VDI study on the life cycle assessment: dead race

VDI study on the ecological balance
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Fueled with synthetic fuel, the diesel wins the CO2 competition

© press-inform – the press office

The automotive future is electric. Correct? Not so fast. A study by the VDI shows that the electric vehicles are not always the best when it comes to the ecological balance over the life of a car. If a diesel is filled with synthetic fuel, the environmentally friendly pendulum swings in its direction.

The life cycle assessment drives the automotive industry. Manufacturers such as BMW or Mercedes want to significantly reduce the CO2 emissions of their vehicles in the medium term. The people of Munich even link board salaries to the achievement of these goals. It’s not just about driving, but of course also about production. How do the electric vehicles compare to diesel or fuel cell cars? The Association of German Engineers (VDI) has addressed this situation in a study. That leads us to the test subjects: The study focuses on compact-class vehicles such as the BMW i3 or the e-Golf, which enter the ring for the battery-electric fraction. The battery size is defined as 48 to 82 kilowatt hours. The batteries are not changed during the running performance. A car with a diesel engine and one with a fuel cell are used as a comparison. All kinds of hybridized drives are outside. The experts set a maximum mileage of 300,000 kilometers according to the WLTC cycle. The electricity mix on which the greenhouse gas / CO2 emissions are based when refueling corresponds to that in Germany.

The analysis of the various drive concepts takes place under certain parameters. The battery size and the resulting CO2 equivalents during production, which are often summarized in the term “craddle to craddle”, are very important. In other words, the ecological balance of a battery over the entire life of the car, which includes production and recycling, among other things. In contrast, the authors of the study did not take charging losses into account. The deviations in real consumption from the manufacturer’s information are also indicated, but not detailed down to the last detail.

The production of the battery-electric vehicle or the battery must also not be neglected in the energy balance. BEVs currently have the main disadvantage of high energy and material consumption in production. Consequently, extensive and energy-saving battery recycling is an important key to the best possible ecological balance. If you now look closely at the various vehicle concepts, you will notice that the electric car is already shouldering 60 percent of its CO2 backpack through production. Based on an annual mileage of 12,000 km, a consumption of 15.8 kWh / 100 km, a battery capacity of 48 kWh and the current electricity mix, the vehicle needs twelve years before the 100 percent mark is reached (production of battery cells in China and Assembly of the car in Europe).

But there is light at the end of the tunnel: In the next few years, the production backpack caused by the batteries will decrease. One measure that should improve this CO2 balance in the medium term is to improve the battery cells. The introduction of NMC622 cells and the development of NMC811 cells with a significantly reduced cobalt requirement and up to 50 percent improvement potential in gravimetric energy density represent real opportunities for battery-electric drives to achieve significantly better results in the life cycle assessment.

How do the electric vehicles perform over the life of the car in terms of the CO2 balance compared to fuel cell vehicles and diesel? “The CO2 emissions caused by the usage phase depend largely on the efficiency of the drive and the CO2 backpack of the energy source,” explains Professor Thomas Koch. With a consumption of 17.6 kWh / 100 km (batteries from China, assembly in Europe), the CO2 balance of the BEV is only reached at 300,000 kilometers from the diesel (filled with B7 fuel, consumption: 4.5 l / 100 km) . Thrift pays off here. If the BEV reaches a consumption of 15.8 kWh / 100 km, the CO2 balance lines of the three drive concepts meet at around 130,000 kilometers. It is obvious that this CO2 balance does not improve with a larger battery.

However, this sequence should improve in the future in favor of the BEV if the electricity mix in Germany changes (minus 40 percent CO2 equivalents by 2030) and cell production in China or the EU is less CO2 intensive. It is noticeable that fuel cell cars (consumption 0.76 kg / 100 km) perform well over the entire life cycle and remain constantly close to the BEV (15.8 kWh / 100 km).

One lever on how the CO2 balance of all drives can be improved is the so-called defossilization of the respective energy carrier: This involves the power supply, hydrogen supply and fuel supply. At some German petrol stations you can already get diesel fuel with 33 percent regenerative content, making the combustion engine even more competitive. The diesel engine becomes the clear winner in the race for the cheapest CO2 balance if it is filled with synthetic fuel.

“The same applies to all drive concepts that the efficiency of the drive is an essential element on the way to CO2-neutral mobility, detached from the drive concept”, states Thomas Koch and adds “A complementary combination of technologies is the only chance that CO2 Goals for 2030 to be achieved. ”


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