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IFEU Heidelberg

9 Conclusions

The purpose of this study is to provide an overview on the potential energy savings by a weight reduction of road and rail vehicles. The life-time primary energy savings mainly depend on the specific primary energy savings and the life-time performance.

Though there are considerable differences between the vehicles and within the vehicle categories, the best available data for typical vehicles have been identified and com- pared. Even with the sensitivities taken into account several trends can be identified. For an absolute weight reduction the main findings are:

The life-time energy savings by 100 kg weight reduction are higher for rail vehicles because of the high life-time performance.


  • Among the road vehicles city buses show outstandingly high life-time en- ergy savings mainly due to the combination of a high life-time performance and high specific energy savings.

  • Among the rail vehicles the short distance trains show high energy savings despite their lower life-time performance in comparison with long distance trains. This is because of their much higher specific energy savings.

  • Some vehicles have a life-time performance very different from the aver- age vehicle in the respective category and may therefore have a high potential for energy savings as a subcategory, like taxis.

Generally, the same findings are true for life-time CO2 emissions. However, in addition, the structure of the energy supply, e. g. the carbon content of the fuels and the share of regenerative primary energy carriers have to be considered. This introduces a further country-specific parameter. Generally, road vehicles will increase the CO2 saving potentials compared to the primary energy savings due to the lower CO2 factor per primary energy unit for electricity production.

For the potential energy savings of vehicle categories, the total energy consumption of the categories becomes of increasing importance. Furthermore it has to be taken into account that it in many cases, a higher absolute weight reduction can be achieved in heavier vehicles. This implies that high total energy savings can be mainly achieved by vehicles with a great total share of the energy consumption, like passen- ger cars. The change in the share between total energy consumption and total energy savings is determined by the relation of net weight to gross weight and the relative en- ergy savings. The share increases for short distance passenger trains and decreases for long distance road vehicles like buses and trucks.

Especially for the life-time performance, data are scarce and may be very different even within the vehicle categories and different countries. This has been visualised by sensitivity ranges in several charts. Despite data uncertainties and great variations, the presented data is believed to provide a solid overview of the average situation. For special vehicles or uses as well as countries with highly specific circumstances which differ from the average adjustments in the individual parameters should be taken into account.

Energy savings by light-weighting

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