Renault: When It Comes to EV Efficiency, Aerodynamics Are More Important Than Weight

DEC 23 2013 BY ERIC LOVEDAY 16

Aerodynamics Are Key to EV Efficiency, Says Renault

Aerodynamics Are Key to EV Efficiency, Says Renault

Renault head of research, advanced studies and materials, Remi Bastien, doesn’t think that reducing weight is as important for EVs as aerodynamics.

Is Black the Most Aerodynamic Color?

Is Black the Most Aerodynamic Color?

As Bastien told Auto Express, the BMW i3’s lightweight structure is mostly for performance gains, not for efficiency.  Bastien says that weight definitely hurts efficiency of ICE vehicles, but not so much when it comes to EVs.

The argument Bastien is trying to make is that Renault could develop an ultra-lightweight EV, but the buyer wouldn’t necessarily see the benefits, aside from performance, which isn’t a core value for Renault.

“Reducing weight is important for petrol and diesel cars, but less so for EVs – aerodynamics is more important for efficiency in electric vehicles. Weight can be used to help regenerative braking in an EV to harvest more kinetic energy when slowing down.”

“I think the main reason BMW uses lightweight carbon fibre on the BMW i3, for example, is because of performance, because of what the brand stands for – not necessarily for efficiency.”

Several comments have been made of the BMW i3’s expensive carbon fiber construction.  Was it done just to boost performance?  Or was BMW hoping to increase efficiency with its use of lightweight material too?  Bastien’s comment seems to suggest that if BMW’s intent was to increase efficiency, then perhaps more focus should have been placed on the vehicle’s aerodynamics, not on its weight.

Despite the i3 low-for-a-BMW price tag, we can’t help but wonder if it would cost i3 buyers $10,000 less if carbon fiber wasn’t used throughout.

Bastien’s comments hint that any future Renault EVs will focus heavily on aero, as we see in the Nissan LEAF and to somewhat less of a degree in the Renault Zoe.

BMW i3's Costly Carbon Fiber Components Are Mostly There for Performance, Not Efficiency, Says Renault.

BMW i3’s Costly Carbon Fiber Components Are Mostly There for Performance, Not Efficiency, Says Renault.

Source: Auto Express

Categories: Renault

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16 Comments on "Renault: When It Comes to EV Efficiency, Aerodynamics Are More Important Than Weight"

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Mikael
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Mikael

Then why don’t they put in a 50 kWh pack and see how that feels in the Zoe…

Warren
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Warren

“Renault EVs will focus heavily on aero, as we see in the Nissan LEAF and to somewhat less of a degree in the Renault Zoe”

Eric,

If you see a heavy focus on aero in any current EV, you have x-ray vision. My fifty year old Saab 96 had a CdA about as good as any current EV….not Cd but CdA…the number that matters.

KenZ
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KenZ

I think a large part, although I’m sure not all, of the reason BMW did CF for the i3 is, as a low volume niche vehicle, it was the PERFECT platform with which to learn and practice CF technology in automobile manufacturing. It would have been incredibly risky, and expensive, to try to start one of their mainstream lines with CF for a new model year. With the i3, it’s OK if they lose some money of the CF part, and it’s OK if they get a bunch of hiccups that delay the vehicle. And, by the time they get all the wrinkles ironed out, they’ll have a damn good idea of what components should and shouldn’t be made in CF, what the tradeoffs are, and how to manufacture them reliably in volume. Again, the i3 was the perfect test platform for them.

Priusmaniac
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Priusmaniac

Honestly I think CF is a bridge too far on a car that is already the very first to introduce the EV + Rex system.
A more conservative aluminum use would have been more appropriate.

Dr. Kenneth Noisewater
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Dr. Kenneth Noisewater

Weight matters for acceleration and performance at lower speeds, CdA matters for higher speeds.

(Weight also matters for manufacturing/logistics/etc. though that doesn’t really affect the consumer as much aside from any costs related to those processes)

Gene
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Gene

“Weight can be used to help regenerative braking in an EV to harvest more kinetic energy when slowing down.”

Uh…didn’t it require more energy to accelerate that weight to that speed before slowing down? At best, this is a moot argument (in = out), but in reality, inefficiencies mean this argument is actually reversed.

Gene
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Gene

…but, OK, relative to a vehicle without any regen braking, the energy cost of accelerating extra weight is partially cancelled by regen. I buy that.

Mint
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Mint

Exactly. It’s all about marginal effect. Weight has a lower marginal penalty on efficiency in EVs and Hybrids due to regenerative braking. The same is true for weight’s effect on performance, because it costs less to add 20% power to an electric drivetrain than to an ICE.

Jeff
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Jeff

@Gene

I think you misinterpreted his point re: weight and regenerative braking.

He’s not saying that extra weight doesn’t reduce overall efficiency in EV’s. He’s just saying that extra weight doesn’t hurt EV’s *with regenerative braking* AS MUCH as it hurts ICE cars *without regenerative braking*.

The guy definitely could have worded it more clearly though.

Jeff
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Jeff

@Gene.

Ha. You beat me to it. 😀

James
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James

I believe that is why Ford is altering the 2014 CMax. The improvements they are making to try to get back to 47 MPG is in aerodynamics.

Dave R
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Dave R

Got any more info on the ’14 CMax changes that Ford is working on? It’s very clear that it’s no where close to a Prius in terms of aerodynamics with a simple glance.

Anon
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Anon

Edison2 (X Prize winner) was working on BOTH Light Weighting and Aero… Haven’t heard much about them lately. 🙁

Warren
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Warren

Yes. Obviously the way to go. But people won’t figure that out until it is too late. Then they will wish they could still afford a bicycle.

Suprise Cat
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Higher weight requires larger tires, BMW i3 and Mitsubishi i-Miev have both significant smaller tires than all other EVs due their lower weight.

Steve
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Steve

Also with the single speed transmission high speed efficiency sacrificed. Aero gains are necessary to counteract this.