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Basic thermodynamics informs us that concentrating solar radiation creates the potential for both higher solar power conversion efficiency, and achieving the ultra-high threshold temperatures and flux densities that are crucial for some novel solar utilization strategies. Three examples constituting distinct solar conversion paradigms will be explored in this presentation.
The first paradigm is ultra-efficient solar electricity generation stemming from the confluence of progress in multi-junction photovoltaic technologies and advanced solar concentrator design. The evolution from the initial optical and solid-state inventions to megawatt-scale commercial concentrator photovoltaic power plants will be reviewed. Several generations of new optics that approach the thermodynamic limit to concentration and optical tolerance, and have been tailored to the exigencies of the latest generations of concentrator solar cells, will be presented.
The second paradigm is the tantalizing prospect of using solar rectifying antennas for solar power conversion. Although direct sunlight is commonly viewed as incoherent – therefore ostensibly not suitable for antenna collection – all radiation exhibits spatial coherence on a sufficiently small scale. The theory and experimental confirmation of basic performance bounds based on the partial coherence of broadband solar radiation will be reviewed. The ramifications for using optical concentrators that can effectively replace orders of magnitude of antenna and rectifier elements will be discussed. In addition, a basic upper bound on the ability to rectify (AC to DC) the inordinately high-frequency broadband signals from solar antennae will be evaluated.
The third distinct solar paradigm is creating valued materials at the service of human technology, rather than using solar to generate heat, electricity or fuels (in collaboration with Reshef Tenne and his group at the WIS). It requires novel optical concentrators, and understanding the unique nature of solar reactor conditions (ultra-high temperatures with strong flux gradients and expansive ultra-hot annealing regions). Successful case studies subsume: cage-like nanostructures of Cs2O; high-yield syntheses for fullerene-like and nanotube MoS2, MoSe2, WS2, WSe2; nanowires and nanospheres of SiO2 generated for the first time from pure quartz; nanorods of pure Si; and SiC nanowires. Some of the MoS2 nanostructures achieve fundamentally minimum sizes predicted by molecular structural theory, as well as unique hybrid nanostructures.