Hybrid electric vehicles

• Soumyashree Biradar

•Kavya E C

•Priyanka B N

•Shruti singh

•Varsha

* A hybrid electric vehicle (HEV) augments an electric vehicle(EV) with a second source of power referred to as thealternative power unit (APU).

* A hybrid can achieve the cruising range and performanceadvantages of conventional vehicles with the low-noise, low-exhaust emissions, and energy independence benefits ofelectric vehicles

* Accordingly, the hybrid concept, where the alternative powerunit is used as a second source of energy, is gainingacceptance and is overcoming some of the problems of pureelectric vehicles.

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* Any vehicle that combines 2 or more sources of power

is said to be hybrid. For example, a moped (a

motorized pedal bike), diesel-electric hybrid

locomotives

* Relies not only on batteries but also on an internal

combustion engine which drives a generator to provide

electricity and may also drive a wheel.

* Alternative power unit to supply the power required by

the vehicle, to recharge the batteries, and to power

accessories like the air conditioner and heater.

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Series hybrid

Parallel hybrid

In a series hybrid system, the combustion engine drives an electric

generator instead of directly driving the wheels.

The electric motor is the only means of providing power to the

wheels.

The generator charges a battery.

Series hybrids can be assisted by ultracaps (or a flywheel), which

can improve the efficiency by minimizing the losses in the battery.

Utracaps deliver peak energy during acceleration and take

regenerative energy during braking.

Therefore, the ulracaps are kept charged at low speed and almost

empty at top speed. Deep cycling of the battery is reduced, the stress

factor of the battery is lowered.

Series structure

Series structure

There is no mechanical link between the combustion engine

and the wheels. The engine generator group can be located

everywhere.

There are no conventional mechanical transmission elements

(gearbox, transmission shafts). Separate electric wheel motors

can be implemented easily.

The combustion engine can operate in a narrow rpm range (its

most efficient range), even as the car changes speed.

Series hybrids are relatively the most efficient during stop-

and-go city driving.

The ICE, the generator and the electric motor are dimensioned to handle the full power of the vehicle. Therefore, the total weight, cost and size of the powertrain can be excessive.

The power from the combustion engine has to run through both the generator and electric motor. During long-distance highway driving, the total efficiency is inferior to a conventional transmission, due to the several energy conversions.

Fuel tank supplies gasoline to the engine.

Set of batteries supplies power to the electric motors.

Both the engine and electric motor can turn the transmission at the same time, and the transmission turns the wheels.

When the APU is off, the parallel hybrid runs like an electric vehicle

When the APU is on controller drives the energy between drive train and batteries

Under acceleration more power is allocated to drive train than to the batteries and during periods of idle,more power goes to the batteries than the drive trains.

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Parallel structure

Flexible in configurations and gives room for optimization of fuel economy and emissions.

Reduced engine size.

Possible plug-in hybrid for further improved fuel economy and emission reduction.

Complicated control strategy.

Complex transmission.

1. Electric motor:

Converts electric energy to mechanical energy.

It is powered by DC sources such as batteries or by AC sources

such as generators.

2. Auxiliary power unit(APU):

It is a device that provides energy for functions other than

propulsion.

APUs use spark and combustion engines as a source of power.

However in recent years fuel cell APUs that nearly eliminate

all emissions are used.

APU in HEVs supplies baseline power required by vehicles,

recharges batteries and power accessories such as air

conditioners and heaters.

3. Generator:

The combustion engine in serial hybrid drives electric

generator.

The generator both charges battery and powers motor that

moves vehicle.

In parallel hybrid there’s no separate generator, motor

functions as generator when needed.

4. Energy storage systems:

Batteries, flywheels or ultra capacitors are used for energy

storage in HEVs

Flywheels store energy mechanically by turning heavy rotor to

store kinetic energy.

Lithium ion batteries are used for their efficiency and high

power to weight ratio for energy storage.

Ultra capacitors store energy in polarized liquid between an

electrode and electrolyte, provides additional power during

acceleration.

5. Regenerative breaking:

Vehicles relay on friction breaks to slow down, dissipating

kinetic energy as heat. Regenerating breaks turns this energy

into electricity and stores in batteries.

This electricity can later be used to run motors and accelerate

vehicle.

* Using the concept of Hybridization of cars results in better efficiency and also saves a lot of fuel in today’s fuel deficit world.

* A hybrid gives a solution to all the problems to some extent.

* If proper research and development is done in this field, hybrid vehicle promises a practical, efficient, low pollution vehicle for the coming era.

* One can surely conclude that this concept and the similar ones to follow with even better efficiency & conservation rate are very much on the anvil in today’s energy deficit world.

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