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The present study evaluates the performance of thirty-eight (38) parametric solar radiation models under a large range of conditions. The models are used to predict the clear-sky DNI at a 1-min time resolution. High quality radiometric databases, recorded at PSDA station, located in the Atacama Desert, Chile, are used for this analysis. The models have been arranged into seven sets according to their crucial inputs to identify the impact of each parameter on models’ performance. The results show that turbidity-independent models (sets A, B and C) are not suitable for the modeling of solar direct irradiance. Besides, turbidity-dependent models (sets D, E, F, and G) perform so much better than turbidity-independent models. However, few models perform well under all conditions. Among 11 AOD-dependent models, only six models are considered “good”. The performance of the models of set F decreases with the increase of β (aerosols’ turbidity), while those belonging set G perform adequately even at high turbidity. Overall, the accuracy of most models is sensitive to solar elevation and atmospheric turbidity. Besides, some models are accurate only under limited conditions. As a result of this detailed investigation, six high-performance models can be recommended: ESRA, Ineichen, Yang, MLWT1, REST and MWLT2.

In order to make the concentrating solar power (CSP) more competitive, an accurate prediction of the solar radiation incident on CSP tower plant receivers is necessary. The extinction in the heliostat-receiver pathway plays an important role in the optical loss of the solar field and therefore, in the performance of the plant. In order to correctly operate these kind of plants and to select new potential emplacements, it is necessary to know the on-site levels of extinction. A methodology was developed in another published work, called Extinction AOT method (EAM), with the purpose of finding out the levels of extinction present at a location using AERONET AOT as input data. However, there is no AERONET AOT data available at any potential site of interest for setting up a solar tower plant, so, alternative approaches were necessary. This paper proposes to determine levels of extinction at any location using AOT satellite data instead of AERONET data. These results have been compared with results obtained applying the EAM with AERONET data and using real extinction measurements obtained with the CIEMAT extinction measurement system. The extinction obtained at PSA has been 5% in all cases considering the error rates.

Soiling is an issue that impacts the performance of photovoltaic (PV) technologies as it attenuates the amount of solar resource reaching the solar cells. The chemical composition of the soil is essential to define cleaning strategies of photovoltaic companies. This paper reports the characterization of the chemical and physical properties of the soiling deposited on photovoltaic modules located in the Atacama Desert. The particle size, shape and chemical composition of dust were studied at 4 different locations (denoted as L1 to L4) with samples taken from the ground and the module surface. It was found that, most deposited material exhibits a diameter between 1 µm and 60 µm. The determination of the particle shape factor shows that smaller particles tend to have a circular appearance, while larger particles exhibit a prismatic form. These small particles show a shape factor close to 1 and occur at the 4 locations with the greatest frequency, 40–70%. The mineral species in both the deposited and ground dust, which were identified by means of X-ray diffraction, were albite, anorthite, calcite, cristobalite, gypsum, halite, quartz, muscovite and orthoclase. The compounds occurring with the highest frequency in both the module and ground dust at all locations were quartz and anorthite. Differences between the locations were found. Calcite was found only at L3. Gypsum was not detected at L1 and L3 but was present in L2 and L4. Similarly, cristobalite was found only at L1 and L3, halite was found at L2 and L3, and muscovite was found at L1 and L2.

The thermoelectric solar tower plants have had a great development in the last years, evolving from a few MWe to reach a hundred MWe. The location of these large plants in desert areas leads to very specific problems in their design and great uncertainty among CSP promoters. In particular, there is no reliable information on the losses due to solar extinction between the heliostats and the receiver. Consistent information on solar extinction at the chosen site would be desirable in the design phase of the plant and later during its regular operation. Currently, a novel and reliable solar extinction measurement system is daily working at Plataforma Solar de Almeria (PSA). After a year of extinction measurements, it has been possible to analyze the daily and seasonal variability of the extinction phenomenon and know the annual extinction average value at PSA.

The current state of photovoltaic (PV) electricity integration is demanding several strategies that control the optimal performance of PV plants. Cleaning the PV plant, controlling PV production or the estimation of the electricity generation, are some relevant items related to the PV systems. In general, the soiling, the clouds and another climatological factorsare involved in the final PV production. For knowing the performance of a PV system, it is necessity to model the PV plant behavior according to these relevant variables. In this work, a Multiple Linear Regression (MLR) model has been presented to determine the hourly PV production by using the Performance Ratio (PR) factor, according to different technologies: Cadmium Telluride (CdTe) and multicrystallinesilicon (mc-Si). In this sense, data from several PV plants were studied in different Chile regions: San Pedro de Atacama and Antofagasta. With this study, it has been determined that the model can be extrapolated to different climatological emplacements, where generally, the root mean square error (RMSE) presents values lower than 16% in all cases, having the best result the CdTetechnology.

Direct normal solar irradiation is a crucial parameter for site selection and design of solar power tower plants. It also has a high impact on economic studies, such as the levelized cost of electricity (LCOE). However, direct solar irradiation can be partially extinguished in its path between heliostats and receivers. Therefore, considering only direct normal solar irradiation in the solar resource assessment for tower plant projects is insufficient and leads to errors. This paper presents an improved methodology to estimate the extinction of radiation in the first 150 m of the lower atmosphere, where solar power tower plants are located. This work also shows the first atmospheric extinction maps, which in this case are elaborated for Chilean territory, and the intercomparison of extinction values with other places of interest in the sunbelt. Chile stands out for having the lowest annual atmospheric extinction values, below 4% for 1 km of slant range, while elsewhere annual losses can reach up to 17%. These values limit the amount of local useful solar resource available directly impacting on the LCOE values calculated for solar tower power plants. A new equation for the calculation of the LCOE considering atmospheric extinction is proposed in this paper.

Atmospheric factors, such as clouds, wind, dust, or aerosols, play an important role in the power generation of photovoltaic (PV) plants. Among these factors, soiling has been revealed as one of the most relevant causes diminishing the PV yield, mainly in arid zones or deserts. The effect of soiling on the PV performance can be analyzed by means of I–V curves measured simultaneously on two PV panels: one soiled and the other clean. To this end, two I–V tracers, or one I–V tracer along with a multiplexer, are needed. Unfortunately, these options are usually expensive, and only one I–V tracer is typically available at the site of interest. In this work, the design of a low-cost multiplexer is described. The multiplexer is controlled by a low-cost single-board microcontroller manufactured by ArduinoTM, and is capable of managing several pairs of PV panels almost simultaneously. The multiplexer can be installed outdoors, in contrast to many commercial I–V tracers or multiplexers. This advantage allows the soiling effect to be monitored on two PV panels, by means of I–V indoor tracers. I–V curves measured by the low-cost multiplexer are also presented, and preliminary results are analyzed, This research was funded by the Spanish Ministry of Economy, Industry, and Competitiveness “PVCastSOIL” project No ENE2017-83790-C3-1-2-3-R, in collaboration with the European Regional Development Fund

Knowledge of the solar spectrum is essential for the design and study of numerous technologies. Due to the area considered, the harsh conditions and the difficulty for accessing to some zones, information and measurement on local parameters and spectral resource are scarce. This fact, along with the special atmospheric conditions prevailing in Atacama Desert, has led to increasing interest on the part of the solar industry to ascertain the spectral variation respect to that of other places around the world. Considering the standard spectrum for a typical air mass as 1.5, the evaluation of PV module behaviour or device calibration under real conditions can generate a source of uncertainty where spectra may differ. This preliminary paper aims to study the influence of using the standard or local spectra in photovoltaic technologies in Atacama Desert, in order to highlight the necessity for a long-term ground-based measurement campaign. For that purpose, a first approach to the spatio-temporal average of solar spectrum in the Atacama Desert from satellite databases is estimated. Then, local spectra are compared against the Reference Spectra in order to show the differences in studies on solar energy applications. Long-term satellite database information is used to average the atmospheric parameters, such as Aerosol Optical Depth, Ozone, Precipitable Water Vapour, Albedo and Relative Humidity, for the entire Atacama Desert area and is then used to obtain the mean Global tilted Irradiance and Direct plus Circumsolar Irradiance solar spectrum. Finally, to study the influence that the shape of the local spectrum has on the performance of the different solar technologies, the photo-current density of two different solar cell types were studied under Atacama and standard conditions. The results indicate that there are considerable differences with the ASTM G173-03 reference spectra for short wavelengths, especially in the UV spectral range, which is 55% points higher than the reference, which influences in the performance of the solar technologies.

In Concentrating Solar Power (CSP) technologies, direct solar radiation is reflected from a concentrating system to a receiver, where it is transformed into process heat. In particular, in solar tower plants, the phenomenon of atmospheric extinction between both systems must be studied since the radiative losses can be important due to the increasingly large distances in the gradually larger plants. Large distances are necessary in order to measure the extinction since, in reduced distances, it can be undetectable. However, the great uncertainty of some available instruments and/or the monochromaticity of others, make it possible to affirm that, at present, there is no experimental device that allows a credible measure of solar extinction to be carried out. Nowadays, digital cameras are used in many scientific applications due to their ability to convert available light into digital images. Their broad spectral range, high resolution and high signal to noise ratio, make them an interesting device for extinction measurement. The aim of this work is to present the description of a novel measurement system for solar extinction at ground level based on two digital cameras and a Lambertian target. The first experimental results show that the system can measure solar extinction in the bandwidth 400–1000 nm with an accuracy of less than an absolute ±2%. This measurement system is currently running on a daily basis at Plataforma Solar de Almeria.

The use of Lambertian targets is usually required in many measurement procedures of great importance in solar concentration field. Activities such as flux measurement, heliostats characterization and solar extinction measurement in tower plants, among others, require a Lambertian target. In these measurement techniques, the target is expected to reflect solar radiation isotropically while it is recorded as an image by a digital camera and analyzed afterwards. The fact that the target is a perfect diffuser allows neglecting the directional influence of the reflected radiation with respect to the position of the camera. However, in the information available of these measurement techniques there are no published descriptions of methods that demonstrate whether the used target is Lambertian or not. If this point is not verified it could result in a lack of confidence in the measurement performed using the methodology described above. This work presents a simple method to characterize a large outdoor target and allows quantifying its degree of homogeneity and diffusivity. As an example, the characterization of a real target is presented for later use. Currently this procedure is being used at Plataforma Solar de Almeria.

The estimation of daily solar radiation is needed in many studies related to solar power plant placements. To optimize photovoltaic (PV) systems, their placement must be as efficient as possible in terms of the prevailing meteorological conditions. There are situations where radiation data are not available, as in the case of desert areas, suitable for the operation of PV systems. In this work, daily global solar radiation has been estimated in desert areas using Artificial Neural Networks (ANN), where the inputs used are daily minimum and maximum temperatures and extraterrestrial radiation. The ANN model is validated with data from deserts in Chile, Israel, Saudi Arabia, South Africa and Australia. The results show that the average Relative Root-Mean-Square Deviation (RRMSD) value is 13%, the average Relative Mean Bias Difference (RMBE) value is less than 4% and the average correlation coefficient (r) value is about 0.8.

The understanding of soiling processes on photovoltaic modules is a necessary step for the development of cost-effective mitigation methods for the solar industry. This paper analyzes the soiling process for photovoltaic modules installed at the Atacama Desert. For this purpose, the dust deposited on photovoltaic modules and glasses (for one year) was characterized and the location's atmospheric parameters were monitored continuously. The dust samples were separated according to difference in solubility, obtaining three samples: soluble (recrystallized), insoluble (filtered), and original. Through x-ray diffraction measurements it was detected that the soluble part corresponds to gypsum and the other dust components are insoluble or low-solubility salts such as albite, anhydrite, calcite, quartz, and orthoclase. Scanning electron microscopy and energy dispersive x-ray spectroscopy of the dust on photovoltaic glasses show the presence of gypsum with a monoclinic prismatic structure covered with smaller dust particles. These prismatic crystals are also observed after recrystallization of the soluble sample suggesting that gypsum, as a soluble hygroscopic material, has a key role in the cementation process. Atmospheric parameters of each season were characterized through wind velocity, temperature, and relative humidity. All these parameters show large daily oscillation, which trigger a cementation process in which gypsum crystallization, after being completely or partially solubilized, causes the encapsulation of insoluble material.

When the availability of solar radiation is not enough to develop experimental investigation in the field of concentrating solar energy, solar simulators are a widely employed solution. They represent a source of artificial light, which can be comparable with concentrated sunlight. Besides, they provide advantages such as better parametric control of the process under study. In this work, it is presented an extensive review of the high flux solar simulators that are available in the different solar energy research centers around the world. Many of them are similarly designed and have common elements. Others are based on different concepts and their particular features are also pointed out. The main applications of solar simulators reported in literature are discussed along the work and remarked then in a specific section. The authors acknowledge the financial support provided by the FONDECYT project number 3150026 of CONICYT (Chile), the Education Ministry of Chile Grant PMI ANT 1201, as well as CONICYT/FONDAP/15110019 "Solar Energy Research Center" SERC-Chile. In addition, the first author wish to thank the University of Almeria and the Plataforma Solar de Almería for the collaboration and assistance devoted to the development of his Ph.D research.

The soling can negatively affect the performance of photovoltaic systems. We studied the species, which deposit on photovoltaic (PV) modules in northern Chile (Atacama Desert). The environmental conditions are the base for the interaction of dust particles and the module’s surfaces. We considered 4 locations for the study. We determined that the particle size of the dust to deposit on PV modules is smaller than 63 μm for all the selected sites. However, the morphology varies from place to place influencing optical response of the modules. After 4 months dust accumulation the transmittance of PV glass reduced by 55%.

In order to evaluate module materials, the maximum theoretical value of the photo-generated current density, was calculated. The calculation was performed for four different solar cells, a standard p-type, passivated emitter and rear contact (PERC), bifacial cell and interdigitated back contact (IBC) considering a solar spectrum of Atacama Desert, the transmittance of several glass-encapsulant-glass structures and quantum efficiency. Regarding the solar spectrum in Atacama, an average air mass (AM) at noon for this location averaged 1.17 and the photovoltaic (PV) modules tilt angle was 20°. When studying the impact of using glass and encapsulants combined with a solar cell under the same solar spectrum, ethylene vinyl acetate (EVA) with low ultraviolet (UV) cutoff led to the higher current density values, up to 2% higher with the IBC solar cell compared to the other solar cells. The highest current gain, when studying the impact of the two spectra in the 300–1200 nm wavelength range, was 7.4% for the IBC solar cell, obtained with a standard 3.2 mm glass, a thermoplastic material (TM) as encapsulant. Considering the UV part of the spectrum, the current gain was maximized with a glass with an anti reflection coating (ARC) combined with the TM encapsulant for the IBC solar cell (25%). A quantification of losses due to reflection in the glass and absorption in the encapsulant revealed that the glass with ARC and the TM encapsulant different than EVA led to the lowest reflection and absorption losses. In this case, the reflection and absorption came down to 4.8% and 0.9%, respectively, contrasting with the 7% and 2.8% loss produced with the standard glass and EVA encapsulants.

This work presents an Energy Storage Systems (ESS) sizing strategy, that allows grid connected PV systems to provide peak-shaved maximum-power-Ramp-Rate (RR) compliant power while storing exceeding power. For this purpose power generation and power loss caused by complying several RR restrictions were estimated. The estimation is based on irradiance and temperature real data from a measuring station located in the Atacama desert in Chile. The presented sizing strategy is based on Discrete Wavelet Transform (DWT) and allows to obtain an energy and power ESS sizing matching different criterion. Moreover, the selection of the ad-hoc wavelet and decomposition level, required filter the estimated PV power, is also presented.

In the search to optimize electricity generation systems based on renewable energy sources, solar power plants are a clear alternative for reducing pollution on the planet. In particular, concentrating solar power plants with central tower technology supply energy to large population centers and they are generally located at desert sites. Production in these plants drops due to the presence of particles in the environment. These particles are complex to measure and doing so usually requires the use of dedicated, expensive instrumentation. In this work, we present a methodology called Extinction that estimates this attenuation phenomenon utilizing meteorological variables, along with the use of artificial neural networks (ANN). Direct normal irradiance, relative humidity, temperature and pressure have been the only meteorological variables needed to estimate the Extinction. The results from the estimations presented a correlation coefficient value (R) of 0.88 (between the measured and estimated atmospheric horizontal extinction with ANN), a normalized Mean Bias Error (nMBE) of 0% and a normalized Root-Mean Square Deviation (nRMSD) of 7%.

The solar conditions in northern Chile, in particular the Atacama Desert, which presents an annual global radiation value of 2500 kW h/m 2 and an index of direct normal irradiance (DNI) of 3500 kW h/m 2 , are among the best worldwide for capturing and storing solar energy. These features are of major importance when considering the saline deposits that are concentrated in this area. There are several factors that make CSP technology an ideal resource for a successful development in northern Chile, highlighting the excellent solar resource and their combination with storage could supply energy to mining industry, which requires energy 24 h per day. The focus of this paper is to develop an economic analysis for computing a projection of LCOE between 2014 and 2050 from a 50 MW CSP plant with five different composition of salts for it TES. Two different scenarios are considered for this study: IEA BLUE Map Scenario and Roadmap Scenario. Additionally, a comparison between the LCOE in the north of Chile and the most influential countries in solar energy (Spain and USA) is made. The research basis lay on contribution of recent Chilean plans together with international researches in order to support the great potential of the implementation of CSP plant in the north of Chile. The results show that new proposed molten salts reduce considerably the storage cost. Thus, it can contribute to a promising future of the growth of CSP in the Plataforma Solar del Desierto de Atacama (PSDA) at north of Chile.

With an elevation of 1000 m above sea level, once the coastal mountain range is crossed, the Atacama Desert receives the highest levels of solar radiation in the world. Global horizontal irradiations over 2500 kWh/(m2 year) and a cloudiness index below 3% were determined. However, this index rises to 45% in the coastal area, where the influence of the Pacific Ocean exists with a large presence of marine aerosols. It is on the coastal area that residential photovoltaic (PV) applications are concentrated. This work presents a study of the soiling impact on PV modules at the coastline of Atacama Desert. The current–voltage characteristics of two multicrystalline PV modules exposed to outdoor conditions were compared, while one of them was cleaned daily. Asymptotic behavior was observed in the accumulated surface dust density, over 6 months. This behavior was explained by the fact that as the glass became soiled, the probability of glass-to-particle interaction decreased in favor of a more likely particle-to-particle interaction. The surface dust density was at most 0.17 mg·cm−2 per month. Dust on the module led to current losses in the range of 19% after four months, which in turn produced a reduction of 13.5%rel in efficiency.

The extinction of solar radiation is considered an important variable to take into account in the design and operation of commercial concentrated solar power (CSP) tower plants, where the distances between the concentrating heliostats and the receiver on top of the tower are, in many cases, around 1 km. Aerosol particles and water vapor in the path traveled by solar radiation are the main causes of its extinction due to the phenomena of scattering and absorption. Since June 2017, solar extinction has been reliably measured daily at Plataforma Solar de Almeria, which has allowed analyzing the dependence of this parameter with other meteorological variables. It has been observed that during high turbidity events there is a clear linear dependence of the solar extinction with the particle concentration and humidity. This work shows that, although this linear character is diluted under normal conditions, artificial neural networks (ANN) allow modeling and predicting extinction as a function of these two magnitudes.

A Typical Meteorological Year (TMY) is frequently used in solar power for long-term energy yield analysis. Different approaches have been reported focusing on concentrating solar power or photovoltaic power plants that have established different relative contributions of the involved variables (mainly solar irradiance components and temperature) according to the application. For PV applications the estimation of the spectral gains and losses requires of on-site spectral measurements. Long-term analysis of the spectral influence on PV technologies has been performed for over seven years of measured spectral global tilted irradiance in Madrid. The experimental spectra were measured with an EKO spectroradiometer in the wavelength range of 300–1100 nm. The TMY methodology has been used to create a typical spectral year of global tilted irradiance that can be used for computing the spectral factor. This paper shows the different steps in applying the TMY methodology to spectral irradiance and the resulting spectral factors computed for seven different PV technologies. Thus, this approach can effectively be used to characterize the long-term spectral influence of PV technologies in a selected site.

In the search for techniques that control the final energy reaching the receivers of central solar power plants, this work presents a novel combination of several methodologies for establishing a complex and valuable system within the user operating system. To establish the final energy level in the central receiver, the direct normal irradiance (DNI) was predicted at ground level using METEOSAT images combined with a novel system involving two digital cameras that determine atmospheric E x t i n c t i o n in the lower atmospheric layer. The predicted values were used as inputs for a solar plant model (Fiat-Lux) to trace the path of the sunlight according to the mirror features. The flux simulations presented a normalized root-mean square error (nRMSE) below 6% and correlation coefficients (R) above 0.94 when compared to real and predicted values. Therefore, it would be possible to quantify the losses produced in the path between the heliostats and the central receiver by integrating different technologies.

The implementation of a different approach for the estimation of the maximum photo-generated current density ($J_{\max}$) regarding internal parameters of the cell and its optical performance was performed introducing an effective optical pathlength enhancement factor, Z($\lambda$). Different PV devices were considered, including dssc, under the world reference and averaged local spectra estimated for the Atacama Desert, under air masses equal to 1.5 and 1.08, respectively. This model was successfully implemented to predict $J_{\max}$ with higher reliability which makes it suitable to be applied to any type of solar cell developed or simulated.

Soiling is currently one of the major issues for decreasing power production of PV plants in Chile. In order to prevent significant power losses cleaning frequencies of more than one time per month are scheduled. In the present study, we investigate the impact of soiling on energy yield (YA) of bifacial solar modules with different material combinations. We fabricated half-size and full-size one cell modules employing different glass thicknesses, encapsulants, transparent backsheets and glass-glass module configurations. Based on indoor current-voltage (IV) measurements which were carried out on front and rear side of each bifacial module type at different irradiance levels, a mathematical YA model was applied. Front and rear measurements were taken separately and simultaneously assuming the same bifaciality factor at a given irradiation. YA estimations show that module groups with half-cell design achieve the highest YA values compared to full-cell design. In addition, vertically mounted bifacial modules (VMBM) produce higher YA than tilted mounted bifacial modules (TMBM) if the power loss rate due to soiling is higher than 0.10% per day. To validate the YA model, real outdoor measurements were carried out in the Atacama Desert in Chile for TMBM and for VMBM.

In this work an alternative method for emittance determination based on pyrometric measurements is presented. The measurement procedure is limited by the spectral range of the infrared sensors used in this work (1400–5000 nm) and by its working temperature range (500–1000 °C). The measurement procedure has been applied to sintered SiC samples in the Plataforma Solar de Almeria solar furnace SF40. The experimental results show that emittance decreases with increasing temperature and wavelength with a main value of 0.80. This behaviour is in agreement with experimental results obtained by other authors. Analysis of tests has revealed a good repeatability (1%) and accuracy (