Ternary comb-like silicon photonic crystal: Oxidation, intrinsic modes, reflection windows and contrastivity
A ternary photonic crystal - A/B/A/C periodic structure is investigated analytically and numerically in the framework of transfer matrix formalism. The influence of oxidation to photonic gaps and positions of reflection windows for (SiO2/Si/SiO2/Air)N structure is calculated. It was shown that intrinsic optical contrastivity has a non-monotone behavior during the process of oxidation of silicon. The found results will allow to determine the optimal regimes of oxidation to obtain needed photonic device properties.
Optical contrastivity and sensitivity of multicomponent ordered structures
Abstract We discuss the definition of an intrinsic optical contrastivity for a complicated structure as a relative total gap taken over a chosen range of frequencies. An optical material contrast sensitivity to the variation of parameters is analyzed for a wide area. The contrastivity and sensitivity parametric maps are calculated for 1D combs with various fillings. The existence of highly sensitive areas on the parametric maps to contrast deviations is shown for different materials. It is shown that for the found parameters the photonic band edge shifts are of the order of 0.3–0.5 eV/bar for glass, silicon and microporous silicon matrices.
Techno-economic analysis of solar thermal power plants using liquid sodium as heat transfer fluid
Abstract Solar thermal power plants with central receiver and thermal storage are expected to be one key technology in future electricity generation, because they are renewable and due to the thermal storage independent of the current solar radiation. State-of-the-art solar power plants often use molten nitrate salts as heat transfer fluid. The use of liquid sodium instead leads to lower electricity generation costs. Sodium has a high thermal conductivity and thus large heat transfer rates are possible. Hence, a smaller absorber surface is sufficient for the same thermal power. As a result, the sodium receiver achieves a higher efficiency at lower investment cost. Additionally, the aiming strategy, which reduces the peak heat flux on molten salt receivers isn’t necessary for sodium. Even at high heat flux densities, the absorber tubes will be cooled sufficiently due to the high heat transfer coefficients. Therefore, the sodium receiver in this analysis is designed for one single aim point, resulting in a heat flux density of q mean = 1.06 MW / m 2 and q peak = 2.99 MW / m 2 . The state-of-the-art system with molten salt considers q mean = 0.51 MW / m 2 and q peak = 1.0 MW / m 2 . The presented techno-economic analysis of two sodium based concepts compared to a reference system with molten salt results in up to 16% lower electricity generation costs.