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The radiation flux distributions produced by the concentrating solar systems used to produce thermal/electrical power are usually non-homogeneous. This results in non-uniform temperature distributions on the solar receivers, causing adverse effects on the system’s overall performance. An approach to better understand the problem is to study the surfaces around the focal zone where the radiation density is homogeneous (isosurfaces), generating them from experimental data. For this, it is necessary to superimpose built volumes of the different irradiance levels using parallel planes in different directions from the focal point of a concentrator. These volumes are known as effective volumes. This study presents the model used to generate effective volume produced by a point focus concentrator, comparing it with experimental results in a direction perpendicular to the focal axis. The effective volumes were developed considering a global optical error of the system of 2.8 mrad. The set of methods used to generate effective volumes has not been previously presented in the literature. The theoretical-experimental research consisted of the combination of the camera-target method and the simulations by the ray-tracing technique. The results showed effective volumes with the highest value of 10 MW/m2 and the lowest value of 4.5 MW/m2.

A method to achieve a uniform flux distribution with a multi-faceted point focus concentrator for laboratory tests is proposed in this work. The method can be applied to different types of receiver - thermal or photovoltaic - and no additional device is required to homogenize the flux. The technique consists in moving the receiver from the focal plane and enlarging the solar spot impinging on it. At the same time, each mirror aim-point is adjusted in order to superimpose the images that have been generated by every facet. To evaluate the method, a real multi-faceted concentrator composed of eighteen spherical mirrors was modeled in a ray-tracing software. The procedure was validated through the comparison of an image of the real solar spot on the receiver generated by three mirrors, and the simulated flux obtained the same way. This way a mean concentrator global optical error of 2.8 mrad was estimated. This value was used then for further analyses. Results show that the concentration factor can be varied in a range of 150–900 suns over a receiver diameter of up to 7 cm. Hence, according to the receiver requirements, it is possible to expand the distribution and to alter the intensity of the flux. Finally, optical parametrical analyses were carried out, from which it is inferred that good quality optics give rise to a more homogeneous solar flux on the receiver.

The potential use of solar furnaces for industrial applications has been an attractive idea in the last years due to their high flux density and the accurate control which satisfies the productive industry requirements and facilitates the implementation of the solar technology within the industrial sector. An important aspect to take into account when designing a solar furnace is the heliostat field layout and its relative size compared to the aperture area of the secondary concentrator of the solar furnace as a consequence of the latitude where the solar facility is located. In this work, the influence of the latitude and atmospheric conditions in the final design and energy cost of solar furnaces for its use in industrial applications has been analyzed. Different criteria have been applied to perform design optimizations for different geographical locations. Results obtained have been discussed and some guidelines regarding solar furnace design and optimization according to the final site location have been indicated.

The numerical evaluation of a multi-channeled solar reactor coated with ZnFe2O4 film is performed by using a pore-level simulation. A ray-tracing in the concentrator allow to obtain the solar flux distribution at the aperture of the channels. Then a MC-ray tracing enable to analyze the radiative heat transfer in the porous media in order to optimize the pore-level geometry for maximum absorptance. The model considers the optical properties of ZnFe2O4 films deposited on zirconia substrate surrounded by argon, which were obtained with the characteristic matrix method. This approach allows to account for important reactor design parameters, such as ZnFe2O4 layer thickness, incoming radiation profile, diameter and length of pore.

The design and optimization of novel type of receiver for a paraboloidal concentrator with 90° rim angle is carried out by means of detailed ray tracing simulations. Cylindrical, conical, and spherical geometries are compared and their dimensions optimized. The chosen design is based on a conical cavity, which differs from similar receivers developed for concentrators with smaller rim angles. In particular, the receiver is able to catch concentrated solar energy both on its outer side and on the inner walls. Water flows inside the receiver along the conical geometry, in a double layer configuration. The receiver was built and implemented in a 90° rim angle paraboloidal concentrator. Thermal efficiency of the system is evaluated for different flow rates and inlet temperatures, both in stationary and in transient regimes, and results for fluid temperatures are compared with the results predicted by a thermal model. The time constant is evaluated.

It is a common practice in the development of point focus solar concentrators to use multiple identical reflecting facets, as a practical and economic alternative for the design and construction of large systems. This kind of systems behaves in a different manner than continuous paraboloidal concentrators. A theoretical study is carried out to understand the effect of the size of facets and of their optical errors in multiple facet point focus solar concentrating systems. For this purpose, a ray tracing program was developed based on the convolution technique, in which the brightness distribution of the sun and the optical errors of the reflecting surfaces are considered. The study shows that both the peak of concentration and the optimal focal distance of the system strongly depend on the size of the facets, and on their optical errors. These results are useful to help concentrator developers to have a better understanding of the relationship between manufacturing design restrictions and final optical behavior.

In the present work, the optical design of a new high radiative flux solar furnace is described. Several optical configurations for the concentrator of the system have been considered. Ray tracing simulations were carried out in order to determine the concentrated radiative flux distributions in the focal zone of the system, for comparing the different proposals. The best configuration was chosen in terms of maximum peak concentration, but also in terms of economical and other practical considerations. It consists of an arrangement of 409 first surface spherical facets with hexagonal shape, mounted on a spherical frame. The individual orientation of the facets is corrected in order to compensate for aberrations. The design considers an intercepted power of 30 kW and a target peak concentration above 10,000 suns. The effect of optical errors was also considered in the simulations.

Since August 2011, the 30 kWt Solar Furnace for Higher Radiative Fluxes (HoSIER) of the Renewable Energy Institute (former Center for Energy Research) of the National University of Mexico (IER-UNAM) is in operation. The optical design of the HoSIER-UNAM includes a total of 409 spherical facets, divided into 5 different focal length groups [1]. A ray-tracing simulation was carried out to realize a three-dimensional analysis of the concentrated solar radiation distribution at the focal area of the HoSIER. In this way, theoretical profiles of the radiative flux were obtained. To get the experimental profiles of the concentrated solar irradiance of the HoSIER, a Lambertian screen was placed in the focal zone, normal to the optical axis of the concentrator. The screen was moved along 10 cm on the focus with each flat separated 5 mm of distance and in front of a CCD 8-bit digital camera. With the CCD was possible to obtain several experimental radiative flux distributions and thus it was possible to validate the ray-tracing simulation. This comparison shows a very good agreement between experimental and theoretical distribution.