Solar Racer Test Drive: Inside the U. Mich's Sun-Powered Car

It looks like a UFO, starts like a turtle, is covered with 2726 solar cells and runs as long as the sun shines. PM's Detroit editor Larry Webster goes behind the wheel of the Continuum, the University of Michigan's sun-powered car.

By Larry Webster

Photographs by Zach Desart

Continuum’s rear aluminum wheels were custom-machined with integrated hubs to reduce weight. The front wheel houses the electric motor. California-based Viper Technologies donated two sets of wheels worth more than $40,000.

The car I’m sitting in is so futuristic and so technically advanced that it would cost nearly a million dollars to duplicate. Yet this Jet Propulsion Lab on wheels lacks the basic features of even the humblest sedan: a radio, roll-down windows, a heater. I had to slither between the rails of a roll cage to access a cockpit so cramped that it feels as though I’m sitting upright in a Niagara Falls barrel.

This three-wheeled car, known as Continuum, isn’t built for comfort—and it’s not exactly built for speed. It’s built for distance. More precisely, it’s built to maximize the distance a featherlight electric car can travel in a given time powered solely by the amount of sunlight that falls on photovoltaic cells plastered all over its upper half.

Working under the supervision of two faculty advisers, more than 100 very bright and very motivated University of Michigan students took two years to build the vehicle, which is designed to compete in a pair of grueling solar-car races. It’s the latest model in a program that has racked up an impressive record since its 1990 inception: Five wins in the college-only 2400-mile North American Solar Challenge and several top finishes running against Honda, GM and Ford in the 1870-mile Australia-based World Solar Challenge.

On this chilly and slightly overcast November morning, faculty adviser Ignacio Garcia, a retired engineering school machinist, and a dozen bleary-eyed team members trailered the car to Chrysler’s Chelsea, Mich., proving grounds. Most team members have never driven Continuum, hence their nervous looks: I’m the first outsider ever to take a spin in a streamliner that cost them an awful lot of late nights and bloody knuckles. “We have a saying,” says head strategist Alex Dowling, a 20-year-old junior from Saline, Mich. “You can have a social life, get good grades or do solar car. Pick two.” A hardcore group of about 30 spends more than 30 hours per week on the project—designing, testing, fabricating and securing sponsorships for the $2.4 million two-year budget.

I’m about 6 ft tall and weigh 180 pounds, which is 3 in. and 20 pounds too much for the cockpit. After an unsuccessful attempt with shoes on, I go socks-only and clear the small carbon-fiber steering wheel. My knees are practically kissing my chin. Luckily, the controls are on the steering wheel: A lever on the right works the “throttle,” and one on the left activates the brakes. The team designed a dash that displays speed, charge state and distance traveled. They also built a rearview video-camera system and a wireless network that links the car to chase vehicles. The team remotely monitors Continuum with a Prius-like energy-flow graphic.

Once I’m buckled in, six students affix the upper part of the car’s body in a series of moves so effortlessly choreographed it would make a Sprint Cup team jealous. The top half carries the solar array; the bottom half is the carbon-fiber and Nomex-honeycomb main structure.

Photo Gallery
The University of Michigan’s solar car, Continuum, glides around Chrysler’s 4.7-mile oval.	Team members lower the top. The blue cloth in front of the driver is attached to the frame with...	The team designed the vehicle’s wheels, brakes and hubs. The three-phase, in-wheel electric motor...	The solar array charges a $17,000, 6-kwh, 66-pound lithium-polymer battery pack.

As I gingerly pull back on the accelerator, the car inches forward at a turtle’s pace. It’s so pokey that a few team members walk alongside as I get underway. Weighing a lithe 480 pounds, Continuum gets all the propulsion it needs from a 16-hp electric motor that resides in the single front wheel. The trike design lowers the car’s surface area, which in turn reduces drag. How slippery is it? “It’s a strategic advantage for other teams not to know,” a cagey Dowling says. He reveals that the team believes a Corvette has five times as much drag as Continuum. But as I am about to learn, when it comes to handling, this is no Corvette.

With a single front wheel, I fear that any turn at speed will tip the car onto its outside edge, like a tricycle turned too hard by a reckless 3-year-old. “We talked to a vehicle dynamics professor when we designed the car,” says John Federspiel, a 21-year-old junior from Rochester, Mich. “He had no idea about three-wheel dynamics. There’s not much on the subject, so we had to figure it out ourselves.” I creep up to about 30 mph and gently turn. The car responds more predictably and confidently than I could have imagined. I progressively wind in more steering angle until I feel the front end safely wash out in classic understeer. It’s not fun, but it’s stable and there is little body roll—these kids have done their homework.

Author begins the delicate entry procedure.

While crisscrossing a vast expanse of proving-ground asphalt known as Black Lake, I buzz by the students at 40 mph. In 10 minutes, my hindquarters have gone numb, but I’m in the groove and ready to head over to Chrysler’s 4.7-mile banked oval so that I can open this baby up. I pull onto a pockmarked two-lane road and brace for the first impact. There’s a loud thud, but the car isn’t bothered by bumps. It feels solid and well-built. Because of the tight confines and lack of air, beads of sweat roll down my face despite the brisk weather. It’s windy too, and I’m a little nervous about how crosswinds might affect a car shaped like a huge Delta wing. So when I get to the oval I stop and ask for a more experienced driver to try it first.

The team descends on the car. Jeff Rogers, a 22-year-old graduate student from Rochester Hills, Mich., shouts, “Waist!” and all six lift the top half about 1 ft. Someone unhooks two safety chains and disconnects the wires that connect the solar array to an electrical device called the maximum-power point-tracking system. The MPPT constantly changes the load on the solar array to extract maximum power. “Up!” Rogers barks. In another precisely timed maneuver, the team carries the top half away from the car and sets it down on sawhorses.

They’re careful with the array since any scratch could reduce the efficiency of the 2726 solar cells. (Racing rules limit the area of the array to 6 square meters—about 7 square yards.) Each $50 cell produces a maximum of 2.6 volts. In full sunlight, the array provides 2.4 hp, which is roughly what it takes to hold the car at 60 mph on a flat road—less than an eighth of the power a normal car requires.

I wiggle out, and Federspiel takes the helm. He moves out with two chase cars in tow. Dowling sits in the lead chase vehicle, staring at a laptop screen. “We monitor everything,” he says. Obsessive Formula One engineers have nothing on these guys.

Federspiel drives a lap and gives the okay. I’m strapped back in. I floor it, the car rocks back slightly on its haunches, and we’re off. The motor makes a loud growl until I clear 10 mph, and then all I hear are little pebbles zapping the bodywork. As speed slowly increases—51 mph, 52, 53—the car feels ever so slightly more eager.

The oval, with its perfectly smooth surface, is the same place Chrysler runs Chargers and Challengers flat out at supercar speeds, so at 60 mph, Continuum is, well, a bit underwhelming. It’s hard to maintain that speed because the stiff winds dramatically slow the car whenever I let out the accelerator. Too bad I didn’t learn to activate the car’s cruise control. The real thrill here is, of course, knowing this car runs as long as the sun shines and the battery has juice—never stopping for a drop of petroleum or a charge from the power grid.

My legs are numb—again—so I prepare to stop. After I climb out, Dowling asks if other team members would like a turn. I can sense their excitement. I wander over to faculty adviser Ignacio Garcia. “So, these kids really built this thing?” I ask.

“Yes. I only step in if there’s a safety issue or if they ask,” Garcia says. “The adults are there for support. It’s amazing what the students have done.”

In addition to engineering know-how, these students run the program like a Fortune 500 tech company. It’s split into four divisions, and team members have weekly progress meetings, workflow charts, a Web-based forum to catalog every move, even custom stationery. They solicit design advice from solar-car alumni and invite companies to teach them carbon-fiber construction.

Several students who have taken their first spin are giddy from the experience. Someone suggests that 6-ft 3-in., 210-pound Chris Hammond, a 21-year-old junior from Clarkston, Mich., give it a go. He makes it halfway into the cockpit before he gets stuck and yells for help. It’s the outcome everyone knew was coming. But they laugh and chide him in a way only a fraternity full of brothers could. They are, after all, still college students.