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The design, construction, and ray simulation of a new compound parabolic concentrator based on a toroidal shape (toroidal compound parabolic concentrator, TCPC) are addressed. Such analysis indicates that the amount of concentrated radiation is independent of the Sun trajectory. Thus, the TCPC has the advantage of concentrating Sun rays in a spot, and if positioned with an inclination corresponding to the latitude, a solar tracker would not be needed. Experimental measurements with a prototype model are shown to be in good agreement with the simulation results. The possibility of a variety of applications, as natural illumination for this TCPC device, is also pointed out. The simple design, fabrication, and implementation of the TCPC make it an excellent alternative for low concentration in a spot. We present the analysis of the TCPC in natural illumination as one of these applications.

Antecedentes y Objetivos: Cestrum nitidum fue descrita con base en ejemplares de herbario recolectados por H. Galeotti alrededor de Ixtlán de Juárez, Oaxaca, México. Posteriormente, se utilizó erróneamente este epíteto en especímenes provenientes de la Sierra Madre del Sur y del Cinturón Volcánico Transmexicano. Este trabajo aclara este conflicto taxonómico.Métodos: Se realizó la revisión de la literatura y de colecciones de herbario (BM, BR, CAS, CIMI, CODAGEM, E, EBUM, ENCB, F, G, GH, IBUG, IEB, K, L, M, MEXU, MICH, NDG, NY, P, PH, QMEX, US) de Cestrum para México.Resultados clave: El nombre Cestrum nitidum sólo debe aplicarse a colecciones provenientes de los alrededores de Ixtlán de Juárez, Oaxaca, con flores aromáticas, largamente pediceladas; arregladas en panículas alargadas y laxas.Conclusiones: Cestrum commune es el nombre correcto para especímenes distribuidos en la Sierra Madre del Sur y el Cinturón Volcánico Transmexicano. Debe mantenerse C. nitidum para aquellos ejemplares de Ixtlán de Juárez, Provincia de Sierras Orientales, Oaxaca.

Heliostats are critical components of solar tower technology and different strategies have been proposed to reduce their costs; among them diminishing their size to reduce wind loads or linking nearby heliostats mechanically, to reduce the overall number of actuators. This document aims to describe the development of a linked array of mini-heliostats which move together in an elevation–Fresnel configuration. This configuration consists of an array of mirrors rotating around linked parallel axes, in a linear Fresnel style with an added elevation mechanism allowing all axes to incline simultaneously in the plane North–South–Zenith; that is equivalent to an array of N linked mini-heliostats moved by only two drives instead of 2N. A detailed analytical study of the Sun-tracking performance of this kind of heliostat arrays was carried out, and an 8-mirror prototype based on optical and mechanical analyses was designed, built and tested. Even though the mirrors are flat, the array produced a rather compact radiative flux distribution on the receiver. The flux distribution is compatible with a slope error of the order of 1 mrad. Peak and mean concentration ratios reached 6.89 and 3.94, respectively.