Energy storage is an increasingly vital aspect of the energy sector in Poland due to the growing prevalence of renewable energy sources. Its primary goal is to support the uptake of renewable energy in the country’s energy mix. The article presented here analyzes the economic potential of buying and selling electricity on the Intra-Day Market and the Day-Ahead Market of Towarowa Giełda Energii SA (Polish Energy Market: TGE) in terms of energy storage. In four scenarios, energy was either bought and sold on the DAM/IDM or bought on one market and sold on the other to identify the most favorable case. Two four-month periods in 2021 and 2023 were examined. An analysis was carried out on a lithium-ion storage facility that has a two-hour charging cycle for energy storage. A methodology was proposed to identify the two highest and two lowest energy prices for imposing constraints on the purchase and sale times. The time of day when these prices occurred was also analyzed. The annual and periodic profits that can be obtained by purchasing and selling stored energy were calculated. The calculations and analyses facilitated inter-market comparison. Energy storage payback time was computed, and investment profitability was examined. The final section presents conclusions, opportunities, and suggestions for further research in this area.
As calculated, the most profitable case after taking efficiency into account was the case of purchase at IDM and sale at DAM in part of 2023: 18,751.61 [EUR/MWh capacity]. In comparison, the highest value for 2021 was obtained for the case of sale and purchase on IDM, with a profit of 7531.23 [EUR/MWh capacity].