A multi-step scheme for spatial analysis of solar and photovoltaic production variability and complementarity

Renewable energy resources are variable by nature. Due to this fact conventional electricity systems, which were designed for centralized generation, have to follow a different management approach when a big share of these technologies take part into the system. The space-time variability characteristics of solar radiation, wind and precipitation are very different and a detailed understanding of them is important for an adequate planning and management of the electricity system. This paper is focused on solar irradiation as source of energy for photovoltaic (PV) generation, but the proposed scheme can generally be applied to other renewable resources and different solar irradiation applications. A comprehensive methodology to analyze variability and complementarity of solar resource and PV production among sub-regions of a wide area is developed. The photovoltaic energy yield is defined as kWh per kW installed, which facilitates the comparison among sub-regions and allows a comparison with other renewable energies like solar thermoelectric or wind energy. The multi-step approach facilitates the spatial evaluation and comparison among areas and it could be applied to different time resolutions, from a short term analysis to climatological perspective as well as a climate change projections analysis. The main steps of the method are the application of an objective clustering method for performing a regionalization of the whole domain, the analysis of the temporal variability of solar radiation and photovoltaic energy yield, and the intercomparison of the obtained clusters for examining their complementarity. As an implementation example, we make use of 30 years of daily satellite data, which is usually considered as the time for defining a climatology, and a long-term overview of solar variability is analyzed over the Iberian Peninsula (IP). In this region, the internal interconnections of the electrical system are strong, but the external interconnections are rather limited. The spatial distribution and variability of photovoltaic (PV) power yield is calculated for different tracking systems. The variability is analyzed on an interannual time scale, which is relevant for energy supply security and year-to-year price stability. The interannual variability shows robustness and stability of solar radiation and PV production on average for the whole domain, but with significant differences among clusters that could allow spatial compensation of PV production. The relationship between the variability of solar irradiation and of PV yield is not uniform among the different clusters. Areas where solar irradiation is higher are more sensitive to tracking type. The whole process described in the article provides the information of how solar resource and the PV energy yield perform in a limited area and provide the tools to analyze the relationships between sub-areas and their variability. In this sense, this method can be applied for isolated or nearly isolated electric systems located in regions with a variety of climates, or for interconnected systems involving several countries.