‘Rayce’ down under
For the first time since its founding in 1990, CalSol, Berkeley Engineering’s solar car team, competed in the international World Solar Challenge (WSC). Held in October in Australia, the WSC drew 37 solar-powered cars to a weeklong “rayce” crossing 3,000 kilometers of the barren Outback from Darwin to Adelaide. CalSol’s Impulse team members posted these reports from the field.
Arriving in the wondrous Oz
G’day mates! The team is ready to begin our month-long adventure in this strange continent. We are picking up Impulse from the port warehouse tomorrow, and we hope everything will go smoothly (have you heard that the Australian Customs are on strike?). If everything goes well, a couple of us will head over to Adelaide for a temporary driving permit for Impulse while the rest of us continue unpacking the container and get ready for the big road trip!
Shake and bake
Today was rayce day on the track. We began with a couple qualifying laps. In the pits, crews worked furiously to prep their cars: checking tire pressure, cleaning arrays, and running diagnostics. Drivers and captains huddled with the head race official: “Remember,” he said, standing atop a crate, “the track rayce is three kilometers; the road rayce is 3,000 kilometers—save your car for the road.”
Our lap time will determine our starting positions tomorrow, and we aimed to push Impulse to its limits and put ourselves at the top. Teams waved and cheered, but with the hatch down I was in my own private oven and could barely hear them. As I came out of the first turn I accelerated, but something was wrong! No power! No rumbling motor! I pulled to the side of the track and restarted the car. I took the next few turns slower, but for the timed lap I had to go fast and decelerate hard. The batteries were too full and were causing the car to quit when too much current was coming from the regen.
I powered up and floored it—10, 20, 30… A rainbow of cheering teams flew past me—40, 50, 60, 70—I reached 80 kph past the tower and 90 kph before I decelerated into the curve. The rest of my timed lap flew by: I floored it. Impulse cruised back to the pit and everyone cheered as I climbed out. At 2:16 we were one of the fastest rookies at the track!
And they’re off!
Thanks to an awesome hot lap by Martin yesterday, Impulse was positioned comfortably in 13th place out of 37 teams. The roll out from Darwin went perfectly, but trouble soon arose—the array was failing to charge the batteries and Impulse was forced to pull over 45 kilometers out of Darwin. The problem was quickly isolated to the power tracker's connectors. Impulse eventually made it to the check point—30 minutes past the time check, but on her own two wheels, which is something to be proud of.
Stuck in Tennant Creek
Three days into raycing, the team began to realize why this is a called a challenge and not a race. On Day One, it was a broken Anderson connector between the MPPTs and battery box. Day Two, it was a broken wire between two out of five of our solar arrays. Day Three, it appears that our top shell is zero water-resistant—the left and right sections of our arrays stop working every time we spray on distilled water to cool down the solar cells.
With patchy clouds and an ashy residual haze from a brush fire, we realized early on that Mother Nature was conspiring against us. Fortunately, we had a full battery pack thanks to our four-hour layover yesterday so we decided to risk it and drive fast.
Jessica started off driving Impulse, then Nicole switched in, taking just a few minutes to change drivers. She took Impulse into Ti Tree at about a half hour past noon, despite nearly being run off the road by half a house loaded on the back of a road train and slowing down to let a billowing dust devil stroll across the road.
The little solar car that could
For a small solar car, every hill is a challenge—by hill, I mean a slight 1 percent incline. Every incline makes Impulse and the telemetry team shudder in horror, because we never know if that will be the one to drain the batteries. Our instruction to the driver is “Speed up by 1 kph every three seconds until you hear low voltage warning noises, in which case, slow down by 1 kph per three seconds until the warning noise goes away.” It was the slowest yet most nerve-wracking race I have ever seen.
Last raycing day
The sun is shining and we’re cruising at a staggering 63 kph using nearly empty battery packs. Really at the final stretch now, we’ve got one more hour left; let’s make the most of this! Impulse is now at 85 kph—Booyah. Fifteen minutes left, and the sun has never shined so brightly. Nice way to finish off the race. And—that’s that! Impulse completed all of the solar kilometers she could and is pulled off the side of the road. Now we await the result, but in the meantime, time to party in Adelaide!
World Solar Challenge provisional results
CalSol arrived in Adelaide on October 22 after completing 1,809 kilometers on solar power. WSC officials released provisional results for the 37 teams that participated in the weeklong challenge. We are very pleased to be ranked 20th among so many great teams from around the world. Congratulations to Tokai University for defending your title.
Considering the fire delay on the third day, haze on the fourth day, and almost no sunlight on the sixth day, Impulse did a great job pushing forward to cover every possible kilometer the sun would allow. Not bad for our first journey into the Outback!
At the finish line, CalSol goes on
Now that WSC has come to an end, we are shifting our focus to the upcoming rayce in June, the American Solar Challenge (ASC). While most of the older crew members will soon leave the university, we are hopeful that the younglings from this trip will continue to carry the legacy.
Thanks to Chris Cartland, Jessica Chang, Martin Taylor, Marc Russell, Ryan Tseng, Michael Vogel, Rafael Send, and Jimmy Hack Visit CalSol's blog at calsol.berkeley.edu.