**7. Conclusions**

In this work, an ultra-low-power supercapacitor-based storage unit with an integrated control scheme was presented, offering flexibility to the applied energy harvesting system. The ultra-low current consumption of only 432 nA at 2.3 V proves the proposed storage unit ideal for energy harvesting systems, even for cases of a few µW input power range. Furthermore, extra modes can be added to the topology with the usage of external control (e.g., an MCU), expanding the operational capabilities of the proposed unit. For instance, the control of an additional charging unit for the backup battery is a highly beneficial mode that will be added in future work.

**Author Contributions:** Conceptualization, V.G.; methodology, E.K., G.D.; validation, V.G., K.K.; writing—original draft preparation, V.G., S.S.; writing—review and editing, V.G., E.K., S.S.; supervision, S.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was co-financed by the European Regional Development Fund of the European Union and Greek national funds through the Operational Program Competitiveness, Entrepreneurship and Innovation, under the call RESEARCH—CREATE—INNOVATE (project code: T1EDK-00360).

**Conflicts of Interest:** The authors declare no conflict of interest.
