Reducing energy consumption for e-cars - in small increments

July 17, 2014 // By Christoph Hammerschmidt
During their final presentation in Vigo (Spain), the participants of the European research project OpEneR introduced driving strategies and driver assistant systems that are believed to significantly improve energy efficiency and safety of future generations of hybrid and battery electric vehicles. This higher efficiency will enable vehicle designers to extend the driving range of the vehicles without increasing size and costs of the batteries.

Within the project OpEneR (Optimal Energy consumption and Recovery based on a system network), the engineers and researchers worked on topics as different as improvements of the electric power train and the regenerative braking system, the navigation system and the surround sensors as well as of functions that interconnect all these building blocks. They built functioning electric vehicles prototypes that already were able to prove their potential for more energy efficient driving under real-world traffic conditions.

One of the tasks was developing a so-called eco routing - a feature in the route guidance that takes into account the specific characteristics of an electric vehicle. The navigation system continuously calculates the real energy consumption into routing. In tests it turned out that energy-optimised routes reduced the energy consumption by up to 30%. However, these optimised routes affected the driving time - it took the cars up to 14% longer to get from A to B. Shortcuts in city traffic had a particularly energy-saving effect.

It is generally accepted that anticipatory driving is the best method to reduce fuel consumption. Based on this insight, the Adaptive Cruise Control (ACC) algorithm was optimised for an energy-saving driving style. In addition, improved navigation data provided information as to ascents, descents, and speed limits, and the vehicles communicated with the traffic lights to know id advance at which speed they would encounter a green traffic light. All these data were aggregated and formed an "electronic horizon", enabling the engineers to further optimise ACC and the soaring function. The latter informs the driver as to when to take the foot off the gas pedal ahead of speed limits or built-up areas. To make the best use of the vehicles momentum, the transmission was switched to idle during soaring phases.

Even the HMI concept was affected; the researchers felt that an intuitive human-machine interface and a programmable instrument cluster facilitated the readability of relevant information. Thanks to