The Importance of Aero Efficiency in EVs: Lessons from Revolutionary Vehicle Designs
Sometimes it takes time for people to appreciate truly innovative designs. Just as many of the greatest composers and visual artists of all time were not fully appreciated during their lifetimes, the most aerodynamic vehicles were not always popular with buyers either.
Streamlining was initially employed by Land Speed Record (LSR) racers as a means of reducing air resistance and achieving faster speeds. This approach gained popularity in the early 20th century and culminated in 1899 when the electric-powered ‘La Jamais Contente’ (The Never Satisfied) became the first automobile to break the 100 km/h barrier. As engines became more powerful and cars could more easily achieve highway speeds, the focus of aerodynamic design shifted towards improving fuel efficiency.
Although enhancing a vehicle's aerodynamic efficiency is important for various reasons, the final outcome does not always produce a design that is favored by potential buyers of the vehicle. One really good example of this is with the 1934 Chrysler Airflow, the first American car to be designed aerodynamically in a wind tunnel. This design improved the high speed stability and the efficiency of the vehicle was improved, but it didn't sell very well. Buyers weren’t impressed with the radical shape and looks of the car.
Since then, several cars have focused on aero engineering, and many have failed to succeed. One of them was the General Motors EV1, a lease-only experimental electric vehicle from the 1990s with a remarkable drag coefficient of 0.19, resembling a UFO. The car's entire production run was repurchased and destroyed. The 2013 Volkswagen XL1, a diesel-powered hybrid with carbon-fiber construction and butterfly-wing doors that returned 260 MPG, was produced in a limited run of only 250. Perhaps the Toyota Prius is the most successful example of an aero-first design, as it is highly popular, efficient, and its exterior is also often subject to harsh criticism.
In today’s automotive world, the focus on aerodynamics is evident in nearly every vehicle on the road. From the overall shape of the vehicle to the design of the wheel wells, manufacturers are focused on making their vehicles more efficient to meet ever increasing government standards from around the world. Owners themselves have been doing this for years as well. These owners, called “ecomodders”, have seen really impressive results.
One notable example of an owner modifying their vehicle for maximum efficiency was the ‘EcoCivic’ project by none other than yours truly. My project was based on a 2003 Honda Civic and I was working towards a goal of achieving more than 100 mpg. While falling short of this goal, the project achieved an impressive 83 miles per gallon on the highway, largely due to the modifications made to the car's aerodynamics. While modifying the aerodynamics of the Civic yielded the most significant improvements, it made the car look really weird, and not in a “good weird” way. Nevertheless, the EcoCivic project demonstrated the potential for significant improvements in fuel efficiency through careful modifications to the vehicle's design.
The Importance of Aerodynamic Efficiency with EVs
As electric vehicles (EVs) become more prevalent on our roads, the importance of aerodynamics in their design is increasingly emphasized. Unlike traditional gasoline-powered vehicles, EVs rely solely on electric motors for propulsion and are powered by batteries, which means that any inefficiency in their design can have a significant impact on their range and overall performance.
One of the biggest challenges faced by EV manufacturers is to increase the range of their vehicles while keeping the battery size and weight in check. Aerodynamics plays a crucial role in achieving this goal by reducing the energy required to move the car through the air. A more streamlined vehicle design means less air resistance, which translates to less power needed to maintain speed and less energy wasted as heat. In other words, the more aerodynamic an EV is, the smaller the battery needs to be. A great example of an EV that is horribly efficient would be the GMC Hummer EV. In order to achieve a range similar to competitors, the Hummer EV is fitted with a battery that is twice the size of many other long-range EVs, and as heavy as a smaller car itself weighing in at more than 2,000 lbs!
Moreover, aerodynamic design also affects the efficiency of the EV's regenerative braking system. Regenerative braking, a feature common in many EVs, converts kinetic energy into electrical energy, which can then be stored in the battery for later use. However, the efficiency of this process depends on how much kinetic energy can be recovered during braking, which is influenced by the aerodynamic design of the vehicle. A poorly designed vehicle with high air resistance will experience more friction during braking, resulting in less energy recovered.
Aerodynamic Design Elements in EVs
One key design element in electric vehicles is the flat underbody. This helps to reduce drag by smoothing out the air flow underneath the vehicle, which is especially important at high speeds. Another important feature is smooth wheel covers, which help to reduce turbulence around the wheels and improve overall aerodynamics.
Active grille shutters are also becoming more common in electric vehicles. These shutters can open and close automatically to control the flow of air through the front of the vehicle, improving aerodynamics and reducing drag. Other design elements that are important in electric vehicles include tapered rear ends, flush door handles, and well-designed side mirrors.
Many electric vehicles on the market today have excellent aerodynamic design, with some models achieving industry-leading levels of efficiency. For example, the Tesla Model S has a sleek and aerodynamic shape with a low coefficient of drag (Cd) of 0.208, making it one of the most aerodynamically efficient production cars ever made.
While the Model S, and most other popular electric vehicles have shown to implement significant aerodynamic improvements to achieve greater range and efficiency, this is quickly becoming the norm in the industry and there aren’t too many manufactures that are truly pushing the boundaries of possibility. One standout exception is the three-wheeled solar electric vehicle from Aptera.
Pushing the Boundaries (Again)
Aptera, a California-based start-up recently resurrected in 2019, is set apart from most EV makers in their unwavering commitment to aero efficiency to increase speed, range, and overall efficiency performance.
Aptera's flagship model is a three-wheeled EV that looks more like a futuristic airplane without wings than a car. In fact, the name ‘Aptera’ comes from the ancient Greek word ‘apteron,’ which means ‘wingless.” The body shape is characterized by a teardrop profile that minimizes drag, while the rear wheel is enclosed to further reduce turbulence. The vehicle also has a flat underbody and a narrow frontal area, which contribute to its exceptional aerodynamics.
According to Aptera, versions of the vehicle will have a drag coefficient of only .13 and, when paired with the largest battery pack, will achieve a range of up to 1,000 miles on a single charge, which is more than double most of the current longest-range EVs on the market (the Lucid Air being the exception with more than 500 miles of range). The vehicle can also accelerate from 0 to 60 miles per hour in as little as 3.5 seconds, making it a formidable performer despite its unconventional design.
Although Aptera's focus on aerodynamic efficiency is commendable, it's important to acknowledge that, like other revolutionary vehicles before it, some potential buyers may find its teardrop shape unusual or unappealing. However, this shouldn't detract from the fact that the innovative design features of the Aptera are likely to influence the industry as a whole. It's highly probable that we will see an increase in future electric vehicles with exceptional aerodynamic efficiency, which will ultimately benefit all consumers.
It is clear that vehicle aerodynamics has had a significant impact on the automotive industry throughout its history. While pushing the boundaries of what is possible in any given time period can lead to revolutionary designs, it can also have negative effects on the marketability of a vehicle. Nonetheless, it is important to recognize the crucial role that these vehicles have played in advancing the industry as a whole.
By constantly pushing the limits of aerodynamics, engineers and designers have been able to create more efficient and faster vehicles that continue to shape the future of transportation. As we move forward, it is exciting to think about the possibilities that await us in the world of vehicle aerodynamics.
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