Conference Presentation Summary

Hybridization of heavy-duty vehicles for meeting European CO2 standards

Reference: Cummins 45th International Vienna Motor Symposium 2024

CO2 standards are getting tighter for both light- and heavy-duty vehicles. We have previously covered the recently revised European standards for heavy-duty (HD) vehicles, which require a 45% reduction in CO2 emissions by 2030, increasing to 65% by 2035 and 90% by 2040. These standards are clearly set with a view of encouraging adoption of zero tailpipe emitting vehicles. Still, in principle they are technology neutral and can be met through a combination of advanced internal combustion engine technologies as well.

 

Hybridization is seen as a powerful tool to reduce CO2 emissions without the need to add large batteries. This is especially popular in the light-duty (passenger car) segment which is seeing a significant increase in market share lately (in Europe and US). Hybridization has not been applied to the same extent in HD vehicles – likely due to the higher share of high-speed on-highway driving (energy recovery with hybrids is especially beneficial for transient driving), and the cost-benefit considerations.

 

Now, with these stringent standards being promulgated, hybridization is being evaluated for HD vehicles as well. Cummins presented their theoretical study on this topic at the recent Vienna Motor Symposium. Here’s a summary.

 

 

The baseline vehicle considered for the study is a “5LH” category, 4 x 2, articulated tractor, with a Cummins Euro 7-capable X10 450 hp diesel engine. A previous publication by ACEA concludes that 5-LH vehicles account for 63% of sales and 68% of HD CO2 emissions in Europe.

Comparison of CO2 emissions were made between the baseline conventional vehicle and a “P2” parallel hybrid configuration, as shown in the figure.

Simulations were done for varying battery sizes, ranging from 25 kWh to 200 kWh. As seen in the summary plot here, the study showed that CO2 reduction of 20% was obtained with a 75-kWh battery, beyond which the reduction was marginal when using a 100-kWh battery pack. The 200 kWh battery results in a further reduction, but that is almost the size of a battery electric vehicle (BEV) pack.

 

Perhaps more interesting are the projected changes that imply for the extent of BEV share, to meet the CO2 targets. As shown by the dashed lines, meeting the 2030 CO2 limit will require a 27% BEV share, which reduces to 5% when hybrids with a 100-kWh battery are included. The 2035 share of BEVs reduces from 53% to 27%.

Of course there are cost implications of adding a battery, and these are compared as well. The battery pack cost is assumed to be 115 euros/kWh in 2030, reducing to 80 euros/kWh by 2035. The cost effectiveness is calculated in terms of Euros per grams of CO2 per ton-km avoided. As seen, the smaller battery provides the best CO2 reduction per incremental cost – but of course the total CO2 avoided is limited. The BEV, on the other hand has a higher cost per ton of CO2 removed but can provide an effective tool for meeting the CO2 targets. Interestingly, by 2035, with the reduction in battery cost, it is projected that BEVs are most effective in terms of both the normalized (to battery size) cost as well as the CO2 reduction delivered.

Concluding Remarks

This study shows that there is a role for hybrids in the heavy-duty sector, especially in in the coming decade. These can help offset the market share growth of BEVs, which could be constrained by infrastructure challenges.

While beyond the scope of the study, it is clear that the combination of such hybrids with a renewable fuel would further deliver deep well-to-wheel CO2 reductions. 

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