Role of long-duration energy storage in solar-wind hybrid systems for drought mitigation: case study of Polish energy system

The long-duration energy storage (LDES) plays a critical role in enhancing the resilience of hybrid solar-wind energy systems, particularly during periods of prolonged low resource availability, known as energy droughts. In this work the energy droughts refer to extended periods when solar and wind generation are simultaneously insufficient to meet demand, posing significant challenges to ensuring power system reliability.

This study investigates the demand for LDES in mitigating energy droughts using 40 years of capacity factor historical data for solar and wind resources in Poland. To relate production from variable renewable energy sources (VRES) to electricity demand, a time series of hourly load data was developed with artificial neural networks, utilizing weather parameters and type of the day (working/holiday) as explanatory variables. By analyzing historical variability and the complementarity of VRES, considering different shares of solar and wind power in the energy mix, this research identifies the temporal patterns of energy droughts and quantifies their impact on energy shortage duration and deficits. To overcome these events, we evaluate the power capacity and discharge duration requirements for LDES solutions in a 100% renewable energy system scenario.

Here we show that the most extreme energy drought events in terms of both duration and energy deficit, occurred in the winter of 2005/2006. Reducing energy droughts to zero would require oversizing the VRES system to cover 160% of the multiannual mean demand, with a solar-to-wind ratio of 30:70. In addition, it would be necessary to implement energy storage capable of sustaining the mean load for 9 days, which is equal to 4.15 TWh of energy storage capacity.

The findings underscore the importance of optimizing the balance between solar and wind energy contributions and deploying substantial long-duration energy storage to ensure the resilience and reliability of a fully renewable energy system based on VRES. These insights provide a foundation for designing energy strategies that address the challenges posed by energy droughts.

 

The results presented in this study build upon the work conducted as part of project no. 2022/47/B/ST8/01113 funded by the National Science Centre (Narodowe Centrum Nauki) titled: Method to quantify the energy droughts of renewable sources based on historical and climate change projections data.