The transportation industry is changing at a mind-boggling rate. Thanks to pollution and climate change. This is the era of EVs and battery technology plays a pivotal role in this development.
But there is a problem with these EVs
- They take more time to charge and
- They have a limited range
Automotive giants like tesla are working to solve these shortcomings and one of the solutions is to use supercapacitors.
But what is a supercapacitor?
A capacitor is an energy storage device similar to that of a battery. But the only difference is that charging and discharge is rapid in a capacitor.
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Advantage
When we consider supercapacitors, it has a very high charge-discharge cycle (~1 million) which is several times more than a battery. This makes them long-lasting.
The most important advantage is high power charging capabilities. Capacitors can charge quickly, which removes the problem of range anxiety.
Charge and discharge comparison of a battery and a supercapacitor
Why do they charge faster than batteries?
This is simple. Consider the working of a capacitor or a supercapacitor and that of a battery. When we charge both of them, we see different phenomenon happening.
A battery uses these flow of current to make a chemical reaction (A redox reaction). This reaction is reversed while the battery powers the vehicle and this reversed reaction produces electricity. And this takes some time, the reaction to completion.
A supercapacitor traps the charge between its electrodes when we try to charge it. And these trapped charges will power the motors. Since this, unlike batteries, does not involve any change in the chemistry, is considerably quicker.
Also, this is the reason for the higher life cycle of supercapacitors as compared with batteries.
Disadvantage
There is one problem associated with supercapacitors. Just like they charge quickly, discharge rate is also quick. This is not desirable.
Also, they have a very poor energy densities (~9 Wh/Kg) which is very low even if compared with batteries. Therefore, it is not practical to build an electric or a plugin hybrid vehicle out of supercapacitors. We always use them along with batteries.
Implementation
There is a wider application of supercapacitors in EV and hybrid vehicles depending on their type.
Micro hybrids
Micro hybrids can save a bit of fuel during traffic. The main requirement of battery here is to power the electric systems like infotainment, multi-info display, lights, wipers, etc. We use a lead-acid battery which has a low energy density.
Therefore, supercapacitors can completely be used instead of batteries.
EVs and other hybrid vehicles
EVs and hybrid vehicle cannot rely on supercapacitors completely. They work with batteries, especially during regenerative braking and sudden acceleration.
While you apply brake, regenerative braking kicks in, this will produce electricity which can be stored in a supercapacitor. The range of your electric vehicle reduces so badly when your driving cycle has lots of sharp acceleration. There are a few reasons for the reduction.
- When you floor the accelerator pedal, it will increase the motor’s load. Thus, the motor consumes more power. Since voltage is the same across the circuit, the current input to the motor increases. This increases the heat produced because of the heating effect of electric current. This results in a loss of energy and reduces the range of the vehicle.
- Increase in speed also increases the rolling friction and the drag coefficient of the vehicle. More you speed up, more will be the average speed increasing the rolling friction.
For detailed information about acceleration and range, Click here. This article deals with this.
A supercapacitor comes handy in such situations. They are capable of high power discharge. Therefore, when you floor the vehicle, high current high power charge flows to the motor without affection the battery life. One more thing, if the battery temperature is high, its efficiency and life gets lowered. So supercapacitors helps to maintain the battery’s health.
Public transport
Supercapacitors have a very important role in public transports like buses. We electrify city buses these days to overcome pollution issues. One important trick that the manufacturers used to increase the range of their buses is to recharge at bus stops and even signals. But the duration of these stops are small. Hence charging a supercapacitor makes more sense than charging batteries.
