Efficiency of Electric Cars Measured in Belgium Study
Electric vehicles are known to be very efficient. Cars with internal combustion engines are not, losing most of their energy as heat. EV advocates have been saying this for years, and there is a ton of data about the efficiency of gasoline and diesel cars. But electric cars are newer and there are few of them, so we've had less documentation...until now. Some Belgians have been given the opportunity to study a fleet of five cars.
There were Peugeot Ion models, exact clones of the Mitsubishi i-MiEV (European version), and the people monitoring them were from Laborelec, with support from Brussels' Vrije University, which has a facility dedicated to automotive technology. The study was funded by Electrabel, the Belgian utility. It lasted two years, but the first part of the story was to define a methodology. A precise, dedicated monitoring system was developed, and things only got started when it received a full approval from the car manufacturer.
This data was recorded from the five cars over two years: battery current, voltage, state-of-charge, odometer, instant speed, GPS coordinates, and ambient temperature. Total distance covered by the five cars was 42,953 miles, and energy consumption in watt-hours per mile for each car was as follows: 289.62 ; 336.28 ; 249.39 ; 291.23 ; 299.27. The different values result mostly because of different drivers—with an average of 293.16 watt-hours per mile for the fleet.
This is the overall energy consumption, but it isn't enough to give a complete picture as regenerative braking has significantly helped to increase the cars' efficiency. For each car, the increase (in percentage) is as follows. 16.1 ; 9.9 ; 12.5 ; 9.1 ; 11.7. That's an average of 11.86%, and it's a clear gain. Regenerative braking was more than sufficient to compensate for the losses of the charging process, where AC electricity from the mains was not converted to DC for the battery.
A very important part of the study then, was to show where the electricity is going: to the motor, or the auxiliaries (for example, heating/cooling, battery management system, and lights). For each car, the share of the energy consumption going to auxiliaries (in percentage) is as follows. 40.1 ; 35.8 ; 21.6 ; 22.0 ; 36.4.
Overall Clear Winner
This is where internal combustion cars shine. Heating is essentially free in a gas car. An internal combustion engine loses so much energy in its normal operation that it costs nothing to get back some of it to heat the car.
We could then conclude that the biggest thing to make EVs more efficient is the heating system. Car manufacturers know that already. The Peugeot EVs tested had a conventional, resistive heater, but the latest models have a heat pump, which is much more efficient technology. There's still room for improvement: some cars from the 1960s have much stronger heaters that EVs have today. Overall, the energy efficiency of each car, plug to wheel, is as follows. 47.0% ; 49.7% ; 63.2% ; 59.1% ; 51.6%. That's much better than any gas or diesel could achieve, even with the addition of a hybrid powertrain.
Another important result is the higher importance of auxiliaries at lower speed, meaning that EVs have better plug-to-wheel efficiency when used on the road outside of the city—but without too much time on the highway where the higher speed reduces efficiency.
Oh, and the test proved convincing. One driver who had an EV as his company car for two years, bought one for himself when the test was over.
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