Abstract :
Any vehicle is hybrid
when it combines two or more sources of power. In fact, many people have
probably owned a hybrid vehicle at some point. For example, a mo-ped (a
motorized pedal bike) is a type of hybrid because it combines the power of a gasoline
engine with the pedal power of its rider.
Hybrid electric
vehicles are all around us. Most of the locomotives we see pulling trains are diesel-electric
hybrids. Cities like Seattle have diesel-electric buses -- these can draw
electric power from overhead wires or run on diesel when they are away from the
wires. Giant mining trucks are often diesel-electric hybrids. Submarines
are also hybrid vehicles -- some are nuclear-electric and some are diesel-electric.
Any vehicle that combines two or more sources of power that can directly or
indirectly provide propulsion power is a hybrid.
The most
commonly used hybrid is gasoline-electric hybrid car which is just a cross
between a gasoline-powered car and an electric car. A ‘gasoline-electric hybrid
car’ or ‘hybrid electric vehicle’ is a vehicle which relies not only on
batteries but also on an internal combustion engine which drives a generator to
provide the electricity and may also drive a wheel. In hybrid electric vehicle
the engine is the final source of the energy used to power the car. All
electric cars use batteries charged by an external source, leading to the
problem of range which is being solved in hybrid electric vehicle.
Components used in
hybrid electric vehicles are given below:
Gasoline engine - The
hybrid car has a gasoline engine much like the one you will
find on most cars. However, the engine on a hybrid will be smaller and lighter,
and is more efficient than the engine in a conventional vehicle, because the
engine runs at a relatively constant speed, and does not need to provide direct
power for acceleration, which is the biggest reason for large engines. Use
advanced technologies to reduce emissions.
Fuel tank - The fuel
tank in a hybrid is the energy storage device for the gasoline
engine. Gasoline has a much higher energy density than batteries do. For
example, it takes about 1,000 pounds of batteries to store as much energy as 1
gallon (7 pounds) of gasoline.
Electric motor - The electric
motor on a hybrid car is very sophisticated. Electric motor used in
hybrid cars are usually dc series motor since it’s versatile and ease with
which a variety of speed-torque characteristics can be obtained, and wide range
of speed control is also possible in this. Advanced electronics allow it to act
as a motor as well as a generator. For example, when it needs to, it can draw
energy from the batteries to accelerate the car. But acting as a generator, it
can slow the car down and return energy to the batteries.
Generator - The generator is similar to an electric motor,
but it acts only to produce electrical power. It is used mostly on series
hybrids. Generator used in hybrid electric vehicle is alternator since cooling
is easy and hence maximum output and also the output/weight ratio is higher
than that of the DC generator.
Power split device –The
power split device is a clever gearbox that hooks the internal combustion
engine and D.C.motor together. The power split device helps the vehicle to
accelerate to a speed of about 15km/hr before switching on the gasoline engine.
The engine starts only after the vehicle attains a certain speed. Once the
engine starts it operates on a narrow speed band. The power split device allows
the engine to stay in its most efficient load and speed range most of the time.
Batteries - The batteries
in a hybrid car are the energy storage device for the electric motor. Unlike
the gasoline in the fuel tank, which can only power the gasoline engine, the electric
motor on a hybrid car can put energy into the batteries as well as draw energy
from them. The batteries used in HEV is Ni-Cd cells since its lighter than the
lead acid cells and its also mechanically strong and can stand very rough use.
Transmission - The
transmission on a hybrid car performs the same basic function as the
transmission on a conventional car. Some hybrids, like the Honda Insight, have
conventional transmissions. Others, like the Toyota Prius, have radically
different ones, which we’ll talk about later.
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