Estimating PV Module Performance over Large Geographical Regions: The Role of Irradiance, Air Temperature, Wind Speed and Solar Spectrum

We present a study of how photovoltaic (PV) module performance varies on continental scale. Mathematical models have been used to take into account shallow-angle reflectivity, spectral sensitivity, dependence of module efficiency on irradiance and module temperature as well as how the module temperature depends on irradiance, ambient temperature and wind speed. Spectrally resolved irradiance data retrieved from satellite images are combined with temperature and wind speed data from global computational weather forecast data to produce maps of PV performance for Eurasia and Africa. Results show that module reflectivity causes a fairly small drop of 2-4\% in PV performance. Spectral effects may modify the performance by up to +/- 6%, depending on location and module type. The strongest effect is seen in the dependence on irradiance and module temperature, which may range from -20% to +5% at different locations.JRC.F.7-Renewables and Energy Efficienc

Spatial Downscaling of 2-Meter Air Temperature Using Operational Forecast Data

We present a method for enhancing the spatial resolution of 2 meter temperature (T2m) estimates. The method is based on operational forecast data supplied by the European Centre for Medium Range Weather Forecast. From the hourly and monthly average temperatures a vertical gradient is determined by linear fitting to the temperature data in larger areas of 1x1° or 2x2°. Validation against data from more than 8000 meteorological stations worldwide shows that the estimates of annual average temperature at these points becomes significantly more accurate when applying the vertical gradients to correct the local temperature estimates to the elevation of the stations. When the elevation difference between forecast and station is larger than 300m, the overall mean absolute deviation of the individual stations bias values decreases from 3.44°C to 1.02°C and the root mean square deviation decreases from 4.11°C to 1.42°C. The gradients have also been applied to the ERA-Interim reanalysis data and the validation results are similar. The vertical temperature gradients will be useful for studies in many fields, including renewable energy and the study of energy performance of buildings.JRC.F.7-Renewables and Energy Efficienc

A New Database of Global and Direct Solar Radiation Using the Eastern Meteosat Satellite, Models and Validation

We present a new database of solar radiation at ground level for Eastern Europe and Africa, the Middle East and Asia, estimated using satellite images from the Meteosat East geostationary satellites. The method presented calculates global horizontal (G) and direct normal irradiance (DNI) at hourly intervals, using the full Meteosat archive from 1998 to present. Validation of the estimated global horizontal and direct normal irradiance values has been performed by comparison with high-quality ground station measurements. Due to the low number of ground measurements in the viewing area of the Meteosat Eastern satellites, the validation of the calculation method has been extended by a comparison of the estimated values derived from the same class of satellites but positioned at 0ºE, where more ground stations are available. Results show a low overall mean bias deviation (MBD) of +1.63W/m-2 or +0.73\% for global horizontal irradiance. The mean absolute bias of the individual station MBD is 2.36\%, while the root mean square deviation of the individual MBD values is 3.18\%. For direct normal irradiance the corresponding values are overall MBD of +0.62W/m-2 or +0.62\%, while the mean absolute bias of the individual station MBD is 5.03\% and the root mean square deviation of the individual MBD values is 6.24\%. The resulting database of hourly solar radiation values will be made freely available. These data will also be integrated into the PVGIS web application to allow users to estimate the energy output of photovoltaic (PV) systems not only in Europe and Africa, but now also in Asia.JRC.F.7-Renewables and Energy Efficienc

Integration of Helioclim-1 database into PV-GIS to estimate solar electricity potential in Africa

pages 2989-2992We present a method for computing high resolution database of global horizontal irradiation for Africa and the Mediterranean Basin. Following this, we analyse the geographical and time variability of the solar energy potential for electricity applications. The primary solar radiation data were previously computed from Meteosat satellite images by the Heliosat-2 method and stored in the HelioClim-1 database. From this database, the long term monthly and yearly averages of global irradiation on horizontal plane (period 1985-2004) were derived. Using the PV-GIS method, based on a clear-sky model, interpolation of the clear-sky index and terrain shadowing, the original spatial resolution of HelioClim-1 database (15') was enhanced to 2 km. Using daily global irradiation from the enhanced PV-GIS database we estimated the electricity generation from a typical solar home system. Assuming a 100 Wp installation with a battery and battery charger, together with a performance ratio of 0.75, the power production ranges from about 0.3 to 0.6 kWh per day in most locations in Africa

Online data and tools for estimation of solar electricity in Africa: the PVGIS approach

We present interactive web tools for map-based query of a solar radiation database and for performance assessment of solar photovoltaic systems. The high-resolution geographic database covers the Mediterranean Basin, Africa and South-West Asia. Daily global irradiation was primarily computed from Meteosat satellite images by the Heliosat-2 method and stored in the HelioClim-1 database. From this database, long term monthly and yearly averages of global horizontal irradiation were derived for the period 1985-2004. Using the PVGIS method, based on the solar radiation model r.sun, interpolation of the clear-sky index and terrain shadowing, the original spatial resolution of HelioClim-1 database (15' x 15') was enhanced to 2 km x 2 km. A set of web tools was developed to query basic climatic and geographic data for a chosen location, and to estimate and optimize energy output from photovoltaic system at arbitrary inclination and orientation of modules. The PVGIS system can be accessed at http://re.jrc.ec.europa.eu/pvgis/pv/

Hydro-economic assessment of the potential of PV-RO desalinated seawater supply in the Mediterranean region: Modelling concept and analysis of water transport costs

Seawater desalination, although a traditional source of water in arid and water-scarce regions, is receiving attention worldwide due to the growing concern on dwindling traditional water resources. Desalination entails significant energy consumption, which may be unsustainable when the latter is provided by fossil fuels. However, when fed with energy from renewable sources, desalination may become more attractive. Until now, desalination has been regarded as a local source of freshwater for coastal areas or islands, but the mapping of regions suitable to be supplied with desalinated seawater has been seldom addressed systematically. Caldera et al., 2016, present a global scale analysis based on a simplified representation of water demand and energy requirements for desalinated water production and transport, suggesting that desalinated seawater could be supplied in water-stressed regions of the world by 2030, using renewable energy only, at a cost between 0.59 and 2.81 Euro/m3. While their analysis provides general indications at global scale, the specificity of regions arising from topography, the distribution of population and land use may warrant a more detailed inspection. Appraising the potential of renewable energy seawater desalination as a water resource requires quantifying its costs of production (construction, operation and maintenance of desalination plants), as well as the costs of transporting desalinated water from the coastal production sites to potential users inland. In this contribution, we describe the cost elements concurring to the total cost of desalinated seawater, and we quantify the component of costs associated to water transport from a coastal production site to the final users inland. We limit our analysis to the case of using renewable energy, and specifically photovoltaic (PV) energy, to feed plants based on reverse osmosis (RO) technology, currently representing the most common choice by desalination engineers. We develop our cost analysis assuming PV to contribute 100% of energy used in both production and transport of desalinated water. Finally, we outline the envisaged steps towards a prioritization of investments in desalination in the Mediterranean.JRC.D.2-Water and Marine Resource

Application of Satellite-Based Spectrally-Resolved Solar Radiation Data to PV Performance Studies

In recent years, satellite-based solar radiation data resolved in spectral bands have become available. This has for the first time made it possible to produce maps of the geographical variation in the solar spectrum. It also makes it possible to estimate the influence of these variations on the performance of photovoltaic (PV) modules. Here, we present a study showing the magnitude of the spectral influence on PV performance over Europe and Africa. The method has been validated using measurements of a CdTe module in Ispra, Italy, showing that the method predicts the spectral influence to within ±2% on a monthly basis and 0.1% over a 19-month period. Application of the method to measured spectral responses of crystalline silicon, CdTe and single-junction amorphous silicon (a-Si) modules shows that the spectral effect is smallest over desert areas for all module types, higher in temperate Europe and highest in tropical Africa, where CdTe modules would be expected to yield +6% and single- junction a-Si modules up to +10% more energy due to spectral effects. In contrast, the effect for crystalline silicon modules is less than ±1% in nearly all of Africa and Southern Europe, rising to +1% or +2% in Northern Europe.JRC.F.7-Renewables and Energy Efficienc

Sources of uncertainty in annual global horizontal irradiance data

The major sources of uncertainty in short-term assessment of global horizontal radiation (G) are the pyranometer type and their operation conditions for measurements, whereas the modeling approach and the geographic location are critical for estimations. The influence of all these factors in the uncertainty of the data has rarely been compared. Conversely, solar radiation data users are increasingly demanding more accurate uncertainty estimations. Here we compare the annual bias and uncertainty of all the mentioned factors using 732 weather stations located in Spain, two satellite-based products and three reanalyses. The largest uncertainties were associated to operational errors such as shading (bias = - 8.0%) or soiling (bias = - 9.4%), which occurred frequently in low-quality monitoring networks but are rarely detected because they pass conventional QC tests. Uncertainty in estimations greatly changed from reanalysis to satellite-based products, ranging from the gross accuracy of ERA-Interim (+ 6.1(-6.7)(+)(1)(8.)(8)%) to the high quality and spatial homogeneity of SARAH-1 (+ 1.4(-5.3)(+)(5.6)%). Finally, photodiodes from the Spanish agricultural network SIAR showed an uncertainty of (+6.)(9)(-5.4)%, which is far greater than that of secondary standards (+/- 1.5%) and similar to SARAH-1. This is probably caused by the presence of undetectable operational errors and the use of uncorrected photodiodes. Photodiode measurements from low-quality monitoring networks such as SIAR should be used with caution, because the chances of adding extra uncertainties due to poor maintenance or inadequate calibration considerably increase.Peer reviewe

Uncertainties in solar electricity yield prediction from fluctuation of solar radiation

We have analyzed the variability of solar radiation in the Mediterranean and Black Sea regions by comparing yearly and monthly averages to long-term average values calculated from the HelioClim-1 database. Daily sums of global horizontal irradiation are considered for 18 years in the period 1985-2004. Standard deviation of yearly sums of global horizontal irradiation shows low interannual variability, being mostly in the range of 4% to 6%. While in arid climate of Northern Africa, Middle East, and Southern Europe standard deviation goes below 4%, values up to 10% are identified along coasts and in mountains. In the least sunny year out of 18, the solar resource was generally never more than 9% below the long-term average, and only in a few regions the radiation deficit reached 15%. The most stable weather is found in summer with standard deviation in June below 12%. The least stable season is winter, with variability higher then 20% in December, and regionally going above 35%. The solar resource has distinctive time and geographical patterns that might affect financing of large photovoltaic systems, as well as management of the distributed electricity generation

Renewable Energy Snapshots 2011

These Renewable Energy Snapshots are based on various data providers including grey data sources and tries to give an overview about the latest developments and trends in the different technologies. Due to the fact that unconsolidated data are used there is an uncertainty margin which should not be neglected. We have cross checked and validate the different data against each others, but do not take any responsibility about the use of these data.JRC.F.8-Renewable Energy (Ispra