Hybrid Power Trains: Here Are Some Basics And Opinions

Hybrid powertrains are gaining huge momentum than never before. 

We briefly looks at their fundamentals and opinions behind them.

Modern automotive industry tries to attune major environmental concerns on emissions and fuel efficiency of burgeoning automobile population on our roads by developing alternative powertrains and hybrid systems. Propulsion systems that are not exclusively based on conventional internal combustion engines (ICE) such as hybrids, full battery electrics, hydrogen fuel cells, compressed air, and many other types have gained enormous attention in recent times. Of the lot, hybrid power systems have relatively marched ahead in terms of better penetration into the production scene due to their practicality and cost management.

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A hybrid vehicle uses two or more distinct power sources to move themselves. It may use different conventional fuels for the engine, or may combine an ICE’s output with that of an another energy source, or generate a part of its energy requirement on its own. Thus, your CNG/ LPG endorsed hatchback is also a “hybrid” theoretically, as does Fiat’s Tetra Fuel car in Brazil that runs on four different fuels. But, what are optimistically considered as Hybrids these days are those that combine a conventional engine and one or more electric motors as they partly eliminate the use of nonrenewable fuels and reduce emissions. However those hybrid mechanisms and combinations are plenty.
There are parallel systems with an ICE and electric motor coupled at a parallel axis, operated using differential gears. The two sources may share same shaft, and with speeds at equal and torque management as required. The Honda Civic Hybrid uses this system. They are called Mild hybrids, as they cannot provide all-electric drive when ICE is turned off.

Most of the range-extended electric vehicles (EVs) possess a serial hybrid design in which the ICE is employed only to recharge the batteries and the car’s propulsion is solely dependent on the electric motor, just like our diesel-electric locomotives with a battery as an energy buffer. Fisker Karma is an example of this system, which in addition has a plug-in system. A plug-in hybrid can be recharged using domestic electric outlets, which stores the energy in batteries. They are full hybrid and can be parallel or series hybrid designs.

Another type is the Power-split Hybrid, which incorporates power-split mechanism to either propel the vehicle either mechanically by ICE or electrically. An electric motor’s ability to churn out higher torque at standstill complements the ICE’s torque deficiency at low RPMs, improving fuel efficiency as in the case of Toyota Prius Hybrid.
Hybrid configuration can be used with Hydrogen-powered Fuel cell vehicles like the now gossiped 2014 Toyota Mirai or compressed-air powered systems as in case of Tata-MDI (France) MiniCat project. A common feature among hybrids these days is the regenerative braking, which retrieves kinetic energy from the wheels using an electric motor as generator. The regular friction based braking system also works in place with energy recovery mechanism.

2015 Toyota’s Mirai will be the world’s first mass-produced fuel-cell car that runs on Hydrogen.
#N for Neutral
More than a million hybrids are sold every year globally and represent a significant bridge to all-electric drive technologies. Yet, Hybrid are full of incongruities. There are more Luxury hybrids than simply hybrids. They are expensive and the trickle-down effect of hybrid technologies is hardly realised for mass motoring. The lithium-ion batteries used in EVs and hybrids are a kind of ‘time bomb’, since their recycling is a concern once hybrids reach our roads in large numbers. It is also less clear how ecofriendly the production of EVs and hybrids themselves are, comparing to regular cars. Just as EVs cannot be claimed as absolutely eco-friendly since 60% of electricity is generated by thermal production, especially for countries like India, plug-in hybrids do face clean electricity shortage.

Photo Credits: Cleanmpg.com, gas2.org

Dhiyanesh Ravichandran

Editorial consultant (Automotive and Technology), academic, and blogger based in India. He can be reached at wagenclub@gmail.com

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