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The Gompertz equation describes the evolution of an epidemic. Applied to the data from France, Spain, Germany, and the United Kingdom, it is adjusted with slight deviations since each country implemented different restriction or distancing measures to prevent the spread. Some countries do not conform to Gompertz. With the data from Mexico, the graphs show that the measured and calculated data are overlapped. The deviations are not noticeable. We made adjustments with data up to recent dates. For the four countries, Gompertz predicts well the evolution of the epidemic. We tried to predict the growth of the epidemic using Gompertz. For Mexico, the maximum number of daily infections was predicted up to a month before it happened. RESUMEN La ecuación de Gompertz describe la evolución de una epidemia. Aplicada a los datos de Francia, España, Alemania y el Reino Unido, se ajusta con ligeras desviaciones, ya que cada país aplicó diferentes medidas de restricción o distanciamiento para evitar la propagación. Algunos países no se ajustan a Gompertz. Con los datos de México, los gráficos muestran que los datos medidos y los calculados se superponen. Las desviaciones no son perceptibles. Hemos realizado ajustes con datos hasta fechas recientes. Para los cuatro países, Gompertz predice bien la evolución de la epidemia. Intentamos predecir el crecimiento de la epidemia con Gompertz. Para México, se predijo el número máximo de contagios diarios hasta un mes antes de que se produjera.

La radiación UV presente en la luz solar es esencial en diversos procesos ambientales del planeta, en la descontaminación de agua y aire, la desintegración de los residuos entre otros. Sin embargo, en el ser humano, la sobre exposición a los rayos UV puede resultar en enfermedades agudas y crónicas con efectos en la piel, los ojos y el sistema inmunitario; a largo plazo, los cambios degenerativos inducidos por radiación en células, tejido fibroso y vasos sanguíneos conducen al envejecimiento prematuro de la piel. Los tiempos de exposición prolongados tienen efectos nocivos en los humanos y otros seres vivos, causando daños biológicos que llegan a alterar el propio ADN. De ahí que en este trabajo se evalúan los niveles de la radiación UV-B a partir del análisis estadístico de las series temporales de datos correspondientes a la ciudad de Tepic, Nayarit, obtenidos de la red Solarimétrica mexicana RESOLMEX para determinar la intensidad y variabilidad del índice UV. Adicionalmente, se evaluó el nivel de conocimiento sobre el índice UV que tienen los turistas de Sol y Playa en costas Nayaritas, con la finalidad de estudiar su experiencia al exponerse, sin cuidado o protección a la radiación solar. El conocimiento del índice UV y sus implicaciones en la salud, ayuda al turista a tomar conciencia y, con ello la decisión de protegerse, disminuir el tiempo de exposición al Sol, y modificar su comportamiento para tomar de decisiones responsables durante sus actividades recreativas que lo protejan de los daños provocados por la sobre exposición a la radiación UV.

The design and location of solar energy technologies are based chiefly on the availability of solar resource. Specialized measurement equipment and solar resource assessment techniques are mandatory in order to identify appropriate locations for deploying solar systems while minimizing risk and increasing the return rate of the site. These needs have given the scientific community a motivation to design highly reliable and cost-competitive sensors. This work presents a novel methodology to estimate solar irradiance components using a low-cost sky-imager system. Captured images are processed to correct the spherical aberration of the dome and to achieve a pixel-radiance model, allowing each pixel of the image to be considered as an individual source of irradiation. The performance of the proposed model is analyzed and compared in four different weather scenarios against a secondary standard solarimetric station, obtaining a normalized mean bias error for direct normal irradiance, global horizontal irradiance and diffuse horizontal irradiance of 4.53%, −6.55% and 19.62% for a sunny day, 0.79%, −6.13% and 7.00% for a partially sunny day, 1.96%, −6.58% and −0.73% for a partially cloudy day, 100%, −10.48% and −0.65% for a cloudy day, respectively. According to the experimental results, the system stands out for its performance, easy setup, low-cost components and a robust estimation in all possible weather scenarios.

The purpose of this article is to present the results of the research project that aims to evaluate the relevance of theacademic program of industrial engineering of the free university, which allowed to determine the degree of social andindustrial relevance, based on the professional profile defined in the PYP (Educational Project of the Program) in force forthe period 2018 - 2020 responding to the accreditation requirements of Agreement 02 of 2020 of the CNA (NationalAccreditation Council). The information for this study was collected through questionnaires, as a research tool, which isaddressed to the entrepreneurs linked to the institution, graduates of the program and the community that is part of thesocial projection of the faculty.In the evaluation was possible to conclude that the Industrial Engineering program has a high percentage of relevance,both social and industrial, values that will be analyzed in this article.

More than 7 thousand wildfires were recorded over Mexico in 2019, affecting almost 640 thousand hectares. Most of these fires occurred during the spring season generating dense smoke plumes, impacting urban areas in the central part of the Mexican plateau. From May 10 to 17, 2019, biomass burning (BB) plumes affected Mexico City (MC) and diffused across the basin, producing PM2.5 levels ~ 2 times higher than the nation's air quality standards. Average PM2.5 concentrations increased sharply from 29.4 ± 7.2 µg m−3 to 65.1 ± 13.6 µg m−3 when the dense smoke plumes were detected. The higher particle concentration impacted the aerosol optical depth (AOD) as values ~ 3 times greater than the annual mean (0.32 ± 0.12) were measured, which resulted in a 17% loss of global horizontal irradiation (GHI). Under these severe pollution conditions, the visibility (Va) was reduced by ~ 80%. The high incidence of strong absorbent particles, such as soot and tarballs was revealed through electron microscopy and X-ray fluorescence (XRF) analysis. These techniques show chemical similarities between MC aerosols and those from the high-altitude (~ 4010 m. a. g. l.) Altzomoni Atmospheric Observatory, evidencing a strong influence of the BB emissions, suggesting a regional transport of these pollutants.

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.

The numerical evaluation of the radiative heat transfer in a multichanneled solar reactor coated with ZnFe 2 O 4 thin-film is performed by using a channel-level simulation. A ray-tracing simulation of a 25 kW solar furnace allows obtaining the radiation distribution at each channel aperture. Then a Monte Carlo ray tracing is performed to analyze the radiative heat transfer on the monolith to optimize the channel-level geometry and film thickness for maximum absorptance and more homogeneous temperature distributions. The model considers the optical properties of ZnFe 2 O 4 films deposited on zirconia substrate, obtained through the characteristic matrix method. This approach allows accounting for important reactor design parameters and operational conditions, such as ZnFe 2 O 4 layer thickness, incoming radiation profile, diameter and length of pores and position of the monolith in the focal zone of the solar furnace.

Climatology of Aerosol Optical Depth (AOD), Single Scattering Albedo (SSA), and aerosol particle-size distribution were analyzed using a 15-year (1999–2014) dataset from AErosol RObotic NETwork (AERONET) observations over the Mexico City (MC) basin. The atmosphere over this site is dominated by two main aerosol types, represented by urban/industrial pollution and biomass-burning particles. Due to the specific meteorological conditions within the basin, seasons are usually classified into three as follows: Dry Winter (DW) (November–February); Dry Spring (DS) (March–April), and the RAiny season (RA) (May–October), which are mentioned throughout this article. Using a CIMEL sun photometer, we conducted continuous observations over the MC urban area from January 1999 to December 2014. Aerosol Optical Depth (AOD), Angstrom exponent (α 440–870 ), Single Scattering Albedo (SSA), and aerosol particle-size distribution were derived from the observational data. The overall mean AOD 500 during the 1999–2014 period was 0.34 ± 0.07. The monthly mean AOD reached a maximal value of 0.49 in May and a minimal value of 0.27 in February and March. The average α 440–870 value for the period studied was 1.50 ± 0.16. The monthly average of α 440–870 reached a minimal value of 1.32 in August and a maximal value of 1.61 in May. Average SSA at 440 nm was 0.89 throughout the observation period, indicating that aerosols over Mexico City are composed mainly of absorptive particles. Concentrations of fine- and coarse-mode aerosols over MC were highest in DS season compared with other seasons, especially for particles with radii measuring between 0.1 and 0.2 μm. Results from the Spectral De-convolution Algorithm (SDA) show that fine-mode aerosols dominated AOD variability in MC. In the final part of this article, we present a classification of aerosols in MC by using the graphical method proposed by Gobbi et al. (2007), which is based on the combined analysis of α and its spectral curvature δα.

Hydrogen is a promising energy carrier for transportation, domestic and industrial applications. Nowadays hydrogen is consumed basically by the chemical industry, but in long term its demand is expected to grow significantly due to emerging markets. Hence production of hydrogen with sustainable methods is a relevant issue. This work presents a review of the different CSP- aided thermochemical processes for hydrogen and syngas production. For each process, some relevant solar-tested reactor prototypes are described. In a second part, the developed solar furnaces for investigation of thermochemical process are also discussed. In addition, relevant research on hydrogen or syngas production in solar tower installations is presented. Finally the current challenges of the technology and the process for its future commercialization are also analyzed.

The atmospheric conditions existing where concentrated solar power plants (CSP) are installed need to be carefully studied. A very important reason for this is because the presence of clouds causes drops in electricity generated from solar energy. Therefore, forecasting the cloud displacement trajectory in real time is one of the functions and tools that CSP operators must develop for plant optimization, and to anticipate drops in solar irradiance. For short forecast of cloud movement (10 min) is enough with describe the cloud advection while for longer forecast (over 15 min), it is necessary to predict both advection and cloud changes. In this paper, we present a model that predict only the cloud advection displacement trajectory for different sky conditions and cloud types at the pixel level, using images obtained from a sky camera, as well as mathematical methods and the Lucas-Kanade method to measure optical flow. In the short term, up to 10 min the future position of the cloud front is predicted with 92% certainty while for 25–30 min, the best predicted precision was 82%.

In this paper, we present a characterization of the optical properties of the aerosols emitted during biomass burning (BB) season in the period 2005–2009. Trends of aerosol optical depth (AOD), Angstrom exponent (α), and precipitable water (PW) were analyzed using a 5-year dataset from AErosol RObotic NETwork (AERONET) observations over Tuxtla Gutierrez (TG), Chiapas. The overall mean AOD (500 nm) during the 2005–2009 period was 0.26 ± 0.18. However, monthly mean values of AOD > 0.5 during the spring months (April and May) would indicate the high load of particles emitted by fires. The overall mean of α (440–870 nm) was 1.40 ± 0.21, which confirms the presence of fine aerosols. Additionally, the combined analysis of the α with its spectral curvature δα, and the results from the spectral de-convolution algorithm (SDA) shows that fine-mode aerosols dominated AOD variability in TG. In this paper, the trajectories of air masses (400 and 1500 m, a.s.l.) arriving at the TG site were classified by using backward trajectory cluster analysis. Trajectory clustering results indicate a BB regional transport from Central America that affects the atmosphere in southeastern Mexico. We use observations of fire radiative power (FRP) from the Moderate Resolution Imaging Spectroradiometer (MODIS) to study the incidence of wildfires and to estimate the BB emissions from 2005 to 2009 in southeastern Mexico. The results indicated a gradual decrease in fires throughout the years. Campeche and Yucatan are the states in southeastern Mexico where BB produces the highest emissions of carbon dioxide (CO2), carbon monoxide (CO), black carbon (BC), and particulate material PM2.5. However, the largest emissions come from wildfires in Guatemala. Finally, to put in context the aerosol optical properties over southeastern Mexico, the sun photometric measurements in TG are compared with those retrieved from AERONET stations located in other tropical biomass burning regions (Brazil and Zambia).

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.

Background Beer gushing is an uncontrolled escape of wet foam when opening a beer bottle, which is not caused by high temperature or shaking. Primary gushing is associated with fungal contamination of barley but the main role in gushing is played by carbon dioxide and surface active proteins called hydrophobins produced by fungi. Secondary gushing is understood as the effect of non-hydrophobin related factors, which either provoke gushing independently and/or can support the expression/intensity of primary gushing. So far there, there is no fully functional gushing suppression strategy at industrial scale. Scope and approach This review article aims to clarify the underlying mechanism of primary gushing and simultaneously provide an overview of knowledge concerning different strategies of suppressing primary gushing. The published methods of reducing and suppressing primary gushing were analyzed and structured according to various technological sections of beer production. Emphasis was placed on the aspects of applicability in industrial practice. Key findings and conclusions By analyzing the available data, the following strategies of reducing the risk of beer gushing were identified as the most promising (i) germination of barley in the presence of micro-organisms inhibiting the hydrophobin producing fungi, (ii) use of hop oil and products with antigushing effect, and (iii) coating of the glass bottle necks with hydrophobin binding layers. This study intends to inspire research and promote application of new approaches to control gushing.

Purification is a critical step to obtain hydrophobin HFBII for use in positive applications. In this study, hydrophobin HFBII was produced by Trichoderma reesei via submerged fermentation. Using the CO2-foam fractionation method yielded a fourfold increase in protein concentration. The foamate (αL-HFBII) was dried using a nano spray-dryer under optimal temperature. The gushing activity of the dried foamate (αS-HFBII) decreased. Addition of Tween 80 to the foamate before the drying process partially prevented the deactivation of hydrophobin HFBII. The purity of the powder was enhanced based on the theory of CO2-nanobubbles in a CO2-rich environment. The collected CO2-nanobubbles were added to an apolar–polar system and the interface of these two phases was collected. After evaporation of the apolar phase, the purity of the hydrophobins assembled on the surface of the liquid was significantly improved.

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Gushing has been recognized as a disastrous phenomenon for contaminated carbonated beverages. Recent advances highlighted the ability of the class II hydrophobin films to interact via the hydrophob...

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.

Hydrophobins have exceptional surface activity with potential applications for food and pharmaceutical industry. In this study, the effect of Class II hydrophobin HFBII on the retention of a volatile compound, ocimene in a water phase was investigated. We observed a negative gushing when 200 μ gp ure HFBII (κ-grade) and 40 μg ocimene (assay ≥ 90%) was added to 1 L sparkling water with CO2 concentration of 7 g/L. The droplet size analysis of κ-HFBII, ocimene and the mixture of them showed that the ocimene was emulsified in a solution containing κ-HFBII. The stability of this emulsion was reduced in function of time and this effect was intensified by increasing the temperature and the presence of CO2. Additionally, the retention of ocimene in a HFBII rich solution was measured by SPME-GC-MS. When 0.26±0.03 mg HFBII/mL is added to ocimene solution, 43% of the original ocimene concentration (i.e. 5.9 × 10 � 6 mg/mL) remained in the solution after 3 days, and 32% after 7 days. In contrast, original ocimene concentration in solutions without HFBII was only retained 20% and 14%, respectively. It showed the potential of HFBII to incor- porate insoluble flavour compounds in beverages and control their release. Copyright © 2015 John Wiley & Sons, Ltd. Additional supporting information may be found in the online version of this article at the publisher' sw eb site

An analysis of the solar radiation database from the network of meteorological stations of the Mexican National Weather Service was carried out. The database includes global irradiance measurements from the oldest 136 stations distributed in the Mexican territory. The consistency of data acquisition from the launch of the stations until 2010 was checked, and visual inspection of graphs of daily irradiance data was carried out, for the first three years operation, to ensure quality and reliability of the data. The results indicate that less than half of the stations have an adequate regularity for data records. With a limited number of selected stations that passed the applied quality criteria, evaluation of hourly and daily global irradiations was carried out. These results were compared to satellite derived data for Mexico, based on NREL's CSR model. The results of the comparison show a good agreement between measured and modeled daily global solar irradiation with an average RMSE of 6.6%. Based on the selected stations, a daily irradiation mean of 5.5 kWh/m²/day is estimated for the country.

The new reference solarimetric network for Mexico is presented, actually 10 stations has been installed around the country with a climatic regionalization, the three principal solar parameters are measured (bean, diffuse and global radiation) in all the stations, and spectral parameters in some stations (long wave radiation, UVB and illuminance)

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.

This paper discusses the methods implemented for the solution of the drift and backlash problems in the heliostat of the High Radiative Flux Solar Furnace recently built at the Renewable Energy Institute (former Center for Energy Research) of the National University of Mexico (IER-UNAM), located at the geographical coordinates 18°50′24″ North latitude and 99°15′00″ West longitude. To solve the observed drift, several algorithms were analyzed for the calculation of the solar vector, and a closed loop through an electronic device (peephole) was implemented which makes corrections to the position of the heliostat. Using the peephole, drift heliostat decreased significantly; 70% in the horizontal direction and 63% in the vertical direction relative to the no use of peephole. The backlash was corrected by means of unbalancing the heliostat.

Production and purification of hydrophobin HFBII has recently been the subject of intensive research, but the yield of production needs to be further improved for a generic use of this molecule at industrial scale. In a first step, the influence of different carbon sources on the growth of Trichoderma reesei and the production of HFBII was investigated. The optimum productivity was obtained by using 40 g/L lactose. Carbon starvation and excretion of extracellular enzyme were determined as two main conditions for the production of HFBII. In the second phase, and according to the physiological mechanisms observed during the screening phase, a bioreactor set up has been designed and two modes of cultures have been investigated, i.e. the classical submerged fermentation and a fungal biofilm reactor. In this last set-up, the broth is continuously recirculated on a metal packing exhibiting a high specific surface. In this case, the fungal biomass was mainly attached to the metal packing, leading to a simplification of downstream processing scheme. More importantly, the HFBII concentration increased up to 48.6 ± 6.2 mg/L which was 1.8 times higher in this reactor configuration and faster than the submerged culture. X-ray tomography analysis shows that the biofilm overgrowth occurs when successive cultures are performed on the same packing. However, this phenomenon has no significant influence on the yield of HFBII, suggesting that this process could be operated in continuous mode. Protein hydrolysis during stationary phase was observed by MALDI-TOF analysis according to the removal of the last amino acid from the structure of HFBII after 48 h from the beginning of fermentation in biofilm reactor. Hopefully this modification does not lead to alternation of the main physicochemical properties of HFBII.

In the mid 70's of the last century, the first attempts were initiated in order to know precisely the Solar Climatology of Mexico. For this, data from heliographs and actinographs were used. Latter, in the 90's models based on the use of satellite images were employed. Currently a number of maps and databases describing spatially and temporally the solar resource distribution in the country can be found on the Internet, but in none of them confidence intervals of data are provided. This is due to a simple reason: historically there were only a handful of weather stations in the country that measured solar radiation over a long period of time. In the last two decades several automatic weather station networks have been established, which include radiometers. However, only very recently the radiometers from these stations have started to be systematically calibrated, and assessment of the quality of the previously measured data initiated.

Food industries are interested in finding highly stable foaming agents for product texture improvements. Hydrophobins have been mentioned many times in that context. For the production and purification of hydrophobin HFBII from Trichoderma reesei we found that foam fractionation of the fungal fermentation media is an interesting first step. After this step, the biophysical properties of the obtained foamate were studied. The foam generated by CO2 as the only sparging gas into a HFBII enriched solution in a closed environment was more stable than the foam generated by sparging with air. The equilibrium surface tension of a foamate containing 100 mg/L HFBII was measured by CAMTEL CDCA-100 tensiometry as equal to 40 mJ/m2, and was confirmed by the maximum bubble pressure tensiometer. Besides, it was found that for a long term foam preservation, the foam created by the HFBII-SDS combination is more stable than that of SDS.

The presence of Class II hydrophobins produced by fungi on barley results in primary gushing of beer. Gushing is the spontaneous overfoaming of carbonated beverages by opening of bottles. Solving gushing problems caused by brewing raw materials has received much scientific attention. Lipophilic extract of hops are introduced to brewers as foam suppressor in fermenters. We studied the effects of hop extract on gushing and found that lipophilic hop extract could reduce gushing. The effects are different when hop extract is added before mashing than when it is added after mashing. Hop extract contains fats and waxes and the effects on gushing are explained by a change in the physical state of its components during mashing which are due to temperature effects. Especially the effect of saturated fatty acids and waxes becomes apparent which are known as gushing inducers. This indicates that with respect to gushing potential of the hop extract's components, it is better to be added to cold wort (after mashing and filtration). Our study also showed an important effect of the filtration step on the amount of gushing.

There are several possible uses of the Class II hydrophobinHFBII in clinical applications. To fully understand and exploit thispotential however, the antioxidant activity and ACE-inhibitory potentialof this protein need to be better understood and have not been previouslyreported. In this study, the Class II hydrophobin HFBII was produced bythe cultivation of wild type Trichoderma reesei. The crude hydrophobinextract obtained from the fermentation process was purified usingreversed-phase liquid chromatography and the identity of the purifiedHFBII verified by MALDI-TOF (molecular weight: 7.2 kDa). Subsequently theantioxidant activity of different concentrations of HFBII (0.01-0.40mg/mL) were determined. The results show that for HFBII concentrations of0.04 mg/mL and upwards the protein significantly reduced the presence ofABTS+ radicals in the medium, the IC50 value found to be 0.13 mg/mL.Computational modeling highlighted the role of the amino acid residueslocated in the conserved and exposed hydrophobic patch on the surface ofthe HFBII molecule and the interactions with the aromatic rings of ABTS.The ACE-inhibitory effect of HFBII was found to occur from 0.5 mg/mL andupwards, making the combination of HFBII with strong ACE-inhibitorsattractive for use in the healthcare industry

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.