Is There a Future for Solar Cars?

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As we see the slow fade of the internal-combustion engine, as well as some thorny problems with the sustainability of the materials used in electric car batteries, might the next step be a “solar car” that gets much of its power from photovoltaic panels on the roof?

That’s the premise of Lightyear One, a Dutch company that raised US$110 million last year to put its large and luxurious five-seat hatchback into production next summer. “We are at the forefront of a historical market opportunity, by introducing the first cars on the market that charge their battery directly from the sun, completely free,” says Lex Hoefsloot, founder and CEO of Lightyear, adding that the company plans to introduce the Lightyear One exclusive model in 2022.

The all-wheel-drive car has a very aerodynamic drag coefficient somewhere under 0.20, similar to the Lucid Air or Mercedes EQS electrics. The attractive shape was drawn by Italy’s GranStudio. Its efficient electric motors are in the hubs of the four wheels, and it rides on ultra-low-rolling-resistance Bridgestone Turanza Eco tires. 

The drivetrain is claimed to have 97% efficiency. Hoefsloot also says the car’s weight is under 2,900 pounds (via aluminum and carbon fiber) and features “the most efficient inverters on the planet.” The flat aero wheels have fender skirts in the rear to make them more aerodynamic, and the wind-blocking rear-view mirrors have been replaced with cameras (not yet legal in the U.S.) 

To achieve this level of efficiency, Lightyear isn’t trying to create a performance car. The One has 136 horsepower on tap, and a zero to 60 miles per hour time of about 10 seconds. 

The solar roof has 53 square feet of solar panels. The result is a car that, when parked on a sunny day, can add about seven miles of range per hour, or 25 miles total on cloudy days. This type of solar add-on is not exclusive—the forthcoming Fisker Ocean also has solar panels, which it says can add four or five miles per day. 

The 2022 cars in Lightyear’s first series, for Europe only, will be priced at US$169,000. Only 946 will initially be put together by Finland’s Valmet Automotive, which builds cars to order. The cheaper mass-produced Lightyear One that could reach American consumers will appear in 2024. 

In June, at Aldenhoven Testing Center in Germany, the company was able to get more than 440 miles on a single charge of its 60-kilowatt-hour battery pack (translating to 7.3 miles per kilowatt-hour). Those results were achieved on a closed track at a steady 53 miles per hour, which is likely to yield better results than moving through stop and go traffic—or driving faster. 

In a video, Hoefsloot predicted that by the end of the decade “people won’t think about charging or range anymore—the energy will just be there.” That seems very optimistic. Unless Lightyear has achieved amazing breakthroughs in solar efficiency, owners of these early solar cars are still likely to be plugging them in. The Lightyear One is fast-charge compatible. 

Sam Abuelsamid,
principal analyst for e-mobility at Guidehouse Insights, points out that vehicles are “highly suboptimal” as a host for solar panels because they have to lie flat on the roof. “Panel output is highly dependent on the angle of incidence of the sun’s rays to the panel,” he says. “Ideally, you want the panel to be as perpendicular to the sun’s rays to generate maximum power. That’s why stationary solar arrays are tilted the way they are.”  

Abuelsamid says he tested a Hyundai Sonata hybrid with the optional solar roof last year, and observed what happened with its power generation gauge. “I parked it in my driveway in the sun, and after eight hours it didn’t even fill the 1.5-kilowatt-hour hybrid battery,” he says. “That means less than two miles of range at even very slow speeds.”

Alistair Weaver,
editor in chief of Edmunds.com, said in an interview that in many current cars, such as the new Mercedes Vision EQXX and Fisker Ocean, the solar panels “are more of a top-up solution, rather than a way to power the whole car. In hot climates, it’s common sense to use solar. If your commute is 15 miles and you live in Arizona and park outside, you will probably get somewhere.”

Toyota offers a solar option on its Prius, but the company said that in 2019, working with Sharp, it has come up with an onboard solar battery panel with an output of 860 watts, 4.8 times higher than that of its own Prius plug-in hybrid model. 

Solar-powered cars work well for racing, and Lightyear One’s panel design grew out of Solar Team Eindhoven’s vehicles for the World Solar Challenge. The team’s latest creation is
Stella Vita,
a mobile home that is described as a “self-sustaining house on wheels.”