Person:
Torres Escribano, José Luis

person.page.identifierURI

https://academica-e.unavarra.es/handle/2454/50087

Last Name

Torres Escribano

First Name

José Luis

person.page.departamento

Ingeniería

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ISC. Institute of Smart Cities

ORCID

0000-0001-9275-8158

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241

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Now showing 1 - 10 of 18

Open Access
Evaluation of two procedures for selecting the CIE standard sky type using high dynamic range images
(International Solar Energy Society, 2019) García Ruiz, Ignacio; Blas Corral, María Ángeles de; Torres Escribano, José Luis; Hernández Salueña, Begoña; Sáenz Gamasa, Carlos; Ormazábal Pagola, Mikel; Ingeniería; Ingeniaritza; Ciencias; Zientziak; Gobierno de Navarra / Nafarroako Gobernua
The characterization of sky conditions according to the CIE Standard General Sky classification requires knowledge of diffuse luminance angular distribution in the sky vault. This variable is usually measured by sky scanners. However, commercial sky scanners have different drawbacks related to their resolution and measurement time. An alternative to these devices is the use of sky images captured with a digital camera equipped with a fisheye lens. The range of luminances that may occur in the sky makes it necessary to use high dynamic range (HDR) images obtained by the fusion of a series of low dynamic range (LDR) images. Two procedures for the characterization of sky conditions according to the CIE standard using HDR images have been applied and evaluated.
Open Access
Validation and calibration of models to estimate photosynthetically active radiation considering different time scales and sky conditions
(Elsevier, 2022) Blas Corral, María Ángeles de; García-Rodríguez, Ana; García Ruiz, Ignacio; Torres Escribano, José Luis; Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Photosynthetically Active Radiation (PAR) is a fundamental parameter for developing plant productivity models. Nevertheless, instrumentation for measuring PAR and to record it is scarce at conventional meteorological stations. Several procedures have therefore been proposed for PAR estimation. In this work, 21 previously published analytical models that correlate PAR with easily available meteorological parameters are collected. Although longer time scales were considered in the original publications, a minute range was applied in this work to calibrate the PAR models. In total, more than 10 million input records were gathered from the SURFRAD station network from a 10-year long time series with data frequencies recorded every 1 min. The models were calibrated both globally, using data from all stations and locally, with data from each station. After calibration, the models were validated for minute, hourly and daily data, obtaining low fitting errors at the different stations in all cases, both when using the globally calibrated models and with the models calibrated for each location. Although the PAR results in general improved for locally calibrated models, the use of local models is not justified, since the global models presented offered very satisfactory PAR results for the different climatic conditions where the meteorological stations are located. Thus, PAR estimation model should then be selected, solely considering the meteorological variables available at the specific location. When applying the globally calibrated models to input data classified according to sky conditions (from clear to overcast), the PAR models continued to perform satisfactorily, although the error statistics of some models for overcast skies worsened.
Open Access
Assessment of the adequacy of EN ISO 15927-4 reference years for photovoltaic systems
(Wiley, 2015) García Ruiz, Ignacio; Torres Escribano, José Luis; Proyectos e Ingeniería Rural; Landa Ingeniaritza eta Proiektuak
The long-term performance prediction of photovoltaic systems requires representative meteorological data from a particular location. Among the numerous proposals in the field of solar energy, most of them include procedures oriented towards the generation of test reference years (TRYs). These synthetic years are composed of the concatenation of 12 actual months of the time series of meteorological measurements. Using TRYs to simulate the performance of different types of solar energy systems reduces the computational effort of the simulation and simplifies the analysis of the results. In this sense, the technical standard EN ISO 15927-4 describes a procedure for constructing a reference year suitable for evaluation of the annual heating and cooling long-term needs in buildings. In this work, the adequacy of the EN ISO 15927-4 reference year for photovoltaic systems was studied. The electricity production obtained by simulation with this TRY was compared with that obtained by the Weather Year for Solar Systems. This latter reference year only uses the monthly thermal energy collected by the system as a selection parameter of typical months. This comparison was performed for seven locations in the USA considering two 5.6 kWp grid-connected photovoltaic systems that only differ in the solar tracking system. The suitability of the EN ISO 15927-4 reference year for the estimation of the electrical energy generated by a photovoltaic system has been proved, showing good results in the annual and daily predictions in most of the cases studied.
Open Access
Temporal downscaling of test reference years: effects on the long-term evaluation of photovoltaic systems
(Elsevier, 2018) García Ruiz, Ignacio; Torres Escribano, José Luis; Proyectos e Ingeniería Rural; Landa Ingeniaritza eta Proiektuak
Representative meteorological data from a given location are necessary to assess the long-term performance of photovoltaic (PV) systems. Test reference years (TRYs) or typical meteorological years (TMYs) are widely used as input to PV models. Most of current procedures propose the construction of TRYs by concatenating 12 months belonging to different years of a dataset. This paper evaluates the effects of the temporal downscaling of typical periods that compose different TRYs on the long-term assessment of PV systems. The Festa-Ratto TRY, WYSS, EN ISO 15927-4 TRY, TMY3, TGY and TDY are used. Thus, an adapted version of these six methodologies aimed at the selection of typical days rather than months is proposed. The electricity production obtained by simulation for daily and monthly TRYs is compared with simulations performed for each actual year of the dataset. This analysis is performed for seven locations in the USA considering a 5.6 kWp grid-connected PV system. The results reveal that the timescale reduction improves the behavior of Festa-Ratto TRY, WYSS, TMY3, TDY and TDY when estimating the long-term production of a PV system considering the hourly, daily, monthly and annual timescales, while the modified EN ISO 15927-4 TRY performs worse than its monthly version.
Open Access
Luminance calibration of a full sky HDR imaging system using sky scanner measurements
(Solar Energy Society, 2022) García Ruiz, Ignacio; Sáenz Gamasa, Carlos; Hernández Salueña, Begoña; García Santos, Rafael; Torres Escribano, José Luis; Zientziak; Ingeniaritza; Institute of Smart Cities - ISC; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias; Ingeniería
A full sky High Dynamic Range imaging system, based on a Single-Lens Reflex camera with a fisheye lens, has been constructed and calibrated with a sky scanner luminance meter. The method considers the geometrical, spectral, timing and orientation issues between instruments. The calibration data sets, having nearly simultaneous measurements under stable sky conditions, were obtained from approximately one month of data using selection variables based in the experimental design. For luminance estimation we use the standard 𝐶𝐼𝐸𝑌 RGB combination and a Spectrally Matched Luminance (𝑆𝑀𝐿) predictor, matching the spectral response of the instruments. With 738 calibration points having luminances up to 23.6 kcd∕m2, covering 98.5% of the sky luminance range, 𝐶𝐼𝐸𝑌 is linearly correlated with sky scanner measurements with a coefficient of determination 𝑅2 = 0.9927 and a Root Mean Squared Error (𝑅𝑀𝑆𝐸) of 7.7%. 𝑆𝑀𝐿 gives better results, with 𝑅2 = 0.9973 and 𝑅𝑀𝑆𝐸 = 5.3%. With 253 calibration points with luminances up to 12.9 kcd∕m2, comprising 94.1% of the sky luminance range, both predictors clearly improve, with 𝑅2 = 0.9964 and 𝑅𝑀𝑆𝐸 = 4.1% in case of 𝐶𝐼𝐸𝑌 and 𝑅2 = 0.9982 and 𝑅𝑀𝑆𝐸 = 2.9% in case of 𝑆𝑀𝐿.
Open Access
Proposal and evaluation of typical illuminance year (TIY) generation procedures from illuminance or irradiance data for daylight assessment in the long term
(Elsevier, 2020) García Ruiz, Ignacio; Blas Corral, María Ángeles de; Torres Escribano, José Luis; Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
When assessing the long-term daylight availability or the performance of natural lighting systems in a given location, it is necessary to have representative data of local daylight conditions. The use of a daylight test reference year (TRY) becomes a good option in these cases. This paper proposes and evaluates a procedure for the generation of a typical illuminance year (TIY) considering illuminance as the only variable for selecting the typical periods that make up the reference year. Two versions of TIY are presented, one composed of 12 typical months selected from the series of observations and another composed of 365 typical days. Each of these versions is used to obtain a global illuminance TIY (TGIY) and a diffuse illuminance TIY (TDIY) from a 27-year dataset corresponding to the Vaulx-en-Velin station (France). Furthermore, 12 luminous efficacy models have been evaluated in order to obtain a TIY from a TRY generated from irradiance data when no illuminance data are available. Thus, a global luminous efficacy model and a diffuse model are selected after benchmarking different models, considering both their original coefficients and those adjusted to local conditions. The results reveal that the monthly version of the TGIY and the daily version of the TDIY show the best overall fit to the long-term dataset. TIYs obtained from illuminance data are also observed to be statistically indistinguishable from those obtained after applying a luminous efficacy model to an irradiance-based TRY.
Open Access
Multitemporal evaluation of topographic correction algorithms using synthetic images
(SPIE, 2012) Sola Torralba, Ion; Álvarez Mozos, Jesús; González de Audícana Amenábar, María; Torres Escribano, José Luis; Proyectos e Ingeniería Rural; Landa Ingeniaritza eta Proiektuak
Land cover classification and quantitative analysis of multispectral data in mountainous regions is considerably hampered by the influence of topography on the spectral response pattern. In the last years, different topographic correction (TOC) algorithms have been proposed to correct illumination differences between sunny and shaded areas observed by optical remote sensors. Although the available number of TOC methods is high, the evaluation of their performance usually relies on the existence of precise land cover information, and a standardised and objective evaluation procedure has not been proposed yet. Besides, previous TOC assessment studies only considered a limited set of illumination conditions, normally assuming favourable illumination conditions. This paper presents a multitemporal evaluation of TOC methods based on synthetically generated images in order to evaluate the influence of solar angles on the performance of TOC methods. These synthetic images represent the radiance an optical sensor would receive under specific geometric and temporal acquisition conditions and assuming a certain land-cover type. A method for creating synthetic images using state-of-the-art irradiance models has been tested for different periods of the year, which entails a variety of solar angles. Considering the real topography of a specific area a Synthetic Real image (SR) is obtained, and considering the relief of this area as being completely flat a Synthetic Horizontal image (SH) is obtained. The comparison between corrected image obtained applying a TOC method to SR image and SH image of the same area, i.e. considered the ideal correction, allows assessing the performance of each TOC algorithm.
Open Access
Generation of the site-adapted clearest-sky year of direct normal irradiance for solar concentrating technologies
(Elsevier, 2018) García Ruiz, Ignacio; Royo Romeo, Alberto; Torres Escribano, José Luis; Proyectos e Ingeniería Rural; Landa Ingeniaritza eta Proiektuak; Gobierno de Navarra / Nafarroako Gobernua
Concentrating photovoltaic and thermoelectric solar facilities base their operation on collecting the direct component of solar radiation. Given that the direct beam that reaches the Earth's surface varies greatly in time and space, it is common to assist the bankability of projects with a solar resource assessment. Sun-tracking collector plants are typically examined via a time series analysis of measured weather data and test reference years. Such analysis, which considers the eventual presence of clouds, may be complemented with the use of the synthetic clear-sky year assuring the maximum theoretical availability of direct normal irradiance at a site. This work introduces for the first time the concept of siteadapted clearest-sky year (CSY) and provides a methodology for its generation. Three methods to build the CSY and one algorithm to detect clear-sky moments are proposed.
Open Access
Evaluación comparativa de 19 modelos de estimación de irradiancia difusa sobre planos inclinados dependiendo del tipo de cielo estándar ISO/CIE
(LNEG, 2020) García Ruiz, Ignacio; Torres Escribano, José Luis; Blas Corral, María Ángeles de; Sáenz Gamasa, Carlos; Hernández Salueña, Begoña; Illanes, R.; Ingeniería; Ingeniaritza; Ciencias; Zientziak
En este trabajo se han evaluado 19 modelos de estimación de irradiancia difusa sobre el plano inclinado, que incluyen tanto modelos isotrópicos o pseudoisotrópicos como modelos anisotrópicos. Dicha evaluación se ha llevado a cabo a partir una serie de 5396 observaciones de irradiancia global, difusa y directa realizadas entre julio y diciembre de 2018 en la estación radiométrica de la Universidad Pública de Navarra (UPNA). El estado del cielo correspondiente a cada observación se ha caracterizado de acuerdo con el CIE Standard General Sky propuesto en la norma ISO 15469:2004(E)/CIE S 011/E:2003. Para esta clasificación se han utilizado las medidas de distribución angular de luminancia y radiancia proporcionadas por un escáner de cielo ubicado en la propia estación de la UPNA. De tal manera que, para cada combinación de orientación e inclinación del plano, se ha evaluado la bondad de los distintos modelos de acuerdo con los 15 tipos de cielo estándar propuestos por la norma ISO/CIE. Los resultados revelan que el modelo de Perez et al. 2 presenta los mejores resultados globales, así como en 5 de los 15 tipos de cielo ISO/CIE.
Open Access
Estimation of the solar thermal power generation potential in Pamplona (northern Spain)
(Universidad Carlos III, 2022) García Ruiz, Ignacio; Prieto Cobo, Eduardo; Torres Escribano, José Luis; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC
In this work, an analysis of the potential of the city of Pamplona to produce solar thermal energy was carried out, according to the solar radiation received. As a result, for each residential, industrial, or service rooftop, information was provided on (1) the area available for thermal installation, (2) the solar thermal installation capacity and (3) the monthly and annual thermal energy generation potential. It was found that, if all suitable areas of the city are used, it would be possible to achieve an annual total solar thermal energy production of 1197.69 GWh. If solar energy supply and thermal demand were perfectly coupled over time, it would be possible to cover 99.1% of Pamplona's thermal energy demand.