author = "Luiz, Eduardo Weide and Martins, Fernando Ramos and 
                         Gon{\c{c}}alves, Andr{\'e} Rodrigues and Pereira, Enio Bueno",
          affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and 
                         {Universidade Federal de S{\~a}o Paulo (UNIFESP)} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and {Instituto Nacional de 
                         Pesquisas Espaciais (INPE)}",
                title = "Analysis of intra-day solar irradiance variability in different 
                         Brazilian climate zones",
              journal = "Solar Energy",
                 year = "2018",
               volume = "167",
                pages = "210--219",
                month = "June",
             keywords = "Solar variability, Effective cloud cover, Satellite data.",
             abstract = "One of the main barriers to increasing the solar energy share is 
                         its intermittency. Solar energys large variability in different 
                         timescales is driven by natural solar astronomical cycles and 
                         weather. Ground-based measurements are important for evaluating 
                         variability at high temporal resolutions, but they are only 
                         representative of small areas close to the measurement sites. 
                         Satellite observations come as an alternative to analysis over 
                         large areas. However, they have coarse temporal and spatial 
                         resolutions. In our study, we first evaluated the variability in 
                         different time steps, using one-year of 1-min resolution 
                         ground-based irradiance measured at three sites located in 
                         different Brazilian climate regimes. The results showed that more 
                         humid months have the largest variability. By contrast, the driest 
                         locations presented more variability on short timescales, probably 
                         due to the presence of a large number of clouds, even in very dry 
                         conditions. This characteristic can be of concern to Brazilian 
                         energy planning since the site is located in the most prominent 
                         region for solar energy generation. We also compared ground 
                         observations with satellite cloud variability, with 30-min 
                         resolution. For the same timescale, the results were promising, 
                         with a Pearson correlation of up to 0.93, depending on the site. 
                         However, when the frequency of the solar irradiance measurements 
                         increased, the correlation decreased. A solution may be to analyze 
                         a larger pixel area around the sites. Another option would be the 
                         use of downscaling methods. This topic, however, will be the 
                         subject of the future study. The most important result achieved in 
                         this study was the development of a simple methodology for 
                         evaluating the surface solar irradiance variability using cloud 
                         cover obtained from visible satellite imagery.",
                  doi = "10.1016/j.solener.2018.04.005",
                  url = "http://dx.doi.org/10.1016/j.solener.2018.04.005",
                 issn = "0038-092X",
             language = "en",
           targetfile = "luiz_analysis.pdf",
        urlaccessdate = "23 abr. 2021"