A Hybrid Electric Vehicle HEV is a vehicle that combines the characteristics of an internal combustion engine and a special electric motor to achieve better fuel economy and lower CO2 emissions than conventional vehicles. The fuel efficiency of a hybrid car is improved considerably because the electric motor compensates the internal combustion engine’s poor torque performance at low engine revolutions.
Internal Combustion engines are inefficient at low speed. Hybrid cars save fuel by operating with their built-in electric motor at low revolutions. At low speed, the IC engines do not drive the Hybrid car; however, they re-charge the batteries as the need arises.
Internal Combustion engines of Hybrid vehicles start to work at high speed when IC engines operate with more efficiency. Hence, Hybrid cars use fuel only when the power requirement demands it. Because, Hybrid cars usually use the IC engines at high speed when IC engines are more efficient, they offer better fuel economy than conventional cars.
Hybrid cars achieve more fuel economy by shutting down engines when in idle mode. For example, when stopped in a roundabout, a Hybrid car shuts off engines. Engine can be re-started by simply engaging the gear and touching the accelerator.
Batteries of Hybrid cars are charged by the internal combustion engine when the car is on the move. Hybrid cars also use a process called regenerative braking to convert energy that would have been lost during braking to electrical energy stored in the battery. Regenerative braking is the primary source for charging Hybrid batteries at low speed.
Hybrid cars requires a motor and a generator, however to save space and weight most Hybrid cars come with a motor, which can also be operated as an alternator. In motor mode, energy is received from the battery and used to drive the wheels. In alternator mode, the internal combustion engine is used to drive the motor in order to generate electricity for charging the battery.
There are two main HEV technology, these are:
- Series Hybrid
- Parallel Hybrid cars
In a series Hybrid vehicle, an IC engine drives an alternator (generator) to generate electricity for charging the battery. The energy stored in the battery is transferred to the electric motor, which then powers the wheel. In a series Hybrid, only the electric motor drives the wheels, the engine only supplies power for charging the battery. Series hybrid cars require separate motor and alternator.
Efficiency is achieved in series Hybrid vehicle because the engine is operated within the narrow range of speed where it is most efficient. Series Hybrid cars also save fuel by shutting of engine when not needed. There is no series HEV currently in production.
Parallel Hybrid has two power paths, either the motor or the engine or both can supply power directly to the wheels. Parallel hybrid allows the motor to also be used as an alternator offering cost and space savings. Parallel hybrid electric vehicles offer higher power output because the engine power can be combined with the power from the motor providing for the practical demands of everyday motoring.
This is why most hybrid cars in production today come with parallel hybrid technology, despite the fact that series hybrid technology offers better efficiency. Some Hybrid cars with parallel hybrid drivetrain include Honda Insight and Ford Escape Hybrid.
Toyota Prius uses a combination of both series and parallel hybrid drivetrain.
Hybrid cars that use a smaller electric motor, than found in full hybrid cars are called mild hybrid vehicles. Some hybrid cars classified as mild are Honda Civic Hybrid and BMW 7-series hybrid.
Some Hybrid electric vehicles can be charged using mains electricity supply. These hybrid vehicles called Plug-in Hybrid Electric Vehicle (PHEV) offer more fuel and cost savings; and is increasingly becoming popular. An example of a PHEV is the Renault Kangoo.
Although hybrid cars promise cheaper running costs and cleaner (greener) operations, compared to an internal combustion engines, they require a petrol/diesel engine in addition to a specialised electric motor, a high capacity battery, a power electronic system, and an advanced control system to ensure everything works well. This has significantly led to high cost of hybrid cars, which has put it out of the reach of many people.
However, as battery technology improves and with more advanced auto electronics now available added to larger production volumes, hybrid car prices are bound to fall bringing them within reach of more people.
Two auto companies with two hybrid cars are global leaders in hybrid technology. They are Honda with Insight and Toyota with Prius.
Some Hybrid electric vehicles in production today include:
- Toyota Prius
- Honda Insight
- Honda Civic Hybrid
- Ford Escape SUV Hybrid
- Nissan Altima Hybrid
- Mercury Mariner Hybrid
Some Hybrid electric vehicles being expected include:
- Saturn Vue-2 PHEV
- Hyundai Avante LPG HEV
- BMW 7-Series hybrid
- Lexus HS250H
- Mercedes S-Class Hybrid
You are not likely to find hybrid cars in Nigeria at authorised dealers place. This is because the Nigerian market is not matured for hybrid. Hybrid cars are still too expensive, and most people would not understand why they should pay more for an HEV when they can get same feature for less if they buy a non-HEV. However, as prices of hybrid cars continue to drop because of improved technology and mass production and with better awareness of the harmful effects of global warming, hybrids will surely sell in Nigeria.
Soon Nigerians will only have hybrid vehicles to choose from as most major auto manufacturers have plans of converting most of their models to hybrids over the next few years.