The drive to increase renewable energy generation, particularly solar, is driven by policies to limit the impact of climate change and a sharp reduction in the average cost per unit of electricity generated. The goal for Italy is to reach 52 GW of installed solar capacity and 74 TWh of photovoltaic energy produced by 2030.

This goal requires careful planning, both for appropriate integration into the territory and for achieving the highest possible efficiency in terms of production. Both aspects require a precise knowledge of the primary resource available. In addition, in recent years, more and more efficient technologies have been developed to convert solar energy into electricity, either through the use of innovative materials or through the use of single- or dual-axis solar tracking photovoltaics.

A common feature of new high-efficiency installations is the ability to selectively use different parts of the solar radiation spectrum. In this context, it is essential to characterize the available resource at the spectral level, a need that is becoming increasingly apparent even at the international level.

The work carried out consists in the development of a methodology (Automatic Radiative TransfEr Model for Irradiance with Satellite data, ARTEMIS) for the calculation of spectra of direct normal and diffuse irradiance with high spatial and temporal resolution. The system is hybrid in the sense that it uses satellite-derived information and data produced by numerical weather prediction models, both global and limited-area.

The method has been developed for clear sky conditions. One of the aspects studied and improved in this year’s release is the calculation of aerosol transmittance, which has allowed a significant improvement in the estimation of direct normal irradiance. Thanks to this, the estimation of the diffuse component was more accurate than in the previous version of ARTEMIS, partly due to the use of new albedo data sets and aerosol parameters. The relative mean errors of the DNI range from 6.7% in Milan to 9.9% in Catania and 10.8% in Piacenza.

Lower values are found for global radiation, 4.3 percent in Milan and 4.0 percent in Catania. All errors are normalized with respect to the mean measured value.

Finally, the report describes the current status of the SunRiSE WebGIS portal, which is used to disseminate measurements, forecasts, and data to support the development and management of nonprogrammable renewable resources.