In this talk, we will discuss our work on how to use doping and porosity effects to manipulate the electrical and thermal properties in nanowire based bulk nanocomposites. Our success in increasing the efficiency of p-type BixSb2-xTe3 at higher temperatures can be largely explained by the increase in the optical band gap, according to the Burstein-Moss shift, due to doping, thus delaying the onset of bipolar conduction, which can shift the operation temperature to over 500K with a much improved ZT over 1. In addition, we will discuss the scalable synthesis of hollow nanostructures and the subsequent sintering of them into a highly porous thermoelectric nanocomposite. The as-sintered material has high porosity and holds a record low thermal conductivity, however, its zT is comparable to or even better than the state-of-the-art. The relative density leads to the less cost in raw material and better portability. We foresee that this large-scale approach can be extended to other types of thermoelectric materials and will inspire the utilization of hollow nanostructure in other fields.