## 5 Conclusions  
In conclusion, the comparative analysis considering the Heliosat-2 solar radiation estimates and ground measurements from diverse sources like BSRN, SAURAN, and SCADA, ranging across various geographic regions, provides significant insights into the model's accuracy and reliability. In the realm of solar energy estimation, clear-sky models offer projections under the assumption of cloudless atmospheres, factoring in variables such as solar elevation angle, site altitude, and atmospheric characteristics. Nonetheless, these models often fall short in accurately assessing the influence of cloud cover. Conversely, cloudy-sky conditions consider the scattering and absorption of sunlight by clouds, resulting in an overestimation attributable to the assumptions of clear-sky scenarios. The study reveals a tendency for Heliosat-2 Global Horizontal Irradiance (GHI) estimates to overestimate during cloudy conditions and underestimate on clear days. This phenomenon can also be attributed to the lower sample size for the cloudy days, compared to that for clear days. The performance of Heliosat-2 in various locations demonstrates its efficacy in solar energy planning and radiation estimation. In Japan, despite notable variability in RMSE during cloudy days, the model achieves high median R\({}^{2}\) values on clear days, indicating robust performance. Similarly, in South Africa and Namibia, Heliosat-2 exhibits commendable accuracy, with a majority of data points falling within acceptable ranges. Although slight underestimations are observed in Saudi Arabia, particularly on cloudy days, the model consistently achieves high R\({}^{2}\) values, affirming its reliability as to solar radiation estimation. In general, the study confirms the effectiveness of Heliosat-2 in providing reliable solar radiation estimates across diverse geographic regions and varying weather conditions. While slight deviations are noted under cloudy conditions, the model's ability to maintain high accuracy during clear skies highlights its potential for widespread application in solar energy resource assessment and planning. Future research should focus on analyzing the performance of Heliosat-2 under varying pollution levels, including different types and sizes of aerosol particles. Conceptualization, S.H.A.R. and R.C. ; Data curation, J.K.M. and R.K.; Formal analysis, J.K.M. ; Investigation, J.K.M. ; Methodology, J.K.M. ; Project administration, S.H.A.R., B.C., and R.C. ; Resources, R.K.; Software, B.C. and Y.T. ; Supervision, J.K.M. and S.H.A.R. ; Validation, J.K.M. ; Visualization, J.K.M. ; Writing--original draft, J.K.M. ; Writing--review and editing, S.H.A.R. and V.S. All authors have read and agreed to the published version of the manuscript. This research was fully funded by Solarad AI Private Limited. Solarad AI provided financial support and resources for the conduct of this research. The analysis and interpretation of data, as well as the decision to publish these findings, were carried out independently by the authors, ensuring the scientific rigor and integrity of the research. The BSRN datasets are publicly accessible via [[https://bsrn.awi.de/](https://bsrn.awi.de/)]([https://bsrn.awi.de/](https://bsrn.awi.de/)). SAURAN data can be retrieved from the public repository at [[https://sauran.ac.za/](https://sauran.ac.za/)]([https://sauran.ac.za/](https://sauran.ac.za/)). Himawari-8 images, intended solely for research and educational purposes, are freely obtainable from [[https://himawari8.nict.go.jp/](https://himawari8.nict.go.jp/)]([https://himawari8.nict.go.jp/](https://himawari8.nict.go.jp/)) following registration with the HIMawARI administration. Similarly, images from MSG can be acquired from [[https://view.meteosat.int/](https://view.meteosat.int/)]([https://view.meteosat.int/](https://view.meteosat.int/)). Heliosat-2 estimate datasets will be provided upon request. However, due to a Non-Disclosure Agreement (NDA) with the respective clients, access to SCADA data is contingent upon signing an NDA with the requesting agency.