Electric hybrid vehicles and their consumptions

 
auto ibride

Photo by Captain Kimo

For all of us, the electric hybrid vehicles and the electric pure ones by now mean reduction in consumption and therefore less CO2 emissions and more environmental protection, even if there are conflicting opinions because of the damages caused from the extraction of metals needed to build electric motors (see the post ‘Interview to professor Ivan Maio of the Polytechnic in Turin‘).

Electric vehicles also offer undeniable advantages as running cost, high performance, the possibility to move freely in restricted traffic zones and park for free, they have little purchase interest from the private client because of their limited autonomy, charging time very high (hours) and the very high price.

It is different and much more complicated when we talk about hybrid, reminding that there are two typologies of solutions: parallel and series hybrid.

Starting from the Toyota Prius, parallel hybrid, there was a continuous crescendo of innovations, to the present day where, almost daily, there are new versions and new brands enhance their range with such products.

But why the car companies invest money, lots of money, in these vehicles in turn with a high price and from not exciting sales?
Sure to reduce the consumptions.

The homologated consumptions of such cars result in fact significantly ameliorative than the traditional versions, but there are other conditions of “normal” use, not included in the type-approval cycle, in which consumptions are higher, and so?

Stazione Benzina

Photo by pepe50

In order to remain on numbers and not on opinions, I asked for help to my “usual” friend, Ing. Barbiero , who has no doubt about it: “hybrid vehicles give certainty of being within the limits of the pollutants established by the type-approval cycle”, but we are going to better explain how they are obtained.

The current European type-approval for consumptions is defined UDC+EUDC, is carried out on a chassis dynamometer braked according to several parameters, primarily on the mass of the car.

The vehicle, before the test, must be kept in a thermostatic chamber at 18° C for at least 8 hours.

The car, then, is pushed or it passes through rolls, the exhaust pipe is connected to a computer analyzer and the test immediately starts in the presence of the type-approval official.
The driver of the car must follow the speed track on the rolls with a minimum error and the exhausted gases are instantly analyzed.

The graphic shows the test cycle, and the different colors explain a possible use of the two propellers of the hybrid, aimed at minimizing emissions and fuel consumptions:
The ECE+EUDC test cycle

THE FIRST PART OF THE TYPE-APPROVAL CYCLE

The first part of the cycle, UDC, provides for several standing starts and a maximum speed of 50 Km/h; if the start is through the electric engine, this removes all the emission cold-starting, the worst, because the thermal engine is turned off as opposed to a normal thermal vehicle tested by the same cycle.

The cycle lasts 780” and is 4 Km long, the car is sitting idle for 240” – the 30% of the total time – and according to the hypothesis proposed by Ing. Barbiero, followed by several cars, accelerations up to 22 Km/h can occur only in electric mode and last about 18% of the total time, furthermore there is an 8% of the time in which the electric engine is used to accelerate, and 18% where it recovers energy during breaking.

The total use of the electric covers 44% of the cycle time and so the heat engine works only for 26%.

It is evident how the hybrid solution is rewarding, especially if you are able to “manage” the engines, right in the basis of the city use.

THE SECOND PART OF THE TYPE-APPROVAL CYCLE

In the second part of the type-approval cycle, EUDC, which lasts 400” and is 7 Km long, things change, because the car is sitting idle only for 10% of the total time. Subdividing the times of use of the engines, as done before, the heat engine works for 52% of the total time, a double time if compared to the previous cycle, and therefore the consumption increases, but it is always lower than an equal thermal vehicle.

Autostrada route 66

Photo by patrice ouellet

If however, type-approval cycles aside, you travel on the highway at constant 130 Km/h, only the heat engine works, which drags on: the electric motor, the weight of the batteries, all the electronics and the other components of the electric traction; the consumptions and so the emissions are higher than the traditional vehicles.

A second situation, in which the fuel consumptions and the emissions will increase, occurs when the traction batteries aren’t recharged at a charging point but on board, while traveling. In this phase the heat engine, in addition to push the car, has to recharge the batteries through the electric traction motor and therefore a further curbing is added.

Therefore the electric hybrid helps a lot in the type-approval cycle, and provides fantastic results for vehicles designed for urban circulation, that means small and with a predominant use at low speed.

And so why supercars, with CO2 emissions up to about 600 gr/Km (!!!) opposed to the 115 gr of a car belonging to segment B, are already converting to the hybrid? Because having the same type-approval cycle, they significantly will cut down consumptions and emissions – although it’s unlikely that they will be used in the urban cycle and at low speed – and reduce taxation also in those markets linked to consumptions.

Yes, however, this is a saving that, considering the typology of customers, will not affect the family budget.

Of course not, but can you imagine how cool is to have an electric motor added as the Ferrari Formula 1?
Actually, you should increase slightly the prices, because beautiful things are expensive… right!

Translated by Federica Izzo

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