OPTION B: bus weight 18 ton

I. Charging Power of 400kW at terminal station:

Figure 3.19 – Electrification costs with charging power of 400 kW at the terminal station

In this scenario, the bus weight is 18 tons, so the energy consumption during uphill route (outbound trip) is greater than in cases with normal weight and auxiliary consumption of 9 kW. However, the consumption for a round trip is lower compared with case B

3.5. Scenario 3: Maximum weight and Auxiliary Consumption 6 kW

energy (regenerates more energy) than when the bus weighs 16 tons and the auxiliary consumption is 9 kW. The solver suggests a battery system here with less capacity than in the previous case B 3.4.2-I. However, the size of the battery system also needs to be bigger in this case, leading to an increase in cost. This increase is due to lower charging power in the route-side fast chargers in this arrangement. Specifically, when the charging power at both the terminal station and along the route is 400 kW, the battery cost is 24.4 millione, and when the charging power at the terminal station is 400 kW but en route is 200 kW, the battery costs increase to 25.31 millione.

The solution for the standardization of the battery system design changes in a similar fashion as in the above case B 3.4.2-I, where the mid-route charging devices have a charging power of less than 400 kW, and the price of the fast charging infrastructure is lower than 46304e. In these conditions, the high energy consumption during the uphill routes constrains the problem in terms of costs. In other words, needing the SOC to have a safety margin of more than 25% and also to minimize costs, the model is sensitive to the decrease in charging power of the route-side fast charger. Thus, the design of the battery system changes when the charging power en route is less than 400 kW, to ensure sufficient energy supply during a round trip.

Therefore, in order to minimize total investment costs, the design of the battery system must work with charging devices that charge at a power of 400 kW at both the terminal stations and bus stops, as in case 3.4.2-I. On the other hand, the battery system design of the cases when the charging power of the chargers en route is lower than 400 kW is not used, since it increases the costs of the battery system and therefore total cost. The design used in case B 3.3.2-Iis not suitable either, since it does not provide the necessary capacity (kWh) for some bus lines and, therefore, is not a feasible solution.

The number of fast charging devices required is the same as in the previous case B 2.1

(24 chargers), with said devices located at the same terminal stations and bus stops.

This result is due to the high energy consumption in this scenario. However, the price of the fast charging devices not decrease too much here, as one additional charging station is needed along the route, as in the previous cases B (Case B 3.3.2-Iand Case 3.4.2-I). In those cases, the price drops to 46068eand adds 2 additional chargers. Here, however, the optimization model adds one additional charger at a higher price than the previous cases B, since the bus of 18 tons consumes more energy when going uphill, and therefore needs to add the additional charger at a higher price than in the other cases.

Another difference in this scenario is that the location of the additional charger is different from that of the others, which is logical since by setting up only one additional charging point, there are more restrictions on the model than in the previous cases.

When the price of the bus chargers is equal to 46068e, 2 additional chargers are needed as in the two B scenarios, but in different locations from those placed previously. One of the chargers is located at the same bus stop as in the case where the price is 46304e^, and the other charger is located on the inbound return trip.

3.5. Scenario 3: Maximum weight and Auxiliary Consumption 6 kW

Figure 3.20 – Electrification costs with charging power lower than 400 kW at the terminal station and in bus stops

As mentioned previously, when the bus weight is 18 tons and the auxiliary consumption is 6 kW, the energy consumption on a round trip is lower compared to when the bus weighed 16 tons with an auxiliary consumption of 9 kW. However, the energy consumed in this scenario is also high, so it is not convenient to use 200 kW to charge en route. This would necessitate placing an excess of chargers en route for each bus line, excessively accelerating the batteries? aging process. That would lead to the need to replace the battery system in less than 2 years. Thus, this solution in the long term would be very expensive and inefficient. Therefore, in this scenario only the 300 kW charging power at both the terminal station and bus stop is considered.

The battery capacity for some bus lines decreases, bringing the cost of the battery cost down along with it. These results arise due to the charging power in the terminal being 300 kW, with an increase in energy consumption of more than 100 kWh in almost all bus lines compared to reference cases B and case B 1. Therefore, it is not possible to replenish the energy consumed during a round trip in only 20 minutes, unlike in the previous case B (with a charging power of 400 kW at the terminal station). As a result, the optimization model does not increase the capacity of the battery system, since it would not be reasonable and would pose an unnecessary increase to the cost of the battery. The design of the battery system used in this scenario is the same as that in case B 3.4.2-II, since it minimizes the total investment costs.

The solver adds 5 fast chargers en route, as in case B 3.4.2-II, but in this solution the location of 3 of them changes. Because the energy consumption during the uphill trip (inbound trip) is higher than in the case where the bus weighed 16 tons with an auxiliary of consumption 9 kW, the fast chargers are located at the previous bus stop.

The battery cost is 24.61 millioneand the fast charger 7.25 millione, bringing the initial investment with these two elements to 31.86 millione, which is lower than the initial investment cost in case B above. However, the solution in this case excessively accelerates the aging process of the batteries. This makes this solution more expensive