## 8 Results of the Parametric Analyses Carried Out with the Proposed Tool
### Impact of the Cable's Active Power
The cases considered had \(V_{rms}=220\) kV, \(cos\varphi=0.9\), and \(L_{line}=50\) km. It is worth noting that the impact of the cost of the superconducting material over the total capital costs increased as the power increased (from 27% at 1 GW up to 58% at 3.5 GW), while the cabling costs were instead considered fixed per unit length. Moreover, Figure 8 expands the different contributions to the operating costs shown in Figure 6. Note that these costs are the sum of all the operating expenses which occurred during the cable's lifespan. It was decided to separate the costs of the intermediate cooling stations from those of the termination ones as they were differently sized, although Equation (25) groups them into a single term \(C_{cool_{op}}\). It can be observed that the operating cost for the cooling station on the arbitrarily designated left side of the cable was higher than that on the right side. This is because the left termination station must manage the nitrogen flow coming from the annular gap (referencing Figure 2), which absorbs the additional contribution \(Q_{cryo}\). Figure 8: Operating costs per kilometer of cable, varying the maximum active power transferred. The cases considered had \(V_{rms}=220\) kV, \(cos\varphi=0.9\), and \(L_{line}=50\) km. Figure 7: Capital costs per kilometer of cable, varying the maximum active power transferred. The cases considered had \(V_{rms}=220\) kV, \(cos\varphi=0.9\), and \(L_{line}=50\) km. Clearly, the operating cost of the intermediate cooling stations is the most significant cost, as it includes the costs of multiple stations. Specifically, for the cases analyzed, the number of intermediate cooling stations (\(n_{stat}\)) ranged from 6 (for the 2 GW case) to 9 (for 2.5-3.5 GW), corresponding to the upper limit imposed on this variable for a 50 km-long line. Notably, the operating cost for the termination stations was slightly higher in the 2 GW case compared with the others. In fact, with fewer intermediate stations over the same cable length, the modular cable segments were longer, resulting in more heat absorption by the fluids in each segment, including those connected to the termination stations. Lastly, maintenance and dismantling costs together corresponded to approximately 5% of the total operating costs, thus being almost negligible. Figure 9 illustrates the trend of losses and heat inputs for the different cases analyzed. The losses presented are calculated along the entire length of the line, with AC losses in the HTS tapes and thermal inputs from the cryostat being the primary contributors. As expected, the trend of operating costs in Figure 8 closely follows the trend of losses, since maintenance and dismantling costs were assumed to be constant per unit cable length. The cost of electricity for pumping the cryogenic fluid, included in Equation (25), had minimal impact, contributing approximately 1% to the total operating costs. An exception to the proportionality between the operating costs and losses occurred when comparing the 1.5 GW and 2 GW cases. Indeed, the 1.5 GW case showed slightly lower total operating costs than the 2 GW case, despite having slightly higher total losses. This discrepancy can be explained as follows. The losses shown in Figure 9 are calculated assuming that the cable carried a constant power equal to \(P_{max}\) for its entire lifespan, represented by the dotted horizontal line in Figure 4. However, this condition did not match the real scenario under which the operating costs were recalculated at the end of the optimization process, as explained in Section 3.4. Figure 10 depicts the trend of hourly operating costs per unit length throughout the year, focusing on the 1.5 and 2 GW cases only and considering the real time-varying cable power, shown as the blue curve in Figure 4. As observed, while the costs at peak power (case at \(h=0\)) reflected the trend in Figure 9, the ratio between the two cases varied over the year until it reversed.