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Methodology for Sizing Regional Energy Storage for Large-Scale PV Deployment

M. Pintarič(1), N. Lukač(1), P. Rijavec Simonič(1), P. Sukič(1), M. Božič(2), G. Dolanc(3), S. Gerkšič(3),
G. Štumberger(1)

1. Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor, Slovenia.

2. Dravske elektrarne Maribor, Maribor, Slovenia.

3. Jožef Stefan Institute, Ljubljana, Slovenia.

2026-06-27

When national plans for the deployment of photovoltaic (PV) systems significantly exceed the installed capacity of existing generation sources, the integration of energy storage systems becomes necessary. This paper presents a methodology for determining the required power rating and energy capacity of energy storage systems at the national level. The methodology is based on hourly electricity consumption and PV generation profiles from previous years, combined with data on the total installed PV capacity by month and projections of electricity demand growth and PV deployment over the next decade and beyond. Power system stability–related issues are not addressed in this study.

The proposed approach enables the identification of the required storage timescale—seasonal, monthly, weekly, daily, or hourly—as well as the corresponding power rating and energy capacity. The methodology is applied to a case study based on the national PV deployment plan in Slovenia. The resulting outputs may subsequently support the selection of appropriate energy storage technologies, which lies beyond the scope of this paper.

Key words: Electrical power systems, Photovoltaic (PV) systems, National deployment planning, Energy storage sizing

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