Sounds like a stupid question, right? Many of you are probably screaming out loud, “light weighting for electric vehicles is 100% about increasing the range of the vehicles.” But before you skip the rest of this, give me a chance to elaborate.
As the topic of electric vehicles becomes more common place and the forecasted production numbers over the next 10 years are regularly being raised, the discussion around increased vehicle range has taken a front seat in many of our conversations with suppliers and OEMs around the world. This is occurring for two major reasons: first, the infrastructure for charging stations still vastly lags behind the capability to produce vehicles – meaning longer range vehicles require fewer charging stations. Second, trying to match drivers’ behavior around internal combustion engine vehicles.
The trap in which we can get caught when discussing vehicle range is shifting the narrative in the direction of batteries, and that technological advancements in this area will achieve targeted vehicle ranges and eliminate the need for light weighting.
If we look at a study performed by the US Department of Energy comparing the average total emissions for vehicles operated in Detroit, Michigan, you will notice two things: first, the emissions associated with operating an e-vehicle are not zero. This is due to the emissions associated with producing and distributing the electricity. Second, the estimated emissions vary by vehicle like their ICE counterparts, where larger vehicles still consume more energy and produce more emissions per mile than smaller, lighter-weight, more efficient vehicles.
From this data, we can determine that even if two different vehicle types, such as Ford Fusion and BMW 530e, have the same range, each is operating at different efficiency levels, consuming different KW/mile. Sound familiar?
While there are many ways we can improve overall vehicle efficiencies, reducing mass has the potential to impact every component on the vehicle. Some of you may be thinking; “What about regenerative braking?” Won’t a vehicle’s additional mass simply translate to increased energy recovered through additional regenerative braking re-charging the vehicles batteries? We have run into this flawed argument a number of times. While in principal, additional mass will drive higher kinetic energy values, state of the art regenerative braking systems employed in EV/HEV have average recuperation efficiencies well below 50% across all speed ranges (e.g. Highway, City). A range of capacity factors including battery current, inverter and electric motor sizes all significantly limit the ability to recuperate kinetic energy in the form of increased battery charge.
Reducing and managing vehicle mass, while maintaining electrical system powertrain size, translates to more opportunities to extract maximum energy recovery before exceeding the capacity of the batteries, inverter and electric drive/regen motor(s), driving up overall vehicle efficiency.
The conversation around light weighting started with achieving defined miles per gallon targets – vehicle operating efficiencies. The conversation could have started by saying that all cars with 20-gallon tanks needed to achieve a range of 800 miles, but instead, we used the common metric defining operating efficiency: miles per gallon.
Today, the same light weighting conversation holds true for vehicles: defining performance targets not in terms of range, but kW/mile. When we allow the conversation to be strictly about vehicle range, we lose the narrative and potential to make an impact through light weighting. We should, rather, begin speaking in terms of efficiencies and the value that products, materials or technologies can deliver to increase “E”(electric) efficiencies.
Adam Harms – Managing Partner, Ruhl Strategic Partners
As appeared in Lightweighting World.
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