Hybrid Electric Vehicle (HEV)

Syllabus: General Studies Paper 3

A hybrid electric vehicle (HEV) uses an ICE (a petrol/diesel engine) and one or more electric motors to run. It is powered by the electric motor alone, which uses energy stored in batteries, by the ICE, or both.

What is a hybrid electric vehicle?

• A hybrid electric vehicle (HEV) uses an ICE (a petrol/diesel engine) and one or more electric motors to run. 
• It is powered by the electric motor alone, which uses energy stored in batteries, by the ICE, or both. 
• The power train of the HEV is more complex than a regular ICE-powered car as it has EV components and a conventional ICE. 
• That means a typical HEV will have a low-voltage auxiliary battery, a traction battery pack to store electricity for the electric motor, an electric generator, an AC/DC converter, a power electronics controller, a thermal system to maintain working temperature, an ICE, a fuel tank, a fuel filler, a transmission and an exhaust system.

How do HEV Powertrains work?

• HEV powertrains are designed to power cars in a series, parallel or series-parallel (power split) methods. 
• A series HEV uses only the electric motor to drive the wheels, while the ICE powers the generator, which in turn recharges the battery. 
• A parallel HEV, based on the driving condition, uses the best power source to power the vehicle. It will alternate between the electric motor and the ICE to keep the car moving.
• A series-parallel HEV offers a combination of both models and allows to split power, wherein power is routed from the ICE alone or from the battery to the electric motor to drive the vehicle. 
• Moreover, in all three designs, the battery is charged through regenerative braking technology.

How does regenerative braking work?

• A regenerative braking system (RBS) used in automotive applications has several advantages like better braking efficiency in stop-and-go traffic which enhances fuel economy and also helps in reducing carbon emissions.
• RBS also helps in energy optimisation resulting in minimum energy wastage.
• A kinetic system can recover the energy lost during braking and then use this energy to recharge the high-voltage battery of the vehicle. 

What are the different types of HEVs?

• The HEVs can be categorised into micro, mild and full hybrid vehicles, based on the degree of hybridisation.
• A Full HEV will have a larger battery and a more powerful electric motor compared with a mild HEV.
• Mild HEV cannot drive using only the electric motor and uses the battery at traffic lights or in stop-and-go traffic to support the ICE.
• Micro hybrids do not offer electric torque assistance as they lack an electric motor, but they have an idle stop-start system and energy management functions. 
• There are plug-in hybrid electric vehicles (PHEVs) that are just like full HEVs, but they can be charged using a wall outlet, as they have an onboard charger and a charging port. 
• PHEVs generally use the electric motor until the battery is almost drained, and then automatically switch to the ICE.

What are the main advantages of using hybrid technology?

• Fuel efficiency is a major factor for most people considering buying a car. 
• Most vehicles with hybrid technology offer better fuel efficiency, more power, and minimum emissions. 
• The design of hybrid vehicles for reduced engine size and car weight as compared to ICE vehicles, translates into increased mileage to favour the demand for these vehicles. 
• Moreover, with the increase in total power and torque, HEVs can deliver instant torque and provide high torque even at low speeds.

What are some challenges of hybrid technology?

• In a price-sensitive market like India, one of the major challenges for HEVs is the high vehicle cost. 
• Battery, a vital component of an HEV, increases the cost of the vehicle, making it pricier than vehicles powered only by an ICE. 
• The RBS also adds to the higher cost of an HEV.