More and more frequently we attend the launch of new pure and hybrid electric cars or heat/electric ones, so it comes naturally to wonder: what is the differences of the product they offer and for what types of use?
To better understand the products offered and their characteristics, I asked a friend and true expert on the subject for help, Ing. Roberto Barbiero, a career dedicated to car design with direct experience in the development of Fiat and Ferrari vehicles, cars with low environmental impact and hybrid/electric cars and busses.
As a general observation, we can say that the challenge, in developing such vehicles, focuses on combining as best one can four different but complementary characteristics: the hill start (15/20 degree slope), autonomy, performance and, of course, relative costs.
We can divide the offer in three categories: pure electric, parallel and series hybrid, each of them with very different performance and features, in order to satisfy different types of use.
Pure electric vehicles OEM
They offer a range of performance very variable and are divided in two main types: those with a maximum speed limited to about 80 Km/h and those with a maximum speed between 130 and 300 Km/h. The first category, which has been developed for fifteen years, uses traction components and outdated batteries, as lead-acid batteries, heavy electric motors etc…
This setting allows limited power-and-torque performance and speed (9.000 rpm max) and therefore also a restricted maximum speed in favour of hill starts and a reliability so so . Factors that have heavily influenced the sales, making them attractive for the Park and Ride or for the car sharing, but not to private customers.
Thereby the new developments, belonging to the second category, are been oriented for obtaining performance similar to the traditional ones, with higher autonomies and possibly lower purchase costs, even offering the traction batteries on hire.
This was possible thanks to the development of new electric engine, better performing. With the same size and torque provided, today they are about four times more powerful and with very high speed about double rpm.
Moreover, the evolution of batteries has led, at equal energy, to a weight reduction of about 60-70% (from about 400 Kg to 120Kg) and also of dimensions.
The price of the batteries depends especially on the capacity of stored energy, which in turns depends on the autonomy offered.
This means that a high autonomy, for example of about 200 Km, involves a battery cost equal to 10,000 € and allows a full charge in 5/10 hours by the house’s electrical system.
Indicatively, the average lifetime of batteries is about 5 years.
Today these vehicles provide benefits such as the reduction of emissions down to nearly zero, a minimal operating cost amounting to 2.5€/100 Km in the urban cycle and the possibility to drive in restricted traffic zones without permission.
So these are interesting vehicles for urban travel or, at most, within the province, but with the certainty to find a charging station.
Parallel hybrid vehicles
The parallel hybrid vehicles have an electric motor added to the heat one, which works on the driving wheels, always intervening at the start and contributing to help the heat engine in accelerated phase, recovering energy during releasing and braking.
This configuration leads to a reduction in fuel consumption and emission in the city, not at the same level of the pure electric ones, but approximately of -20/25% vs. the heat engine.
The current trend of developments of these cars shows the increase of the autonomy during the electric, in order to drive about 30 km in pure electric, especially for an urban use, thanks to the implementation of the energy stored in traction batteries, obviously after an increase in costs and weight.
These are vehicles fit for circulation in the city and suburban, which can travel on the motorway due to the heat.
However be careful, because the electric motor, always connected to wheels for the energy recovery, involves more weight if compared to a traditional car and, having to drag the rotor of the electric motor, leads to a greater increase of consumptions and emissions on the route at average speed.
Series hybrid vehicles
They travel always by electric and have a supportive heat engine for the production of energy in case of need, under specified conditions.
The autonomies, according to statements, lasts up and even over 600 Km but in “range extender”, which means with the support of the heat engine.
But how many kilometres with only electric?
They can be highly variable, from a few Km up to 150 Km.
Interesting implementation for bus and LCV as well, on routes normally limited and known, because there is a small but non negligible problem: outside the large urban centre, where to recharge cars?
There are several technical challenges to be overcome in the development of series hybrids:
- the capacity of the system of electricity generation for traction, to take into account, in a very short time, the functioning of the vehicle in gear, during acceleration, deceleration and arrest, because today the recovery of braking energy cannot be added to that generated from the heat engine;
- finding the constant operating point of the heat engine, at low speed, to have a high efficiency of the generator;
- the safety, modern electric motors offer extremely high performance and efficiency, theoretical voltage of battery of about 360 Volts continuously and electric current absorption equal to 2/300 Ampere.These are very high values, which involve completely new technical solutions, in order to ensure the occupants’ safety.
Electric cars, both pure and not, are joined by two sore points:
- the sales price, not exactly within most of the customers’ reach, the cost of small/medium cars ranges from € 25,000-odd for a vehicle of A-segment up to € 40,000 and more for a C-segment one;
- in the event of failure of electrical installations of traction, even if a single fuse goes out… call the tow truck!
In short, this is a difficult challenge for engineers, which requires significant investments in research and therefore not indifferent governmental financial aid.
It will require quite a lot of time both to find better technical solutions and to build the necessary infrastructures for a widespread distribution.
Today the commercialization of such vehicles is mainly due to policies to promote the image and the brand value of a company – even to the detriment of costs incurred – and sales incentives.
It is hard to imagine, in the near future, high sales volumes because of the process and the limitations of use if compared to conventional cars.
But, aside from this, it will also be necessary a radical change in customers’ mentality during the purchase, less emotions and more judgment, and new mobility strategies especially within the urban area.
Translated by Federica Izzo