The study “Impact of inlet fluctuations on the stratification of a sensible thermal energy storage” has been recently published in Renewable Energy, born from the need to study and quantify how temperature and flow rate fluctuations in thermal storage systems affect their ability to maintain stratification – a key parameter for energy efficiency.
The intermittent nature of solar energy causes variations in inlet temperature in stratified tanks, which in turn reduces overall system performance.
In this study, the EFESTO team developed a two-dimensional numerical model validated using real industrial data. The results show that:
- Even apparently modest temperature variations, as small as ±2.5 °C, can double the level of internal mixing, while larger oscillations can degrade stratification by more than 300%.
- The impact of the frequency of fluctuations is only secondary, while variations in fluid velocity do not have a significant effect.
The research also demonstrated that the impact of fluctuations depends exclusively on their amplitude, regardless of the fluid’s mean temperature, allowing the development of empirical correlations useful for predicting stratification losses.
This analysis opens the way to the development of both passive and active control strategies aimed at mitigating the effects of inlet fluctuations. On the one hand, passive solutions, such as the integration of PCM–embedded composite inserts, can act as thermal filters to smooth temperature oscillations directly at the diffuser level. On the other hand, active approaches, including advanced control frameworks, can dynamically adjust system operation to counteract disturbances in real time. Together, these directions lay the groundwork for smarter and more resilient thermal storage systems, capable of maintaining high efficiency and stability even under variable solar and operational conditions.
For further details, please refer to the full article available in Open Access mode.
📄 Full Reference:
Anacreonte A. V., Vitobello R., Musto M. (2025). Impact of inlet fluctuations on the stratification of a sensible thermal energy storage. Renewable Energy, Vol. 252, 123484.
DOI: https://doi.org/10.1016/j.renene.2025.123484