Perla M. Viera-González

Design of a solar collector system formed by a Fresnel lens and a CEC coupled to plastic fibers

Among the main challenges for systems based in solar concentrators and plastic optical fibers (POF) the accuracy needed for the solar tracking is founded. One approach to overcome these requirements is increasing acceptance angle of the components, usually by secondary optical elements (SOE), however this technique is effective for photovoltaic applications but it has not been analyzed for systems coupled to POFs for indoor illumination. On this subject, it is presented a numerical analysis of a solar collector assembled by a Fresnel lens as primary optical element (POE) combined with a compound elliptical concentrator (CEC) coupled to POF in order to compare its performance under incidence angle direction and also to show a trade-off analysis for two different Fresnel lens shapes, imaging and nonimaging, used in the collector system. The description of the Fresnel lenses and its designs are included, in addition to the focal areas with space and angular distribution profiles considering the optimal alignment with the source and maximum permissible incident angle for each case. For both systems the coupling between the optical components is analyzed and the total performance is calculated, having as result its comparison for indoor illumination. In both cases, the systems have better performance increasing the final output power, but the angular tolerance only was improved for the system with nonimaging concentrator that had an efficiency over 80% with acceptance angles 𝜃𝑖 ≤ 2° and, the system integrated by the imaging lens, presented an efficiency ratio over 75% for acceptance angles 𝜃𝑖 ≤ 0.7°.

Optics outreach activities: measuring learning outcomes

The objective of this work is present diverse ways to measure the impact and quality of the informal optics education activities for its improvement in content, quality and didactic techniques; including a list of recom- mendations about how to measure the impact of the outreach events, including the target audience and the staff involved. Also, for measuring the outcomes, it is added a list of techniques about how to know the best activities for each audience, understands the perception of the activity for the public and the application of quizzes based in QR technology for a quick outcome.

Mathematical Analysis of Nonimaging Fresnel Lenses Using Refractive and Total Internal Reflection Prisms for Sunlight Concentration

During the design of nonimaging Fresnel lenses, the reflectance losses at the refracting surfaces should be taken into account because, depending on the parameters of each prism, semiacceptance angle and output angle , these losses can decrease the total efficiency of the lens. On this subject, an analysis and comparison between a Fresnel lens composed only of refractive prisms and others with total internal reflection (TIR) prisms are presented and, using this information, a design method of hybrid Fresnel lenses composed of refractive and TIR prisms is proposed to reduce reflectance losses from the surface. The work presents the radiance profile and transmittance for a Fresnel lens of each type, to compare its advantages and disadvantages providing an alternative for the design and construction of nonimaging Fresnel lenses according to optical devices requirements.

Design of a segmented nonimaging Fresnel dome for nontracking solar collection

Abstract. The efficiency of sunlight collection systems is related to the optical element used as a collector. On this subject, the design of a nontracking solar collector that consists of a segmented nonimaging Fresnel dome is presented. It is formed by the conjunction of different zones for solar collection, where each one is a nonimaging Fresnel lens that collects a specific angular range (θin) of sunlight received in the northeast of Mexico, but the methodology presented can be easily extended to other geographic locations. The final design is a semistationary segmented collector with a 100-cm diameter and 50-cm focal length that needs a 180-deg rotation over the XY-plane in each equinox. The numerical simulations show that the nontracking segmented collector has a combined acceptance semiangle of θin=±105  deg with an average efficiency of over 67% from 9:00 to 18:00 h. The spatial and angular distributions of the sunlight collected are also included. This design has a collection area equal to that of a single nonimaging Fresnel lens with an acceptance semiangle of θin=±45  deg. These results are reproducible and provide valuable data for designing nontracking solar collectors based on nonimaging Fresnel lens.

Optimization design of nonimaging Fresnel lens using total internal reflection prisms for sunlight concentration

The efficiency in Fresnel lenses is affected by three principal sources: energy loss by absorption, chromatic dispersion and reflectance losses at refracting surfaces. On this subject, the design of nonimaging Fresnel lenses integrated by refractive and total internal reflection prisms is presented. This design method uses iterative calculations for design every prism and it selects the best option for avoid reflectance losses. A design and characterization of a Fresnel lens that takes chromatic aberration into account is shown, including a comparison with a nonimaging Fresnel lens composed only by refraction prisms is performed and with other integrated by only total internal reflection prisms. In addition, the study about how acceptance angle and the number of prisms affects the final transmittance of the lens is included.

Numerical analysis of lateral illumination lightpipes using elliptical grooves

Lightpipes are used for illumination in applications such as back-lighting or solar cell concentrators due to the high irradiance uniformity, but its optimal design requires several parameters. This work presents a procedure to design a square lightpipe to control the light-extraction on its lateral face using commercial LEDs placed symmetrically in the lightpipe frontal face. We propose the use of grooves using total internal reflection placed successively in the same face of extraction to control the area of emission. The LED area of emission is small compared with the illuminated area, and, as expected, the lateral face total power is attenuated. These grooves reduce the optical elements in the system and can control areas of illumination. A mathematical and numerical analysis are presented to determine the dependencies on the light-extraction.

Design of a segmented nonimaging Fresnel lens optimized for non-tracking solar collection

The success of solar systems, such as photovoltaic and sunlight illumination systems, is principally determined by the primary optical element used as collector. On this subject, the design of a segmented nonimaging Fresnel lens is presented; this collector is formed by the conjunction of different zones for solar collection, where every zone is made of a nonimaging Fresnel lens that collects a specific angular range of sunlight, according to the solar radiation of the northeast received in Mexico. Every collector section focus in a common area. The different zones are designed considering the apparent solar movement due to the daytime and the seasonal displacement over the year. The collector total performance is presented, including spatial and angular distribution. The collector presents an average performance over 80%, with an acceptance half-angle of 120°, and a collection area similar to that in a collector with 45° of acceptance half-angle.

Optics 4 every1, the hands-on optics outreach program of the Universidad Autonoma de Nuevo Leon

The Fisica Pato2 (Physics 4 every1) outreach group started as a need of hands-on activities and active Science demonstrations in the education for kids, teenagers and basic education teachers in Nuevo Leffon maintaining a main objective of spread the word about the importance of Optics and Photonics; for accomplish this objective, since November 2013 several outreach events are organized every year by the group. The program Optics 4 every1 is supported by the Facultad de Ciencias Fisico Matematicas of the Universidad Autonoma de Nuevo Leon and the International Society for Optics and Photonics and consist in quick hands-on activities and Optics demonstrations designed for teach basic optical phenomena related with light and its application in everyday life. During 2015, with the purpose of celebrate the International Year of Light 2015, the outreach group was involved in 13 different events and reached more than 8,000 people. The present work explains the activities done and the outcome obtained with this program.

Modeling of efficient light extraction in light-pipes through specular surfaces with elliptical and lineal front shapes

Extraction light in light-pipes with different specular surfaces was analyzed. In the analysis, the impact of the surface shape in all properties of the extracted light in order to obtain an efficient extraction and a uniform illumination using a LED as light source. Also, several parameters of the specular surface to obtain spatial uniformity inside the light-pipe are considered. In this case, the simulation was made for a rectangular lightpipe. One objective of this work is to compare how the front face shape of the specular surface can affect the extraction of light in the lateral face of the light-pipe, only straight and elliptical front faces were used in this work and the comparison between them at different tilts and lengths were made. The main purpose of the front face was extract the light uniformly at the lateral face and this was done by studying simulations on OpticStudio Zemax. The results show how the extraction length is lower in the elliptical front but its total power performs better than the line front.

Light extraction method for mixing rods based in grooves with elliptical shape

Homogenize light is the principal purpose of mixing rods. Light extraction from mixing rods is proposed by changing the shape of the face, the rod or a combination of both for many applications. Light extraction also can be done by its lateral face by cutting the Mixing rod. In this work a simulation of square and hexagonal poly(methyl methacrylate) (PMMA) mixing rods were made in Radiant Zemax ® 12 release 2 designed with an elliptical transversal cut to extract light from a lateral face. The cut is specular for rays that fulfill the total internal reflection condition, the reflected rays are deviated and the Total Internal Reflection (TIR) condition broken, then, extracted. An advantage of this cut is that it can be controlled in depth to extract the amount of light required and the remaining light used for other purposes. Also it can reduce the size of the mixing rods and optical components. For the simulation, an LED light were used as source, the light were homogenized by the mixing rod and due to it, the light extracted is also homogenous. The polar power map, radiant intensity and color of the light extracted are presented and compared in both mixing rods.