Old windows with the wind whistling through? Thin brick walls or even an uninsulated roof? Energy consultants give homeowners and landlords tips about where energy is being lost unnecessarily and about which measures to adopt to save electricity and heat. On the trail of energy loss, Mercedes-Benz also benefits from the assistance of an energy consultant: the "energy-transparent vehicle" provides a detailed picture of the flow of energy throughout the vehicle.

At an early stage in the development process, an S 400 HYBRID was fitted with more than 300 measurement points across the drive system and on-board electronics and the analysis software was programmed. The prototype then completed hundreds of test cycles, allowing Mercedes-Benz engineers to observe the engine, transmission, hybrid system and all consumers in real time. "We meticulously conducted an analysis of every aspect of energy flow," says Christoph Müller, head of the consumption team, explaining how this innovative development tool is used. "That is the only way we are able to realise our aspiration to lead on efficiency in all power categories."

The "energy-transparent vehicle" development tool was created in-house by Mercedes-Benz. It can detect the possibilities for optimisation in even the most minute component, thereby making a major contribution to improving efficiency. An exact and meticulous examination of the flow of energy 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 than its predecessor is ultimately the result of a variety of measures and the painstaking work of our development specialists," adds Müller. His colleague Roland Lütze looks back: "The idea for the energy-transparent vehicle came about in 2009, working on the ML-Class. In 2011, we built on the methodology further to create the first energy-transparent hybrid." For five years, Lütze has been the driving force and "energy consultant" at Mercedes-Benz Cars and is responsible for analysing losses and optimising CO2 emissions. "The need for the energy-transparent hybrid stemmed from the failure in the past to verify or demonstrate clearly the many factors affecting consumption and the interaction between fuel-saving measures, especially for hybrid vehicles." It is now possible to detect detailed potential optimisation measures by breaking down energy flows into cause and effect and analysing energy interactions, including between the combustion engine and electric motor.

The process for the energy-transparent hybrid 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.

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 case of the S 400 HYBRID, the energy-transparent hybrid was used to optimise the management of braking energy, for example: "The issue was how to best distribute brake power between the conventional hydraulic wheel brake and the additional electrical brake power on a hybrid provided by the electric motor when it's working as a generator. Thanks to the energy-transparent hybrid we found the right answer for a range of operating conditions," continues Lütze. Christoph Müller adds that "It was exceptionally important to us to cover the entire spectrum of the way customers drive worldwide – from winter in Sweden to driving on an American highway at 35°C. We always focused on understanding which vehicle component was consuming what and when. It involved a lot more than looking at the New European Driving Cycle (NEDC)!"