Suggested Citation:
Burke, Andrew (2014) "Ultracapacitors in Hybrid and Plug-in Electric Vehicles," chapter in Encyclopedia of Automotive Engineering. Institute of Transportation Studies, University of California, Davis, Journal Article UCD-ITS-RP-14-28

Suggested Citation: A. Burke (2014) "Ultracapacitors in Hybrid and Plug-in Electric Vehicles" in D. Crolla, D.E. Foster, T. Kobayashi and N. Vaughan (Eds.) Encyclopedia of Automotive Engineering, John Wiley & Sons Ltd: Chichester. DOI: 10.1002/9781118354179.auto140. Published 4/22/2014. 

This chapter is concerned with the characteristics of carbon/carbon (double-layer) and hybrid ultracapacitors (electrochemical capacitors, ECCs) and the application of these devices in micro-hybrid and charge sustaining hybrid and plug-in hybrid vehicles. The carbon/carbon devices have energy densities up to 6.9 Wh/kg, 10 Wh/L, and power capabilities up to 8.8 kW/kg for a 95% efficient pulse, and the hybrid capacitors have energy densities up to 30 Wh/kg and power densities up to 3.5 kW/kg.

Simulation result for midsize passenger cars using the ultracapacitors in micro-hybrid and charge sustaining hybrid (HEV) powertrain designs were performed. The results for the micro-hybrids indicate that significant improvements (10–25%) in fuel economy can be achieved using a small electric motor (4 kW) and small ultracapacitor units (5–10 kg of cells). The simulation results for charge sustaining hybrids indicate fuel economy improvements ranging from 72% on the FUDS to 22% on the US06 driving cycles. The prime advantage of the high power electric driveline and the larger energy storage possible with the hybrid ultracapacitors is that the larger fuel economy improvements can be sustained over a wide range of driving conditions. The hybrid ultracapacitor technologies give the vehicle designer more latitude in powertrain design and in the selection of the control strategies for on/off operation of the engine.

Keywords: double-layer capacitor; hybrid capacitor; energy density; power density; efficiency; cycle life; control strategy; vehicle simulations