement effects increase charge-carrier mobility (thereby increasing the Seebeck coefficient) and reduce thermal conductivity. The predicted net effect of reducing diameters to the order of tens of nanometres would be to increase its efficiency or ZT index by a factor of 3. The objective of this five year proposal is to investigate and optimise the fabrication parameters influencing ZT in order to achieve a power conversion efficiency of >20%. For that, low dimensional nanowires arrays of state of art n and p-type materials will be prepared by cost-effective mass-production electrochemical methods. In order to obtained devices with a ZT >2 for application in energy scavenging and as cooler/heating devices, three approaches will be followed: a) determination of the best materials for each temperature range (n and p type) optimizing composition, microstructure, shapes (core/shell, nanowire surface texture, heterostructures), interfaces and orientations, b) advanced characterization, device development and modeling will be used iteratively during nanostructures and materials optimization, and c) nano-engineering less conventional thermoelectric like cage compounds by electrodeposition methods. This proposal aims to generate a cutting edge project in the thermoelectric field and, if successful, a more efficient way to harness precious, but nowadays wasted energy.