Assessment and forecasting of solar resource: applications to the solar energy industry

En la presente tesis doctoral se lleva a cabo un estudio de la evaluación y de la predicción del recurso solar para su aplicación en el campo de la industria solar. El objetivo principal es mejorar el conocimiento sobre varios aspectos de la radiación solar como fuente primaria de energía. Sin embargo, a pesar del incesante desarrollo tecnológico y el considerable abaratamiento de costes, su grado de introducción dentro de los sistemas eléctricos a gran escala está todavía lejos de su potencial real. Esto es debido en gran parte a que, a pesar de que la radiación solar es la fuente primaria de energía más abundante del planeta, presenta de forma natural una gran variabilidad espacio-temporal. Esta característica constituye la mayor fuente de incertidumbre en el desarrollo de los proyectos solares, tanto en la fase inicial de estudio de viabilidad como durante la fase de operación. Con el fin de contribuir a la reducción de dicha incertidumbre, en el trabajo de investigación llevado a cabo en esta tesis doctoral se han desarrollado y evaluado métodos para la caracterización y la estimación de la irradiancia solar en superficie, tanto para la componente global (GHI) como para la directa (DNI).In this thesis a study of the assessment and forecasting of the solar resource for its application in the solar industry is carried out. The main objective is to improve the knowledge about various aspects of solar radiation as primary energy source. . However, despite the relentless technological development and the considerable cost reductions, its degree of introduction at large-scale into power systems is still far from its real potential. This is due mainly to the fact that, although solar radiation is the most abundant primary energy source in the planet, it naturally presents a great spatial and temporal variability. This characteristic constitutes the major source of uncertainty in the development of solar projects, both in the initial phase of feasibility study and during the phase of operation. In order to contribute to the reduction of this uncertainty, the research work carried out in this thesis has developed and evaluated methods for the characterization and estimation of surface solar irradiance, both components: global (GHI) and direct (DNI).Tesis Univ. Jaén. Departamento de Física. Leída el 24 de julio de 2017

Analysis and comparison of weather models for solar irradiance forecasts in Sweden

Solar radiation is affected in a variety of different ways through the atmosphere and on its way down to the Earth’s surface. Clouds are the main factor in this attenuation of solar radiation, but aerosols, ozone and other different gases have a significant impact too. Understanding these processes is fundamental to solar forecasting. However, the atmosphere is constantly changing, which makes forecasting weather a challenging task even with today’s complex numerical weather prediction models. In this study of solar irradiance, two different numerical weather models are analyzed: the global IFS-model and the regional ensemble prediction system MEPS. Both models include normal forecasts and ensemble forecasts. This analytical comparison was made in forecasts of up to 24 hours of three locations in Sweden over the time period of 2017-04-01 to 2017-06-30. The purpose was to see differences in the accuracy of the models, and also to see the influence of ensemble forecasts. Ensemble forecasts are used to better handle uncertainties in the weather and are more frequently used in today’s weather prediction. Observation data collected from SMHI’s radiation network was used as reference values in order to get forecasting errors. A generally better result for the ensemble forecasts was identified. Some variations between the stations were also detected where especially the result from one of the three stations was different. That was a location far away from the other two indicating that topography and climatology can affect the precision of the weather models. The regional high-resolution MEPS-model had overall better solar irradiance forecasts during the analyzed time, but the model had a consistent negative bias. A consistent problem with the MEPS-model is most likely that it predicts too much clouds which leads to less amount of solar irradiance in the forecasts.Vad tänker du på när du hör ordet solprognos? För vissa är det viktigt i planeringen av semestern, andra kanske för att skydda sig mot farlig UV-strålning. Vad många inte vet är att solprognoser är en viktig komponent i vårt energisamhälle där förnyelsebara energikällor som solkraft och vindkraft ökar kraftigt runt om i världen. Att göra träffsäkra prognoser för inkommande solstrålning har dock visat sig vara svårt för meteorologerna på grund av snabba och osäkra förändringar i atmosfären. Osäkerheten och variabiliteten för solstrålningen beror framförallt på molnen men också aerosoler, ozon och andra gaser i atmosfären. För att förutse solstrålning och andra meteorologiska parametrar används numeriska vädermodeller där avancerade superdatorer behövs. Genom att veta atmosfärens nuvarande tillstånd och sedan använda fysikens lagar kan man alltså med hjälp av datorer köra simulationer som får fram hur atmosfären och vädret kommer att se ut. Trots att olika vädermodeller bygger på samma fysikaliska teorier och lagar så finns det ändå ofta signifikanta skillnader mellan dem. I den här studien jämförs och analyseras två numeriska vädermodeller för solprognoser i Sverige. Det är den globala modellen IFS och den regionala modellen MEPS (som bygger på modellen HARMONIE-AROME) som jämförs i solprognoser på upp till 24 timmar. Normala prognoser men även de båda vädermodellernas ensembleprognoser analyseras under tidsperioden 2017-04-01 till 2017-06-30. Ensembleprognoser är sannolikhetsprognoser som numera används för att försöka förbättra väderprognoser. Resultatet visar att ensembleprognoser generellt förbättrar prognoserna för solstrålning i Sverige. Den regionala och högupplösta modellen MEPS visar sig för det mesta vara träffsäkrare än den globala IFS-modellen. Detta trots att MEPS har en tydlig tendens att förutse för lite solstrålning. Olika platser i Sverige undersöktes och resultatet varierar dock en aning mellan platserna. Troligtvis beror detta på skillnader i modellernas fysikaliska egenskaper och i att hantera topografi och olika meteorologiska förhållanden

Evaluation of the accuracy of GHI and DNI forecasts by IFS and Harmonie models over Spain

Póster elaborado para la conferencia "SolarPaces 2016" celebrada los días 11-14 de octubre de 2016 en Abu Dhabi.This Project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 654984

A Postprocessing methodology for direct normal irradiance forecasting using cloud information and aerosol load forecasts

A method for direct normal irradiance (DNI) forecasting for specific sites is proposed. It is based on the combination of a numerical weather prediction (NWP) model, which provides cloud information, with radiative transfer simulations fed with external aerosol forecasts. The NWP model used is the ECMWF Integrated Forecast System, and the radiative transfer information has been obtained from the Library of Radiative Transfer (libRadtran). Two types of aerosol forecasts have been tested: the global Monitoring Atmospheric Composition and Climate (MACC) model, which predicts five major components of aerosols, and the Dust Regional Atmospheric Model (BSC-DREAM8b) added to a fixed background calculated as the 20th percentile of the monthly mean of AERONET 2.0 observations from a different year. The methodology employed is valid for all meteorological situations, providing a stable and continuous DNI curve. The performance of the combined method has been evaluated against DNI observations and compared with the pure ECMWF forecasts at eight locations in the southern half of mainland Spain and the Canary Islands, which received high loadings of African dust for 2013 and 2014. Results for 1-day forecasts are presented. Although clouds play a major role, aerosols have a significant effect, but at shorter time scales. The combination of ECMWF and MACC forecasts gives the best global results, improving the DNI forecasts in events with high aerosol content. The regional BSC-DREAM8b yields good results for some extremely high dust conditions, although more reliable predictions, valid for any aerosol conditions, are provided by the MACC model

A postprocessing methodology for direct normal irradiance forecasting using cloud information and aerosol load forecasts

A method for direct normal irradiance (DNI) forecasting for specific sites is proposed. It is based on the combination of a numerical weather prediction (NWP) model, which provides cloud information, with radiative transfer simulations fed with external aerosol forecasts. The NWP model used is the ECMWF Integrated Forecast System, and the radiative transfer information has been obtained from the Library of Radiative Transfer (libRadtran). Two types of aerosol forecasts have been tested: the global Monitoring Atmospheric Composition and Climate (MACC) model, which predicts five major components of aerosols, and the Dust Regional Atmospheric Model (BSC-DREAM8b) added to a fixed background calculated as the 20th percentile of the monthly mean of AERONET 2.0 observations from a different year. The methodology employed is valid for all meteorological situations, providing a stable and continuous DNI curve. The performance of the combined method has been evaluated against DNI observations and compared with the pure ECMWF forecasts at eight locations in the southern half of mainland Spain and the Canary Islands, which received high loadings of African dust for 2013 and 2014. Results for 1-day forecasts are presented. Although clouds play a major role, aerosols have a significant effect, but at shorter time scales. The combination of ECMWF and MACC forecasts gives the best global results, improving the DNI forecasts in events with high aerosol content. The regional BSC-DREAM8b yields good results for some extremely high dust conditions, although more reliable predictions, valid for any aerosol conditions, are provided by the MACC model.The authors acknowledge the libRadtran developers for their radiative transfer tools used in this work and ECMWF for their forecasts. We thank the MACC project, funded by the European Commission under the EU-Horizon 2020 Programme and coordinated by the ECMWF, for their AOD data, freely available on its website (http://www.gmes-atmosphere.eu/)