We report conversion efficiencies of experimental single and dual light guide luminescent solar concentrators. We have built several 5 cm × 5 cm and 10× cm × 10 cm luminescent solar concentrator (LSC) demonstrators consisting of c-Si photovoltaic cells attached to luminescent light guides of Lumogen F Red 305 dye and perylene perinone dye. The highest overall efficiency obtained was 4.2% on a 5 cm × 5 cm stacked dual light guide using both luminescent materials. To our knowledge, this is the highest reported experimentally determined efficiency for c-Si photovoltaic-based LSCs. Furthermore, we also produced a 5 cm × 5 cm LSC specimen based on an inorganic phosphor layer with an overall efficiency of 2.5%.

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Abstract:We demonstrate a low-cost optical method for measuring the gloss properties with improved sensitivity in the low gloss regime, relevant for skin gloss properties. The gloss estimation method is based on, on the one hand, the slope of the intensity gradient in the transition regime between specular and diffuse reflection and on the other on the sum over the intensities of pixels above threshold, derived from a camera image obtained using unpolarized white light illumination. We demonstrate the improved sensitivity of the two proposed methods using Monte Carlo simulations and experiments performed on ISO gloss calibration standards with an optical prototype. The performance and linearity of the method was compared with different professional gloss measurement devices based on the ratio of specular to diffuse intensity. We demonstrate the feasibility for in-vivo skin gloss measurements by quantifying the temporal evolution of skin gloss after application of standard paraffin cream bases on skin. The presented method opens new possibilities in the fields of cosmetology and dermatopharmacology for measuring the skin gloss and resorption kinetics and the pharmacodynamics of various external agents.

In high-pressure discharges, arc instabilities may occur due to acoustic resonances inside the discharge vessel. We have observed experimentally the presence of longitudinal acoustic resonances in a high-pressure sodium discharge well below the threshold above which the arc is unstable. A dye laser, tuned to about 17 140 cm−1, proved to be able to excite the acoustic standing waves, and their galvanic effects have been measured. A local thermodynamic equilibrium discharge model is presented, which qualitatively describes the measurements. It is shown that the instability threshold is correlated to an acoustic pressure amplitude in the ventral segments of about 6 kPa.