Solar energy has attracted keen attention because it is a unique, clean, and sustainable energy resource. It is also widely utilized as a power source in space exploration. A lightweight, durable, deployable, and highly efficient all polymer-based solar power panel was developed comprising a highly efficient thermoelectric conducting polymer composite layer and highly efficient solar absorbance/passive cooling coatings for maximizing efficiency of the power conversion.
First, the efficiency of the power conversion is maximized by increasing temperature difference between a hot side and a cold side by coating novel, energy-manageable polymer composites with tailored solar absorptivity and thermal emissivity coatings, and controlling the surface morphology. Second, a novel, highly efficient thermoelectric polymeric nanomaterial is developed by introducing n-doped and p-doped carbon or silicon carbide nanotubes into the conducting polymers. The lightweight, flexible, and durable characteristics of the conducting polymer thermoelectric materials, combined with the energy-manageable polymer composite layers, enable development of a wide range of terrestrial and space applications, including a deployable space-based solar power panel, which has great merits in launch cost and flexibility.
To overcome the critical shortcomings of inorganic thermoelectric materials, polymeric thermoelectric materials such as polyaniline, polypyrrole, polythiophene, polyacetylene, and their derivatives have been developed. These organic thermoelectric polymers are mechanically durable, but have a thermoelectric figure of merit of less than 0.1 due primarily to their relatively low Seebeck coefficient of 10 μV/K. Chemical doping can increase the electrical conductivity of the nanotube conductive polymer composites without increasing thermal conductivity, improving the thermoelectric figure of merit dramatically.
The seamless, dopant-graded, multilayered films composed of moderately electrically conductive nanotube/undoped poly aniline layers and highly conductive nanotube/doped polyaniline layers decrease the overall thermal conductivity because phonon scattering at the layer interfaces prevents effective thermal conduction through the layers.
Additionally, adding nanophase metals or semiconductors into the nanotube or silicon carbide nanotube/conducting polymer composites through a newly developed supercritical fluid infusion technology or in-situ metal infusion technology increases the electrical conductivity and Seebeck coefficient further while the thermal conductivity is sustained or only slightly increased.
The polymeric solar power panel will have practical advantages of light weight, simplicity, flexibility, easy processability into versatile forms, and deployability to enhance or augment existing ceramic-based solar photovoltaics.
This work was done by Sharon E. Lowther, Peter T. Lillehei, and Joycelyn S. Harrison of Langley Research Center; Jin Ho Kang, Jae- Woo Kim, Godfrey Sauti, and Cheol Park of the National Institute of Aerospace; and Chase Taylor of the University of Nebraska- Lincoln. LAR-17746-1