1. 1 Alternative Energy Storage System for Hybrid Electric Vehicles Tobias Andersson, Jens Groot, Helena Berg, Joachim Lindström, Torbjörn Thiringer

2. 2 Purpose and Method Hybrid electric vehicle: demands on an efficient energy storage system

3. 3 Energy Storage Energy- and power density

4. 4 Supercapacitor Extremely high capacitance (kF) Low voltage (< 3 V)  1000-2000m 2 /kg  5 Å  10-100 F/g A.k.a Electrochemical Double Layer Capacitor (EDLC), Ultracapacitor, Electrochemical Capacitor (EC)

5. 5 Battery - Supercapacitor

6. 6 Simulation of the system

7. 7 Performance Parameters Reducing of RMS-current Reducing of power losses in battery Total energy efficiency

8. 8 Load Cycle (ECE15-L) Acceleration Constant velocity Regenerative braking

9. 9 Control Strategy Low pass filtering Braking energy to EC Loading of EC

10. 10 Control Strategy Low pass filtering Braking energy to EC Loading of EC

11. 11 Test System

12. 12 Test System EC 10 units 2.5V, 2600F / 28 units 2.0V, 2700F Battery 50V / 100V, 60Ah NiMH DC/DC 160 kW, 330A 2-quadrants DC/DC converter

13. 13 Results - simulations and experiment Battery, 100V EC, 56V Equal to car with the weight of 250 kg

14. 14 Results - system performance

15. 15 Example -Simplified system for a city bus, 220kW Battery310 kg EC280 kg DC/DC 90 kg Total weight680 kg NiMH-battery + EC Battery1150 kg DC/DC 45 kg Total weight1195 kg NiMH-battery Weight reduction:43 %

16. 16 Conclusions DrawbacksAdvantages Weight reduction Improved battery lifetime Reduced temperature dependency EC could replace batteries Complexity Difficult to estimate the price Not tested in full scale