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• Several cloud enhancement event definitions compared. • A novel model-independent, statistically driven detection framework is proposed. • Cloud enhancement events are quantified, described and analized at eight locations. • Results contextualized against maximum expected clear sky irradiances. • Record irradiance values for thermopile and photodiode sensors are reported. Cloud enhancement events are instances in which the cloud pattern increases global horizontal irradiance on the ground above levels higher than would otherwise be expected during clear sky with cloudless conditions, and in general, these events are characterized by high irradiances occurring during highly changing transient conditions. Even though it is a well-known although infrequent phenomenon, currently no consensus exists as to its formal definition. However, several studies point out to a need for a better understanding of this phenomenon due to their effects on mathematical models or photovoltaic systems behavior during these instances, as results show significant deviations with respect to the expected results in normal conditions. Due to these issues, the present work intends to explore cloud enhancement definitions and detection methods, for which a novel model-independent, statistically-driven approach is proposed and compared to three other models found in the literature. Assessments are made regarding the main aspects of the phenomenon: frequency of occurrence, clearness index, diffuse fraction and its relationship with solar resource variability. Data from eight measurements sites throughout Chile, with different climatic characteristics is used. To further support the analysis made, monthly maximum expected clear sky irradiance for each site was estimated through satellite-based data as well as with estimation from ground measurements. Finally, the highest irradiances are presented for each measurement site reporting, the record irradiances for one-minute data thermopile and photodiode pyranometers. [ABSTRACT FROM AUTHOR]

Highlights • An exergy cost assessment of cogeneration, trigeneration, and polygeneration plant is performed. • A multi-generation schemes are configured to generate electricity, fresh water, cooling, and heat. • Replacing the condenser by multi-effect distillation is cost effective in terms of unit exergy cost. • Coupling the refrigeration plant and process heat module to turbine extractions are more cost effective. • Solar collectors and productive subsystems constitute the key equipment to improve the design. Abstract An exergy cost assessment of integrated solar multi-generation schemes, which includes cogeneration, trigeneration, and polygeneration schemes, for the joint production of electricity, fresh water, cooling, and process heat, is carried out. This evaluation process allows finding out the key equipment to improve the design, detect potential energy savings, and establish the best configurations of these schemes, in terms of unit exergy cost, total exergy cost, and exergy efficiency. The methodology includes modelling and evaluating the performance of solar multi-generation schemes and stand-alone systems, by applying the symbolic exergoeconomic methodology. The solar multi-generation schemes consider a concentrated solar power as the prime mover, which is coupled to a multi-effect distillation, an absorption refrigeration, and a process heat plant. Twenty-one configurations were investigated, twenty of them regarding solar multi-generation plants: eight of cogeneration, eight of trigeneration, four polygeneration schemes, and the other one considering stand-alone systems. This study reveals that the recommended configurations for the solar multigeneration schemes are those in which the desalination plant replaces the condenser of the power cycle, and the refrigeration plant, as well as the process heat module are coupled to turbine extractions. Furthermore, the main components contributing to the cost formation of electricity are, in this order, solar collectors, evaporator, and reheater. In the case of by-products generated, the main components are dissipative systems, solar collectors, and productive subsystems (multi-effect distillation, refrigeration, and process heat plants). In consequence, they constitute the key equipment that could be improved. Finally, solar multi-generation schemes are more cost effective than stand-alone systems. For instance, the best option within the polygeneration schemes analyzed allowed reducing the unit exergy cost about 6.8%, 59.2%, 45.6%, and 32.2% for electricity, water, cooling, and process heat respectively. Therefore, solar multi-generation schemes are identified as a promising alternative for zones with high irradiation conditions and scarcity of water, where the CSP technology can be the prime mover. [ABSTRACT FROM AUTHOR]

Numerical simulations were performed to investigate a microchannel heat sink device as cooling option for a high concentration photovoltaic system. COMSOL Multiphysics 5.1 software is used to solve three-dimensional equations which consider conjugate heat transfer, viscous dissipations, and temperature-dependent-properties. This study investigates the integration of microchannels with complex geometric features on its inner walls into the solar cell structure, to enhance the heat transfer performance of a microchannel heat sink-based active cooling system. Inner sidewall mounted forward triangular ribs are considered in aligned and offset distributions along the microchannel walls. In addition, numerical analysis is developed for a conventional flat plate heat sink integrated to a high concentration photovoltaic system to stablish a baseline solar cell temperature. The numerical results show that a micro-channel heat sink device can control and keep in very low range the solar cell temperature (<301 K). Compared to a smooth microchannel, forward triangular ribs installed on the sidewalls enhance the heat transfer capability. Microchannels with aligned and offset rib distributions increase the Nusselt number between 1.8 and 1.6 times, respectively, and increase the average friction factors between 3.9 and 2.3 times, respectively. The microchannel heat sink device with forward triangular ribs is more efficient and effective at Re ≤ 200, since the pumping power reaches a high percentage of the total power generated by solar cell when Re > 200. At Re = 400, the pumping power reaches 41% and 23% of the total power generated by a multi-junction solar cell in the aligned and offset rib distribution, respectively. The pumping power is greatly reduced while using smooth microchannel, because the maximum pumping power is only 9.5% of the solar cell power at Re = 400, however, the resulting solar cell temperature is slightly higher compared to microchannels with aligned and offset rib configurations. A microchannel heat sink provides a more effective cooling solution compared to a passive flat plate heat sink for a high concentration photovoltaic system. In addition, the possibility of direct integration of a microchannel heat sink into a solar cell structure as proposed in this study, represents an interesting option to feasibly increase thermal performance to a considerable level by maintaining the solar cell temperature in a very low range. [ABSTRACT FROM AUTHOR]

The present work shows a comparison between the levelized cost and the thermoeconomic methods in their application to assess the performance of a solar polygeneration plant. The aim is to analyze the costs allocation process, the unit specific costs of each product, as well as the energy and exergy efficiencies, which allows to identify the main advantages of both the evaluated methods. The methodology is applied in a case study configured by a concentrated solar power with thermal energy storage and backup system, combined to a multi-effect distillation plant, an absorption refrigeration plant, and a process heat module. The present study reveals that through the levelized cost method, the cost associated to the electricity generation is higher than it is by applying the thermoeconomic method, whereas the costs of water, cooling and process heat are significantly lower. Those differences represent an increase of about 35.1% in the case of the electricity, and a reduction in the cost associated to the water, cooling, and heat production by around 34.4%, 78.1%, and 97.6%, respectively. Results show that the thermoeconomic method is an equitable and rational cost allocation method which is suitable for a solar polygeneration plant. This method is recommended when a more precise analysis is required to assess the proper costs of different products, and for assessing the benefits of a polygeneration plant, when compared to stand-alone plants. However, the levelized cost method is a simple and fast method, and a deep knowledge of thermodynamics is not required, being recommended when in need to perform a first approach of the costs of each product. [ABSTRACT FROM AUTHOR]

A thermoeconomic assessment of the joint production of electricity, fresh-water, cooling and heat for a solar polygeneration plant is carried out. The aims are to assess the actual cost of each product, to conduct a sensitivity analysis of investment, fuel cost and demand, and to evaluate the effects of solar field size and the sizing of thermal energy storage, for a polygeneration plant located in an area with high solar irradiation conditions and where there is demand for its production. The solar polygeneration plant is configured by a concentrated solar power (CSP) parabolic trough collector field with thermal energy storage and backup system, multi-effect distillation (MED) module, single-effect absorption refrigeration module, and process heat module. The solar polygeneration plant is simulated in a transient regime, in a representative location with high irradiation conditions, such as in northern Chile. Three configurations are investigated: two polygeneration schemes and one considering stand-alone systems. This study reveals that a solar polygeneration plant is more efficient and cost-effective than stand-alone plants for a zone with high irradiation conditions and proximity to consumption centers, such as mining industries, which require continuous operation and energy supply with fundamentally constant demand. Furthermore, according to northern Chilean market, solar polygeneration configurations are competitive regarding electricity, fresh-water, cooling and heat productions. Additionally, solar polygeneration plants can increase the economic profit by selling carbon credits and credits of renewable-energy quotas based on the Kyoto Protocol and Chilean legislation, respectively. [ABSTRACT FROM AUTHOR]

In this study, a polygeneration system incorporating concentrating solar power (CSP) integrated with a desalination plant is investigated. Parabolic trough collectors (PTC) and multi-effect distillation (MED) technologies are considered, and a transient system model has been simulated using the TRNSYS software. Two alternative desalination integration options and two potential locations in Venezuela and Chile with electricity and freshwater supply problems were selected and studied. Chile has also set a 20% target for non-conventional renewable energy production by 2025; therefore a polygeneration system coupled with desalinization plant is aligned with the needs of both countries. The results show that the CSP polygeneration plant can provide electricity and freshwater to more than 85,000 inhabitants at a reasonable cost; however the costs and feasibility depend principally on the irradiation, the location of plant with respect to the sea, and the specific conditions of each country. With the projected costs expected to decrease, it could be feasible to develop a CSP polygeneration plant in either country. For the Chilean case, LEC and LWC can be reduced to competitive prices if the initial PTC investment cost could be reduced by 15% for the Chilean case, and by 25% for the Venezuelan case. [ABSTRACT FROM AUTHOR]

The progress in solar energy resource assessment for Chile is reported, including measurements from a ground station network spanning more than three years of data, satellite estimations from the recently developed Chile-SR model including three full years of data, and simulations that evaluate the potential for solar thermal, photovoltaics (PV) and concentrated solar power (CSP) utilization. The satellite estimation model adapts the Brasil-SR methodology with the combined use of visible and infrared (IR) satellite images, an enhanced treatment for altitude-corrected meteorological variables and an effective cloud cover computations that allows the estimation of the global horizontal and diffuse horizontal irradiation on an hourly basis. Direct normal irradiation (DNI) is computed from the direct horizontal irradiation by applying the Boland–Ridley–Laurent (BRL) model of diffuse fraction and proper solar geometry corrections. Comparison of the satellite-derived data with the ground station data shows good agreement and low error levels thus served for model validation. The results indicate that Chile is endowed with one of the highest levels of solar resource in the world in terms of annual irradiation for large portions of its territory. There is a small decrease in yearly levels of GHI and DNI with latitude that in practice indicate that most of the country shares exceptional conditions for solar energy. However, coastal regions have a large decrease in both GHI and DNI due to the persistence of seasonal cloud covers with daily cycles. The use of irradiation data from the Chile-SR model for system simulation indicates that solar fractions over 80% are achievable for residential-sized solar thermal systems in most of the country, with PV systems yielding between 4.5 and 8 kW h/kWpv, and CSP annual yields of up to 240 GW h/year for a 50 MW parabolic trough plant. These results indicate that the country has the potential for ample utilization of solar energy conversion technologies in most of its territory when considering annual GHI and DNI, suitable terrain availability and energy (electricity and heat) demand from industrial, commercial and residential activities. [ABSTRACT FROM AUTHOR]

The latest generation of concentrated solar power (CSP) systems uses supercritical carbon dioxide (s-CO2) as the working fluid in a high-performance recompression Brayton cycle (RcBC), whose off-design performance under different environmental conditions has yet to be fully explored. This study presents a model developed using the Engineering Equation Solver (EES) and System Advisor Model (SAM) to evaluate the operation of two solar-driven s-CO2 RcBCs over a year, considering meteorological conditions in northern Chile. Under design conditions, the power plant outputs a net power of 25 M W with a first-law efficiency of 48.3%. An exergy analysis reveals that the high-temperature recuperator contributes the most to the exergy destruction under nominal conditions. However, the yearly simulation shows that the gas cooler's exergy destruction increases at high ambient temperatures, as does the turbine's during off-design operation. The proposed cycle widens the operational range, offering a higher flexibility and synergistic turndown strategy by throttling the mass flow. The proposed cycle's seasonal first-law efficiency of 39% outweighs the literature cycle's 29%. When coupled to a thermal energy storage system, the proposed cycle's capacity factor could reach 93.45%, compared to the value 76.45% reported for the cycle configuration taken from the literature. [ABSTRACT FROM AUTHOR]

The progress from the last four years in solar energy resource assessment for Chile is reported, including measurements from a ground station network spanning from two to three years of data, and satellite estimations from the recently developed Chile-SR model including two full years of data. The model introduces different procedures for the meteorological variables and the effective cloud cover computations that allow estimation of the global horizontal and diffuse irradiation on an hourly basis. Direct normal irradiation is computed by applying proper solar geometry corrections to the direct horizontal irradiation. The satellite estimation model was developed as an adaptation from Brazil-SR model, with an improved formulation for altitude-corrected atmospheric parameters, and a novel formulation for calculating effective cloud covers while at the same time detecting and differentiating it from snow covers and salt lakes. The model is validated by comparison with ground station data. The results indicate that there are high radiation levels throughout the country. In particular, northern Chile is endowed with one of the highest solar resources in the world. [ABSTRACT FROM AUTHOR]

OBJECTIVES To determine if there is any real difference between complete preservation (CP) and partial preservation (PP) of the mitral valve apparatus during mitral valve replacement (MVR) in terms of hard outcomes. METHODS MEDLINE, EMBASE, CENTRAL/CCTR, SciELO, LILACS, Google Scholar and reference lists of relevant articles were searched for clinical studies that compared outcomes [30-day mortality, postoperative low cardiac output syndrome (LCOS), 5-year mortality or left ventricle ejection fraction (LVEF) before and after surgery] between MVR-CP vs MVR-PP during MVR until July 2012. The principal summary measures were odds ratios (ORs) with 95% confidence interval (CI)—for categorical variables (30-day mortality, postoperative LCOS, 5-year mortality); difference means and standard error (SE)—for continuous variables (LVEF before and after surgery) and P values (that will be considered statistically significant when <0.05). The ORs were combined across studies using DerSimonian–Laird random effects weighted model. The same procedure was executed for continuous variables, taking into consideration the difference in means. RESULTS Eight studies (2 randomized and 6 non-randomized) were identified and included a total of 1535 patients (597 for MVR-CP and 938 for MVR-PP). There was no significant difference between MVR-CP or MVR-PP groups in the risk for 30-day mortality (OR 0.870; 95% CI 0.50–1.52; P = 0.63) or postoperative LCOS (OR 0.35; 95% CI 0.11–1.08 and P = 0.07) or 5-year mortality (OR 0.70; 95% CI 0.43–1.14; P = 0.15). Taking into consideration LVEF, neither MVR-CP nor MVR-CP demonstrated a statistically significant improvement in LVEF before and after surgery, and both strategies were not different from each other. No publication bias was observed. CONCLUSIONS We found evidence that argues against any superiority between both techniques of preservation (complete or partial) of mitral valve apparatus during MVR. [ABSTRACT FROM PUBLISHER]

Abstract: The deployment of renewable energy power plants is a priority of the Chilean government. A mandatory quota system requires that 5% of the electricity generated in the country must come from renewable energy sources, gradually increasing to 10% by 2024. As of 2010, solar energy has received attention only for small-scale future demonstration projects. Concentrated solar power (CSP) plants are an interesting option for the country, especially when considering the high levels of solar radiation and clearness index that are available in northern Chile. Here we present a thermal and economic analysis of CSP plants of the parabolic trough type, comparing five different configurations including thermal energy storage and fossil fuel backup. The electricity yields are obtained from hourly simulations that consider radiation levels, solar field, and power plant characteristics. An economic model that includes the costs of construction, operation and maintenance allows predicting the levelized electricity cost (LEC) as a function of plant configuration and location. The results indicate that the plants can produce dispatchable electricity at a cost that is competitive and inversely proportional to radiation levels. A sensitivity analysis is conducted in order to determine the influence of solar field area and radiation levels, and the optimal plant configuration and solar field area are obtained as a result. [Copyright &y& Elsevier]

Abstract: Chilean energy policy goals attempts to promote efficiency and sustainability in the energy system. These objectives have been considered in recent modifications to the electricity generation laws by establishing that generation companies must reach a quota of up to a 10% from renewable energy sources by 2024. Concentrated solar power (CSP) is an interesting alternative to help achieve those objectives, as it is estimated that northern Chile has high radiation levels, coupled with the high values of the local clearness index and flat land availability. However, from the sustainability point of view it seems necessary to assess if a CSP plant is effectively an energy source. Here we propose a hybrid solar power plant lifecycle model which through a net energy analysis obtains and analyzes the plant energy sustainability attributes such as net energy, energy return over investment and energy payback time. The stages of construction, operation, maintenance and decommissioning are considered in the lifecycle analysis. The model is then applied in order to determine good locations where to install a CSP plant in the Chilean Atacama Desert. Monthly means of solar radiation are used in order to estimate the solar fraction for a 100MW direct steam generation parabolic trough collector plant. The results indicate that solar power plants are effectively a net energy source for the analyzed locations, and that higher energy costs are related to the fossil fuel backup lifecycle. A relation is established between yearly radiation, energy return over investment and energy payback time. It is estimated that the net energy analysis is a useful tool for determining under which conditions a power plant becomes a net energy source and therefore a more convenient option from the sustainability point of view, and thus can be utilized in order to define best geographical locations and operation conditions for different renewable energy sources. The sustainability attributes are greatly enhanced when considering a solar-only operation mode, which highlights the advantages of using that configuration, and presents a case for the use of thermal energy storage systems rather than fossil fuel hybridization if a constant or dispatchable energy profile is required. [Copyright &y& Elsevier]

This study investigated changes in the urine dihydroxyphenylglycol to norepinephrine ratio in patients with attention-deficit hyperactivity disorder (ADHD) treated with atomoxetine. The possible relationship with clinical response was also explored. Newly ADHD diagnosed, treatment-naïve children or adolescents were double-blindly randomized (2:1) to atomoxetine (n = 28) or placebo (n = 13). The dihydroxyphenylglycol to norepinephrine ratio decreased in both groups, showing significantly greater changes with atomoxetine than with placebo at week 6 (-42% versus -14%; P = .001), when dosed at 1.2 mg/kg/day, than at week 2 (-20% versus -2%; P = .118) with a dose of 0.5 mg/kg/day. Although the significant dihydroxyphenylglycol to norepinephrine ratio decrease with atomoxetine indicated norepinephrine transporter blockade, no association with ADHD clinical response (ADHD Rating Scale-IV-Parent:Investigator) was found. Therefore, dihydroxyphenylglycol to norepinephrine ratio might be a useful pharmacodynamic/pharmacokinetic biomarker, although not sufficiently sensitive to predict clinical efficacy. It remains a possibility that this ratio might have value to facilitate personalized atomoxetine pharmacotherapy in ADHD patients. [ABSTRACT FROM AUTHOR]

Abstract: The Chilean government has determined that a renewable energy quota of up to 10% of the electrical energy generated must be met by 2024. This plan has already sparked interest in wind, geothermal, hydro and biomass power plants in order to introduce renewable energy systems to the country. Solar energy is being considered only for demonstration, small-scale CSP plants and for domestic water heating applications. This apparent lack of interest in solar energy is partly due to the absence of a valid solar energy database, adequate for energy system simulation and planning activities. One of the available solar radiation databases is 20–40 years old, with measurements taken by pyranographs and Campbell–Stokes devices. A second database from the Chilean Meteorological Service is composed by pyranometer readings, sparsely distributed along the country and available from 1988, with a number of these stations operating intermittently. The Chilean government through its National Energy Commission (CNE) has contracted the formulation of a simulation model and also the deployment of network of measurement stations in northern Chile. Recent efforts by the authors have resulted in a preliminary assessment by satellite image processing. Here, we compare the existing databases of solar radiation in Chile. Monthly mean solar energy maps are created from ground measurements and satellite estimations and compared. It is found that significant deviation exists between sources, and that all ground-station measurements display unknown uncertainty levels, thus highlighting the need for a proper, country-wide long-term resource assessment initiative. However, the solar energy levels throughout the country can be considered as high, and it is thought that they are adequate for energy planning activities – although not yet for proper power plant design and dimensioning. [Copyright &y& Elsevier]

Abstract: In response to environmental awareness, Chile introduced sustainability goals in its electricity law. Power producers must deliver 5% from renewable sources by 2010 and 10% by 2024. The Chilean desert has a large available surface with one of the highest radiation levels and clearest skies in the World. These factors imply that solar power is an option for this task. However, a commercial plant requires a fossil fuel system to backup the sunlight intermittency. The authors developed a thermodynamical model to estimate the backup fraction needed in a 100 MW hybrid -solar-fossil- parabolic trough power plant. This paper presents the model aiming to predicting the performance and exploring its usefulness in assisting site selection among four locations. Since solar radiation data are only available in a monthly average, we introduced two approaches to feed the model. One data set provided an average month with identical days throughout and the other one considered an artificial month of different daylight profiles on an hourly basis for the same monthly average. We recommend a best plant location based on minimum fossil fuel backup, contributing to optimal siting from the energy perspective. Utilities will refine their policy goals more closely when a precise solar energy data set becomes available. [Copyright &y& Elsevier]

Abstract: The lattice Boltzmann method (LBM) is used to investigate one-dimensional, multi-length and -time scale transient heat conduction in crystalline semiconductor solids, in which sub-continuum effects are important. The implementation of this method and its application to electronic devices are described. A silicon-on-insulator transistor subject to Joule heating conditions is used as a case study to illustrate the essence of the LBM. We compare our LBM results, for the diffusive to the ballistic transport regimes, with various hierarchical methodologies of heat transport such as the Fourier, Cattaneo, and ballistic-diffusive transport equations. [Copyright &y& Elsevier]

Computational investigations of flow mixing and oxygen transfer characteristics in an intravenous membrane oxygenator (IMO) are performed by direct numerical simulations of the conservation of mass, momentum, and species equations. Three dimensional cam putational models are developed to investigate flow-mixing and oxygen-transfer characteristics for stationary and pulsating balloons, using the spectral element method. For a stationary balloon, the effect of the fiber placement within the fiber bundle and the number of fiber rings is investigated. In a pulsating balloon, the flow mixing characteristics are determined and the oxygen transfer rate is evaluated. For a stationary balloon, numerical simulations show two well-defined flow patterns that depend on the region of the IMO device. Successive increases of the Reynolds number raise the longitudinal velocity without creating secondary flow. This characteristic is not affected by staggered or non-staggered fiber placement within the fiber bundle. For a pulsating balloon, the flow mixing is enhanced by generating a three-dimensional time-dependent flow characterized by oscillatory radial, pulsatile longitudinal and both oscillatory and random tangential velocities. This three-dimensional flow increases the flow mixing due to an active time-dependent secondary flow, particularly around the fibers. Analytical models show the fiber bundle placement effect on the pressure gradient and flow pattern. The oxygen transport from the fiber surface to the mean flow is due to a dominant radial diffusion mechanism, for the stationary balloon. The oxygen transfer rate reaches an asymptotic behavior at relatively low Reynolds numbers. For a pulsating balloon, the time-dependent oxygen-concentration field resembles the oscillatory and wavy nature of the time dependent flow. Sherwood number evaluations demonstrate that balloon pulsations enhance the oxygen transfer rate, even for smaller flow rates. [ABSTRACT FROM AUTHOR]

The failure of subjects to complete clinical trials is a common problem with important implications for the interpretation of study results. Although a substantial literature exists on the high prevalence of premature termination from psychiatric and substance abuse treatment settings, there has been little attention paid to early discontinuation in clinical trials. There is evidence that the presence of substance abuse predicts higher rates of early discontinuation. This, combined with a recent increase in efforts to develop medications for treatment of substance use disorders, led us to conduct a literature review to determine whether pharmacotherapeutic trials for patients with these disorders have higher rates of premature discontinuation than comparable studies of patients with other psychiatric disorders. Of 267 articles that were initially identified, 83 met predetermined criteria for inclusion in the analysis. As hypothesized, after controlling for a number of potential contributing variables, treatment trials with substance abuse patients showed a significantly poorer retention rate than those of patients with other psychiatric diagnoses. The difference in retention rate was also evident when studies specific to alcohol dependence, the largest subgroup of substance use disorders, were evaluated separately. Although the retrospective nature of the study design limits the conclusions that can be drawn, the results suggest that, in pharmacotherapy trials with alcoholics or other substance abuse patients, particular attention should be paid to enhancing treatment retention. [ABSTRACT FROM AUTHOR]

Concentrated Solar Power (CSP) and geothermal energy systems are outlined as two of the most promising technologies for sustainable and reliable electricity generation. Several studies in the technical literature have pointed out that the hybridization of solar and geothermal energy sources could lead to a reduction of the levelized cost of energy (LCOE) of geothermal systems, as well as improving the capacity factor of CSP systems. However, the technical literature shows that the integration of solar thermal collectors does not present a positive impact in all scenarios analyzed. The present study aims to further analyze the competitiveness of the hybridization of solar and geothermal systems under high irradiation conditions such as those observed in the Andean region in northern Chile. The evaluation was carried out by coupling a thermodynamic model in Engineering Equation Solver (EES) with a solar thermal model in the System Advisor Model (SAM). The assessment considers the configuration of an existing geothermal plant, considering the design constraints associated with the actual operating conditions of the plant. The analysis is based on an energy and exergy assessment, allowing us to identify the efficiency of the subsystems introduced for the hybridization and assess the competitiveness of the hybrid schemes by an economic assessment in terms of the LCOE. The results show that the hybrid schemes allow a reduction of the LCOE of a geothermal stand-alone plant by about 10 USD / MWh , increasing the competitiveness of the geothermal system. However, a large variation on such a reduction is observed depending on the size of the solar field and the storage tank of the solar system. [ABSTRACT FROM AUTHOR]

Thermal energy storage (TES) systems can be used for recovering industrial waste heat and increasing energy efficiency, especially when coupled to batch thermal processes. Stratified water thermal storage tanks are the preferred technology for low-temperature applications, while molten salts are commonly used in medium and high-temperature applications with large storage capacities. No clear consensus exists on the appropriate TES technology for different industrial demands characteristics and their respective heat supply systems for medium and high-temperature applications. The present study analyzes several industrial sectors and their thermal processes, analyzing their temperature ranges, heat demands, and available TES technologies, which are classified by their operational conditions. The study presents two novel indicators for a preliminar compatibility assessment between TES and industrial sectors: a temperature compatibility indicator and exergy efficiency for TES and thermal processes. The results show that low and medium-temperature applications such as food, chemical, or textile industries exhibit high compatibilities with water (over 64%), high-temperature PCM (over 61%), and solid-state TES (100%), whereas molten salts and chemical looping demonstrate lower compatibility (below 24%). The exergy analysis for industrial cases shows that a lower temperature operating range for a TES induces low exergy efficiency. Regarding this scenario, high-temperature cPCM reaches efficiencies of over 44% for mid and high-temperature processes. Conversely, solid-state TES emerges as the most viable option for integration in high-temperature industries, exhibiting an efficiency of 62% with minimal exergy losses. The indicators defined in this study can be used for an early evaluation of TES integration in industrial applications, thus promoting emerging technologies selection through a quantitative comparison of the compatibility metrics. • Assessment of the potential for using TES in industrial heat supply systems. • Definition of compatibility metrics for TES based on temperature and exergy losses. • TES sizing and evaluation of compatibility indicators in industrial plant scenarios. • Applications below 300 °C exhibit several compatible TES, such as Water or PCM. • Solid-state TES shows the best results for high-temperature industrial heat demand. [ABSTRACT FROM AUTHOR]

Santiago de Chile frequently suffers from atmospheric pollution that contributes to the decrease of solar irradiance on the surface, leading to losses in the energy output of photovoltaic systems. In this study, a simple model is used to estimate the effect of aerosols on the solar irradiance over the city throughout the year, using as input AERONET sunphotometer data and other in-situ measurements. The results show reductions of 3.5% and 14.1% for global horizontal and direct normal irradiance respectively and an increase of 35.4% for diffuse horizontal irradiance between the actual condition in Santiago and a hypothetical atmosphere free of aerosols. These effects translate approximately to an annual difference in the energy output of −7.2% and −8.7% for monocrystalline and amorphous silicon PV technologies respectively, and an annual difference of −16.4% for a CPV technology, showing that aerosols can have a significant effect on the photovoltaic energy production. • Aerosols produce a significant decrease of incoming solar irradiance in Santiago. • This reduction also translate to less power output using different PV technologies. • Observations and a model were used to estimate the irradiance and PV power year long. • Losses due to the atmospheric column of aerosols depends on the PV technology. [ABSTRACT FROM AUTHOR]

Highlights • Soiling rate of 0.236%/day is obtained for the bifacial module during experiment. • Soiling rate of 0.301%/day is obtained for the monofacial module during the experiment. • Soiling rate of 0.0394%/day calculated for the rear side of the bifacial module. • Not cleaning the rear side of the bifacial PV system might be a suitable strategy. Abstract Bifacial photovoltaic (PV) modules and cells can transform solar radiation into electricity from both front and rear sides, unlike traditional solar technologies which can only generate power through the front face. This ability has shown to increase electric output with various levels of increment, depending on parameters such as distance to the ground, distance between modules, and albedo. This power gain characteristic versatility has attracted the industry, gaining both commercial and research interest. Measuring soiling effects in bifacial modules is an important milestone for the technology, since it is an important source of efficiency loss, thus relevant to the industry when evaluating and designing bifacial systems. In this work soiling rates are measured for bifacial minimodules and compared with traditional monofacial minimodules. The experiment was carried out for a period of two months in Santiago, Chile, measuring short circuit current of the minimodules along with the irradiance in the module plane and albedo. Also, a methodology is proposed to distinguish between soiling in the front and rear sides of bifacial modules, with which a mixed integer lineal problem is designed to obtain optimum cleaning frequency under different strategies and conditions for a period of three years, from 2014 to 2016. It is observed that soiling rate in the monofacial minimodule is 0.301%/day, meanwhile a rate of 0.236%/day was measured for the bifacial module. Also, a rate of 0.0394%/day was calculated for the rear side of the bifacial module, roughly 8.8 times smaller than the front side rate. Finally, several optimizations and simulations where performed to see the effects of soiling rate, albedo, rain, cleaning costs and strategy in cleaning frequency of both the front and rear sides of a bifacial PV system. [ABSTRACT FROM AUTHOR]

Climate change has caused growing concern in the international community. The Kyoto Protocol was signed by a majority of the world with the clear intention of reducing emissions. Clean Development Mechanism (CDM) is a part of the Kyoto Protocol and allows industrialized countries to reduce their emission by making contribution to developing countries. In this study, several research papers related to sustainability and multi-criteria analysis of energy projects were reviewed and classified based on their focus, motivation and contribution to achieve a comprehensive summary. Additionally, this paper presents a review of multi criteria decision methods and sustainability indicators under five pillars: technical, economic, social, environmental, and risk. Moreover, sustainability analysis of worldwide CDM concentrated solar power (CSP) projects was performed by using MAUT method. The analysis was repeated based on several scenarios including different criteria and criteria weights. The purpose of this research is proposing a framework and providing an understanding for decision makers to evaluate the sustainability of CDM energy projects. This work can provide perceptions to future installations and further insights for the development of sustainable CDM energy projects around the world. [ABSTRACT FROM AUTHOR]

Sustainable greenhouses have gained relevance in recent years due to their potential to reduce the carbon footprint of the agricultural sector by being integrated with renewable systems, contributing to the decarbonization of energy. Although solar technologies tend to be more accessible to cover the system's energy demands, greenhouses are subject to installation area restrictions, limiting their energy potential. This research evaluates the energy advantages of hybridizing solar thermal collector fields with photovoltaic module fields to cover a greenhouse's cooling and heating demands. For this purpose, the solar thermal field and the photovoltaic solar system were simulated with TRNSYS and MATLAB, respectively, while a method was developed to simulate the performance of a single-effect absorption chiller that was validated using the temperature measurements of a chiller in operation. The results show that the general method maintains differences between measurements and simulation smaller than 5 % with set temperatures between 5.5 and 12 degrees Celsius. The hybrid system, with an air-to-water chiller as the main machine and absorption chiller, reached a solar fraction of 0.85 and a fractional energy saving of 83 % . This represents a 27 % reduction in area concerning an individual solar thermal system. This research highlights that the solar hybrid configuration reduces fossil energy consumption by improving the global efficiency of energy conversion, thereby reducing the area of the solar field. [ABSTRACT FROM AUTHOR]

Renewable energy has experienced a significant growth on its rate of deployment as a clean and competitive alternative for conventional power sources. The reduction on the installation costs for PV systems has converted this technology into a relevant player regarding the electricity matrix. However, a larger penetration of PV systems is restricted to the availability of affordable technological options for storage. The integration of thermal energy storage to CSP systems is, on the other hand, straightforward through technologies already available in the market. Hence, the hybridization of CSP and PV systems has the potential for reducing operational and installation costs, as well as increasing significantly the capacity factor of solar power plants. The present study describes a methodology for design and sizing such hybrid plants, by implementing a transient simulation model, coupled to an evolutionary optimization algorithm, allowing to address the trade off between costs and capacity factor. The simulation model is applied to a case study considering the characteristics of a location in northern Chile. The results are presented in terms of the Pareto Frontiers that summarizes the compromise between the economic performance and the capacity factor of the plant. It is observed that the capacity factor achieves values higher that 85%, and the LCOE is lower than those observed for stand alone CSP plants. The methodology developed constitutes a useful tool for decision makers, who can assess the performance of the hybrid plant based in a detailed transient simulation and selecting the best configuration according to market constraints or its willingness for achieving certain level of capacity factor. [ABSTRACT FROM AUTHOR]

Lattice Boltzmann method (LBM) based on Boltzmann transport equation is developed to simulate the nanoscale heat transport in solids. The LBM can simulate both the metals and semiconductors by properly incorporating the energy carriers. We found that boundary scattering of phonons results in an anisotropic thermal transport in nanoscale solids. The electron-phonon coupling is introduced to accurately describe the thermal behavior of nanoscale confined solids. Our numerical tool will be suitable for simulating complex multiscale systems involving multiple energy carriers with different length and time scales, and is useful in magnetic recording technology when the thermal response plays a crucial role such as for reliability of the head-disk interface and the heat assisted magnetic recording systems. [ABSTRACT FROM AUTHOR]

Process heating is the activity with the most energy consumption in the industrial sector. Solar heating (SH) systems are a promising alternative to provide renewable thermal energy to industrial processes. However, factors such as high investment costs and area limitations in industrial facilities hinder their utilization; therefore, hybrid systems that combine two different solar thermal or photovoltaic technologies where each technology operates under conditions that allow a higher overall performance than conventional configurations have been proposed. In this review, we discuss the limitations of conventional SH systems and the potential of hybrid configurations to overcome them. First, the current literature about conventional and hybrid systems is presented. Then, the application of common performance indicators to evaluate hybrid configurations is analyzed. Finally, the limitation, advantages, and potential applications of conventional and hybrid systems are discussed. This work shows that conventional systems are the most promising alternatives in low and high-temperature industrial applications. At the same time, in medium and processes, hybrid configurations have great potential to increase the performance of SH systems and help to boost their adoption in the industrial sector. There are few studies about hybrid systems in industrial applications, and further research is required to determine their potential. [ABSTRACT FROM AUTHOR]

Electricity systems in Chile are characterized by a variable hourly demand in the central grid and an almost constant demand in the northern grid, which require different operation strategies for solar power plants depending on their location. Hybridizing a CSP plant with a PV system can increase the overall plant capacity factor by allowing thermal energy to be stored while the PV plant is in production and thus help to achieve a fully dispatchable solar electricity production system. A power generation and economic analysis of two hybrid CSP + PV plant models were developed considering a range of plant capacities based on parabolic trough or central receiver plants, combined with a PV system. Environmental conditions were considered for a site in the Atacama Desert, which is a hotspot of solar energy development in the country and shares the solar radiation characteristics of northern Chile. The study conducts a parametric analysis and optimization of the storage and power block sizes for the CSP plants in terms of the levelized cost of energy (LCOE), when the nominal capacity of the PV plant is varied. The annual production of the plants is calculated using the Transient System Simulation program (TRNSYS), which uses a new component library developed for that purpose. From the results of the simulations, the high potential for hybrid CSP + PV plants in the Atacama Desert is clear, because the high levels of irradiation available in northern Chile provide a competitive electricity cost, allowing investors to access PPA contracts at competitive prices and achieving competitive costs with respect to other energy sources. [ABSTRACT FROM AUTHOR]

Numerical simulations of time-dependent thermal energy transport in semiconductor thin films are performed using the lattice Boltzmann method applied to phonon transport. The discrete lattice Boltzmann Method is derived from the continuous Boltzmann transport equation assuming nonlinear, frequency-dependent phonon dispersion for acoustic and optical phonons. Results indicate that the heat conduction in silicon thin films displays a transition from diffusive to ballistic energy transport as the characteristic length of the system becomes comparable to the phonon mean free path and that the thermal energy transport process is characterized by the propagation of multiple superimposed phonon waves. The methodology is used to characterize the time-dependent temperature profiles inside films of decreasing thickness. Thickness-dependent thermal conductivity values are computed based on steady-state temperature distributions obtained from the numerical models. It is found that reducing feature size into the subcontinuum regime decreases thermal conductivity when compared to bulk values, at a higher rate than what was displayed by the Debye-based gray lattice Boltzmann method. [ABSTRACT FROM AUTHOR]

Numerical simulations of time-dependent thermal energy transport in semiconductor thin films are performed using the lattice Boltzmann method applied to phonon transport. The discrete lattice Boltzmann Method is derived from the continuous Boltzmann transport equation assuming nonlinear, frequency-dependent phonon dispersion for acoustic and optical phonons. Results indicate that the heat conduction in silicon thin films displays a transition from diffusive to ballistic energy transport as the characteristic length of the system becomes comparable to the phonon mean free path and that the thermal energy transport process is characterized by the propagation of multiple superimposed phonon waves. The methodology is used to characterize the time-dependent temperature profiles inside films of decreasing thickness. Thickness-dependent thermal conductivity values are computed based on steady-state temperature distributions obtained from the numerical models. It is found that reducing feature size into the subcontinuum regime decreases thermal conductivity when compared to bulk values, at a higher rate than what was displayed by the Debye-based gray lattice Boltzmann method. [ABSTRACT FROM AUTHOR]

Lattice Boltzmann method (LBM) simulations of phonon transport are performed in one-dimensional (1D) and 2D computational models of a silicon-on-insulator transistor, in order to investigate its transient thermal response under Joule heating conditions, which cause a nonequilibrium region of high temperature known as a hotspot. Predictions from Fourier diffusion are compared to those from a gray LBM based on the Debye assumption, and from a dispersion LBM which incorporates nonlinear dispersion for all phonon branches, including explicit treatment of optical phonons without simplifying assumptions. The simulations cover the effects of hotspot size and heat pulse duration, considering a frequency-dependent heat source term. Results indicate that, for both models, a transition from a Fourier diffusion regime to a ballistic phonon transport regime occurs as the hotspot size is decreased to tens of nanometers. The transition is characterized by the appearance of boundary effects, as well as by the propagation of thermal energy in the form of multiple, superimposed phonon waves. Additionally, hotspot peak temperature levels predicted by the dispersion LBM are found to be higher than those from Fourier diffusion predictions, displaying a nonlinear relation to hotspot size, for a given, fixed, domain size. [ABSTRACT FROM AUTHOR]

Industrial energy accounts for a large percentage of global consumption and, thus, it is a target for decarbonization by renewable and in particular solar energy adoption. Low uncertainty simulation tools can reduce the financial risk of solar projects, fostering the transition to a sustainable energy system. Several simulation tools are readily available to developers; differences exist in the format of input data and complexity of physical and numerical models. These tools can provide a variety of results from technical to financial and sensitivity analysis, often producing significant differences in yield assessment and uncertainty levels. IEA SHC Task 64/SolarPACES Task IV—Subtask C aims to address the lack of standard simulation tools for Solar Heating of Industrial Processes (SHIP) plants. This article describes the collaborative work developed by the researchers participating in the task. The identification and classification of several currently available simulation tools are performed on the basis of their capabilities and simulation approaches. A case study of solar heat supply to a copper mining operation is defined, allowing a comparison of the results produced by equivalent simulation tools. The proposed methodology identifies the main sources of differences among the simulation tools, the assessment of the deviation considering a series of statistical metrics for different time scales, and identifies their limitations and bias. The effects of physical characteristics of SHIP plants and different simulation approaches are discussed and quantified. The obtained results allow us to develop a basic guideline for a standardized yield assessment procedure with known uncertainties. Creating this common framework could partially reduce the risk perceived by the finance industry regarding SHIP systems. [ABSTRACT FROM AUTHOR]

This study delves into the techno-economic benefits of integrating Proton Exchange Membrane electrolyzers with photovoltaic systems for hydrogen production, with a keen focus on cost optimization strategies. A comprehensive analysis of several system scales and cost scenarios unveils the critical roles of Proton Exchange Membrane stack systems and the Balance of Plant components in influencing capital expenditures. Notably, the research identifies that incorporating the grid via a complementary Power Purchase Agreement, alongside clipped solar energy, innovatively redistributes cost elements. This approach significantly reduces the levelized cost of hydrogen, thereby enabling the feasibility of hydrogen production in regions characterized by low solar radiation at the cost of high grid electricity penetration. Sensitivity to energy costs, accentuated by different integration schemes, highlights the pivotal role of the stack cost and the Balance of Plant cost reductions in achieving economic viability for large-scale deployments. The study underscores the necessity of holistic cost optimization, revealing that strategic grid support coupled with solar energy enhances the techno-economic performance and broadens the scope for renewable hydrogen production in less favorable locales. These insights offer invaluable guidance to stakeholders, advocating for advanced integration strategies that promise both efficiency and financial sustainability in the burgeoning field of renewable hydrogen production systems. • Oversized PV fields for clipping enhance hydrogen production versatility over PPA-powered PEM schemes. • Electricity and stack cost cuts key to LCOH 2 reduction in all scenarios. • LCOH 2 as low as 1.62 USD/kgH 2 achieved with clipped energy use. • Grid and clipped energy integration hit LCOH 2 lows of 1.57 USD/kgH 2 , aiding areas with low solar radiation. [ABSTRACT FROM AUTHOR]

The use of molten salt mixtures as a storage medium in Concentrating Solar Power (CSP) plants has been shown to have a significant impact on increasing the reliability of CSP plants and reducing the levelized cost of energy. In this context, the present work presents the implementation of a detailed simulation procedure that contemplates different design considerations for the Rankine cycle to maximize its efficiency according to the temperature constraints established by utilizing different molten salt mixtures. To achieve this, three commercial CSP plant configurations were considered: an indirect coupling using parabolic trough collectors (PTC) with thermal oil as field heat transfer fluid (HTF) and molten salts as the storage medium, a direct coupling of PTC using molten salt as HTF and storage medium, and a central receiver plant (solar tower). The analysis considers the integration strategy between the solar system and the thermal storage, where all of those configurations considered the integration of the two-tank (hot/cold) approach. The analysis enables the development of an accurate estimation of the economic performance of changing the HTF in CSP plants, as well as the assessment of the parasitic consumption due to freezing protection systems, the effect of increasing the current field temperature, and the effect on the plant's capacity factor. The results show that the improvement in conversion efficiencies associated with salt mixtures operating at higher temperatures induces a higher electricity generation; however, such improvement is not compensated by the material change costs within the specified considerations. • Performance assessment due to the molten salt mixture in CSP systems. • Cycle optimization considering temperature constraints associated with salt mixture. • Capital expenditure assessment based on temperature and corrosion requirements. [ABSTRACT FROM AUTHOR]

Abstract: Overheating, high cooling energy demand and glare are recurrent problems in office buildings in Santiago. It is necessary to know the influence of different architectural strategies in energy demands to meet thermal comfort of the users and energy efficiency. Based on dynamic simulations, cooling and heating demand are estimated for an office building located in Santiago. It is shown that the size of envelope''s glazed areas highly influences the energy demand. A totally glazed façade building might reach up to 155kWh/m2 year for total cooling and heating demands. On the other hand, in a building with a window-to-wall ratio (WWR) of 20%, external solar protection and selective glazing, demand might be as low as 25kWh/m2 year. If night ventilation is applied during cooling periods an additional reduction of 37% can be achieved. A WWR of 20% is enough to keep a useful daylight around 80% of the time throughout the year. Main conclusions are: (i) for the climate conditions of Santiago, completely glazed façades are not recommended, even with selective glazing; (ii) night ventilation shows to be highly effective to reduce cooling demand; and (iii) lower WWRs with solar protection can achieve a better daylight performance than larger WWRs due to prevention of glare. [Copyright &y& Elsevier]

Objectives: To explore the influence of age on treatment responses to atomoxetine and to assess the relationship between core symptoms of attention deficit/hyperactivity disorder (ADHD) and health-related quality of life (HRQoL) outcomes. Data Sources: Data from five similar clinical trials of atomoxetine in the treatment of children and adolescents with ADHD were included in this meta-analysis. Study Selection: Atomoxetine studies that used the ADHD Rating Scale (ADHD-RS) and the Child Health and Illness Profile Child Edition (CHIP-CE) as outcome measures were selected. Interventions: Treatment with atomoxetine. Main Outcome Measures: Treatment group differences (atomoxetine vs placebo) in terms of total score, domains, and subdomains of the CHIP-CE were compared across age groups, and correlations between ADHD-RS scores and CHIP-CE scores were calculated by age. Results: Data of 794 subjects (611 children, 183 adolescents) were pooled. At baseline, adolescents showed significantly (p < 0.05) greater impairment compared with children in the Family Involvement, Satisfaction with Self, and Academic Performance subdomains of the CHIP-CE. Treatment effect of atomoxetine was significant in both age groups for the Risk Avoidance domain and its subdomains. There was a significant age-treatment interaction with greater efficacy seen in adolescents in both the Risk Avoidance domain and the Threats to Achievement subdomain. Correlations between ADHD-RS and CHIP-CE scores were generally low at baseline and moderate in change from baseline and were overall similar in adolescents and children. Conclusions: Atomoxetine was effective in improving some aspects of HR-QoL in both age groups. Correlations between core symptoms of ADHD and HR-QoL were low to moderate. [ABSTRACT FROM AUTHOR]

Solar energy is an economic and clean power source subject to natural variability, while energy storage might attenuate it, ultimately, effective and operationally feasible forecasting techniques for energy management are needed for better grid integration. This work presents a novel deterministic forecast method considering: irradiance pattern classification, Markov chains, fuzzy logic and an operational approach. The method developed was applied in a rolling manner for six years to a target location with no prior data to assess performance and its changes as new local data becomes available. Clearness index, diffuse fraction and irradiance hourly forecasts are analyzed on a yearly basis but also for 20 day types, and compared against smart persistence. Results show the proposed method outperforms smart persistence by ~10% for clearness index and diffuse fraction on the base case, but there are significant differences across the 20 day types analyzed, reaching up to +60% for clear days. Forecast lead time has the greatest impact in forecasting performance, which is important for any practical implementation. Seasonality in data gaps or rejected data can have a definite effect in performance assessment. A novel, comprehensive and detailed analysis framework was shown to present a better assessment of forecasters' performance. [ABSTRACT FROM AUTHOR]

Solar eclipses are astronomic phenomena in which the Earth's moon transits between the planet and the Sun, projecting a shadow onto the planet's surface. As solar power installed capacity increases, detailed studies of this region-wide phenomenon's effect in irradiance is of interest; however, the literature mainly reports its effects on localized scales. A measurement campaign spanning over 1400 km was pursued for the 2 July 2019 total solar eclipse in Chile, to register the event and establish a modeling framework to assess solar eclipse effects in irradiance over wide regional scales. This work describes the event and presents an estimation framework to decompose atmospheric and eclipse effects on irradiance. An analytical model was applied to study irradiance attenuation throughout the Chilean mainland territory, using satellite-derived and astronomical data as inputs compared to ground measurements in eight stations. Results showed good agreement between model and observations, with Mean Bias Errors of −0.008 to 0.98 W/m2 for Global Horizontal Irradiance and −0.004 to −4.664 W/m2 for Direct Normal Irradiance, with Normalized Root Mean Squared Errors of 0.7–5.8% and 1.4–12.2%, respectively. Energy losses due to obscuration corresponded between 20–40% for Global Horizontal Irradiance and 25–50% for Direct Normal Irradiance over Chilean territory. [ABSTRACT FROM AUTHOR]

We describe four schemes designed to estimate spectrally resolved direct normal irradiance (DNI) for multi-junction concentrator photovoltaic systems applications. The schemes have increasing levels of complexity in terms of aerosol and circumsolar irradiance (CSI) treatment, ranging from a climatological aerosol classification with no account of CSI, to an approach which includes explicit aerosol typing and type dependent CSI contribution. When tested against ground-based broadband and spectral measurements at five sites spanning a range of aerosol conditions, the most sophisticated scheme yields an average bias of + 0.068 % , well within photometer calibration uncertainties. The average spread of error is 2.5 %. These statistics are markedly better than the climatological approach, which carries an average bias of − 1.76 % and a spread of 4 %. They also improve on an intermediate approach which uses Angström exponents to estimate the spectral variation in aerosol optical depth across the solar energy relevant wavelength domain. This approach results in systematic under and over-estimations of DNI at short and long wavelengths respectively. Incorporating spectral CSI particularly benefits sites which experience a significant amount of coarse aerosol. All approaches we describe use freely available reanalyses and software tools, and can be easily applied to alternative aerosol measurements, including those from satellite. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Solar radiation is partially extinguished between heliostat and receiver. • A new methodology validated at PSA allows the development of extinction maps. • The first atmospheric extinction map useful for tower plants in Chile is presented. • Sunbelt analysis shows that extinction is having a major impact on Saudi Arabia. • LCOE formula for solar tower plants considers atmospheric extinction is proposed. [ABSTRACT FROM AUTHOR]

• Estimation of Aerosol Optical Depth at 550 nm using Direct Normal Irradiance. • Results are compared with existing ground measurements from AERONET. • Two radiative transfer models are used backwards to derive AOD from DNI. • Results are found of similar accuracy to satellite retrievals. Aerosols are part of the attenuation processes that impact solar radiation within the atmosphere. They influence the availability and spectrum of the solar resource for each location at the earth's surface. The present study presents advances in the development of a methodology intended to estimate the aerosol optical depth (AOD) at a given location from broadband direct normal irradiance (DNI) measurements and an appropriate radiative transfer model (RTM) operated backwards. For this purpose, databases provided by AERONET and BSRN at 16 stations throughout the world are jointly employed as inputs to the proposed methodology. The validation of two RTMs (SMARTS and SOLIS) is first undertaken to estimate DNI under clear-sky conditions at each station, assuming both AOD and additional atmospheric inputs are known from sunphotometric measurements. Results indicate that both models achieve good performance, characterized by a relative rRMSE of 3.2% for SMARTS and 3.8% for SOLIS. In the second, and most important stage, the AOD at 550 nm (AOD550) is derived using these models again, but in an iterative mode, now using the 1-minute DNI measurements as inputs. Periods of clear line of sight to the sun first need to be selected from the irradiance measurement record. This, along with other difficulties, make this operation prone to errors when only DNI measurements are available. In spite of this, the results show that AOD can be estimated with a 16-site average mean bias error of only between −0.024 and 0.015 AOD unit and an absolute RMSE between 0.025 and 0.050 AOD unit (compared to the AERONET ground truth), depending on model. Notable improvements are obtained if secondary atmospheric variables are extracted from the MERRA-2 reanalysis and are included as inputs for local computations. The present results suggest that the method is able to compare favorably with AOD estimates from MERRA-2 predictions or MODIS observations, for instance. [ABSTRACT FROM AUTHOR]

• CSP plant performance was the most affected by the time resolution. • Control procedures were more realistically captured with 1–5 min time steps. • A low time resolution leads to an information lost of variability effects. • 5–60-minute data leads to an overestimation of 2–6% in the annual totals. • Balance between accuracy and computational time is critical to select a time step. This study analyzes the time resolution impact on the modeling of a hybrid CSP-PV plant integrated with thermal storage and a battery bank for two locations in Chile. Daily and annual results were evaluated varying the time resolution from 1, 5, 10, 15, 30 to 60 min, as well as the capacity factor and LCOE. In this way, the CSP plant was the component most affected by the time resolution, followed by the battery dispatch, while the effect on PV production estimation was marginal. Control procedures of the receiver and power block were more realistically captured with time steps between 1 and 5 min, while with higher time steps, variability effects were neglected. Annual and techno-economic results indicate an overestimation of the total yearly production of the hybrid plant as the time step is increased, leading to an underestimation of the LCOE. Variations in the capacity factor and LCOE were around ±2–3% in both locations using the 5-minute time step (with respect to the 1-min results), and between ±4–6% using 10–60 min time steps. Different cases of study varying the dispatch strategy and components sizing were evaluated, showing that time resolution impact is lower for oversized PV configurations with respect to the CSP plant, and higher when the CSP plant is oversized with respect to the PV, regardless the dispatch strategy. Finally, this work provides some recommendations analyzing the advantages and drawbacks of implementing different time steps at each stage in the development of a hybrid solar power plant. [ABSTRACT FROM AUTHOR]