## 3 Results  
### Cost of Transportation  
The cost calculations of the transportation were performed per unit panel area for each PV technology. We made our analysis using a typical \"dry-van\" trailer which has approximately 67 m\({}^{3}\) of volume. However, with that in mind, the typical gross carry weight of a single truck and trailer is 36,281 kg, with a typical truck and trailer weighing approximately 16,327 kg. That leaves 19,954 kg (appr. 67 m\({}^{3}\)) of carrying weight/volume within each trailer for each trip. Both volume and weight were used for the calculation to determine the number of modules able to be carried in one trip. The smaller values were chosen as the limiting factors and, consequently, we found that one truck can carry 893 c-Si, 1155 CdTe, and 644 CIGS PV modules. Using these values, we analyzed how many trucks are needed to carry the waste PV from 1 MW, 50 MW, and 100 MW solar farms that consist of these different PV types (Table 3). As shown in Table 3, the number of trucks required for transportation is not linearly related with the output of the solar farm, which affects the cost of transportation of the waste PV modules. Figure 1 shows the cost of transportation of different PV modules that are disassembled from a 1 MW solar farm while the error bar captures the variations in the transportation cost due to the number of trucks required for 1 to 100 MW solar farms (shown in Table 3). The upper bounds of the error bars equal the cost for disassembling PV modules from a 1 MW solar farm while the lower bounds show the transportation cost of PV panels dismantled from a 100 MW solar farm. \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Per Module** & **c-Si [44]** & **CdTe [45]** & **CIGS [46]** \\ \hline Output [Watt] & 360 & 100 & 160 \\ Surface area [m\({}^{2}\)] & 1.63 & 0.72 & 1.6 \\ Weight [kg] & 18.6 & 12 & 28 \\ Weight [kg/m\({}^{2}\)] & 11.4 & 16.6 & 17.5 \\ Volume (m\({}^{3}\)) & 0.075 & 0.058 & 0.104 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The specifications of the PV technologies. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**DC Output of the Solar Farms** & **c-Si** & **CdTe** & **CIGS** \\ \hline
1 MW & 4 & 9 & 10 \\
50 MW & 156 & 433 & 486 \\
100 MW & 312 & 866 & 971 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The numbers of truck needed to dissemble different types of PV panels from different sizes of the solar farms. Our results show that c-Si modules are the most economical for shipping, mainly because they have the lowest weight per square meter of surface area, primarily due to the assumption of a polymer backsheet for c-Si modules and a glass backsheet for the other two types. Furthermore, the cost of transportation of CdTe modules is about 20%-30% higher than for transportation of CIGS and c-Si PV modules. We also found that the cost of transportation for carrying PV modules by truck for 2000 km is only 12% more than for 2000 km. The reason is that as the distance of transportation increases the unit cost of transportation decreases drastically in the US. This brings us to the conclusion that unless the recycling centers are short distances to the installment locations, the cost of transportation between middle distances vs. long distances will be similar. For example, carrying PV modules 1100 km or 2000 km is almost similar. This information will be important in arranging the locations of new PV recycling plants in the US. Lastly, note that we made our analysis considering fully loaded trucks with these different solar panels. As such, we may consider the presented cost values as \"minimum\" values. Figure 1 shows the cost of transporting 1 m\({}^{2}\) of a PV module for 1000 km is USD 2.3, 3.2, and 2.6 for c-Si, CdTe, and CIGS modules, respectively when the trucks are fully loaded according to the volumes of the PV modules. These cost values will increase if the loads of trucks decreases.