Solar Cars? Very Cool, but Still a Pipe Dream

Jim Motavalli

Jim Motavalli | Aug 19, 2015

It’s sleek, aerodynamic (kind of like the 313-mpg Volkswagen XL1) and covered with solar panels. It’s the new Immortus from the Aurora Solar Car Team in Australia, and its builders claim it can drive at up to 37 mph on just the sun’s rays.

Sleek, aerodynamic and with a bizarre and pompous name! (Aurora Solar Car Team)Everybody loves the idea of solar cars. No polluting gas engine. No messy and heavy battery to cart around. Like the “air car” or “water car” (more about them later) it runs on a benign, cheap, everyday substance, and it’s completely zero emission. The planet is saved!
The Immortus is crawling with solar panels. (Aurora Solar Car Team)Would that it were that simple. But there’s no free energy lunch, unfortunately. Renewable energy, including solar and wind, is intermittent, meaning you can’t rely on it all the time. A solar car with no battery backup would only run when the sun is shining. I used to judge a solar car race, and those suckers would stop dead with cloud cover.

The problem is translating the modest amount of solar power that panels supply to actual motive energy in the car. For superlightweights, it works, but for actual production cars with infotainment, baby seats, airbags and crash zones, it’s hugely harder.  

This four-seat beauty is called the Stella, and it recently toured California. (Eindhoven Team)Still, solar car engineers keep at it, and the product is getting better. A lot better. The Immortus gets around the intermittency problem with a 10-kilowatt-hour lithium-ion battery pack. It has a pair of 20-kilowatt electric motors in the hubs of the drive wheels (like the first Porsche), and combines insanely low weight (1,212 pounds) with that slippery shape to reduce drag.

The team is hoping for a zero-to-62-mph time of under seven seconds. Thanks to the battery backup, it should be able to drive more than 340 miles (at cruising speeds) on one sunny day charge.

The two-passenger Immortus isn’t headed for volume production or anything like that, but if you happen to have $370,000 lying around they’ll build you one. A total run of only 100 is planned. And there’s the little matter of needing $1.5 million to begin production.
Ford's solar C-MAX: Bets are hedged with a battery pack and backup gas motor. (Ford photo)You may never hear of the Immortus again, and there’s precedent for such oblivion. Remember the Ford C-MAX solar car? No? I ran into it in a corner of the 2014 CES show in Las Vegas.  “Ford C-MAX Solar Energi Concept is first-of-its-kind sun-powered vehicle with the potential to deliver the best of a plug-in hybrid without depending on the electric grid for fuel,” the company said.

Ford hedged its bets on the “solar car.” The display C-MAX had both a battery pack and a gas engine. But there was cool tech. “Researchers developed an off-vehicle solar concentrator that uses a special Fresnel lens to direct sunlight to the solar cells while boosting the impact of the sunlight by a factor of eight,” Ford said.

The Cadillac Provoq show car had a solar panel on its roof, but do you think that itty bitty thing could move such a big tub of guts? (Cadillac photo)And let’s go back in time. Ed Passerini built a solar Bluebird in 1977, and Larry Perkins the Quiet Achiever in 1982. There’s lots of solar used on show cars, including the Mazda Senku, Ford Reflex and Cadillac Provoq. The ill-fated Fisker plug-in hybrid had a solar panel, and the Toyota Prius uses one to cool the car’s interior while the driver’s away. The latter use shows what solar is best for now—powering minor functions.   
This homemade Nigerian car includes not only the add-on solar panel shown, but wind turbines, too.And check out this guy, who created a decidedly homemade VW Bug-based wind and solar car. I'd die of embarrassment before I got behind the wheel of anything that ugly, but maybe that's just me.

Solar is actually great for racing, where it doesn’t matter how ridiculous or how impractical your car is. A four-passenger EV called the Stella from the Netherlands-based Eindhoven team won the World Solar Challenge (Cruiser Class) in 2013. The Stella, claiming to be the world's first solar family car (see the video), actually completed a U.S. tour last year, commemorating National Drive Electric Week. It went between Los Angeles and San Francisco on a single charge. But that doesn’t mean the backwards bullet, which sits close to the ground for aerodynamics, is ready for production.

The World Solar Challenge, a race from Darwin to Adelaide in Australia, takes place in October this year. It sounds like a 100 percent sun-powered event, but that’s not quite the case. “Solar cars are allowed a nominal five kilowatt-hours hours of stored energy,” the judges say. “All other energy must come from the sun or be recovered from the kinetic energy of the vehicle.”

So even when freed from all weight and safety constraints, cars can’t rely solely on solar power. It’s nice, but it’s a pipe dream awaiting a major breakthrough in panel design, lightweighting,or both.

Oh, and those air and water cars? Air cars are a perennial I’ve debunked a few times—for some reason, the French are enamored of the idea, but nothing has gotten to production. The usual problem is it takes too much energy to compress the air, and range is really limited.

Water cars could work if they carried onboard chemical factories to extract hydrogen from H2O using an electrolysis process. But it’s easier just to carry hydrogen gas around. And those are the fuel-cell cars that are actually hitting the road this year.

Solar cars? Your best bet is to see them in a science-fiction movie at a multiplex near you. Here's some relevant video showing the Stella on the road:

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