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Stanford Solar Car Project History
by Dorian West
created 4/21/1999
submitted 4/5/2002 12:36:10 AM

A brief history of the Stanford Solar Car Project, up until Sunrayce 99.

A Decade of Solar Racing at Stanford
Dorian West
4/21/99

Ten years ago in the winter of 1989, a wandering graduate student and a visiting professor decided that Stanford students might be interested in devoting their lives to a solar car project. They both knew that just over a year before, the GM Sunraycer had amazed the world by crossing Australia on the power of the sun alone, beating it’s closest competitor by days. Basking in their victory, General Motors decided to bring the race to the U.S., restricting it to North American colleges and universities. Sunrayce ’90 was just 15 months away, and these transient founders of the Stanford Solar Car Project were bound to get their school in the race.

Their expressed intention was to bow out as soon as the team was on its feet, and they made good on this promise a few weeks later. Thus, with absolutely no idea what it really meant to build a car from the ground up, a group of clueless undergraduates plunged headfirst into “The Project.” Through all-nighters, dropping grades, non-existent social lives and the persistent smell of freshly mixed epoxy, the team persevered. A year and a half later they stood back and realized that, despite the chaos, they had managed to build a car that ran solely on the power of sunlight. The SunSurfer finished 7th out of a field of 32, and 2nd in performance per cost.

The team returned to Stanford, underwent its first of many cycles of attrition and began a new project. The goal this time was bigger and better than before. Not only were we aiming to enter the next World Solar Challenge in Australia, we wanted to win it. The Sunburner was a radical new design, incorporating a parabolic mirror to drive a concentrating solar array and a second driver to operate the behemoth. WSC allows 50% more solar array area for 2 person cars, and the strategic models predicted superior performance for this configuration. This car would break all records and bring home the gold.

Halfway through construction, however, the team came to the sad realization that the concentrator just wouldn’t work. It would require precise alignment with the sun, a virtually impossible demand for a vehicle moving upwards of 60 miles per hour. With less than a year before the Sunrayce ’93 the team was struck with the grossly voluminous body, already built and tested. Wind tunnel tests helped the team’s aerodynamicist design the optimal top given the less than optimal bottom. The result was one of the strangest looking solar cars ever built, difficult to visualize given a photo, and even more difficult to describe.

The decision to not rebuild the whole car turned out to be an excellent one however, allowing more than 1000 test miles to be logged before the race. Test drives took place in 3 locations: local side streets, a major nearby expressway, and long straight open roads in California’s Central Valley.

It was on one such “Valley Drive” that disaster struck the Sunburner, a car cursed from its inception. Late on the evening of April 9th, the team finished packing up and rolled out of the gravel driveway in front of the site. After less than an hour on the road, one of the support vehicles radioed ahead, reporting wisps of smoke coming from the trailer. By the time the doors were opened, the Sunburner had melted in the flames. The battery pack had been improperly restrained, and it sparked, igniting a pile of blue styrofoam in the car. While the composite materials the car was built from were not flammable themselves, the blue foam burned so hot, 60% of the car was destroyed.

Fortunately, the chassis and half of the solar array were salvaged, and the car was repaired during a painful 6 weeks of furious work, just in time for Sunrayce ’93. The team was rewarded for its efforts by capturing 5th place in the race, far exceeding most competitors’ expectations. The teams excellent placing was not due to a superior car, but because of a superior team with many test miles. In fact, the car did not experience a single mechanical or electrical failure for the entire 1200 miles from Texas to Minnesota.

This experience led to another great performance in World Solar Challenge ’93. A second driver allowed the addition of 50% more solar cells. A switch from lead acid to silver zinc batteries resulted in a 240 lb. weight savings. The car had only one electrical failure (overheated motor controller) and no mechanical failures for the entire 300 mile cross-continental trek from Darwin to Adelaide. The car finished in 14th place overall, and 2nd for 2 person cars. According to the strategist, the car finished extremely close to its theoretical maximum.

In the wake of this incredible marathon, only the two youngest team members were eager to build another car. Their experience was mostly limited to racing but they were both excited to start building something new. Heavy recruiting and initial design filled the winter of ’94, and by summer, the car had a name. Finally able to start from scratch, the Afterburner was designed first and foremost for minimum aerodynamic drag. Test results estimated that the losses due to air resistance were cut by 50% from the Sunburner. A smaller car also meant less weight. By the time the Afterburner was completed, it was clearly a superior car. But alas, the great lessons of extensive test miles were pushed aside due to the pressures of time.

Sunrayce ’95 was a greater struggle than ’93, and the car saw many more failures, but we finished again in 5th place. While the Afterburner had lingered in the 8th to 12th place range for the entire race, horrible weather on the last day allowed it to leapfrog up to 5th. Most teams had drained their batteries on the second to last day, hoping that it would get sunny near the finish. As the racers awoke for the final day, a dark overcast sky greeted them, but Stanford had fortunately saved enough power in its super-capacity Electrosource batteries that it could finish the last day with barely any sun. Ironically, it was a couple of rainy days that kept the Afterburner from doing worse (in terms of placing) than the Sunburner.

After the race, the team felt that the car was far from reaching its potential. A month later, Yomiuri Shimbun, the biggest newspaper in Tokyo, paid full expenses for the team to travel to Suzuka, Japan to race on an F1 racetrack. The car again got 5th place and the team began to wonder if a higher power was at work.

The Afterburner returned a year later for Suzuka ’96 only to face a tougher competition, finishing 7th. But the team was looking to something bigger now. The team had purchased a used school bus (“Stanley”) and modifications were being made to prepare it for World Solar Challenge ’96. UC Berkeley and Stanford had officially merged to form “Team California”, a joint group aiming to win in Australia. Many modifications were made to the Afterburner, including a new experimental motor, a set of super-high efficiency solar cells from SunPower, and new tires and wheels with lower rolling resistance. With these superior components, Stanford-Berkeley was poised to dominate the race.

Unfortunately, the team was plagued with electrical problems, costing serious time during the race. The motor had developed a horrible tendency to switch to regenerative braking on its own, instantly bringing the car to a halt. Only by resetting the entire system could the problem be fixed, but only until the motor decided to misbehave again. This hurt the team tremendously, leading to a disappointing 25th place. The team recovered by taking a month-long tour of Australia in the school bus. Off-road driving and plenty of surf and sun helped the wounds start to heal.

By the time the team returned Sunrayce 97 was just around the corner. With less than 6 months to get the car in shape, a new team rose from the ashes of WSC ’96. Once again determined to see the full potential of the Afterburner, further modifications were made including a better bubble (windshield), better wheel fairings, and brand new sets of solar cells and batteries. While the team had very little time to get ready for the race, they were confident that the car would do better than ever before.

Despite our scrambled together team, the car refused to let us down. We were able to drive the speed limit for the last 2/3 of the race, losing time to the leaders only once because of an annoying blown fuse (courtesy of yours truly). On the final day of the race, not only did we secure our overall 3rd place finish, but we managed to have the fastest time for the day, something neither Stanford nor Berkeley had ever attained in any of the previous 3 Sunrayces. The Afterburner had finally matured. It was now able to cruise happily at 45mph under the power of the sun alone and reach a top speed of 75mph with a little help from the batteries. Once again our friends in Japan invited the team back for Suzuka ’97, held later that summer. Some minor modifications were made, and the team returned with another 5th place title.

The past year and a half have been spent organizing the team, building a new trailer, and cleaning up the Site (at Stanford) and the RFS (at Berkeley). Of course, a great deal of work has been done on the car in preparation for our next round of races. Sunrayce ’99 is coming up in June, and World Solar Challenge ’99 is happening in October. Be sure to root for us!

[Since this article was written, Stanford built a new car, the Third Degree Burner, to compete in Sunrayce 99. This car was also raced in the American Solar Challenge 2001 along side a resurrected Afterburner, renamed the Backburner. -DW]

1724 words | dorian

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