UM Solar - WSC - Day 4

Submitted by Bronco648 on October 9th, 2013 at 9:52 AM

As I scan thru the Live chat sessions, I am starting to get a distinct flavor of disappointment and frustration from the former team members that participate. A few of them were mulling over the possible causes of why Generation doesn't seem to have the top speed that other teams are showing. The speculation is that the aero package is not right and is costing the car in terms of performance (speed and energy consumption). In all fairness, this is the first time UM Solar has built a 4 wheel car in a long time. Due to changes in the rules (because some teams experienced instability with three wheels) existing data sets, from which you can base calculations, aren't really valid. However, with the support of ex-team members these issues could have been addressed, quickly.

Yesterday's run had another natural factor causing issues; wind. Cross winds not only make things difficult due to aero but create mechanical trouble, too. Have a look at this tire:

That's worn right down to the Kevlar cords and perhaps past them. This is simply from the wind pushing the car sideways and the driver countersteering to keep the car on the road.

Sadly, those very same cross winds caught out Generation as they turned into the Coober Pedy control stop. A strong cross wind gust caught the car and forced it off the road, damaging it severely enough that they could not continue. The WSC is showing that the car was put on a trailer but that does not seem to be the case. The team will fix the car and they will finish.

The top five, again, remian static. Nuna7 and Tokai Challenger are approximately 125 km from Adelaide. That's just a few hours of racing left, for those two teams. What's far more interesting is the battle between RED (Team Twente), in third and Luminos (Stanford) in fourth. Fourteen minutes separates them on the clock. However, they're both about 300 km behind the front two. So, they've got a full day of racing, ~425 km, ahead of them. Even more interesting is the weather. According to some ex-UM Solar weather experts (and each solar team has a group of these folks), there will be increasing clouds and a significant possibility of rain as they approach Adelaide and the coast. So, the final results will be impacted by; weather, State of Charge (how much electricity in the batteries) and the ability to get a charge from the evening and morning sun. It should be an interesting finish.

Comments

santy

October 9th, 2013 at 11:01 AM ^

As fans I think we have the right to be disappointed and ask questions when things don't go down in a desirable fashion. which ironically is exactly what 99% of the Mgoblogosphere does when the football team does poorly. 

As for alumni support, there's been a good amount, believe me. For example, one of our electrical engineers came out of solar retirement,  took a couple weeks vacation from his day job just to fill a crucial spot on the team when one of the current students fell sick and couldn't go to Australia. But we can/should only do so much. If alumni do everything, nobody learns anything.

Bronco648

October 9th, 2013 at 11:33 AM ^

I was hoping you would chime in here because clearly, me, as an outsider, doesn't quite get the tone of ex-UM Solar team members. You know them better than I (after reading your article, posted in the Day 3 thread, I know who you are). Am I disappointed, yep. Same as football after Akron and UConn? Yep. However, this isn't the same. As someone that used to race (cars), I know there are days where things don't go as planned. Some times you're good enough to overcome adversity, sometimes it's too much. It's happened to me on many occasions.

I meant no disrespect, to you or any (ex) team members. I, for one, know how hard you all work, in addition to being a UM student. I'm just trying to play "reporter" here but do have the benefit of your insight but do not have the benefit of being on-site. The dearth of information has made this pretty difficult (which is a downer for me - I've looked forward to this for some time) and II'm doing this by "seat of the pants" and "reading tea leaves". You're certainly more qualified to publish these posts than I am. =) Perhaps I should touch base with you during ASC 2014...?

gbdub

October 9th, 2013 at 11:38 AM ^

And it's also worth realizing the time pressure this project is always under. It's fairly easy to look at the finished car and say, man, that could have been done better. But the design was locked in months ago and there are only so many iterations you can do before you have to pick one. And no system on the car is designed in a vacuum - everything has to play nice with everything else and sometimes you have to make some conservative assumptions so you don't end up with a car that doesn't fit together at the end.

The first car after a major rule change (like this one) will always be really tough because you have to decide between exploring every possible configuration and just picking one and refining it. We had similar challenges in 2007 - looking at all the competitors that year, they all look pretty unrefined compared to 2009 and 2011.

gbdub

October 9th, 2013 at 12:36 PM ^

Santy? I'm not tied in enough to know the exact decision making process of the team. The impression I got was that they did not believe that the better cells would be available in time and/or were not aware of their availability until they'd already locked in their cells.

These arrays are not off the shelf units - basically you buy bare solar cells from the manufacturer, then send them to an "encapsulator" (there are basically two guys, one in Arizona, one in Germany, who do all the encapsulation for the vast majority of competitive teams). Encapsulation is the process of wiring and laminating the cells into modules that can be safely handled and attached to the car.

The process is not fast, and the logistics can be challenging, meaning there's usually a bit of "schedule chicken" involved in getting your array.

gbdub

October 9th, 2013 at 4:54 PM ^

I'm simplifying a bit, but the best gallium cells will produce about 50% more power compared to the best silicon cells (gallium is ~35% efficient, silicon ~23%). Silicon is much cheaper however. Typically gallium cells are only used in concentrators (where the actual cell area is small) and space applications (where weight and efficiency trump cost).

Gallium vs. silicon is not the issue here. In 2011, WSC went to new rules that limit gallium arrays to 3m^2 but allow 6m^2 for silicon. Basically all of the real competitors moved to silicon (less competitive teams were already using silicon due to cost).

The particular issue in this case is that latest generation of silicon cells, which started being produced commercially quite recently, have a higher efficiency than the cells on Generation. The teams that bought and used these newer cells have a significant power advantage, probably greater than the aero differences.