So where is the energy in fuel used in urban driving vs highway driving?
How much of each type of driving is done on average?
ie: On average; is vehicle's weight more important than it's aerodynamic drag, because it spends most of it's time doing urban commutes?
Is that why most car manufacturers haven't bothered flat undersides and boat tails etc?
Because the extra weight (and inconvenience) they add actually increase the fuel consumption of their cars, on average..?
Then, to muddy the waters: What effect does the energy recuperation during regenerative braking actually have in EVs?
My initial research points to the overcoming of inertia during acceleration as being the main consumer of fuel in cars:
Fundamentals of Fuel Consumption
National Academies of Sciences, Engineering, and Medicine. 2011. Assessment of Fuel Economy Technologies for Light-Duty Vehicles. Washington, DC: The National Academies Press. https://doi.org/10.17226/12924.
"...To illustrate the dependence of tractive and braking energy on vehicle parameters, Sovran and Blaser (2006) used the following three sets of parameters. Fundamentally the energy needed by the vehicle is a function of the rolling resistance, the mass, and the aerodynamic drag times frontal area. By combining the last three into the results shown in Table 2.4, Sovran and Blaser (2006) covered the entire fleet in 2004. The “high” vehicle has a high rolling resistance, and high aerodynamic drag relative to its mass. This would be typical of a truck or an SUV. The “low” vehicle requires low tractive energy and would be typical for a future vehicle. These three vehicles cover the entire spectrum in vehicle design.
The data shown in Table 2.5 were calculated using these values. The low vehicle has a tractive energy requirement that is roughly two-thirds that of the high vehicle. It should also be noted that as the vehicle design becomes more efficient (i.e., the low vehicle), the fraction of energy required to overcome the inertia increases. As expected, for both driving schedules the normalized tractive energy, ETR /MS, decreases with reduced rolling and aerodynamic resistances. What is more significant, however, is that at each level, the actual tractive energy is strongly dependent on vehicle mass, through its influence on the rolling and inertia components. This gives mass reduction high priority in efforts to reduce vehicle fuel consumption.
The numbers for "low" vehicle:
In the UDDS (urban) driving cycle: (98% of driving)
Rolling Resistance (%): 19
Aerodynamic Drag (%): 14
Inertia (%): 68
In the HWFET (highway) driving cycle: (2% of driving)
Rolling Resistance (%): 29
Aerodynamic Drag (%): 47
Inertia (%): 24
https://nap.nationalacademies.org/re...4/chapter/4#20
For EV's and recuperation from regen I have found this so far:
The amount of energy an EV recovers through recuperation depends on a few key things. Heavier vehicles may consume more energy to accelerate, but their momentum helps them generate more electricity during braking.
Similarly, electric motors with higher power ratings are better at converting braking energy back into electricity.
Additionally, the best time to maximize recuperation is in city driving.
Constant stopping and starting gives the system lots of opportunities to recapture energy. Recuperation is less effective on highways with their consistent speeds and limited braking.
To illuminate these factors, the German automobile club ADAC conducted a fascinating experiment.
They tested three EVs - the nimble Dacia Spring, the luxurious BMW i7, and the best-selling Tesla Model Y Long Range - on an uphill and downhill route.
Not surprisingly, the hefty BMW i7 came out on top in downhill energy recovery.
However, the lighter Dacia Spring turned out to be the most efficient overall during the mountainous journey.
This underscores the delicate balance between energy consumption and recuperation – while heavier EVs may recover more, they also need more power to move in the first place.
Beyond mountainous routes, how do EVs fare in regular driving? Data from Green NCAP reveals that - on average, an EV recaptures around 22% of its driving energy through recuperation. Standout EVs like the Nio ET7 and Hyundai Ioniq 6 boast impressive figures of 31% and 29%, respectively.
While recuperation partially offsets the energy penalty of heavier EVs, it emphasizes the potential of lightweight construction.
Innovative materials and designs hold the key to maximizing EV efficiency.
Reducing a vehicle's weight is similar to giving your EV a continuous energy boost, both when accelerating and while using recuperation.
https://www.arenaev.com/road_test_re...-news-3326.php
So when you boil it down; light weight wins out over adding weight to improve aerodynamics for the average car, doing the average commute?
That would explain why manufacturers don't generally bother with the added weight (and inconvenience) of flat undersides and (unparkable) boat tails etc..?
I'd like to keep this about the science/research rather than 'knee jerk' opinion, so plz do link 'the research' when posting.
I'll post more links either way as I find them.