ASC 18: Convoys


A typical convoy (click to zoom, photo of solar car by Jorrit Lousberg)

Solar cars in the American Solar Challenge each form part of a convoy – a typical convoy is shown above. The lead (front) escort vehicle must travel 500 metres or less ahead of the solar car, with headlights on and roof-mounted amber lights flashing.

The chase (rear) escort vehicle follows directly behind the solar car, also with roof-mounted amber lights flashing, and bearing a sign that says “CAUTION: SOLAR CAR CARAVAN AHEAD.” Both escort vehicles must carry safety equipment such as first aid kits and fire extinguishers. The chase (rear) escort vehicle typically also houses the team’s Decision-Making Unit (DMU), who plan the strategy for the race.


Left: Michigan’s lead and chase vehicles for the 2010 American Solar Challenge (credit). Right: interior of Nuon’s chase vehicle for the 2011 World Solar Challenge (credit).

The truck (or car with a trailer) rides further behind (at least 1 km). It carries equipment and provides the ability to transport the solar car in the event of a breakdown.


Left: Michigan’s semi-trailer driving down the Stuart Highway in the 2011 World Solar Challenge (photo: Marcin Szczepanski). Right: Calgary’s road crew truck from the 2005 North American Solar Car Challenge (photo: James Tworow).

The (optional) scout vehicle rides well ahead (at least 1 km), checking out road conditions and potential hazards. There may also be additional vehicles, like media cars, or a weather car watching for clouds an hour or so ahead of the solar car. All the cars in the convoy stay in touch using CB radio. It takes a whole team to race a solar car! Here are some team descriptions of their convoys:

This post has been adapted and updated from a previous one.


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ASC 11: Leadership


Nuon Solar Team celebrates their 2017 WSC win (photo: Anthony Dekker)

Ernest Hemingway famously said that “war is fought by human beings.” It’s the same with solar cars – they are built and raced by human beings. Or, as Solar Team Twente likes to say, they are “powered by human energy.

There are many aspects to this human side of solar car racing. I’ve written before about how little things like team clothing contribute to team cohesion. A diversity of skills is important if a team is to succeed. During the race, nutrition is one of the things necessary to keep people working at top efficiency. But today, I want to talk about team leadership.

Engineering leadership is critically important, although surprisingly little is written about it. Tracy Kidder produced a fantastic, almost ethnographic, description of real-world engineering in his 1981 book The Soul of a New Machine, but even that book has the actual leadership happening mostly in the background.

A century earlier, Leo Tolstoy opened his novel Anna Karenina with the words “Happy families are all alike; every unhappy family is unhappy in its own way” (“Все счастливые семьи похожи друг на друга, каждая несчастливая семья несчастлива по-своему”). That is true also for solar car teams. Many things have to be done right if a team is to succeed, but doing one thing badly is enough to stop a team in its tracks.

A team leader must, first of all, motivate team members to do their best – it is no accident that all the solar car team leaders I’ve met have been really nice people. A team leader must make sure that the overall problem of building, racing, and finding sponsorship for a solar car is broken down into manageable pieces, and that the right person is in charge of each piece – this is the essence of engineering.

A solar-car team leader must also have – and promote – a clear vision of the car that the team is going to build. It is possible to have a world-class suspension, a world-class body, world-class solar cells, and world-class everything else, and still fail, because the components were designed under different assumptions, and don’t actually fit together to make a world-class car.

A team leader must keep an eye on the critical path as well. Building a solar car for a race is one of the most challenging kinds of engineering project – one where the delivery date is fixed in stone. What project managers call the critical path is the sequence of activities which, if they take any longer than planned, are guaranteed to delay project completion. Generally, the schedule for building and testing a solar car doesn’t leave much room for that kind of schedule slippage.

One perennial question with solar car team leaders is how long it takes them to realise that there is a problem requiring the team to either (a) change the way it operates or (b) pull out of the competition. Each year, I am reminded by somebody or other of Napoleon’s 1812 invasion of Russia, summarised so well in the famous data visualisation above (by Charles Minard).


Napoleon’s death march (painted by Illarion Pryanishnikov)

Napoleon began his invasion with 422,000 men, and reached Moscow with only 100,000 survivors. This was not enough to do anything, so he turned around and went home again, losing most of his remaining troops to cold and skirmishes in the process. I have often wondered at what point Napoleon realised that his plan was not working the way that it was supposed to. In a similar way, there is always a solar car team that begins a last-minute “death-march,” working until 3:00 AM each night, desperately trying to finish their car. The early hours of the morning are not a good time to be making safety-critical engineering decisions, and teams which leave it so late to panic generally don’t do very well.

But enough of Napoleon. Let us listen to some men and women who know how it’s done (translations from Dutch are my own best attempts):

Olivier Berghuis, Solar Team Twente (2017): “As team leader you are the one ultimately responsible for the success of the project. That means that you have to keep a close eye on the progress of the project’s technical, communication, and financial aspects. The mood of the team and the personal development of each team member are also critically important important responsibilities of the team leader.” (“Als teamleider ben je eindverantwoordelijk voor het slagen van het project. Dat betekent dat je de voortgang van het project op technisch, communicatief en financieel gebied in de gaten moet houden. Daarnaast is de sfeer binnen het team en de persoonlijke ontwikkeling van elk teamlid een zeer belangrijke verantwoordelijkheid van de teamleider.”)

Shihaab Punia, University of Michigan (2016): “… build the best possible team and team culture …”


Photo: Jerome Wassenaar

Irene van den Hof, Solar Team Twente (2015): “I think that I am a good listener for my teammates. I try to put a lot of emphasis on that. Everyone is young and inexperienced, and that can sometimes cause problems, but together we are indeed a team, and everyone has to reach the finish line – I make sure of that.” (“Ik denk dat ik heel goed kan luisteren naar mijn teamgenoten. Daar probeer ik ook veel aandacht aan te besteden. Iedereen is jong en onervaren en dat kan voor problemen zorgen, maar samen zijn we wel een team en iedereen moet de eindstreep halen, daar zorg ik ook voor.”)

And it’s worth repeating the excellent insights from Rachel Abril, who was on the Stanford solar car team for four years (“Go fast, but not recklessly fast. Test it. Test it again. Test it more. Use failure as a foundation for success.”):


ASC 9: Aerodynamics

For both the Challenger class and the Cruiser class, solar car racing is to a large extent about aerodynamic drag. That’s overwhelmingly what the hard-earned solar energy is being wasted on, and therefore it’s what teams need to concentrate on minimising. The drag force on a car is given by the equation:

F = ½ Cd A ρ v2

Breaking that down, v is the speed of the car, ρ is the density of air (about 1.2), A is the frontal area of the car, and Cd is the drag coefficient, a number which indicates how aerodynamic (and therefore, how energy-efficient) the shape of the car is. For Challengers, minimising Cd allows the speed v to be increased, while for Cruisers (for which the average v is essentially given), minimising Cd allows non-solar energy use to be minimised. Of course, minimising frontal area is important too (and that is the motivation behind asymmetric Challenger cars).

To give a feeling for the all-important Cd, here are some vehicles with values ranging from 0.19 to 0.57:


Drag coefficients for a selection of vehicles. Clockwise from top left: 0.57 – Hummer H2 (photo: Thomas Doerfer); 0.30 – Saab 92 (photo: “Liftarn”); 0.26 – BMW i8 (photo: “youkeys”); 0.19 – General Motors EV1 (photo: Rick Rowen)

Because Cd is so all-important, it is the one thing that solar car teams are really secretive about. Challengers generally have values under 0.1. With no need for practicality, they chase their way towards the impossible goal of Cd = 0, trying to come up with the perfect race car, which will slice through air like a hot knife through butter:


Nuon’s 2005 car, Nuna 3, with Cd = 0.07 (photo: Hans-Peter van Velthoven)

Cruisers, on the other hand, have to balance aerodynamics with practicality. Bochum’s early SolarWorld GT had Cd = 0.137:


Bochum’s 2011 car, SolarWorld GT, with Cd = 0.137 (photo: “SolarLabor”)

Eindhoven’s recent Stella Vie, with its sleek aerodynamic shape, does much better than that (but they won’t say how much better):


Eindhoven’s 2017 car, Stella Vie (photo: TU Eindhoven, Bart van Overbeeke)

I understand that Sunswift’s 2013–2015 car eVe had Cd = 0.16. Appalachian State (Sunergy) have stated that their newly-built ROSE has Cd = 0.17. PrISUm’s Penumbra has a higher value (Cd = 0.2), because of the blunt end which they chose for practicality reasons (although they did do a few clever things to reduce the impact of that blunt end). I’m not aware of the Cd values for other ASC cars.


Appalachian State’s beautiful ROSE, with Cd = 0.17 (image credit)


Solar Car Racing Status Check

In solar car racing news, preparations are beginning for the SASOL Solar Challenge in South Africa (September 22 to 30). It seems that both Nuon and Tokai will attend this event, along with local teams.


Nuon at WSC 2017 (photo: Anthony Dekker)

Thirteen teams have registered so far for the 24 hour iLumen European Solar Challenge in Belgium (September 19 to 23), and Twente will be defending their title there. I am maintaining an information page and teams list for this race. See also the official iESC social media at  


Twente at WSC 2017 (photo: Anthony Dekker)

The American Solar Challenge is a lot closer than those two races, with scrutineering beginning on July 6, track racing on July 10, and the road race running from July 14 to July 22. I am maintaining a detailed information page and teams list for this race. At last count, 34 teams were registered, with Anderson, UCSD, Principia, UC Irvine, Phoenix, and UT Austin having, sadly, dropped out.

Six teams are attending with cars that raced at WSC 2017, although these cars will require adjustment to satisfy ASC rules (Michigan, Western Sydney, Principia, and Illini, plus the Cruisers PrISUm and Minnesota). Six other teams are attending with cars that previously raced at ASC.


PrISUm at WSC 2017 (photo: Anthony Dekker)

Twenty-two other teams are frantically building cars for ASC. Car unveils that have been announced include team 42 (Missouri) on 18 April, team 55 (Esteban) on 23 April, team 101 (Eclipse) in mid May, team 828 (AppState) in mid June, and team 65 (Calgary) on 16 June.


Missouri’s unfinished car (picture credit)

See my detailed information page and teams list for this race for more information and for social media links. I will continue to update that page as news comes in.


WSC: three gem awards


Nuna9, the car from Nuon Solar Team

It has been my tradition to hand out “Gem Awards” after major solar car races. This WSC, the “Faster Than Lightning” gem again goes to Nuon Solar Team, the undefeated Challenger champions.


The 2017 “Faster Than Lightning” gem goes to Nuon Solar Team

 


Stella Vie, the car from Solar Team Eindhoven

The “Solar Family Car” gem again goes to Solar Team Eindhoven. They completely dominated the Cruiser class.


The 2017 “Solar Family Car” gem goes to Solar Team Eindhoven

 


Western Sydney Solar Team

The “Solar Car Family” gems go to Western Sydney Solar Team, for the way that they welcomed international teams passing through Sydney. Western Sydney Solar Team are, of course, also Australian champions in the Challenger class.


The 2017 “Solar Car Family” gems go to Western Sydney Solar Team


WSC: South to the border

The afternoon of race day 3, and several teams have been struggling. In the Cruisers, Singapore and Sunswift were forced to trailer. On the other hand, Nuon is streaking ahead to the South Australian border, and Michigan might be breaking the “curse of third.”

The map above (click to zoom) shows GPS positions extrapolated using GPS time lag and the average speed since the start of the race (i.e. it’s a best guess for the true position of the car at the indicated time). Adventure-class teams are not shown. The table below shows team numbers, raw road distance from Darwin, average speed, extrapolated road distance, class (or number of seats for Cruiser class), team name, team social media links, and links to pictures or status reports. For a live map of raw GPS data, see the official tracker.

3 1757.5 km 80.7 kph 1758.4 km C Nuon  photo
2 1682.8 km 77.4 kph 1685.5 km C Michigan 
21 1667 km 76.6 kph 1668.9 km C Twente  video
10 1656.1 km 76.1 kph 1657.2 km C Tokai 
8 1626.7 km 74.8 kph 1629.6 km C Punch  photo
11 1493.6 km 67.1 kph 1493.7 km 4 Bochum 
88 1487.2 km 66.9 kph 1489.9 km C Kogakuin  photo
15 1487.1 km 66.8 kph 1487.7 km C WSU  photo
42 1485.8 km 66.8 kph 1485.8 km A TAFE SA  Adventure
40 1473.8 km 66.3 kph 1476.5 km 5 Eindhoven 
28 1435.3 km 64.5 kph 1435.3 km A KNUT  Adventure
30 1429.8 km 64.3 kph 1432.5 km 2 Arrow 
35 1430.4 km 64.2 kph 1431.3 km 2 HK IVE 
75 1394.7 km 62.8 kph 1394.7 km A Sunswift  Adventure
94 1394.3 km 62.6 kph 1394.3 km 2 Minnesota  video
95 1359.8 km 61.4 kph 1367.4 km 2 Apollo 
4 1364.4 km 61.3 kph 1365.5 km C Antakari 
5 1364.2 km 61.3 kph 1364.2 km A Singapore  Adventure
16 1352.2 km 60.7 kph 1352.9 km C Stanford 
77 1345 km 60.4 kph 1345.6 km C Blue Sky 
43 1320.9 km 59.4 kph 1320.9 km A ANU  Adventure
25 1317 km 59.2 kph 1317.9 km C Nagoya 
46 1294.8 km 58.2 kph 1296.1 km C JU 
38 1263.4 km 56.7 kph 1264 km C NWU 
70 1262.5 km 56.7 kph 1263.6 km C Aachen  video
32 1251.6 km 56.2 kph 1253 km C Principia 
53 1228.9 km 55.2 kph 1228.9 km A Choctaw  – Adventure
71 1210.3 km 53.4 kph 1210.3 km C ITU 
22 1210.3 km 54.1 kph 1210.3 km A MDH  Adventure
82 1169 km 51.3 kph 1169.3 km C KUST 
20 1168.2 km 51.3 kph 1168.2 km A Durham  Adventure
9 1160.4 km 51 kph 1161.2 km 4 PrISUm 
49 1147.6 km 50.4 kph 1147.6 km A Siam Tech  Adventure
45 1145.9 km 50.3 kph 1146.2 km 5 Lodz 
52 1126.3 km 49.5 kph 1126.3 km A Illini  Adventure
37 1124.5 km 49.4 kph 1125.3 km C Goko 
18 1118.2 km 49.2 kph 1118.2 km A EcoPhoton  Adventure
7 1069.7 km 47 kph 1069.7 km A Adelaide  Adventure

Bochum heading into Alice


World Solar Challenge: Challenger dimensions

MostDece has written a superb blog post on the WSC challengers. Based on that, I’ve updated my previous post on dimensions. The infographic above (click to zoom) shows the reported length and width of 16 WSC cars (Challenger class only, this time). The widest car (at 2.05 m) is the South African car from NWU (below), but of course that includes the outrigger wheels. The narrowest is the long narrow bullet car from Michigan. There are also short zippy little cars from Nuon, Principia, and Punch.

Update: The chart below clusters cars with similar length/width combinations. NWU is a visible outlier. Below NWU, we have big cars (ITU, MDH, Adelaide, Aaachen, JU – over 1.6 m wide and at least 4 m long), short catamarans (Nuon, Principia, Punch – 1.55 to 1.6 m wide and at most 3.5 m long), narrow catamarans (Nagoya, Stanford, Twente, WSU – 1.38 to 1.5 m wide and at least 4 m long), and monohulls (Tokai, Kogakuin, Michigan – at most 1.2 m wide and over 4.9 m long):

Update: Unfortunately, the two charts above reflect incorrect information from the Stanford team. The Stanford car is actually substantially wider.