**4. Conclusions**

This study compares di fferent energy storage systems for electric minibuses. They were prototyped and tested. A cost-benefit analysis was carried out to compare the di fferent solutions from two points of view: economic and performance.

The compared solutions are based on experimental data of four projects (from to P1 to P4). The performance analysis shows that each prototype reaches maximum speed of 33 km/h in 60 s with same maximum acceleration of 0.6 m/s2.

By economic point of view, the best choice is SC + lithium, which has the lowest actualized costs (so the best NPV), but they are close to SC + Pb. These results can change with fluctuation of product prices. Moreover, expected lifecycle of batteries must be demonstrated under several di fferent conditions that were at this stage hypothesized. Indeed, P2 and P3 have both a large cost reduction compared to P1, so, P4 joins their technical advantages and have at same time a favorable actualized cost.

Technology choices in transport must consider several technical factors, i.e., in case of failure of supercapacitors, the battery must guarantee enough range to reach next stop or even to return to the depot. Other important factors are the capabilities of fast charging and the high power.

Based to the aforementioned considerations indicate P4 as the best option. lithium-ion battery coupled with SC guarantees required energy, su fficient power and highest charging rates.

Further developments may come from new testing campaigns to demonstrate the lifecycle increasing of a LiFePO4 battery combined with SC (as hypothesized in P4)—or even with a new battery chemistry. Experimental counting of the number of cycles will allow a realistic evaluation of battery life and could enrich the current economic evaluation.

**Author Contributions:** All the authors equally contributed to state-of-the-art survey, prototype project and experiments design. A.G. acquired funding and supervised, A.A. and F.O. managed resources and administrated projects. The data curation was conducted by L.B., R.B., F.C. and L.P. Moreover, L.B., F.O. and L.P. developed software required to manage electronic devices. F.C. together with L.P. and R.B. validated the results. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by Italian Ministry for Economic Development (MISE), program agreemen<sup>t</sup> MISE-ENEA 2015–2017.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses or interpretation of data; in the writing of the manuscript or in the decision to publish the results.
