Question

11. How could capacitors be best used in electric vehicles to improve performance? What are some of the pros and cons of capacitors as applied to EVs? How might this change in the future? Research beyond classroom discussion!

Answer 1

Capacitors are devices made to store charges and energy in form of the electric field .

In small scale applications we need small capacitors but since driving an electric vehicle needs high mechanical power  , we need large rated capacitors or equivalently much improved supercapacitors .

Today Capacitors are mostly used for these performnce improvements :

a) To filter out the ripples in the current that comes back to the DC battery pack , so that those currents with rippples within them do not reach back the power source which is a DC battery pack . So the capacitors thus helps to improve the quality of power being supplied within the system. See in figure below for more clarity.

b) To protect the IGBT , a power electronic device by the use of thin metal film coating over the dielctrics  that evaporates and so isolates the defect during high rated power transmission via IGBT .

Pros of Capacitor Usage in EV :

1) Ripple free power transfer

2) Helps to prevent spreading of electromagnetic interference that may arise due to inverter components .

3) Compact medium for extra energy storage that can be used as back up power for quick acceleration.

Cons of Capacitor Usage in EV :

1) They might be bulky as the requirement of rating increases within system, if simple ordinary capcitors are used ( instead of supercapacitors )

2) Since cost increases with size increase , so overall price of EV also shoots up .  

Future Trends Expected

We may increase using supercapacitors , that are devices that can store large amount of energy than same sized ordinary capacitor and thus may be used :

a) To replace more bulky Lithium based batteries to act as energy source . They also help in decreasing the charging time of the EV that may push up the current usage of EV that have long charging times when used with batteries. So this RAPID charging and discharging of supercapacitors might help in better efficiency and more usage of EV on roads .

b) To act as backup power source in hybrid EV , in which while using regenrative braking , these supercapacitor can store the energy within them and release them when need arises like low fuel or quick acclearation needs for steep curves over the traction path .