Nowadays, the use of renewable energy is a priority for governments around the world since it gives rise to energy saving and environmental sustainability. In the case of photovoltaic systems, it is fundamental, to know how much energy can be generated and how much energy is needed in order to maintain a suitable balance between supply and demand. In this paper, a formal analysis of solar power and weather data is performed in order to study how the energy generated by solar panels depends on sunny days and weather conditions. In particular, a software architecture is proposed which is formed by three modules. The first and second ones allow us to transform open data files to formal contexts. In the third module, two important processes are performed: (i) a characterization of the states of the sky and (ii) an analysis of the weather conditions under which the energy production is optimal.