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Sunday, April 14, 2024

How the ‘Dead Zone’ Could Help This Car Take on Tesla

When Lucid Motors unveiled an all-electric concept car called the Air in 2016, the company claimed it would have a range of 500 miles and supercar-like performance. (And, in fact, a prototype shredded a test track the next year, hitting 235 miles per hour.) But many startups have unveiled electric concepts over the past decade, all aspiring to beat Tesla in both range and efficiency, while few have crossed the finish line and actually entered production.

However, Newark, California–based Lucid might just be the one to do it. The production version of the Lucid Air sedan that debuted in September arrives on seemingly solid corporate footing—thanks largely to a billion-dollar investment from Saudi Arabia—and with a new factory in Casa Grande, Arizona, that is already cranking out production cars for eventual sale early next year. (The Dream Edition model will arrive first, selling for $169,000, with three progressively less expensive models rolling out over the following 12 months, the cheapest at $77,400, or $69,900 with the Federal tax credit.) In terms of hitting its numbers, the Air Grand Touring edition will provide up to 517 miles on a single charge, pending final EPA validation, while the performance-optimized Dream version will generate a withering 1,080 horsepower thanks to two fine-tuned electric motors—though with slightly reduced range of 503 miles.

Perhaps more critically, the car could be the first to match Tesla’s powertrain efficiency and the first to beat its overall efficiency. Briefly, powertrain efficiency reflects how well the motor, power electronics, and battery systems convert electricity to motion, while overall efficiency incorporates external factors including coefficient of drag, frontal area, weight, and rolling resistance. PE is what powertrain engineers obsess over, as it directly reflects how much performance can be squeezed out of a given battery and motor combination; OE is what consumers ultimately care most about, since that produces the final usable range.

According to Carnegie Mellon University electric vehicle researchers Shashank Sripad and Venkat Viswanathan, who track the relative efficiencies of various electric powertrains and have been analyzing the Lucid Air over the past several weeks, the new car scores 218 watt-hours per mile in overall efficiency—factoring in the car’s stated range, weight, drag, frontal area, and rolling resistance—while the Tesla Model S requires 250. (The lower the number, the less energy the car consumes with each mile.) “So far most of the new EVs unveiled were not able to achieve the powertrain efficiency of Tesla,” Sripad says. “All of the previous EVs needed much bigger battery packs to achieve similar ranges because of their lower powertrain efficiencies. This car breaks the trend that all the new EVs faced when being compared to Tesla.”

Using the same metrics, the Audi E-Tron comes in at 435 watt-hours per mile in overall efficiency; the Porsche Taycan clocks in at 420; the Jaguar I-Pace and Mercedes EQC both require 365 watt-hours per mile. In a realm where hard performance and efficiency data increasingly holds as much sway in consumer minds as creature comforts and vehicle design, those can be highly persuasive numbers, helping range-nervous buyers warm up to the fancy new cars.

Keep It Cool

How Lucid achieves this efficiency comes down to myriad small and large design and engineering decisions—but also the not-insignificant detail that many staffers, including two of the leading engineering minds, came from Tesla. The team sought to apply the same engineering that helped Tesla succeed to the work at Lucid, focusing on component lightness, low-drag aerodynamics, and, perhaps most critically, cooling.

Yes, cooling—and not just of the battery. Though that does indeed heat up significantly during use, requiring persistent circulation of cooling fluid, the motor itself is also a significant heat source that can sap efficiency if not carefully managed. “There's a good reason some people are skeptical about our range and efficiency, but we don't believe our solution is vaporware. It's very genuine,” says CEO and CTO Peter Rawlinson, who was the vice-president of engineering at Tesla during the Model S development a decade ago. “In terms of just cooling the motor, everything else looks super old fashioned.”

At the heart of the challenge is the temperature of the copper wires that conduct electricity inside the motor, wires that run those electrons from the battery into the motor, causing the rotor to spin, which generates the power that makes the car move. But as electrons flow through the copper wires, they build up heat. This heat buildup generates resistance, thereby reducing the wires’ ability to speed electricity along efficiently. Engineers attempt to manage that by running coolant as close as they can to the copper wires, but the bulky iron stator—the stationary assembly that shrouds the spinning rotor and conducts electricity to it—tends to get in the way.

According to Rawlinson, his team did some mathematical modeling of the electromagnetic fields inside the motor, and found that there were several “dead zones” in the stator that weren’t contributing to electricity conduction and therefore could potentially be used to bring coolant closer to the wires. “No one really had identified these areas before, these places where you can't get any flux,” he says, referring to the flow of electricity through the motor. “We first thought just to remove the material and put some holes in to save weight. But then we realized that we can bring the cooling systems through those areas right to the core of our motor.”

The wires in the stator were also designed with an eye toward temperature control, says Eric Bach, vice president of hardware engineering and another former Tesla engineer. The wires in most EV motors are wound imprecisely, which adds variance from one motor to the next, thereby impacting the engineers’ ability to accurately predict and shape the magnetic fields. “We used a computerized coil-winding system with a distinct winding pattern in a continuous wave,” Bach says, noting that this enabled more consistent temperatures. “This also allowed us to avoid having to weld all the wires together to ensure a continuous path for the electrons. ”

Finally, the drive unit itself, with the inverter, control unit, and transmission, weighs 163 pounds, compared to similarly powerful units in other EVs that are twice as heavy. Lucid wouldn’t go into detail in how they achieved this lighter weight, except to say that it involved a “revolutionary design” and a lot of computer simulation to optimize that design, but the resulting power density allows Lucid to save interior space and package the drivetrain with additional motors if desired. One planned future powertrain variation includes a three-motor assembly that will be capable of generating nearly 2,000 horsepower.

Keep It Smooth

For the exterior, designer Derek Jenkins focused on a sleek and stylish look, but also one that’s slippery in the airstream, in order to help maximize the powertrain. The Air has a coefficient of drag of 0.21, which is a record for its class, beating the Tesla Model 3’s 0.23. This required, among other things, precision channeling of the air, in order to modulate flow into the car for component cooling in such a way that it doesn’t back up in front of the car. “Coupled with the channeling of air smoothly around the car,” Jenkins says, “it makes for a very efficient aerodynamic profile.”

Ultimately, this nuanced, multipronged effort generated a vehicle that Lucid says is 17 percent more efficient than the Tesla Model S—2 percent of that improvement comes from the aerodynamic tweaks, 15 percent from faster-flowing electrons in the motor. This is without even discussing the battery system itself—something that Lucid knows how to do: The company was originally founded as Atieva, a battery supplier to EV manufacturers as well as the all-electric Formula E race series.

The compact 113 kWh pack could, therefore, make the Air the first EV to bring electric-racecar engineering directly to the street. Its 900-volt architecture handily beats out the current front-runner, the 700-volt system in the Porsche Taycan—an enhancement that Bach says will improve both battery discharge efficiency and the critical metric of charging speed. At stations with high-speed charging capabilities, the car could get up to 300 miles of range in 20 minutes on the plug.

In spite of all these advances,even reaching the production finish line doesn’t necessarily mean a car will be successful. Automotive analyst Stephanie Brinley, with IHS Markit, thinks it’s too soon to be certain of success or failure. “The company has adopted an approach very similar to Tesla’s, but more than a decade later,” she notes. “For a period of time, Tesla’s Model S was essentially the only game in town, and Lucid does not have the benefit of being first down this path. Having strong battery technology can be a competitive advantage, but not enough alone to ensure long-term success.”

She also notes that Lucid will now be up against the progress made by traditional carmakers who are now offering far more affordable options—Lucid’s cars are niche products.

For now, anyway. Rawlinson says that affordable electrification has always been his goal, but he had to start with a premium product to build out the technology, just as Tesla did. Furthermore, he argues that the second-mover advantage could work even more in his favor than Tesla’s first-mover play. “Take just as an example the introduction of ground-effect aerodynamics in Formula One racing, which was spearheaded by Lotus,” he notes. “It was the second movers that took it to new heights. They observed and thought, ‘We can do that even better.’ I’ve seen the missteps that Tesla has made with their charging network—they’re stuck at 400 volts charging capacity and can’t go higher—and their manufacturing struggles. We won’t make such mistakes.”

Lucid expects the cars to go on sale by the middle of next year, at which point EV drivers will determine whether the range and performance—coupled with the sleek design and a luxury vibe—are enough to move it as quickly off the showroom floor as it moves off the starting line.

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