Nanostructures typically exhibit thermo-physical properties that are different from their bulk counterparts. The size dependence of thermo physical properties is attributed to changing energy and mass transport phenomenon with varying length scales. This size dependence can be profitably leveraged to build cheap and efficient energy storage and harvesting systems when the materials are highly abundant. In this thesis, we study two different materials which exhibit favorable properties at lower length scales. In the first case, we study the dependence of particle size on energy storage and Carbon dioxide absorption capability of Calcium oxide particles. We theoretically establish in this work that the CaO nanoparticles achieve higher and faster reaction conversions than the micrometer sized particles. We identify the parameters which contribute to the superior performance of CaO nanoparticles and thereby provide design recommendations to sustain the enhanced performance. In the second case, Silicon, another abundant material, in the form of a nanowire has been experimentally examined as a candidate material for thermoelectric applications to harvest waste heat. We designed and fabricated a device to gauge the thermoelectric figure of merit of nano-structured materials by simultaneous characterization of thermal, electrical and seebeck properties. Using the fabricated device, the silicon nanowires are shown to have a tenfold reduction in thermal conductivity from its bulk value thereby establishing silicon nanowires as a promising thermoelectric material
