Stanford Places Fourth in 2013 Bridgestone World Solar Challenge
Static & Dynamic ScrutineeringBefore the competitors in the 2013 race set out from the coastal city of Darwin, all teams had to complete a series of rule compliance and safety checks. The process, called scrutineering, requires all teams to allow race officials to inspect their vehicles before the race begins during a four hour inspection session. Event officials inspect everything from driver vision to brake lights. Luminos passed all stages of static scrutineering on the first try, except for a rear-vision camera problem that was solved with a quick software fix. Upon completion of static scrutineering, Luminos underwent dynamic scrutineering - including a braking test and "flying lap" around the track to determine starting position in the race. With a lap time of 2:07 around the Hidden Valley Raceway, Luminos was the third car at the starting line.
The RaceThe 2013 race began at the Parliament House in Darwin on the northern coast of Australia. Teams were released at the starting line with a one minute gap between teams. Day 1 began with a frenzy of teams attempting to claim a competitive position in the race. In the first hours of the race Stanford exchanged positions with the Nuon Solar Team and the University of Michigan Solar Car Team multiple times, passed the entire Michelin Cruiser Class field, and passed a number of other solar cars broken down on the side of the road. Luminos arrived at the first control point of the race (the city of Katherine) in 3rd place! The rest of the day was spent in a tense race between Stanford and Michigan - culminating in camping on the side of the road just a few hundred yards from our Ann Arbor rivals. Day 2 was an equally close race between Luminos and Generation, Michigan's solar car. Just a few kilometers away from each other, our teams sent convoy vehicles to spy on the speed of each other. After the Tennant Creek control point, we opened the gap with our arch-rivals and steadily pulled away over the course of the next few days. Day 3 was significantly more mellow, with no teams in direct sight. We continued along at a steady pace until 5pm without incident. By the end of day 3 our team still followed Nuon (Netherlands), Tokai (Japan), and Twente (Netherlands).
Day 5 began with both a headwind and more rain than our weather models predicted before the race began. Our team knew that we were close to Twente, and we wanted to be right behind Twente if they broke down due to additional mechanical problems or rain damaging their electronics on the last day of racing. We chased patches of sun and followed Twente to the Port Augusta control point. However, midday rain and a low battery pack charge in Luminos allowed Twente to defend third place in the afternoon. Twente ended up driving an apparently problem-free last day of racing, so our team didn't have an opportunity to close the final gap and pass Twente. Luminos had expended a large amount of battery pack energy attempting to catch Twente, so we ended up driving much of the last day at 50kph. We reached the official end of timing just outside of Adelaide at 4:31pm securing our standing in fourth place after crossing the continent on the power of the sun. Twente, Tokai, Sunswift alumni and surprise SSCP alumni were there to greet us as we celebrated Luminos's 2013 finish.
The next day we drove the car across the ceremonial finish line to join Nuon, Tokai, and Twente at Hindemarsh Square. Nuon thought ahead to make up for the lack of the traditional fountain at the finish line (past races have finished in Victoria Square fountain which was under construction this year). As soon as we completed our finish line photo-op, we found ourselves tackled and thrown into the three kiddie-pools they had filled up nearby. It was the proper finish of a solar car race. The rest of the day was spent asking and answering questions about cars, swapping shirts with other teams, cheering on other arriving teams, and otherwise relishing the joy of successfully completing the race.
Our team is incredibly grateful for the support of Stanford University, our sponsors, our alumni, and everybody else who has made possible our success as the highest-placing team run by undergraduates in the 2013 Bridgestone World Solar Challenge!
- Place: 4th
- Average Speed: 75.86 kph
- Time to Finish: 39.52 hours
- Top Speed: 105 kph (reached while passing Generation)
- Ending State-Of-Charge: 2%
State of Charge (SOC) is in many ways the most important single number to a solar car team on a race. Some things worth noting on the above plot are:
- Array stand charging in the morning (before 8am) and the evening (after 5pm) provide astounding amounts of energy.
- At approximately 90% SOC, battery charging enters constant-voltage mode, reducing the power into the battery pack. Charging up to this point during the race should be avoided.
- Worse weather than expected on day 5 caused our SOC to drop extremely quickly after Port Augusta.
- Although we experienced significant battery drain on day 4 (passing Coober Pedy and Glendambo), the car covered over 700km in one day due to strong tailwinds. A shift to strong headwinds the next day provided incentive to cover as much ground as possible.
Array performance is clearly reduced on the first day in trees, and the last day in bad weather between Port Augusta and Adelaide.
(This post includes text and media from Max, Anna, and Wesley)Read more blog posts