The technology powering hybrid electric vehicles

The technology powering hybrid electric vehicles

Subject: Science and tech

Section: electric vehicle

Context: In recent months, automakers Maruti Suzuki, Toyota and Honda have launched hybrid electric vehicles in India, offering car buyers more choices in the nascent electric vehicle market

What is a hybrid electric vehicle?

• A hybrid electric vehicle (HEV) uses an internal combustion engine (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 powertrain of the HEV is more complex than a regular ICE-powered car as it has EV components and a conventional ICE.

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.
• In all above three designs, the battery is charged through regenerative braking technology.

What is Regenerative Braking Technology (RBT)?

• Regenerative braking is an energy recovery mechanism that slows down a moving vehicle or object by converting its kinetic energy into a form that can either be used immediately or stored until needed.

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. An electric system generates electricity through a motor during sudden braking. Lastly, a hydraulic system uses pressurised tanks to store the vehicle’s kinetic energy and can offer a high energy recovery rate which is ideal for heavy vehicles.
• The efficiency of HEVs and EVs will in large part be determined by their ability to recover as much energy as possible while braking, with a higher degree of energy recovery lowering fuel consumption
• The amount of recoverable energy depends upon factors like vehicle speed and stopping pattern.

What are the different types of HEVs?

• The HEVs can be categorized into micro, mild and full hybrid vehicles, based on the degree of hybridization.
• A full HEV will have a larger battery and a more powerful electric motor compared with a mild HEV. As a result, a full HEV can power the vehicle for longer distances using just electric mode, whereas a 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.

Advantages of hybrid technology:

• 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
• With the increase in total power and torque, HEVs can deliver instant torque and provide high torque even at low speeds.

Challenges of hybrid technology:

• A major challenge 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