Bijan Nouri

German Aerospace Center (DLR) | DLR · Department of Qualification

The interest in shortest-term solar irradiance forecasts (nowcasts) increases steadily with the increase share of distributed solar power generation. Such solar irradiance nowcasts are beneficial for different stakeholders, from generation to transmission and demand, in order to tackle challenges caused by the variability of solar irradiance. In sp...

Improved solar irradiance nowcasts based on all-sky imagers. Hybrid physical and end-to-end machine learning (ML) model. The ML model is based on an multi-modal deep learning model combining an vision transformer (for images) with an time series transformer (for time series data). Skill score improvements >12% points are achieved. Correct detection...

All-sky imagers (ASIs) can be used to model clouds and detect spatial variations of cloud attenuation. Such cloud modeling can support ASI-based nowcasting, upscaling of photovoltaic production and numeric weather predictions. A novel procedure is developed which uses a network of ASIs to model clouds and determine cloud attenuation more accurately...

Fluctuations of the incoming solar irradiance impact the power generation from photovoltaic and concentrating solar thermal power plants. Accurate solar nowcasting becomes necessary to detect these sudden changes of generated power and to provide the desired information for optimal exploitation of solar systems. In the framework of the Internationa...

Concerning current efforts to improve operational efficiency and to lower overall costs of concentrating solar power plant with prediction-based algorithms this study investigates the quality and uncertainty of nowcasting data regarding the implication for process predictions. DNI (direct normal irradiation) maps from an all-sky imager based nowcas...

Solar forecasting constitutes a critical tool for operating, producing and storing generated power from solar farms. In the framework of the International Energy Agency’s Photovoltaic Power Systems Program Task 16, the solar irradiance nowcast algorithms, based on five all-sky imagers (ASIs), are used to investigate the feasibility of ASIs to fores...

The rapid increase in solar photovoltaic (PV) integration into electricity networks introduces technical challenges due to varying PV outputs. Rapid ramp events due to cloud movements are of particular concern for the operation of remote islanded microgrids (IMGs) with high solar PV penetration. PV systems and optionally controllable distributed en...

Parabolic trough (PT) power plants focus the sun's irradiation onto an absorber tube using collector mirrors to increase the temperature of the heat transfer medium (HTF). In the power plant, the HTF is used to generate electricity. To heat up the HTF, PT solar fields are set up in large areas and pipes are used to distribute the HTF in the solar f...

Smart4RES is a European Horizon2020 project developing next generation solutions for renewable energy forecasting. This paper presents highlight results obtained during the first year of the project. Data science is used throughout the proposed solutions in order to process the large amount of heterogeneous data available to forecasters, and derive...

Semantic segmentation of ground-based all-sky images (ASIs) can provide high-resolution cloud coverage information of distinct cloud types, applicable for meteorology-, climatology- and solar-energy-related applications. Since the shape and appearance of clouds is variable, and there is high similarity between cloud types, a clear classification is...

This paper presents the solutions on renewable energy forecasting proposed by the Horizon2020 Project Smart4RES. The ambition of the project is twofold: (1) increase substantially the performance of short-term forecasting models of Renewable Energy Sources (RES) production and associated weather forecasting and (2) optimize decisions subject to RES...

Accurate, robust and cost-efficient measurements of diffuse horizontal irradiance (DHI) and global tilted irradiance (GTI) are of great interest for solar energy applications. However, the available measurement techniques exhibit at least one of these shortcomings: restriction of GTI measurement to a single plane, intensive maintenance, high acquis...

New technical challenges arise due to the growing share of distributed and intermittent solar power generation. Intra-minute and intra-hour variabilities, when insufficiently accounted for, could lead to grid instabilities. Shortest-term forecasts, often referred as nowcast, can anticipate such variabilities with high resolutions in space and time....

The integration of solar photovoltaic (PV) into electricity networks introduces technical challenges due to varying PV output. Rapid ramp events due to cloud movements are of particular concern for the operation of remote islanded microgrids (MGs) with high penetration of solar PV generation. PV plants and optionally controllable distributed energy...

The share of distributed solar power generation is continuously growing. This increase, combined with the intermittent nature of the solar resource, creates new challenges for all relevant stakeholders from generation to transmission and demand. Insufficient consideration of intra-minute and intra-hour variabilities might lead to grid instabilities...

Cloud base height (CBH) is an important parameter for many applications such as aviation, climatology or solar irradiance nowcasting (forecasting for the next seconds to hours ahead). The latter application is of increasing importance for the operation of distribution grids and photovoltaic power plants, energy storage systems and flexible consumer...

A huge amount of observations (radiometers, ceilometers, sky images, satellites as well as solar plants) are used to derive solar nowcasts as well as the initial state of the atmosphere used by improved numerical weather models. The evolution of which is then predicted by NWP and LES. For solar power prediction, both observations from the ground an...

Semantic segmentation of ground-based all-sky images (ASIs) can provide high-resolution cloud coverage information of distinct cloud types, applicable for meteorology, climatology and solar energy-related applications. Since the shape and appearance of clouds is variable and there is high similarity between cloud types, a clear classification is di...

Subject Solar thermal power plants are utility scale power production systems that work with an intermediate thermal cycle and a conventional steam turbine cycle. Whereas other entries in this book give insights into the different CSP technologies this entry focuses on the dynamic behavior of concentrating solar power plants. The solar irradiation...

Solar field developers include innovative solutions to optimize the energy production of their plants. Simulation tools play a significant role in the design and testing phases as they provide estimations of this yield in different conditions. Transient processes, like passing clouds and solar field start-up, are specifically challenging to optimiz...

Cloud base height (CBH) is an important parameter for many applications such as aviation, climatology or solar irradiance nowcasting (forecasting for the next seconds to hours ahead). The latter application is of increasing importance to operate distribution grids as well as photovoltaic power plants, energy storage systems and flexible consumers....

Solar fields of parabolic troughs are extensive complex thermal hydraulic facilities. Intra-hour and intra-minute variabilities of the DNI, mainly caused by passing clouds, pose an operational challenge for parabolic trough power plants. Under perfect circumstances a solar field controller would adjusts the mass flow in such a way, that the design...

All sky imager (ASI) based nowcasting system can provide spatially and temporally highly resolved solar irradiance information for the next minutes ahead. Nowcasts, which capture the intra-hour variability of the incoming downward shortwave solar irradiance, have the potential to optimize the operation of solar power plants as well as electrical gr...

The solar field of a parabolic trough power plant is a complex thermal and hydraulic system. It is used to bring the heat transfer fluid (HTF) up to the desired temperature. The mass flow for the entire solar field is usually controlled from the plant control room. In the ideal case, the controller will adjust the mass flow so that the desired temp...

The aim of this paper is to present the objectives, research directions and first highlight results of the Smart4RES project, which was launched in November 2019, under the Horizon 2020 Framework Programme. Smart4RES is a research project that aims to bring substantial performance improvements to the whole model and value chain in renewable energy...

The detection and segmentation of clouds in images taken by ground based cameras is of utmost importance for a large number of applications including all-sky imager based nowcasting systems which optimize solar power plant operation, calculation of the global irradiance, estimation of the cloud base height and support of optical satellite downlink...

The aim of this paper is to present the objectives, research directions and first highlight results of the Smart4RES project, which was launched in November 2019, under the Horizon 2020 Framework Programme. Smart4RES is a research project that aims to bring substantial performance improvements to the whole model and value chain in renewable energy...

One of the greatest challenges facing humanity in the 21st century is the transition to a fully decarbonized society. The most abundant energy resource available to mankind is the Sun. Concentrated solar thermal power (CSP) plants with thermal energy storages (TES), such as parabolic trough (PT) power plants, could provide a renewable source of dis...

The continuously growing penetration of intermittent electricity sources will increase the future demand for dispatchable power plants, which balance out fluctuations within the electrical grids. Parabolic trough power plants with thermal energy storages could be one renewable solution for regions with a high yearly direct normal irradiance (DNI) s...

Spatially and temporally highly resolved direct normal irradiance (DNI) maps of the solar field can be used to significantly improve the operation of concentrating solar power (CSP) plants. Further improvements are expected if DNI nowcasts are also used for the plant operation. Currently, the most widely used method to create spatially resolved DNI...

The magnitude of the direct normal irradiance (DNI) depends on seasonal differences due to the sun-earth geometry, and atmospheric extinction processes caused by aerosols and clouds. The most relevant source for intra-hour variability in the DNI are clouds. Suitable sites for concentrating solar power (CSP) plants have an annual average DNI above a...

The rapid growth of solar power generation and the variable nature of the solar resource pose challenges for our electricity grids. Forecasting future changes in the irradiance might help to cost-efficiently manage this variability both for photovoltaic and concentration solar plants as well as grids with high solar penetrations. So far, for shorte...

The incoming downward shortwave solar irradiance is harvested to an increasing extent by solar power plants. However, the variable nature of this energy source poses an operational challenge for solar power plants and electrical grids. Intra hour solar irradiance nowcasts with a high temporal and spatial resolution could be used to tackle this chal...

Im Zuge der fortschreitenden Integration von stark fluktuierenden Energiequellen wie insbesondere der Photovoltaik entsteht ein wachsender Bedarf an hochwertigen Erzeugungsdaten, wobei zunehmend Informationen zur zeitlich und räumlich hochaufgelösten Struktur und zur Variabilität der Erzeugung benötigt werden. In diesem Zusammenhang entsteht derzei...

The demand for accurate solar irradiance nowcast increases together with the rapidly growing share of solar energy within our electricity grids. Intra-hour variabilities, mainly caused by clouds, have a significant impact on solar power plant dispatch and thus on electricity grids. All sky imager (ASI) based nowcasting systems, with a high temporal...

All-sky imager based systems can be used to measure a number of cloud properties. Configurations consisting of two all-sky imagers can be used to derive cloud heights for weather stations, aviation and nowcasting of solar irradiance. One key question for such systems is the optimal distance between the all-sky imagers. This problem has not been stu...

Solar irradiance nowcasts can be derived with sky images from all sky imagers (ASI) by detecting and analyzing transient clouds, which are the main contributor of intra-hour solar irradiance variability. The accuracy of ASI based solar irradiance nowcasting systems depends on various processing steps. Two vital steps are the cloud height detection...

Electric power grids are increasingly penetrated by generation from photovoltaic (PV) systems. The volatility of solar irradiance can therefore cause problematic fluctuations of grid voltage and frequency. For local low voltage power grid sections highly accurate nowcasts of the short-term local PV-power generation may enable higher PV penetration...

Concentrated Solar Power (CSP) projects require accurate assessment and monitoring of the available direct beam resource. To this end, ground measurements on site are inexpendable. Pyrheliometers with thermopile sensors as specified in [ISO 9060] are the standard instruments for field measurements of direct beam irradiance. During long-term deploym...

The yield of solar thermal power plants is strongly affected by disturbances in the irradiation condition through passing clouds. This effect is even more prominent when the clouds shade the solar field only partially as the irradiance situation cannot be fully measured by few measurement points in the field. In this paper, the benefit of using now...

The cover image, by Pascal Kuhn et al., is based on the Special Issue Paper Validation of an all‐sky imager–based nowcasting system for industrial PV plants, https://doi.org/10.1002/pip.2968.

Kurzzeitprognosen der Solarstrahlung für die nächsten 15 Minuten bergen ein großes Potenzial zur Betriebsoptimierung von solarthermischen Kraftwerken, PV-Systemen als auch des Netzbetriebs. Kameragestützte Prognosesysteme erfuhren in den letzten Jahren einen signifikanten Entwicklungsschub, begünstigt durch die Verfügbarkeit von günstigen hochauflö...

Pyrheliometer calibration must be done following strict procedures in order to ensure the required robustness and accuracy. These procedures are described in the ISO 9059:1990 and ASTM E 816 – 15 international standards. However, their application requires information that may not always be available or may be subjective, inaccurate or incomplete,...

Politischer Wille sowie die Photovoltaik-Preisreduktionen der letzten Jahre werden wahrscheinlich in naher Zukunft zu einem hohen Solarstrom-Anteil in unseren Stromnetzen führen. Die solare Einstrahlung unterliegt jedoch Schwankungen. Genaue Vorhersagen dieser Schwankungen können teure, technische Maßnahmen wie das Vorhalten von Reservekraftwerken,...

Cloud height information is crucial for various applications. This includes solar nowcasting systems. Multiple methods to obtain the altitudes of clouds are available. In this paper, cloud base heights derived from the European Centre for Medium-Range Weather Forecasts (ECMWF) and three low-cost and low-maintenance ground based systems are presente...

A clamp-on measurement system for flexible and accurate fluid temperature measurements for turbulent flows with Reynolds numbers higher than 30,000 is presented in this paper. This noninvasive system can be deployed without interference with the fluid flow while delivering the high accuracies necessary for performance and acceptance testing for pow...

Because of the cloud-induced variability of the solar resource, the growing contributions of photovoltaic plants to the overall power generation challenges the stability of electricity grids. To avoid blackouts, administrations started to define maximum negative ramp rates. Storages can be used to reduce the occurring ramps. Their required capacity...

Accurate nowcasts of the direct normal irradiance (DNI) for the next 15 min ahead can enhance the Overall efficiency of concentrating solar power (CSP) plants. Such predictions can be derived from ground based all sky imagers (ASI). The main challenge for existing ASI based nowcasting systems is to provide spatially distributed solar irradiance inf...

Because of forward scattered radiation in the atmosphere, the circumsolar region closely surrounding the solar disk looks very bright. The radiation coming from this region, the circumsolar radiation, is in large part included in direct normal irradiance (DNI) measurements at the usual 2.5° pyrheliometer opening half angle, but only partially inter...

Controlling parabolic trough solar thermal power plants during transient events, such as passing clouds, is challenging for the power plant operators. Solar field controllers try to operate the field with the suitable fluid mass flow to reduce any waste of solar irradiation under very different weather and operational conditions. However, finding t...