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Evolution of Electric Vehicles

 

Electric vehicles (EVs) can be broadly classified into 2 categories; Hybrid-Electric vehicles and Battery electric vehicles. But, for a better understanding of EV evolution and the concept behind it, we will further classify these categories of EV. This further classification will allow us to understand the diversity of the vehicles in a better and simplified way which can later be used for utility and comparative analysis of different EVs.

 

Classification of Vehicles

We will first try to classify the hybrid electric vehicles. Hybrid Electric Vehicles (HEV) are vehicles that are powered by both fuel as well as electricity. They have an Engine control unit (ECU) for transmission between electric motor and IC engine. This type of system (hybrid) mainly servers the purpose of fuel-saving and low carbon emission. Below are the classifications of the HEV based on the technological evolution:


Classification of Hybrid Electric vehicles (HEV)
Classification of hybrid electric vehicles


I) Micro-Hybrid

Left: Micro hybrid technology, Right: BMW 1

This was the first progress in the development of hybrid vehicles. This system switches OFF the IC engine when the vehicle is stationary and switches it ON again either by letting off the brake or pressing the clutch or accelerator, depending upon the type of transmission. This saves the fuel that is burnt while idling (vehicle stopped). The fuel efficiency increases by 10%. This system saves the fuel, but ROI is null as the saved fuel cost is compensated for the reduced engine life due to an increase in the number of start and stop. Also, another electronic circuit is required for monitoring the battery of the electric engine starter unit. Some Micro hybrid vehicles available in the market are: BMW 1, BMW 3, SMART car, Ford focus and transit, Fiat 500, Peugeot Citroen C3, Mercedes-Benz A-class.

ii) Mild-Hybrid

Left: Audi A8, Right: BMW 7

Mild hybrid vehicles have all the functions of a micro-hybrid, but in mild hybrid electric motor acts as a power booster that assists vehicle propulsion also. A mild hybrid vehicle saves the fuel by shifting OFF the IC engine when the vehicle is stopped, braking, or cruising/ starting. This increases fuel efficiency by around 20-25%. A 30-60 kW motor is installed for supporting the IC engine. There is no external charging option available; batteries get charged by regenerative braking. Some mild hybrid vehicles available in the market are: Audi A8, BMW 7 series, Chevrolet Malibu w/e-Assist, Suzuki Hustler, and Mercedes-Benz S400 Blue Hybrid. 

iii) Full Hybrid (HEV)

Left: Toyota Prius EV, Right: Kia Optima EV

The full hybrid vehicles has all the features same as of a mild hybrids, but the difference between a mild and a full HEV is that a full HEV uses a smaller IC engine, as it's motor and battery are capable to drive the vehicle alone. The electric motor is generally used at low speed as the electric motor is more efficient than an IC engine; it also reduces the engine idling when the vehicle is stopped. This improves fuel efficiency by 40-45%. Full hybrid vehicle batteries are charged only by regenerative braking as there is no external battery charging option provided. These vehicles are highly efficient for city drives mainly. Some full hybrid vehicles available in the market are:  Chevrolet Tahoe hybrid, Kia optima hybrid, Ford C-max, Toyota Prius, Honda CR-Z, and Camry Hybrid. 

iv) Plug-in Hybrid Electric Vehicle (PHEV)

Left: BMW i8, Right: Mahindra e-Verito

The plug-in hybrid has all the features of a full hybrid but has a smaller engine than a full hybrid and larger electrical components. It has the same fuel efficiency as a full hybrid, but the difference is Plug-in hybrid vehicles batteries can also be charged using external power sources like charging stations, plugged into the vehicle, and also by IC engine and regenerative braking. It is ideal for city commute but can also be used for long trips. Some PHEV vehicles available in the market are: Kia Niro PHEV, Honda clarity PHEV, Ford C-max Energi and Fusion energy, Porsche Panamera S E-Hybrid, Chevy Volt, Toyota Prius plug-in, Mahindra e-Verito, BMW i8, and Volvo XC90 T8.

v) Hybrid with Range Extender (Rx-HEV)

Left: BMW i3 EV, Right: Chevrolet Volt EV

Range extender hybrid vehicles can be driven only using electricity until the batteries are discharged. When batteries get discharged IC engine is switched ON but the purpose of the IC engine in an Rx-HEV is to charge the batteries and not in propulsion of the vehicle. The energy generated from running the IC engine goes to power the electric motor batteries. Some Rx-EV vehicles available in the market are: Chevrolet Volt, and BMW-i3

 

Now we will classify the electric vehicles (EVs). Electric vehicles are those vehicles in which there is no IC engine and the vehicle is only powered by electricity. There is 0 carbon emission in these vehicles. These vehicles are more than 90% energy efficient. The batteries are charged from both external power supplies (DC fast charger or AC normal charger) as well as from the regenerative braking. Below are the classifications of the EVs based on the technology available in the market:

 

Classification of EV

i) Battery Electric Vehicles (BEV)


Left: Mahindra e2o plus, Right: Tesla model 3

             Battery electric vehicles (EVs) are those categories of EVs which are powered by high voltage Batteries, like Li-ion, Lead-acid, Nickel-cadmium. These batteries are charged externally on charging stations or internally by regenerative braking. BEV takes around 6-8 hrs to get fully charged in normal charging mode using AC supply, this charging time is significantly reduced to 1 hr by using DC fast charging. These vehicles have a range varying from 250 km to 500 km, depending upon the type and capacity of the battery and the motor that is being used. Examples of BEV available in the market are: Tata Nexon EV, Mahindra e2O plus, Hyundai Kona Electric, MG GS EV, and Tesla Model 3. Some 2-wheeler Electric vehicles available in the market are: Hero electric flash, TVS iQube Electric, Ather 450X, PURE EV Epluto and Komaki XGT KM. 

ii) Fuel Cell Electric Vehicles (FCEV)

Left: Roewe 950 fuel cell, Right: Volkswagen HyMotion Fuel cell

Fuel cells EV are powered by Hydrogen. They are significantly more efficient that the IC engine vehicle and have no carbon emission, they only emit water vapors and warm air. The energy stored as hydrogen is converted to electricity by Polymer electrolyte membrane (PEM) fuel cells. It takes less than 4 minutes to refuel a FCEV and can run up to 300 miles. Batteries of a FCEV are also charged by regenerative braking ie energy generated from braking. Some FCEV available in the market are: Volkswagen Golf HyMotion and Roewe 950 fuel cell.

Conclusion:

    Electric vehicles are completely environment friendly and are economic than IC engine-based vehicles in long run. Even Hybrid vehicles are very environmentally friendly than an IC engine car. Infrastructure development and battery technology are growing rapidly and 5 years down the lane the battery cost and availability of charging stations will be popular. Research works have also been going on regarding Fuel cell cars in the USA to reduce the economic stress due to crude oil or gasoline. ML-based models are used in cars for auto-drive modes and lots of engineering is going on in Advanced Driver Assistance System (ADAS) for revamping of EVs. 


Anshu Prakash,

email: send2anshup@gmail.com 


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