The core concept of the ThermoMag project revolves around developing and delivering new energy-harvesting thermoelectric materials and proof-of-concept modules, based on nanostructured bulk Mg2Si solid solutions. This class of TE material would have the following attractive characteristics: (i) ZT value >1.5 for both n-type and p-type doped material, (ii) operational in the temperature range 300-550ºC, (iii) very low density of 2 g/cm3, especially suitable for transportation applications, (iv) high melting point of >1000ºC, and good thermal stability up to 600ºC, (v) good oxidation and corrosion resistance and mechanical strength, (vi) isotropic thermoelectric properties, (vii) non-toxicity of elements, (viii) widely-available pure materials with very large EU supply chains and (ix) low raw material cost <15 Euros/kg, combined with low manufacturing costs. A number of methods will be looked at to achieve 3D bulk nanocrystalline Mg2Si including low-cost combustion synthesis, mechanical alloying and high-temperature solid-state synthesis in inert crucibles. Various ball milling approaches will be used to produce doped Mg2Si nanoparticle constituents that can then be compressed via rapid spark plasma sintering or hot pressing in vacuum. 3D nanocomposite material will also be produced with the addition or in-situ production of inert nanoparticles, as well as thin films using multilayer approaches. Doping using various elements will be predicted by ab-initio density-functional theory modelling. These methods will lead to the safe production of nanostructured n- and p-type legs for further thermoelectric and materials testing. In order to prove the concept works, demonstrator modules will be assembled that integrate the new energy-harvesting nanostructured material. Such modules have widespread applications in automotive, aerospace and manufacturing sectors, where waste heat can be usefully recovered, with clear environmental benefits.