## 3 Life Cycle Inventory
### Assumptions  
The discussed EVs are assumed to be charged with the average European energy mix, characterized by an average CO\({}_{2}\) emission intensity of 276 g per kWh of electricity produced [49]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Parameter [Unit]** & **30 kWh EV** & **40 kWh EV** & **60 kWh EV** & **90 kWh EV** \\  & **(Nissan Leaf)** & **(Renault Zoe)** & **(Chevrolet Bolt)** & **(Tesis Model S90)** \\ \hline Capacity [kWh] & 30 & 40 & 60 & 90 \\ Mass in Running Order [kg] & 1591 & 1450 & 1624 & 2200 \\ Weight battery [kg] & 272 & 305 & 435 & 540 \\ Average consumption [kWh/km] & 0.15 & 0.15 & 0.15 & 0.25 \\ Highway consumption [kWh/km] & 0.20 & 0.20 & 0.20 & 0.26 \\ Highway consumption with ReK trailer [kWh/km] & & 0.21 & & \\ EU electricity mix in g/kWh & & 276 & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Specifications of the discussed electric vehicles (based upon [47]). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Unit** & **Petrol** & **Petrol Hybrid** & **Diesel** & **Petrol Plug-in Electric Vehicle** \\ \hline I/100 km] & 6.8 & 5.6 & 5.3 & 3.4 \\ gCO\({}_{2}\)/km & 162.7 & 134.0 & 140.0 & 81.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Overview of the real-world tank-to-wheel fuel consumption indicators per technology (based upon [29; 30]). The authors of this paper deliberately chose not to address marginal energy production for generating the electricity for EVs, as EVs are thought to be part of the total load system, confirming the viewpoints found in Refs. [35; 50; 51; 52]. For the comparison of the different powertrain technologies, the 40 kWh EV is chosen as the reference to be combined with the range-extender. Also, the marginal application of the trailer is assumed to be 5 percent of the vehicle's lifetime driven distance, reflecting the outcome of the aforementioned travel surveys and the fact that long distances are in general only seldom performed. Next, one trailer is assumed to be shared by a maximum of 15 users on a rental basis, resulting in the fact that its manufacturing impact is subsequently shared over these 15 users. In the sensitivity analysis in Section 5, we assess the impact of a higher trailer uptake and thus a lower number of users per unit. For the remaining 95 percent of the EV's lifetime, it is assumed to drive purely electric. Equation (2) represents how well-to-tank emissions are based on both the EV's average consumption (kWh/km) and the increased consumption while towing the trailer. This increase is assumed to be capped at 5 percent as the trailer is closely coupled behind the EV and therefore has a minimal influence on its aerodynamics. In case of towing the battery trailer, an extra consumption of 10 percent is considered. The specifications for the trailers per power source concept are given in Table 3, while Table 4 presents the use stage emissions for a suitable generator. \[WTT_{EV40+ReX}=\left(0.95\times WTT_{EV40,\ avg}\right)+\left(0.05\times \left(WTT_{EV40,\ highway}+WTT_{ReX}\right)\right) \tag{1}\]  
Based on a life cycle inventory (LCI), the elementary flows which are linked to the various vehicle technologies need to be converted to the different impact categories. These allow quantification and a comparison between the potential impacts. This step is referred to as the life cycle impact assessment (LCIA). An exemplary full LCIA of a 30 kWh EV is given in Table 10 in the Appendix A. Concerning the environmental performance of both the generator and the battery ReX trailer concepts, please refer to Tables 5 and 6, respectively. These tables show a deliberate distinction between the production of the 'trailer body' and the production of the power source, while the operation of the latter was analyzed during its use phase. This choice was made to allow better insight into the allocation of their respective contribution to the midpoint indicators. The total lifetime of the trailer was chosen to be identical to that of a passenger car itself, namely 210,000 km.