Stanford Solar Car, The Early Years
Stanford Solar Car, The Early Years
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 Sunrayce amazed the world by crossing Australia on the power of the sun alone, beating its 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.
However, as soon as the team was on its feet, the founders intentionally left the scene. 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 Sunburner was a radical new design, incorporating a parabolic mirror to drive a concentrating solar array and a second driver to operate the behemoth. 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.
However, disaster struck the Sunburner. Late on the evening of April 9th, as the team headed to California’s Central Valley for a test drive, the battery pack had been improperly restrained and sparked, igniting a pile of styrofoam in the car. While the composite materials the car was built from were not flammable themselves, the burning of the foam destroyed 60% of the car. 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.
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. The Afterburner was designed first and foremost for minimum aerodynamic drag, cutting losses due to air resistance by 50% from the Sunburner. 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.
This experience led to another great performance in World Solar Challenge ’93 in Australia. A second driver allowed 50% more solar cells and a switch 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, extremely close to its theoretical maximum.
Sunrayce ’95 was a greater struggle than ’93, and the car saw many more failures. 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, but Stanford had fortunately saved enough power in its super-capacity Electrosource batteries that it could finish the last day with barely any sun. 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. Unfortunately, the team was plagued with electrical problems. The motor had developed a horrible tendency to switch to regenerative braking on its own, instantly bringing the car to a halt. 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, ultimately securing an overall 3rd place finish. 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.
Before the 2001 American Solar Challenge (ASC2001) Stanford and Berkeley decided to go separate ways and try their luck with the sun individually. Both teams were young and unsure as to the next step. After the young and inexperienced Stanford team spent considerable effort and time on fruitless endeavors for almost a year, it was decided to again race the 3rd Degree Burner (3DB). Few changes were made, including modifications to the fairings, repairs to the old solar array, and a new battery pack. Additionally, given that the Afterburner was still intact and several project alumni had the itch to race, it was decided Stanford would race with two teams! The young team would race stock while the alumni team would race the Afterburner in the open class. Given the lack of time for a new vehicle, the team spent the time testing and modeling the car to compete under the stock class of the upcoming race.
The qualifications for the race went flawlessly for the 3DB. The alumni team had a more hands-on experience, finally racing a wholly and functional vehicle about 1/3 into the race. After a fairly uneventful performance the 3DB came in 2nd place within the stock class and 15th overall. The Afterburner came in at 18th place. Not bad given the 3DB array was producing about 700 watts on a sunny day!
Soon after the return from ASC2001 the team decided it was time for a new car. After going for several race cycles with recycled cars, the team decided to not only build a new car, but be innovative as well. Stanford was going to race a 2-seater. The young team began earnestly to design. Airfoils were modeled and built to scale, CAD renderings began to take their virtual shape, and work began on the brainchild termed the Back2Back Burner (B2B). An innovative fairing design, a bubble to drool over, a fancy battery pack and jewel-like dual junction array were among the additions. The car did not begin to fully take shape until late in the second year. A massive effort was put forth from the dedicated team to finish the car the just months before the race. With many sessions of straining work and sweat and no sleep the car finally took shape.
The B2B stood impressively and elegantly dwarfing its predecessors. Unfortunately, the team again lacked the test miles so predictive of actual success in the coming race. Qualifications proved to be another set of all-nighters but again, the team persevered. The race, however, would almost demoralize the team to forfeiture. An electrical failure with the experimental high capacity lithium polymer battery pack the team was using would cause a severe handicap and a day of racing. Luckily, the driver and passenger reacted and escaped unharmed from what could have been a very bad scenario. Given this and several failures with the array, the team pushed on. The lack of sleep and discouraging performance was almost too much. Eventually the car was debugged and performed as expected.
The team finished in 2nd place within the 2-person category and 15th place overall. A grueling race indeed, and a tired team returned a bit disheveled to the Farm.Luckily for them, only three members graduated, and the youngsters carrying on, with a small group of new recruits, using the lessons learnedfrom the B2B and applying them toward a new car, dubbed Solstice, for the 2005 race from Houston to Calgary, Canada.