On Building & Driving a Solar Car…

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Someone representing Stanford’s Solar Car team recently reached out and shared the interview featured below with me. It’s and interview with a multi-year member of the team. I thought it was interesting enough to post here on CleanTechnica, so here it is (reposted from CJEnvironmental):

Stanford’s Solar Car, Xenith, cost about $480,000 in parts to build. Photo courtesy of Stanford Solar Car Project.

Stanford senior and Club Business Manager Wesley Ford spoke with CJ Environmental about the project, Xenith’s last race, and driving down California’s Ventura Highway in a carbon-fiber solar car that weighs only 375 lbs – less than half the weight of the world’s fattest man (Xenith is street legal). As the business manager and member of the Stanford Solar Car Club since his freshman year, Ford has been involved in almost every aspect of the car’s production: from contributing to the manifacturing of the car during his freshman year to acting as the team’s financial manager. The Project is almost entirely student-run.

When the school year ends in mid-June, Ford and some other members of the squad will head to North Carolina to perform wind-testing on Xenith, in which they hope to gather data that will help them develop even better technologies for the next iteration of the solar car. Here’s what Wesley had to say:


CJ: When did you join the Stanford Solar Car Project?

WF: I joined just after my freshman year. It’s the largest student engineering project on campus, and it looked like a lot of fun.


CJ: So the club is between solar cars right now?

WF: Xenith raced in October, so we’re starting a brand-new cycle. We’re designing the car through this coming summer. Next fall, winter and spring we’ll be building the car, and the following October (2013) we’ll be racing it. So we’re trying to improve the current design, see how well our computer models matched the real world performance of the car.


CJ: So how does the car itself work compared to a normal car?

WF: There are three big subsystems: The solar panels on top that convert solar energy into electrical energy that we can use, a battery pack that either charges or receives power from the solar panels directly, and a motor that propels the car forward on the highway.

Most of the other systems are the same (as a regular car). Same steering system, hydraulic brakes. It’s street legal, but it’s a little bit hard to see when you’re in the car. But there are no worries about merging in traffic. Driving it isn’t bad. It can go highway speeds. It’s a bit loud on the side and the compartment’s tight, and the car only fits one driver.


CJ: What’s the fastest you’ve taken it?

WF: About 80 miles an hour using the battery pack to pass a car on the highway. But if we’re cruising on solar power, we target speeds of 45 to 55 mph.


CJ: How long does the battery pack last for?

WF: Throughout the day you’ll be charging or recharging the battery pack. Midday you’re probably burning the pack more. One charge can go 150 to 200 miles with just the battery alone.


CJ: That’s crazy. Who developed the battery?

WF: We developed it ourselves. The actual cells we sourced from Panasonic.


CJ: Doesn’t the Nissan Leaf only go 100 miles on a single charge?

WF: We make compromises that most car makers wouldn’t want to make. Our biggest motivations in designing a car are making it aerodynamic and light weight, with low power consumption. A normal car would be much heavier with a lot of different amenities and luxuries. Our intention is to get the best components we can to make it as efficient as possible. We build with no limits.


CJ: So what technologies can be taken to the real world?

WF: The solar panels we developed are being tested for how their efficiency ranks compared to those produced by the world record holders. Some of our battery monitoring systems are unique and new, as well.

We don’t do a lot in terms of licensing technologies directly, but our alumni leave to use their expertise in their professional careers. JB Straubel (Chief Technology Officer of Tesla) worked on the solar car, and he presumably took some of the ideas he developed at Stanford to design the Tesla Roadster.


CJ: Since you can’t reuse Xenith for the next race, what are you going to do with the car?

WF: Right now we’re hoping to put it in a museum. Otherwise it’ll be housed at an alumni’s home. It’s also good to use as a training tool for new members, and we also do a lot of outreach events with Xenith. We’re going to visit schools, trying to show the connection between green technology and the automotive (world). We do a lot of outreach work to show the community what’s possible.


CJ: Any big scares when you guys have taken Xenith on the road?

WF: Nothing too big. It’s nice in the fact that we have escort vans in front of and behind the solar car that act as its eyes and ears. The one thing that does freak out other drivers is that the car can turn all three wheels in different directions to optimize airflow. All of a sudden a car on the other side of the highway will notice that the solar panels are pointed towards them (even though it’s staying in its lane), and they’ll suddenly veer off the road thinking it’s going to hit them.


Stanford’s Solar Car, Xenith, may look like it’s heading right for the big rig, but it’s three wheels are actually pointed parallel to the road. Three-wheel steering helps the car optimize windflow efficiency. Photo courtesy of Stanford Solar Car Project.


CJ: Tell me more about the last race.

WF: We place fourth in the production class (editors note: in the group of cars that were street legal) and 11th overall out of 40 cars. We had higher aspirations, but we had a breakdown on the first day and a bunch of flat tires. We fell to 17th after the first day but rallied back to 11th.


CJ: How long did it take?

WF: Five to six days. It varies from year to year. Last race was a slow year because there were thunderstorms. You do get some power production through the solar panels but it’s much less than if there were clear blue skies.


CJ: Must be a fun experience, though.

WF: It’s definitely exciting. We go down a few weeks before the race and do the press work, ship the car by ocean freight, test it in the Outback. The race itself is 3,000 km from coast to coast from Darwin to Darwin to Adelaide. You start at 8 or 9 am each day and you stop the race at 5 pm each day. Wherever you are, you just pull off the road and spend the night there. Hopefully you have your tents and water supplies ready. There aren’t many towns in the outback, so you’re setting up a tent and cooking in the dark.


CJ: So do you make the freshmen trek to towns for supply runs? 

WF: Not really (small laugh). By the time you get to Australia after two years of building a car you’re going to be pretty good friends.


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Zachary Shahan

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