In praise of duct tape

It’s a common joke that engineers fix everything with duct tape. I’m happy to say that there’s no truth in that whatsoever.*

Photos: Punch Powertrain Solar Team (iLumen European Solar Challenge 2018), Tshwane University of Technology (Sasol Solar Challenge 2018), Solar Energy Racers (Sasol Solar Challenge 2018), Western Sydney University (World Solar Challenge 2015).

*: not everything.


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A Day in the Life of Solar Energy Racers

By special request, here is another day in the life post, this time for Swiss solar car team Solar Energy Racers (SER). The day is 29 September, the last day of the Sasol Solar Challenge. I am relying on information from a blog by SER strategy person Georg Russ, together with GPS data screen-scraped off the race tracker by a friend, and elevation data from the Shuttle Radar Topography Mission. As before, the horizontal axis of the chart represents distance.

The day began at Swellendam, and the team drove to the control stop at Bredasdorp, stopping there for 30 minutes the first time (it can be seen from the chart that SER was not quite so good as Nuon at maintaining a consistent speed). The team drove two loops, the first of them to Cape Agulhas (the southernmost point of the African continent, and the site of a picturesque lighthouse). It can be seen from the chart that they had to stop on the way (to repair a loose left rear wheel fairing – with duct tape, of course).

The team completed one more, shorter, loop, before heading on to the finish at Stellenbosch (Nuon drove that shorter loop three times). Knowing when to quit driving loops was an important strategy decision. The chart highlights the hilly nature of that final leg (going through part of the Cape Fold Belt), as well as some stops to change drivers.

Georg Russ notes an energy output for the day of 5.35 kWh (with 0.64 kWh recovered), and a photovoltaic input of 4.63 kWh, giving a net battery drain of 0.08 kWh. Pretty good!


Solar Car World Rankings Revisited


Nuon at WSC 17 (photo: Anthony Dekker)

Below is my personal world ranking of the top 21 Challenger-class solar car teams (revised with new data from an earlier list). It was produced entirely algorithmically by using linear regression on historical data to build mappings between WSC rankings and those of other races, and then applying those mappings to the results of four recent events (WSC 17, ASC 18, ESC 18, and Sasol 18). For example, this is the mapping between Sasol placings and WSC placings. It was used to map all Sasol 18 teams to expected WSC placings:

There is as yet insufficient data to rate Cruiser-class teams (apart from the actual WSC 17 results: 1 Eindhoven, 2 Bochum, 3 Arrow). But here is the table of Challengers:

Rank Previous Team WSC17 ASC18 ESC18 Sasol18
1 1 NL  Nuon Solar Team 1 1
2 ↑ 3 NL  Solar Team Twente 5 1
3 ↓ 2 US  University of Michigan 2 2
4 4 BE  Punch Powertrain Solar Team 3 6
5 5 JP  Tokai University 4 2
6 ↑ DE  Sonnenwagen Aachen P 3
7 ↓ 6 AU  Western Sydney Solar Team 6 1
8 ↑ 18 CH  Solar Energy Racers 3
9 ↓ 8 HU  Kecskemét College GAMF (Megalux) 4
10 ↓ 7 JP  Kogakuin University 7
11 ↓ 9 SE  JU Solar Team 8
12 ↓ 10 US  Stanford Solar Car Project 9
13 ↑ ZA  Tshwane University of Technology (TUT) 4
14 ↓ 11 CL  Antakari Solar Team 10
15 ↓ 13 CA  University of Toronto (Blue Sky) 11
16 ↓ 14 CA  ETS Quebec (Eclipse) 3
17 ↓ 15 JP  Nagoya Institute of Technology 12
18 ↓ 12 ZA  North West University P 5
19 ↑ FR  Eco Solar Breizh 7
20 ↓ 17 CA  Poly Montreal (Esteban) 4
21 ↓ 19 US  Massachusetts Institute of Technology 5

Note that Cruiser teams like Eindhoven, Bochum, and Arrow are excluded from the list. The letter P marks cars that participated in WSC 17, but did not finish, and thus were not ranked at the time. It must also be said that Western Sydney, Eclipse, Esteban, and MIT should probably be ranked higher than they are here – the algorithm is not taking into account the dramatic improvement in ASC teams this year. However, good ESC and Sasol performance has bumped up Aachen, SER, Eco Solar Breizh, and South Africa’s new champion team, TUT.


Michigan at WSC 17 (photo: Anthony Dekker)


Sasol Race Report #8

Here are the final results for the Sasol Solar Challenge in South Africa, after 8 days of racing (click to zoom). The photo is from here (taken on day 8), and the daily “loops” are marked. Only the Challenger class is shown (City U, the only car in the Sustainability class, did 175.5 km). The big news was the penalty of 117.4 km imposed on Nuon when a sick team member dropped their bag in the wrong van. The kilometres subtracted by the penalty are marked with light orange in the chart above. They did not, in the end, affect the outcome of the race.

Nuon has some excellent videos about the race (Dutch with English subtitles) for day 1, day 2, day 3, day 4, day 5, day 6, day 7, and day 8. In addition, I should note that SER came 3rd in a tough race, which probably puts them in the world top 10. Tshwane University of Technology (TUT) have taken over as South African champions. Congratulations! And the high school team Sonke (from St Alban’s College and St Augustine’s LEAP School) also deserves a special commendation, displaying both talent and persistence.

After WSC 2017, several people (including me) attributed Nuon’s large lead (see the chart below) to clever weather strategy. But this race, where all cars have been more or less in the same part of the country, suggests that, as well as having flawless race strategy, Nuon have a car that really is significantly faster than all the others (roughly 7% faster than Tokai in Australia, and 6% faster here). This fact may encourage other WSC teams to stick with a tried-and-true catamaran design (as Canadian teams Poly Montreal and ETS Quebec have done). And Nuon themselves? I cannot see how they can possibly improve on Nuna 9S. Maybe they will try something radically different, just for a change.


Sasol Race Report #7

Here are the results for the Sasol Solar Challenge in South Africa, as at day 7 out of 8 (click to zoom). The photo is from here (taken on day 6). The big news is the penalty of 117.4 km imposed on Nuon when a sick team member dropped their bag in the wrong van. The kilometres subtracted by the penalty are marked with light orange in the chart above, and move Nuon down to 2nd place. In my view, it reflects poorly on Tokai that they made a formal complaint about this incident, and it reflects poorly on the Sasol Solar Challenge that they imposed such a large penalty.

Nuon has some excellent videos about the race (Dutch with English subtitles) for day 1, day 2, day 3, day 4, day 5, day 6, and day 7.


A Day in the Life of Nuon Solar Team

This blog post is something a little different: it will use the GPS tracker data feed to describe a day in the life of Nuon Solar Team during the Sasol Solar Challenge. Specifically, it will describe Wednesday 26 September, which Nuon’s media team summarised in this 90-second video:

Wednesday 26 September (day 5 of the race) opened in Graaff-Reinet. On the Tuesday, Nuon had fallen 36 km behind Japanese team Tokai, due to electrical problems. The support engineers began work at 4:00 AM to return their car Nuna to tip-top condition. The morning was chilly, but sunny, which allowed some solar recharging of the batteries.

The plan for the day, as outlined in this livestream by media team-member Bianca Koppen, was to drive to the control stop in Jansenville faster than Tokai. At Jansenville there was an optional 65-km “loop” to Klipplaat and back. The plan was to drive this “loop” six times (Tokai was expected to do so only five times) and then continue to the end-of-day stop in Port Elizabeth, arriving there just before 5:00 PM. In line with this plan, Nuna sets off at around 85 km/h, soon overtaking Tokai:

The chart below (click to zoom) shows the progress of the day. The horizontal axis is distance, and the vertical axis of the main chart is the speed of the solar car. Underneath the main chart is an elevation plot. The letter A marks the start for the day.

The letter B marks the control stop at Jansenville, where Nuna initially stops for 30 minutes (as per the regulations; later stops will only be 5 minutes). Nuna then continues to the small town of Klipplaat, where the route simply loops and returns along the same road (see the map). However, the road to Klipplaat is uphill, and from Klipplaat is downhill. As the chart above shows, the shiny new “intelligent cruise control” adjusts the car’s speed to suit, running more slowly while climbing.

Point C on the chart is interesting. A few minutes into the 4th Jansenville–Klipplaat leg (shortly after noon), Nuon’s strategy team decides that the plan isn’t going to work. Either because of the weather, or the state of the car (I don’t know the reason), they decide that they will only drive five loops today, not six. The whole plan for the day is recalculated, so as to still get to Port Elizabeth just before 5:00 PM (but having used less energy). Instead of peaking around 87 km/h, the next two loops only peak around 70 km/h. The strategy team in the mission control (chase) vehicle must have been working furiously on this plan. On the chart, there is a sudden slow-down at 12:05 PM, but the new driving pattern is established just a few minutes after that. A good strategy team is critical to winning a race!

Point D on the chart marks the last stop in Jansenville, around 2:10 PM:

Race regulation 6.1 requires that a driver can operate the car for at most 2 hours. Given the distance to Port Elizabeth, Nuna stops briefly for a driver change at around 3:45 PM, shortly after this photograph was taken (point E on the chart):

And just before 5:00 PM, Nuna indeed reaches Port Elizabeth. After some more repair work, taking advantage of the energy saved during today’s run, and as the result of teamwork and skill, the plan to drive one more loop than Tokai succeeds the next day.

Of course, much more goes on during a typical day than this story suggests. People are feed and housed. Sick team-members are looked after. Media reports are produced. Nuna, go, go, go!


Sasol Race Report #6

Here are the results for the Sasol Solar Challenge in South Africa, as at day 6 out of 8 (click to zoom). Only the Challenger class is shown. The optional daily “loops” are marked, the black spots indicate time penalties, and the photo is from here (taken by Tokai on day 4). I have calculated average speeds for the cars (hopefully correctly), and the short dashed lines show distances travelled in the 2016 event (which was a faster race, because the cars had larger solar panels).

On Wednesday, Nuon tried to do one more loop than Tokai, but decided halfway through the day that they couldn’t manage it, and slowed down again. On Thursday, they did manage it, and are now 22.7 km ahead of Tokai.

Despite some troubles on Wednesday (a strong wind gust ripped the array off the car, requiring some repairs), the Swiss team (Solar Energy Racers) is hanging on to 3rd place.

Nuon has some excellent videos about the race (Dutch with English subtitles) for day 1, day 2, day 3, day 4, day 5, and day 6. See also the online tracker and my teams list and information page, which includes links to team social media.