Reduction of trip time and energy demand

The Eco-Routing algorithm developed in the CEVOLVER project solves the problem of finding a time- and energy-optimal route for an electric vehicle requiring multiple battery charging events to complete a long-distance trip. The proposed routing strategy also provides the optimal sequence of charging events, as well as the optimal average speed for each road segment to reduce charging needs and save trip time.

For the Ford demonstrator, the main benefit of optimal average speed advice is expected for highway traffic where the travel speed can be adapted largely without constraints. Thus, an example for a 350 km trip was analyzed. For that purpose, the energy demand was considered for different vehicle speeds between 70 and 130 km/h assuming for simplicity that the whole trip is driven at constant speed. In addition, the total trip time was evaluated based on the time demand for driving and the time demand for battery charging with 20 to 150 kW just to the state of charge that is required to reach the target destination. The resulting graphs that show the interdependency between available charging power, energy demand and trip time are shown below.

Figure: Dependency between available charging power, energy demand and trip time for a long distance tripIt is obvious that the energy demand is increasing strongly with increasing vehicle speed which is due to the big frontal area and the resulting air resistance of a typical 3.5 t transporter. Comparing the vehicle speed with the total trip time, the graphs indicate that depending on the available charging power an increase of vehicle speed is not always beneficial in terms of trip time. For an average charging power of 20 kW, the trip time demand at 80 km/h is by far less than for 130 km/h. The reason for that is the difference in driving energy demand and the related amount of charging energy that results in heavily increased time demand for charging. This effect is mitigated with the availability of higher charging power but even for 100 kW average the time savings for travelling at 130 km/h instead of 100 km/h are negligible whereas the increase in energy demand is significant.

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