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Hybrid 101: How does it work?
On TDI Curious, we have set ourselves the goal to talk about responsible mobility, which involves discussing all the forms of new technologies currently available, and the hybrid is one of them. So in view of better understanding the issues, here is how a hybrid vehicle works.
The main principles
Driving a hybrid is identical to driving a traditional car. A hybrid vehicle is a vehicle whose propulsive force is supplied by two engines, fuel and electric, and whose energy is stored in two reservoirs, one containing fuel and the other electricity (batteries). You must fill the first one up with fuel, but the second is filled automatically when driving, by collecting the vehicle’s energy during braking and descents. Today, you cannot yet plug in a hybrid vehicle to recharge the batteries. The recuperation of this “free” energy, for it would otherwise be dissipated in heat by the brakes, allows fuel savings of around 20%.
Beyond the presence of an electric engine and a battery, hybrid vehicles often add optimized drive-trains (an Atkinson cycle internal combustion engine, an epicyclic gear train), low rolling resistance tires and aerodynamic design, etc., which also participate in low fuel consumption.
The technologies
In 2009, all hybrid highway vehicles are of the “parallel” type, in other words; the two motors help each other to produce the movement, working in concert to make all four wheels turn. One could also subdivide this category into “mild” hybrids and “full” hybrids.
Mild Hybrid
The mild hybrids can call upon a simple alternator-starter, driven by a belt, and a low-capacity battery, or an electric motor installed between the internal combustion engine and the transmission. In the two cases, the mild hybrids cannot move the vehicle on only the electric motor; it serves only to help the fuel engine during acceleration phases and to collect braking energy to recharge the batteries. The improvements in fuel consumption and performance are modest.
Full Hybrid
The full hybrid can power the vehicle in one or the other of the two modes, electric or fuel, or both at the same time. In this type of hybrid, one or two small electric motors are mounted in the transmission, and an epicyclic gear train (controlled by computer) is charged with sharing the power demand between the fuel and electric motors. The operation of this gear train is similar to that of the continuously variable transmission, but it is not one. The gains are greater, but the complexity of the ensemble comes at significant additional expenditure.
The two types (mild and full) offer engine shutdown at red lights, and automatic restarting as needed.
The future
In the future, we may see another type of hybrid, called a “series”. Here, the internal combustion engine will only work as a generator to produce current, either for powering the vehicle, recharging the battery, or both at the same time. This series hybrid technology has existed for a long time in the locomotives that we know in Canada, as well as immense mining trucks.
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