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IFEU Heidelberg


3 Goal and scope definition

The objective of this literature study is to determine the energy and CO2 emis- sion savings by weight reduction for the whole operational life-time of selected transport vehicles. Therefore, the energy savings for single vehicles as well as the life-time energy savings for the annual new registrations of a whole country (Germany has been selected for exemplification) have been analysed.

The energy savings for a single vehicle directly depend on the specific energy savings by weight reduction and the life-time performance of the vehicles. Both variables are also influenced by a number of sub-parameters a selection of which are listed in Fig. 1. For the energy savings of the annual new registrations, a relative weight reduction of

10 % was assumed.

Fig. 1: Important Parameters of the life-time energy and CO2 savings

Life-time energy/ CO2 savings =

Specific energy/ CO2 savings


Life-time performance

  • Use pattern (driving cycle)

  • Durability of the vehicle

  • Driving behaviour

economical, etc.)


  • Daily performance

  • Resistance factors

  • Possibility for revision/

re-use of components

  • Tank-to-wheel efficiency

  • Efficiency of energy


  • Climate


  • CO2 intensity of used fuels

(coal, petrol, etc.)

Source: IFEU 2002

IFEU 2003

Other specifications, like the power to weight ratio of the vehicle, change with the weight of the vehicle. This means that the performance of the original vehicle and thus the functional unit is not maintained. This is not as important for cargo vehicles, which are designed to carry their maximum load, as it is for passenger vehicles. For these vehi- cles adjustments to the new power to weight ration maintain the performance of the original vehicle and therefore conserve the functional unit. This effect has been taken into account for passenger cars only. No data, however, is available for other passenger vehicles like buses and passenger trains. The performance of these vehi- cles will improve by a weight reduction and the full energy savings can not be achieved. Though this effect is hardly significant for a 100 kg weight reduction in the heavier vehi- cles, it may be of importance e. g. for a 10 % weight reduction of passenger trains.

With road and rail vehicles we are comparing two different transport systems. While most road vehicles are defined units with good data for the average weight and energy consumption, trains are composed of locomotives as well as rail cars. The total weight, energy consumption and energy savings can therefore be very different. In contrast to the specific fuel savings in l/ (100 km*100 kg) for the well defined road vehicles, we will

Energy savings by light-weighting

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