Recent research from Portugal sheds light on the often-overlooked variability of solar irradiation and its significant implications for the performance of photovoltaic (PV) and concentrating solar power (CSP) plants. Conducted by Ailton M. Tavares from the Cátedra Energias Renováveis at the University of Évora, this study provides critical insights into how inter-annual variability can affect energy production, ultimately influencing the bankability of solar projects.
The study, which analyzed 17 years of meteorological data, reveals a long-term upward trend in solar irradiation, with Global Horizontal Irradiance (GHI) increasing by 0.4148 kWh/m²/year and Direct Normal Irradiance (DNI) by 3.2711 kWh/m²/year. This phenomenon, known as solar brightening, suggests favorable conditions for solar energy harvesting. However, Tavares notes a disconnect between this increase in irradiation and the actual production capacity of PV and CSP plants. “Despite the rise in solar radiation, we did not observe a corresponding increase in the capacity factor for either type of plant,” he states. This discrepancy is largely attributed to a simultaneous rise in ambient temperatures, which reduces the efficiency of solar technologies.
The implications of this research extend beyond academic interest; they pose real challenges for energy investors and developers. When solar power contracts are signed, estimates of energy production are often based on typical meteorological years, which do not account for inter-annual variability. This oversight can lead to significant deviations between projected and actual energy output, potentially jeopardizing financial returns. Tavares emphasizes the importance of understanding these variations, stating, “A thorough analysis of the variability of the solar resource is essential to assess financial risks and ensure the long-term economic viability of solar projects.”
The spatial analysis conducted in the study shows that southern regions of Portugal, particularly Alentejo and Algarve, exhibit both high irradiation and low inter-annual variability, making them prime candidates for solar energy investments. With inter-annual variability for PV ranging from 2.45% in Faro to 12.07% in Santarém, and even higher for CSP, these findings could guide future installations and policy decisions in solar energy development.
As the energy sector increasingly turns to renewable sources, this research underscores the need for enhanced modeling techniques that incorporate inter-annual variability. By doing so, stakeholders can better forecast production and mitigate the financial risks associated with solar energy projects. Tavares’s work not only contributes to the academic literature but also offers practical solutions for improving the reliability of solar energy systems in a rapidly evolving market.
This significant study was published in ‘Energies,’ a journal that translates to “Energies” in English, highlighting the ongoing discourse around renewable energy and its commercial viability. For more information about the research and its implications, you can visit the Cátedra Energias Renováveis at the University of Évora.
