**7. Conclusions**

The optimization method for RES, ES allocation and energy curtailment under the criterion of minimization costs of distribution system development is presented. The novelty lies in comparing energy storages (ES) and energy curtailment (EC) as additional tools to RES sizing and allocation.

This combination of mentioned tools allows for the achievement of a desirable target (reducing costs of distribution system development). Due to the modelling of power units with energy generation or consumption profiles, it is possible to consider specific operational cases and select the best structure and location of renewables.

The results also show that energy curtailment is more efficient than energy storages with the growth of the share of energy from RES in total demand. This is due to the high prices of the ES and its limitation connected to the efficiency and level of charge. It shows that energy curtailment can be an efficient tool to control the operation of RES.

**Funding:** This research received no external funding.

**Acknowledgments:** Author would like to express the gratitude to the FICO® corporation and Microsoft corporation for programming support and provision of academic licenses for Xpress Optimization Suite and Office 365 to Lodz University of Technology.

**Conflicts of Interest:** Author declare no conflict of interest.
