Understanding Short-Term PV Power Variability Based on Solargis Time Series Data and Simulations

This study analyzes the variability of PV power plant output (PVOUT) and Global Horizontal Irradiance (GHI) at both 15-minute and 1-minute temporal resolutions. The PVOUT data is calculated using the detailed Solargis PV simulator. The variability is expressed through the occurrence of ramps in the GHI and PVOUT data, and the ramps are categorized based on their severity. The results highlight that 15-minute GHI data may underestimate high-severity variability events observed in the 1-minute data, especially in tropical, temperate, and continental climates. In moderate latitudes we observe seasonal and diurnal patterns in the GHI and PVOUT ramps, suggesting that single-value variability metrics are insufficient for feasibility analysis of PV projects. To better capture the impact of high-severity events and allow for a more nuanced assessment of variability risk, we propose the Root Mean Square Ramp (RMSR) as a new metric. The findings emphasize the importance of high temporal resolution data and advanced PV simulation for accurate variability assessment, particularly for high criticality PV projects, while keeping the computationally and analytically simpler single-value metrics for prefeasibility analysis.