2.2.3. Auxiliary Data

Temperature and solar irradiation values at each time step are the key components that decide the power output of photovoltaic panels. However, there are other variables that may modulate the effect of those weather variables. In particular, the position of the Sun affects the amount of solar radiation flux that can be used by the solar panels. Said position follows a daily cycle between dawn and dusk, but also a yearly cycle due to the relative positions of the Earth and the Sun, leading to differences in solar flux incidence angles between winter and summer, and between early morning, noon, and late afternoon.

To include the aforementioned differences in the prediction models, two additional input variables are used: the hour of the day, ranging from 0 to 23, and the hour of the year, ranging from 0 to 8759. These two auxiliary variables are inspired by a previous study by one of the authors [26] where they were both used (in addition to the hour of the week) to characterise the evolution of thermal demands of a large building during different time periods. However, the nature of the system modelled in the present study does not have a direct dependency on the day of the week, so the hour of the week is not included as an input variable. The two selected variables are added to both monitoring and GDAS datasets.
