Prospect
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Methodology
Accuracy and comparisonsSeveral independent comparisons of solar radiation databases have been performed in recent years. In all these comparisons, Solargis has been identified as the best performing database. Results of two of these comparison studies are available publicly and are summarised below.
As a result of a new collaborative effort of international experts in the field of solar energy, International Energy Agency (IEA) released the report titled "Worldwide Benchmark of Modeled Solar Irradiance Data 2023". This work was done under one of the IEA’s tasks in the PV Power Systems Programme. Specifically, under Task no. 16 with the title "Solar Resource for High Penetration and Large-Scale Applications".
The report presents a benchmark of model-derived direct normal irradiance (DNI) as well as global horizontal irradiance (GHI) data at the sites of 129 globally distributed ground-based radiation measurement stations.
The benchmark results show "noticeable deviations in performance between the various modeled data sets" that were evaluated.
In particular, deviation metrics of data sets based mainly on geostationary satellite imagery are closer to each other than to the NWP-based and polar satellite-based data sets. Specifically, the report mentions that “lowest average deviation metrics are often achieved by a single data set (Solargis)”.
This study presents results of a validation in the European and Mediterranean region of satellite-derived irradiation databases in hourly, daily and monthly values. GHI and DNI data from 6 satellite-irradiance-models were compared with high quality measurements from 18 locations. Up to 16 years of continuous measurements have been used for the validation. The locations chosen for validation cover different climate conditions - from desert to oceanic, the latitude varies from 20°N to 60°N, and the altitudes from sea level to 1580 metres.
Solargis has been identified as the data source with the lowest overall bias, lowest mean bias deviation, and lowest RMSD. A summary of the validation results in presented in the table below.
| Solargis | Helioclim 3 | Solemi | Heliomont | CM-SAF | IrSOLaV | ||
| GHI | Mean bias | 0% | 1% | 2% | 1% | 0% | 1% |
| Standard deviation of biases | 2.1% | 5.1% | 4.8% | 3.6% | 3.7% | 4.2% | |
| DNI | Mean bias | -2% | 6% | -11% | 0% | 2% | 0% |
| Standard deviation of biases | 5.9% | 13.9% | 14.5% | 9.3% | 9.1% | 12% |
In this study, GHI and DNI data from five satellite derived irradiation database are compared with high quality measurements from 23 locations across Europe, Middle East and Africa for the year 2006 (365 days). The models validated in this study include:
The Solargis database demonstrated the lowest bias and RMSD values amongst all data sources.
This study undertook a cross comparison of the annual global horizontal irradiation data sources available for Australia. The models validated in this study include: Solargis, Meteonorm 7.2, NASA POWER, Vaisala, MERRA-2, Australian Bureau of Meteorology (BoM) gridded solar data.
Besides other conclusions also this study found that Solargis database demonstrated the lowest bias and RMSD values amongst compared data sources.
| Solargis | NASA POWER | MERRA-2 | Australian Bureau of Meteorology | ||
| GHI | Mean bias | 0.0% | -0.9% | 5.9% | -0.4% |
| Standard deviation of biases | 1.50% | 3.72% | 4.46% | 2.23% |
Solar Resource Assessment over Kuwait: Validation of Satellite-derived Data and Reanalysis Modeling by Majed AL-Rasheedi, Christian A. Gueymard, Alaa Ismail and Salem AL-Hajraf, EuroSun 2014 Conference Proceedings, 16-19 September 2014
Satellite or ground-based measurements for production of site specific hourly irradiance data: Which is most accurate and where? by Diane Palmer, Elena Koubli, Ian Cole, Tom Betts, Ralph Gottschalg, Solar Energy, Volume 165, 1 May 2018, Pages 240-255
Validation of solar resource and meteorological data for Japan by Solargis, 2021
