Introduction
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Measured data, with different quality measuring and from different years.
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Interpolating data, which come from grids of different densities in the input data and from different years.
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Estimation data, that need to take into account the model features (years of data and images used in the development), the characteristics of images (resolution and geometry), and the time periods of the used data.
Data and methodology
Measured data
Sites | Latitude (N°) | Longitude (E°) | Latitude (m) | Climate |
---|---|---|---|---|
Algiers
| 36.43 | 3.15 | 25 | Mediterranean |
Ghardaia
| 32.36 | 3.81 | 450 | Desert arid |
Tamanrasset
| 22.87 | 5.51 | 1,377 | Desert arid |
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Three EKO pyranometer and a pyrheliometer with a sun tracker for measuring global, diffuse, and direct normal radiations.
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A data Logger “Micrologger CR 3000” with data acquisition system for reading measurements every 5 min since 2011 to the present day.
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A fixed part consisting of two EKO pyranometer for the measurements of global and diffuse horizontal solar radiations.
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A second moving part with EKO pyrheliometer pointed at the sun disk for measuring direct normal irradiance.
DNI satellite-derived databases
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NASA-SSE (Surface Meteorology and Solar Energy): it combines the results from GEWEX/SRB3 and ISCCP projects with NCAR reanalysis products (1983–2005), and provides monthly and annual (global, diffuse horizontal, and direct normal irradiations values). Its web page is (http://eosweb.larc.nasa.gov/sse/) in a version that is more applicable to renewable energy technology with the data accuracy and its methodology.
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Solar-Med-Atlas (Solar Atlas for the Mediterranean): it has high-resolution (1 km), and long-term coverage of at least 20 years of data (1991–2010). The free access to the data includes historical annual and monthly averages of the global horizontal and direct normal irradiance data for the southern and eastern Mediterranean regions. The current database can be accessed at http://www.solar-med-atlas.com.
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HelioClim1 (SoDa): these data are modeled from Meteosat imagery covering Europe, Africa, the Mediterranean Basin, the Atlantic Ocean, and part of the Indian Ocean, with 20-km spatial resolution and a period of record (1985–2005). The databases of HelioClim1 can be accessed through the SoDa service in the page http://www.soda-is.com/eng/index.html.
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SolarGIS: it is a geographic information system (GIS) that uses a new model for high-performance calculation of global and direct irradiances for the regions covered by Meteosat MSG (Europe, Africa, and the Middle East) for a period (2004–2010). Its web page is solargis.info/.
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Meteonorm: it is a global database that is developed by interpolation of the observed data of 7,756 ground stations (1981–2000) with the support of satellite images (2003–2005) of MSG and four other geostationary satellites. Its web page is http://www.meteonorm.com.
DNI estimation procedure
Comparison technique
Results and discussion
Measured | Model 1 | Model 2 | Model 3 | NASA-SSE | Solar-Med-Atlas | SoDa (HC1) | SolarGIS | Meteonorm | |
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DNI annual values | 1,620 | 1,621 | 1,871 | 1,783 | 2,110 | 1,950 | 1,949 | 1,673 | 1,838 |
e (%) | 0.043 | 15.494 | 10.062 | 30.247 | 20.370 | 20.309 | 3.272 | 13.457 |
Measured | Model 1 | Model 2 | Model 3 | NASA-SSE | Solar-Med-Atlas | SoDa (HC1) | SolarGIS | Meteonorm | |
---|---|---|---|---|---|---|---|---|---|
DNI annual values | 2,419 | 2,409 | 2,610 | 2,083 | 2,405 | 2,377 | 2,481 | 2,104 | 2,815 |
e (%) | −0.406 | 7.923 | −13.863 | −0.563 | −1.730 | 2.600 | −13.005 | 16.389 |
Measured | Model 1 | Model 2 | Model 3 | NASA-SSE | Solar-Med-Atlas | SoDa (HC1) | SolarGIS | Meteonorm | |
---|---|---|---|---|---|---|---|---|---|
DNI annual values | 2,658 | 2,665 | 2,753 | 2,098 | 2,480 | 2,758 | 2,631 | 2,428 | 2,719 |
e (%) | 0.261 | 3.56 | −21.079 | −6.709 | 3.613 | −1.029 | −8.665 | 2.281 |
Parameter | Model 1 | Model 2 | Model 3 | NASA-SSE | Solar-Med-Atlas | SoDa (HC1) | SolarGIS | Meteonorm |
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MPE | 2.290 | 30.066 | 30.474 | 40.354 | 40.730 | 37.918 | 48.167 | 23.616 |
MAPE | 6.439 | 30.066 | 30.569 | 40.354 | 40.730 | 37.918 | 51.347 | 24.893 |
MBE | 0.173 | 1.250 | 0.978 | 1.514 | 1.493 | 1.468 | 1.485 | 0.768 |
MABE | 0.322 | 1.250 | 0.985 | 1.514 | 1.493 | 1.468 | 1.697 | 0.828 |
RMSE | 0.461 | 1.322 | 1.158 | 1.599 | 1.636 | 1.712 | 1.922 | 0.960 |
R
2
| 0.977 | 0.974 | 0.896 | 0.868 | 0.778 | 0.732 | 0.257 | 0.843 |
NSE | 0.893 | 0.119 | 0.324 | −0.291 | −0.350 | −0.479 | −0.865 | 0.535 |
t
sta
| 1.347 | 9.663 | 5.246 | 9.746 | 7.425 | 5.524 | 4.036 | 4.426 |
Parameter | Model 1 | Model 2 | Model 3 | NASA-SSE | Solar-Med-Atlas | SoDa (HC1) | SolarGIS | Meteonorm |
---|---|---|---|---|---|---|---|---|
MPE | 0.153 | 7.983 | −13.493 | 0.339 | −0.976 | 3.481 | −11.892 | 18.094 |
MAPE | 4.805 | 7.983 | 13.493 | 24.039 | 12.736 | 17.486 | 16.563 | 20.477 |
MBE | −0.036 | 0.528 | −0.920 | −0.059 | −0.123 | 0.157 | −0.878 | 1.063 |
MABE | 0.341 | 0.528 | 0.920 | 1.534 | 0.802 | 1.128 | 1.134 | 1.265 |
RMSE | 0.491 | 0.577 | 1.073 | 1.835 | 1.001 | 1.333 | 1.244 | 1.546 |
R
2
| 0.773 | 0.952 | 0.683 | 0.051 | 0.295 | 0.129 | 0.211 | 0.052 |
NSE | 0.748 | 0.652 | −0.201 | −2.517 | −0.046 | −0.855 | −0.616 | −1.494 |
t
sta
| 0.243 | 7.470 | 5.532 | 0.107 | 0.412 | 0.393 | 3.299 | 3.144 |
Parameter | Model 1 | Model 2 | Model 3 | NASA-SSE | Solar-Med-Atlas | SoDa (HC1) | SolarGIS | Meteonorm |
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MPE | 1.061 | 12.479 | −13.192 | −4.792 | 13.829 | 8.111 | −8.044 | 4.041 |
MAPE | 4.986 | 12.479 | 15.022 | 14.356 | 15.196 | 13.387 | 8.044 | 14.886 |
MBE | 0.006 | 0.860 | −1.100 | −0.498 | 0.884 | 0.503 | −0.623 | 0.146 |
MABE | 0.379 | 0.860 | 1.210 | 1.087 | 1.008 | 0.948 | 0.623 | 1.093 |
RMSE | 0.586 | 0.969 | 1.574 | 1.299 | 1.301 | 1.190 | 0.815 | 1.247 |
R
2
| 0.846 | 0.646 | 0.046 | 0.033 | 0.329 | 0.298 | 0.816 | 0.040 |
NSE | 0.741 | 0.292 | −0.867 | −0.273 | −0.277 | −0.068 | 0.500 | −0.173 |
t
sta
| 0.033 | 6.390 | 3.241 | 1.377 | 3.071 | 1.548 | 3.931 | 0.391 |