5.2.4. Economic Comparison

As reported in Section 2, the present value of total cost and the annual cost of energy are computed, considering the following hypothesis: an expected lifetime of 30 years; ESS lifetime of 10 years; an interest rate of 4% for electrification and 6% for ESS [45]; an average cost of electricity of 15 €/MWh [49]; charge efficiency equal to 90%; four daily connections between Station A–Station B. In Figure 21 it is shown the total cost (a) and the ACOE of the proposed scenarios. 3 kV DC electrification shows a present value of the total costs of approximately €13 M and an ACOE of over 700,000€ per year. Most of these costs come from the high investment cost necessary for the electrification, estimated at €10 M, as it is necessary to install a traction power substation, a contact line and carry out works such as track lowering in correspondence of tunnels already present in the route and raising of the overpasses. The ESS with recharge station has a present value of the total cost of approximately €7 M, considering the replacement of the storage system every 10 years (it will depend on the correct operation in charge/discharge phases), and the installation of the necessary system for charging. The ACOE of this solution is about 500,000€ per year, due to the lower costs associated with the charging station compared to those associated with the installation of TPS. Finally, the high autonomy ESS, with a total cost of €5.5 M and ACOE of 400,000€ per year, could be advantageous solution from the economic point of view, since it does not involve the installation of any infrastructure for the recharge.

**Figure 21.** Different scenarios comparison: (**a**) Present value of total cost; (**b**) ACOE.

The main advantage of on-board ESS with high autonomy is that it does not require the installation of additional charging systems as this is provided for in the already electrified section of the railway line. Consequently, investment costs are limited. Moreover, on-board storage systems work with shallower charge and discharge cycles.

It should be emphasized, once again, that apparently the total costs linked to the solutions related to the use of trains with on-board storage would seem to be lower but it is necessary to underline that the total cost will strongly depend on the costs related to the construction of new rolling stock. Subsequently the real lifecycle of the batteries could lead to a further increase in costs due to their early replacement. However, investments in e-mobility lead to an increasing mass production of batteries. Consequently, if high demand growth is sustained, battery solutions are expected to be more profitable.

The feasibility of trains with on board ESS is similar to that of fully electrifying the ships that will sail the North Sea in the near future [63]. In both cases, current reliable solutions (i.e., electrified railway lines and heavy fuel oil powered shipping vessels, respectively) may lead to a previous hybridization stage before achieving the complete on-board energy supply system.
