In search of lost energy.
Transparent energy flow.
Old windows that let the wind whistle through? Thin walls, or even an uninsulated roof? Energy consultants give homeowners and builders advice on where energy is unnecessarily wasted, and tell them which measures will allow them to save energy. Mercedes-Benz is likewise helped by an energy advisor when searching for lost energy: The “energy-transparent vehicle” (ETV) reveals the energy flows in a vehicle down to the last detail. During the development, an S 400 HYBRID was equipped with 300 measuring points in the powertrain and onboard electronics, and analytical software was programmed. Then it was subjected to hundreds of test cycles. This meant that the Mercedes-Benz developers were able to observe the energy flows in the engine, transmission, hybrid system and all electrical loads in real time.
“We painstakingly conducted analysis into the last nook and cranny”, says Christoph Müller, head of the consumption team. “Only in this way can we substantiate our claim to be the leader in efficiency in all performance classes.”
Energy consumption in real time.
The “energy-transparent vehicle” is an in-house development by Mercedes-Benz, and is able to detect improvements down to the finest detail. The ETV therefore contributes decisively to improved efficiency. An exact and meticulous examination of the energy flows throughout the vehicle (tank-to-wheel) helps the development engineers to optimise every single assembly that has an impact on fuel consumption, right down to individual components such as wheel bearings. “The fact that the new S-Class consumes up to 20 percent less fuel than its predecessor is the result of numerous measures, plus the painstaking work of an expert development team”, says Müller.
His colleague Roland Lütze looks back: “The idea for ETV began in 2009 with the ML-Class, and in 2011 we developed the approach further and produced the world’s first ETH (energy-transparent hybrid).” Lütze has been the driving force for five years, the “energy advisor” at Mercedes-Benz Cars, who is responsible for loss analysis and CO₂ optimisation.
Precise energy data, even from the hybrid.
“The need for ETH in particular results from the fact that in the past, many consumption effects and interactions between fuel economy measures could not be definitely verified or proven with hybrids.” Using ETH, improvement potentials are now precisely recognised, the energetic inter-dependencies can be examined and the mutual effects of the internal combustion engine and electric motor can be analysed. The ETH process draws on complex, highly precise metrology which records some 300 energy-relevant measurement points with a sampling rate of up to 1000 measured values per second. Every minute some 2.4 million measured values are generated, which can subsequently be analysed to reliably pinpoint optimisation potential.
The process is complemented by energy simulation models which are validated by means of the measured variables. This enables the energy efficiency of individual major assemblies and components as well as the entire vehicle to be analysed and quantified.
Optimization in every range.
Once the specialists have identified a vehicle component with energy shortcomings, they team up with the relevant specialist departments to devise solutions. This cooperation focuses on design, or the properties of the materials used in individual vehicle components such as wheel or axle bearings. In addition, modified control strategies can also produce the desired outcome. In the S 400 HYBRID, for example, ETH was used to determine the best possible control for the braking system: “The question was how best to distribute the braking power between the conventional hydraulic wheel brakes and the electric braking effect of the hybrid’s motor when acting as a generator. Thanks to ETH we found a suitable answer for numerous driving situations”, says Lütze.
Worldwide good performance.
Christoph Müller adds: “It was important for us to cover the entire breadth of customers in different regions of the world – from the Swedish winter to driving on an American highway at 35°C. Our focus was always on understanding which vehicle component causes what fuel consumption, and when. So we are not only looking at the New European Driving Cycle (NEDC)!”