## 4 Vehicle Applications of Supercapacitors
### Hybrid-Electric Vehicles (HEVs)
\begin{table}
\begin{tabular}{l c c c c c} \hline \hline \multirow{2}{*}{**Energy Storage System**} & \multicolumn{2}{c}{**Weight of the**} & \multirow{2}{*}{**Energy Density**} & \multirow{2}{*}{**Density Kg/L**} & \multirow{2}{*}{**Density Kg/L**} \\  & **Ultracaps.** & & & & \\  & **(kg) \({}^{*}\) & & & & \\ \hline
**Mild HEV 20 kW motor** & & & & & \\ Yunasko hybrid & 12 & 300 Wh & 47.4 & 46.5 & 32.2 \\  & 6 & 150 Wh & 45.3 & 46.0 & 31.6 \\  & 11 & 100 Wh & 47.8 & 47.2 & 31.9 \\  & 22 & 100 Wh & 46.0 & 46.4 & 31.6 \\  & 28 & 100 Wh & 47.2 & 47.5 & 32.2 \\  & 2014 C/C 3200F & 13 & 115 & 47.8 & 47.0 & 31.9 \\  & 14 & 1120 & 40.6 & 40.3 & 30.5 \\  & 201 kW & & & & \\ Fuel economy & & & & & \\ improvement & & & & & \\ \hline
**Micro start stop HEV** & Supercap with a lead-acid battery, 4 kW electric motor & & & & \\ Yunasko hybrid & 5 kg & 150 Wh & 32.4 & 41.4 & 28.9 \\  & 3 kg & 75 Wh & 32.1 & 41.2 & 28.5 \\  & 11 kg & 50 Wh & 32.2 & 41.2 & 28.6 \\  & 12 kg & 50 Wh & 32.3 & 41.3 & 28.3 \\  & 50 Wh & 33.1 & 40.2 & 28.0 \\
**Fuel economy** & & & & & \\
**improvement** & & & & & \\ \hline \hline \end{tabular}  
* Mid-size passenger car: weight 1660 kg, C\({}_{4}\) 0.3, A\({}_{7}\) 2.2 m2, fr 0.009, \({}^{*}\) Weight of cells only without packaging in a pack.  
\end{table} 
Table 6: Mild and Micro-HEV Advisor simulation results using various supercapacitors [12]. \begin{table}
\begin{tabular}{l c c c c} \hline \hline \multirow{2}{*}{**Storage Technology**} & \multirow{2}{*}{**Voltage V\({}_{\tau}\)**} & \multirow{2}{*}{**Energy Density**} & \multirow{2}{*}{**Density Kg/L**} & \multirow{2}{*}{**Power Capacity**} \\  & & & & \\  & & & & (W/kg)95\% \\ \hline NCM lithium battery & 4.2 & 161 & 2.5 & 485 \\ EDLC capacitor & & & & \\ Skeleton & & & & \\ Aowei hybrid & 3.8 & 40 & 1.4 & 1142 \\ capacitor 3.8 V & & & & \\ Aowei hybrid & 4.1 & 65 & 1.4 & 2284 (1/2R) \\ capacitor 4.1 V & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Characteristics of the energy storage device used in the simulations. control strategy [13; 14] for the HEV powertrain is that the electric motor provides the power demanded alone when possible, and when the SOC of the energy storage device permits. When that is not possible, the engine provides the power demanded by the vehicle and recharges the energy storage device. This strategy results in the engine operating at high efficiency nearly all the time. The engine maps used in the simulations assumed maximum engine efficiencies of 38% for gasoline engines and 44% for diesel engines. The results of the simulations for each of the vehicles are shown in Table 8. City and highway fuel economy results are shown in the table for each vehicle type and energy storage device. Advisor output graphics for several HEVs are shown in Figure 4, comparing the results for the operation of the vehicle with the lithium battery and the 4.1 V supercapacitor on the FUDS cycle. The energy storage units were sized such that their round-trip efficiency on the simulated driving cycles were close to 90%. For all vehicle types, the weight and volume of the capacitors decreased in the expected order: EDLC, hybrid 3.8 V, hybrid 4.1 V. The 4.1 V hybrid capacitor in all cases was lighter and smaller than the lithium battery, and its energy storage capacity was lower by a factor of 5-6. The fuel economies of the HEVs on the FUDS cycle were significantly higher (30-50%) than that of the corresponding ICE vehicle, except for the long haul truck, for which the fuel economy improvement was 20%. The effect of hybridizing on fuel economy on the highway cycles was small, being at most 10%, but it was much less in most cases. The effect on the highway fuel economy of the long haul truck was 4-6%. In almost all cases, the fuel economy improvement was highest when using the 4.1 V hybrid capacitor.