The Experts below are selected from a list of 8022 Experts worldwide ranked by ideXlab platform

Jesús Polo - One of the best experts on this subject based on the ideXlab platform.

  • assessment and improvement of modeling the Atmospheric Attenuation based on aerosol optical depth information with applicability to solar tower plants
    Energy, 2020
    Co-Authors: Jesús Polo, Jesús Ballestrín, Elena Carra
    Abstract:

    Abstract Accurate modeling of Atmospheric Attenuation phenomena is a crucial aspect for the performance of solar tower plants. The development of suitable models requires of reliable measurements of the extinction coefficient near surface. Continuous monitoring of the extinction coefficient at ground is being recorded at Plataforma Solar de Almeria (PSA) facility in south-east Spain since July 2017 offering a unique and long experimental database for model assessment. This work presents the assessment of Polo’s model with over two years of ground measurements. In addition, a new corrected and improved version of the model is presented here with a very good performance, maintaining the versatility of the model. Hourly estimations of the Atmospheric Attenuation at PSA with the new version of the model resulted in a 6.1% of RMSE and very good agreements in both inter- and intra-annual variability is found. The new model proposed here is easy to be used in both ray-tracing, optimization software and performance tools commonly and widely used for modeling solar tower plants behavior and production. This new model offers a better and novel approach that can be used at any site where AOD information is available.

  • modelling Atmospheric Attenuation at different aod time scales in yield performance of solar tower plants
    SolarPACES 2017: International Conference on Concentrating Solar Power and Chemical Energy Systems, 2018
    Co-Authors: Jesús Polo, Elena Carra, Jesús Ballestrín, Joaquin Alonsomontesinos, Gabriel Lopezrodriguez, J L Bosch, Javier Barbero, Jesus Fernandezreche, F J Batlles
    Abstract:

    Optical losses in central receiver systems may be enhanced by the Atmospheric Attenuation taking place along the optical path between the heliostat mirrors and the receiver. Ray-tracing and performance codes usually estimate the Atmospheric Attenuation by a third order polynomial whose coefficients can be input by the user in the model. A sensitivity study on the time-resolution for modelling the Atmospheric Attenuation is presented in this work by modelling two reference solar tower plants (Ivanpah 1 and Crescent Dunes) with the System Advisor Model (SAM). The input for the Atmospheric Attenuation has been computed from daily, monthly means and annual mean aerosol optical depth for the Tamanrasset site. The impact of considering one unique polynomial for the whole year to one polynomial every day is higher in the case of Crescent Dunes due to its larger solar field, and relative averages differences in the daily output power may be from around 2% to 4.5% due to the daily peaks of AOD that result in event...

  • analysis of solar tower plant performance influenced by Atmospheric Attenuation at different temporal resolutions related to aerosol optical depth
    Solar Energy, 2017
    Co-Authors: Jesús Polo, Elena Carra, Jesús Ballestrín, Joaquin Alonsomontesinos, Gabriel Lopezrodriguez, J L Bosch, Javier Barbero, Jesus Fernandezreche, F J Batlles
    Abstract:

    Abstract The optical losses associated with the Attenuation of the reflected direct irradiance by the heliostats along the optical path to the receiver may be significant in large solar tower plants. This phenomenon, known as Atmospheric Attenuation loss, may have a stronger impact at those tower plants where high aerosol loads are expected. Performance models like the System Advisor Model (SAM) and the ray-tracing models (DELSOL, MIRVAL) usually estimate the Atmospheric Attenuation loss by a polynomial expression which is function of the slant range (the optical path between the heliostat and the receiver). Most of the polynomial models proposed to determine this optical loss use two established extreme attenuating conditions corresponding to a clear or hazy atmosphere. This paper presents a sensitivity study of the impact of time-dependent variability of the Atmospheric Attenuation in the yield performance of two reference large solar tower plants (one similar to Ivanpah 1 and the other one to Crescent Dunes as examples of direct steam and molten salt tower plants, respectively). Five sites have been selected from the AERONET ground station network to obtain the aerosol loading at different time-scales: annual, monthly and daily. Multiple SAM runs have been performed to simulate the annual yield of each plant and site creating different inputs to the code corresponding to each time-scale condition. The results show a significant impact of the time-scale for modeling the Atmospheric Attenuation on the annual yield and daily energy output of the plant. Although the annual and monthly means produce some compensation of the impact, the differences in several particular days can be significant. Up to 20% difference in the daily energy output is found when the extinction is modeled as a steady-state polynomial representing the annual mean compared to the case of daily time-dependent variability of the Attenuation. The sensitivity results presented here show that for more realistic yield performance calculations in solar tower plants, particularly at desert and arid climates, the modeling of the Atmospheric Attenuation should be performed in a time-dependent way according to the climatological variability conditions characteristic of the site.

  • Sensitivity study for modelling Atmospheric Attenuation of solar radiation with radiative transfer models and the impact in solar tower plant production
    Solar Energy, 2016
    Co-Authors: Jesús Polo, Jesús Ballestrín, Elena Carra
    Abstract:

    Abstract The solar radiation reflected by the heliostats towards the receiver in solar tower plants may be attenuated by scattering and absorption processes along the optical path. This phenomenon has been traditionally computed by the solar tower plant codes using simple models based on polynomial functions of the slant range and taking very extreme conditions for the turbidity based on the standard visual range. Radiative transfer codes (libRadtran) allow modelling the Atmospheric Attenuation as a function of the slant range considering different aerosol conditions taken from several AERONET stations in regions of interest for CSP. The methodology presented in this work for modelling Atmospheric Attenuation with libRadtran can be used with any other radiative transfer model. The results showing the sensitivity of the Attenuation loss to the aerosol optical depth, assuming homogeneous vertical distribution, have been fit to a simple model that can be used in Solar Advisor Model (SAM). The Attenuation loss in the model proposed reaches around 20% at 1 km of slant range for highly aerosol load typical of some desert sites. Sensitivity estimations with SAM have been performed also for two reference solar tower plants (Ivanpah 1 and Gemasolar) to study the impact of Atmospheric Attenuation in the output power of the plant. The different Attenuation loss between low and very high turbidity conditions can result in a reduction of the power output of a large plant like Ivanpah 1 of around 12% of average daily production, 20% in the field optical efficiency and 11% in the power absorbed by the receiver. In smaller plants with large thermal storage system (Gemasolar) the impact of the Attenuation loss is significantly smaller (around 4%). Modelling the Atmospheric Attenuation in the solar tower codes should include aerosol optical depth as input in a daily basis for allowing the inclusion of the expected aerosol variability of desert and arid sites.

  • stochastic model to describe Atmospheric Attenuation from yearly global solar irradiation
    Atmospheric Research, 2015
    Co-Authors: J M Vindel, Jesús Polo, L F Zarzalejo, Lourdes Ramirez
    Abstract:

    Abstract A new stochastic model to describe Atmospheric Attenuation from yearly global solar irradiation has been developed and implemented. The proposed model takes into account the consideration that the whole of all attenuating elements can be thought of as a population where the higher the number of individuals the lesser the clearness index. Thus, the inverse of the clearness index is considered as the variable of a stochastic process. From the proposed master equation as starting point, the new model is characterized by transition rates (assessed from a growing parameter - G - and a decreasing parameter - D) which depend mainly on the climatological characteristics at each location. In this sense, different regions with an Attenuation level calculated from the yearly global irradiation have been established using the Koppen–Geiger climate classification as a first approach. The model parameters G and D have been determined for different regions using the inverse of the clearness index as variable. The probability density function obtained after the application of the stochastic model for each climate zone shows how the index mode increases from the zones with lower levels of Attenuation to those with higher levels of Attenuation. This result confirms the proposed null hypothesis related to the use of the inverse of the clearness index as an Attenuation population indicator. The fit between the empirical data and the data provided for the model is good enough according to a Kolmogorov–Smirnov test with a significance level of 0.05. Nevertheless, it is necessary to slightly modify the climate zones of Koppen–Geiger initial classification for a better explanation of the Atmospheric Attenuation. This climate zones modification can be considered as an additional result.

A G Mariazzi - One of the best experts on this subject based on the ideXlab platform.

  • the effect of Atmospheric Attenuation on inclined cosmic ray air showers
    Astroparticle Physics, 2003
    Co-Authors: M T Dova, L N Epele, A G Mariazzi
    Abstract:

    Abstract The increasing cosmic ray statistics collected by present experiments and the future prospects with new large arrays demand accurate calculations of the extensive air shower (EAS) parameters. The energy of the primary particle is estimated by ground arrays fitting a lateral distribution function (LDF) to the particle densities at a given observing level. However, the lack of appropriate parameterization for these distributions, able to reproduce the data collected from all arrival directions, makes the experimental analysis difficult. We propose a method to parametrize particle density distributions of EAS at any incident zenith angle. Starting from analytical LDF for vertical showers we present a detailed study of the Atmospheric depth dependence of the shower parameters. The results obtained are used to calculate the corresponding LDF for non-vertical showers including for the first time both, geometrical and Atmospheric Attenuation effects. We check the method analysing electron and muon LDF generated by Monte Carlo simulations from incident cosmic ray particles at different zenith angles. A comparison of the proposed LDF with experimental results, as well as MC data including detector effects, is also presented.

  • the effect of Atmospheric Attenuation on inclined cosmic ray air showers
    arXiv: Astrophysics, 2001
    Co-Authors: M T Dova, L N Epele, A G Mariazzi
    Abstract:

    The increasing cosmic ray statistics collected by present experiments and the future prospects with new large arrays demand accurate calculations of the extensive air shower parameters. The energy of the primary particle is estimated by ground arrays fitting a lateral distribution function (LDF) to the particle densities at a given observing level. However, the lack of appropriate parameterization for these distributions, able to reproduce the data collected from all arrival directions, makes it difficult the experimental analysis. Starting from analytical LDF for vertical showers we study the Atmospheric depth dependence of the shower parameters, which is necessary to obtain the corresponding particle density distributions for inclined showers. In our approach both geometrical and Atmospheric Attenuation effects producing a lateral asymmetry in non-vertical showers are included. The resulting electron and muon LDF fit very well the Monte Carlo simulated data at all zenith angles.

Elena Carra - One of the best experts on this subject based on the ideXlab platform.

  • assessment and improvement of modeling the Atmospheric Attenuation based on aerosol optical depth information with applicability to solar tower plants
    Energy, 2020
    Co-Authors: Jesús Polo, Jesús Ballestrín, Elena Carra
    Abstract:

    Abstract Accurate modeling of Atmospheric Attenuation phenomena is a crucial aspect for the performance of solar tower plants. The development of suitable models requires of reliable measurements of the extinction coefficient near surface. Continuous monitoring of the extinction coefficient at ground is being recorded at Plataforma Solar de Almeria (PSA) facility in south-east Spain since July 2017 offering a unique and long experimental database for model assessment. This work presents the assessment of Polo’s model with over two years of ground measurements. In addition, a new corrected and improved version of the model is presented here with a very good performance, maintaining the versatility of the model. Hourly estimations of the Atmospheric Attenuation at PSA with the new version of the model resulted in a 6.1% of RMSE and very good agreements in both inter- and intra-annual variability is found. The new model proposed here is easy to be used in both ray-tracing, optimization software and performance tools commonly and widely used for modeling solar tower plants behavior and production. This new model offers a better and novel approach that can be used at any site where AOD information is available.

  • modelling Atmospheric Attenuation at different aod time scales in yield performance of solar tower plants
    SolarPACES 2017: International Conference on Concentrating Solar Power and Chemical Energy Systems, 2018
    Co-Authors: Jesús Polo, Elena Carra, Jesús Ballestrín, Joaquin Alonsomontesinos, Gabriel Lopezrodriguez, J L Bosch, Javier Barbero, Jesus Fernandezreche, F J Batlles
    Abstract:

    Optical losses in central receiver systems may be enhanced by the Atmospheric Attenuation taking place along the optical path between the heliostat mirrors and the receiver. Ray-tracing and performance codes usually estimate the Atmospheric Attenuation by a third order polynomial whose coefficients can be input by the user in the model. A sensitivity study on the time-resolution for modelling the Atmospheric Attenuation is presented in this work by modelling two reference solar tower plants (Ivanpah 1 and Crescent Dunes) with the System Advisor Model (SAM). The input for the Atmospheric Attenuation has been computed from daily, monthly means and annual mean aerosol optical depth for the Tamanrasset site. The impact of considering one unique polynomial for the whole year to one polynomial every day is higher in the case of Crescent Dunes due to its larger solar field, and relative averages differences in the daily output power may be from around 2% to 4.5% due to the daily peaks of AOD that result in event...

  • analysis of solar tower plant performance influenced by Atmospheric Attenuation at different temporal resolutions related to aerosol optical depth
    Solar Energy, 2017
    Co-Authors: Jesús Polo, Elena Carra, Jesús Ballestrín, Joaquin Alonsomontesinos, Gabriel Lopezrodriguez, J L Bosch, Javier Barbero, Jesus Fernandezreche, F J Batlles
    Abstract:

    Abstract The optical losses associated with the Attenuation of the reflected direct irradiance by the heliostats along the optical path to the receiver may be significant in large solar tower plants. This phenomenon, known as Atmospheric Attenuation loss, may have a stronger impact at those tower plants where high aerosol loads are expected. Performance models like the System Advisor Model (SAM) and the ray-tracing models (DELSOL, MIRVAL) usually estimate the Atmospheric Attenuation loss by a polynomial expression which is function of the slant range (the optical path between the heliostat and the receiver). Most of the polynomial models proposed to determine this optical loss use two established extreme attenuating conditions corresponding to a clear or hazy atmosphere. This paper presents a sensitivity study of the impact of time-dependent variability of the Atmospheric Attenuation in the yield performance of two reference large solar tower plants (one similar to Ivanpah 1 and the other one to Crescent Dunes as examples of direct steam and molten salt tower plants, respectively). Five sites have been selected from the AERONET ground station network to obtain the aerosol loading at different time-scales: annual, monthly and daily. Multiple SAM runs have been performed to simulate the annual yield of each plant and site creating different inputs to the code corresponding to each time-scale condition. The results show a significant impact of the time-scale for modeling the Atmospheric Attenuation on the annual yield and daily energy output of the plant. Although the annual and monthly means produce some compensation of the impact, the differences in several particular days can be significant. Up to 20% difference in the daily energy output is found when the extinction is modeled as a steady-state polynomial representing the annual mean compared to the case of daily time-dependent variability of the Attenuation. The sensitivity results presented here show that for more realistic yield performance calculations in solar tower plants, particularly at desert and arid climates, the modeling of the Atmospheric Attenuation should be performed in a time-dependent way according to the climatological variability conditions characteristic of the site.

  • Sensitivity study for modelling Atmospheric Attenuation of solar radiation with radiative transfer models and the impact in solar tower plant production
    Solar Energy, 2016
    Co-Authors: Jesús Polo, Jesús Ballestrín, Elena Carra
    Abstract:

    Abstract The solar radiation reflected by the heliostats towards the receiver in solar tower plants may be attenuated by scattering and absorption processes along the optical path. This phenomenon has been traditionally computed by the solar tower plant codes using simple models based on polynomial functions of the slant range and taking very extreme conditions for the turbidity based on the standard visual range. Radiative transfer codes (libRadtran) allow modelling the Atmospheric Attenuation as a function of the slant range considering different aerosol conditions taken from several AERONET stations in regions of interest for CSP. The methodology presented in this work for modelling Atmospheric Attenuation with libRadtran can be used with any other radiative transfer model. The results showing the sensitivity of the Attenuation loss to the aerosol optical depth, assuming homogeneous vertical distribution, have been fit to a simple model that can be used in Solar Advisor Model (SAM). The Attenuation loss in the model proposed reaches around 20% at 1 km of slant range for highly aerosol load typical of some desert sites. Sensitivity estimations with SAM have been performed also for two reference solar tower plants (Ivanpah 1 and Gemasolar) to study the impact of Atmospheric Attenuation in the output power of the plant. The different Attenuation loss between low and very high turbidity conditions can result in a reduction of the power output of a large plant like Ivanpah 1 of around 12% of average daily production, 20% in the field optical efficiency and 11% in the power absorbed by the receiver. In smaller plants with large thermal storage system (Gemasolar) the impact of the Attenuation loss is significantly smaller (around 4%). Modelling the Atmospheric Attenuation in the solar tower codes should include aerosol optical depth as input in a daily basis for allowing the inclusion of the expected aerosol variability of desert and arid sites.

M T Dova - One of the best experts on this subject based on the ideXlab platform.

  • the effect of Atmospheric Attenuation on inclined cosmic ray air showers
    Astroparticle Physics, 2003
    Co-Authors: M T Dova, L N Epele, A G Mariazzi
    Abstract:

    Abstract The increasing cosmic ray statistics collected by present experiments and the future prospects with new large arrays demand accurate calculations of the extensive air shower (EAS) parameters. The energy of the primary particle is estimated by ground arrays fitting a lateral distribution function (LDF) to the particle densities at a given observing level. However, the lack of appropriate parameterization for these distributions, able to reproduce the data collected from all arrival directions, makes the experimental analysis difficult. We propose a method to parametrize particle density distributions of EAS at any incident zenith angle. Starting from analytical LDF for vertical showers we present a detailed study of the Atmospheric depth dependence of the shower parameters. The results obtained are used to calculate the corresponding LDF for non-vertical showers including for the first time both, geometrical and Atmospheric Attenuation effects. We check the method analysing electron and muon LDF generated by Monte Carlo simulations from incident cosmic ray particles at different zenith angles. A comparison of the proposed LDF with experimental results, as well as MC data including detector effects, is also presented.

  • the effect of Atmospheric Attenuation on inclined cosmic ray air showers
    arXiv: Astrophysics, 2001
    Co-Authors: M T Dova, L N Epele, A G Mariazzi
    Abstract:

    The increasing cosmic ray statistics collected by present experiments and the future prospects with new large arrays demand accurate calculations of the extensive air shower parameters. The energy of the primary particle is estimated by ground arrays fitting a lateral distribution function (LDF) to the particle densities at a given observing level. However, the lack of appropriate parameterization for these distributions, able to reproduce the data collected from all arrival directions, makes it difficult the experimental analysis. Starting from analytical LDF for vertical showers we study the Atmospheric depth dependence of the shower parameters, which is necessary to obtain the corresponding particle density distributions for inclined showers. In our approach both geometrical and Atmospheric Attenuation effects producing a lateral asymmetry in non-vertical showers are included. The resulting electron and muon LDF fit very well the Monte Carlo simulated data at all zenith angles.

Pedro Garciadelpino - One of the best experts on this subject based on the ideXlab platform.

  • an application of igs zenith tropospheric delay data to propagation studies validation of radiometric Atmospheric Attenuation
    IEEE Transactions on Antennas and Propagation, 2016
    Co-Authors: Gustavo A Siles, Jose Manuel Riera, Pedro Garciadelpino
    Abstract:

    The objective of this paper is to continue exploring the use of International GNSS Service (IGS) products as a tool to be used in Earth-space propagation experiments. With this purpose, 4 years of Zenith Tropospheric Delay data from IGS Villafranca station, in Madrid, Spain, have been processed with the aim to estimate the Attenuation due to gases. These values are then used for the validation of a concurrent database of 4 years of radiometric measurements at 19.7 GHz, collected at Universidad Politecnica de Madrid (UPM) with the purpose of studying the Attenuation effects of gases and clouds. The suggested validation procedure includes both an automatic routine and visual inspection. The validated measurements are statistically analyzed on a yearly and seasonal basis. Results point toward the usefulness of IGS data in propagation experiments as well as their integration in their processing routines.

  • Atmospheric Attenuation in wireless communication systems at millimeter and thz frequencies wireless corner
    IEEE Antennas and Propagation Magazine, 2015
    Co-Authors: Gustavo A Siles, Jose Manuel Riera, Pedro Garciadelpino
    Abstract:

    This paper intends to give an overview about Atmospheric propagation effects affecting millimeter and terahertz (THz) communication systems. The main focus is on Attenuation caused by Atmospheric gases and liquid water droplets, either in the form of suspended particles into clouds or rain falling hydrometeors. Theoretical aspects about each of them are presented, emphasizing on those that deserve special attention as frequency increases. Statistics of Attenuation estimated from meteorological data and some experimental results, as in the case of rain Attenuation, obtained in Madrid, Spain, are presented throughout the paper, thus providing further insights about the phenomena discussed.

  • Atmospheric Attenuation in wireless communication systems at millimeter and thz frequencies
    2015
    Co-Authors: Eva Rajoiglesias, Gustavo A Siles, Jose Manuel Riera, Pedro Garciadelpino
    Abstract:

    This paper intends to give an overview about Atmospheric propagation effects affecting millimeter and terahertz (THz) communication systems. The main focus is on Attenuation caused by Atmospheric gases and liquid water droplets, either in the form of suspended particles into clouds or rain falling hydrometeors. Theoretical aspects about each of them are presented, emphasizing on those that deserve special attention as frequency increases. Statistics of Attenuation estimated from meteorological data and some experimental results, as in the case of rain Attenuation, obtained in Madrid, Spain, are presented throughout the paper, thus providing further insights about the phenomena discussed.

  • comparison of Attenuation measurements at 19 7 ghz from radiometer observations gnss delay data and radiosondes
    European Conference on Antennas and Propagation, 2014
    Co-Authors: Gustavo A Siles, Jose Manuel Riera, Pedro Garciadelpino
    Abstract:

    A single-channel radiometer operating at 19.7 GHz has been working at Universidad Politecnica de Madrid with the aim of retrieving Atmospheric Attenuation under non-scattering conditions. With the purpose of validating these estimates, they have been compared with Attenuation values obtained by a GNSS receiver and radiosondes. From the first results obtained, the three instruments agree quite well. However, GNSS is considered the best option to evaluate concurrent radiometric time-series due to its better time resolution. Single comparisons between radiometer and GNSS, as well as visual inspections of data, suggest that the combined analysis of measurements of both instruments can provide useful inputs during satellite propagation experiments.

  • estimation of Atmospheric Attenuation at 99 ghz using a total power radiometer
    European Conference on Antennas and Propagation, 2013
    Co-Authors: Gustavo A Siles, Jose Manuel Riera, Pedro Garciadelpino, B Menciaoliva, Jesus Grajal
    Abstract:

    A total power radiometer operating at 99 GHz was implemented for a propagation experiment aimed to estimate Attenuation along a slant path, in Madrid. Valuable data was collected during a measurement campaign in mid-april of 2012. The retrieved time series of radiometric Attenuation allow the use of this technique at this frequency to be validated, under clear sky and cloudy conditions, using a low cost instrument calibrated with simple procedures. In spite of some hardware limitations, this experiment shows an interesting application of radiometric technique in order to study Atmospheric propagation at 99 GHz.