Sun backward gazing method for measuring optomechanical errors of solar concentrators: experimental results.

This paper presents the first experimental results obtained with the four cameras backward gazing method for measuring the optomechanical errors of solar concentrating surfaces in operation. It consists in combining the images simultaneously acquired by four cameras placed near the solar receiver in order to reconstruct the slope errors of the mirrors digitally. New algorithms adapted to real acquired images are described. The experiment has been conducted on a sun-tracking heliostat of the experimental solar tower THEMIS with canting error measurement accuracy estimated as 0.2 mrad. The main experimental error sources are analyzed, and possible ways of mitigation are proposed, giving reasonable hope of reaching an ultimate measurement accuracy of 0.1 mrad.

Calculation of the orientational linear and nonlinear correlation factors of polar liquids from the rotational Dean-Kawasaki equation.

A calculation of the Kirkwood and Piekara-Kielich correlation factors of polar liquids is presented using the forced rotational diffusion theory of Cugliandolo et al. [Phys. Rev. E 91, 032139 (2015)]. These correlation factors are obtained as a function of density and temperature. Our results compare reasonably well with the experimental temperature dependence of the linear dielectric constant of some simple polar liquids across a wide temperature range. A comparison of our results for the linear dielectric constant and the Kirkwood correlation factor with relevant numerical simulations of liquid water and methanol is given.