World Solar Challenge 2017 Rules

The World Solar Challenge website has just put up the 2017 WSC regulations, which include the following changes:

  • Control stop procedures have changed.
  • The maximum allowable size for cars has been increased to allow greater diversity of design, and provisions made to find synergy with other international events.
  • Challenger solar collector area has been reduced from 6 m2 to 4 m2 (for silicon PV), half of what was allowed in the first World Solar Challenge in 1987. However, for GaAs, the area has been increased to 3.56 m2.
  • Cruiser solar collector area is reduced to 5 m2 for silicon PV cells, to make it easier to fit a solar collector on a practical car. For GaAs, the area has been increased to 4.44 m2.
  • The apertures of solar reflectors and concentrators will be restricted, and external devices intended to increase the irradiance on the solar collector must not be used at any time.
  • Refinements have been made to the requirements for occupant protection and vehicle dynamics. In addition there is a new requirement for mechanical braking on all road wheels.
  • Energy storage (and recharge) limits have been removed for Cruiser Class, which will be run as a single stage ‘regularity trial.’ Success in the Cruiser Class will be based on energy efficiency, practicality, and adherence to time targets. The winner will be the Cruiser team that completes the route, arriving in Adelaide within the target time window, and has the highest value of 80 E/E* + 20 P/P* (where E is energy efficiency score, P is practicality score, and X* is highest X).
  • Adventure Class will be non-competitive.

Here is a simplistic comparison of old and new Cruiser Class scoring methods on the 2015 results (although bear in mind that the new rules change strategy, and that Eindhoven’s Stella Lux is no longer legal under the new rules):

Update: For a more detailed analysis of the new rules, see


11 thoughts on “World Solar Challenge 2017 Rules

  1. Hi Tony
    There is always intrigue at this time, the real start of a new cycle, and the organizers have certainly not let us down this time.
    As Chris Selwood said, the devil is in the detail and it looks like there are more devils than ever here.
    No doubt there will need to be some clarification of different points but the first thing that strikes me is the method of determining the allowable size of the cars. If, and I must emphasize the IF, I understand the rule correctly then the frontal elevation of the vehicle must fit within an Isosceles triangle with a base of 2200mm and a height of 1600mm. As there is no other rule for vehicle dimensions It appears that this applies to both Challenger and Cruiser classes. It also means that, contrary to the headline, the allowable size of the vehicles is reduced and not increased!

    A quick exercise throws up some interesting dimensions. Assuming that wheels are 500mm diameter including tyres then the width of the vehicle at the top of the wheels could be no more than 1512mm. Moving up to the occupants’ eyeline at a minimum 700mm the width of the vehicle can be no more than 1237mm. At 1000mm from the ground, the sort of height that teams might consider building to, the maximum width is 825mm.
    Now this throws up the likelihood of some very interesting Challenger class cars but I am struggling to see how Cruisers will fit these dimensions unless a) drivers and passengers are going to get very cosy with each other or b) passengers sit in a line behind the driver.

    Looking at the other regulations, as much as I’ve been able to so far, there are some good things, in my opinion, and some that are rather disappointing.
    It is good that the size of the array is to be reduced but a shame that the allowable size of GaAs cells is increased. This increase is huge when you consider it as a proportion of the allowable area of Silicon cells. Previously Gallium arrays could be 50% of the size of Silicon arrays, now it is
    Personally I would ban the use of GaAs until the cost of them falls to a level that might make them commercially viable.

    Whilst on the electrical system, it is a shame that the WSC and most other events continue with the policy of penalising teams for using the most efficient batteries. The biggest advances in electric vehicles will come from improved batteries and teams should be encouraged to explore this area more than any other. Apart from a very small gain from having a lighter vehicle there is no benefit in having more efficient batteries as the organizers will just reduce the amount that you are allowed to carry.

    The new control stop procedures are very welcome, although perhaps a little heavy handed. We will no longer have the ridiculous sight of dozens of people running around and setting up the car to charge. I suspect that now that the configuring has to be done by the driver alone, and as an addition to the control stop time, teams will simply not bother with anything too elaborate. On the other hand, to say that no-one must “touch” the car during the control stop is perhaps a bit much. Surely a quick wipe of the windscreen or a check of the wheelnuts could be allowed.

    Now to the real bugbear – the Cruiser class. It seems to me that by now, the third running, we ought to be getting closer to a sensible set of regulations but I’m not sure that this is it.
    Glossing over the fact that the organizers still consider that a vehicle can only be practical if it carries more than one person ( whilst 61% of journeys are with single occupancy), the headlines are once again misleading.
    The result will not be decided by energy efficiency because once again energy use will not be measured. Instead, the number of charges will be counted and this number will be multiplied by the battery capacity. Unless a team can work out how to drain their batteries at exactly 5pm each day, without going too fast of course because the must not finish early, then they will lose out on the calculation.
    These teams know exactly how much energy they have in their batteries at all times. In a so called “Brain Sport” surely it is not beyond the wit of man(or woman) to calculate how much energy is put into the batteries during a charge.

    Finally, there is one other possibility thrown up by these rules in the Cruiser class. If you can find a car that fits into the aforementioned triangle(if that is indeed the requirement) then you could purchase an electric vehicle, fit one solar cell on the roof and enter the race. You would probably need a couple of spare battery packs and you would be nowhere near winning. But you could enjoy the adventure, in comfort, and at a fraction of the price of building a car.

    • Thanks for those insights (I note you have corrected your comments on size below). I tend to agree with the GaAs changes – modern silicon is not much less efficient than GaAs. I don’t see anybody going out and buying bulk GaAs, but Bochum now have the option of adding a few more cells to their car.

      I see why the Cruiser class changes were made, since the 2015 rules stopped the majority of the field from finishing. But it is a radical change, and I hope the WSC will converge on a stable approach eventually. Effectively, it’s now a contest on people carried per charge. As you say, this lets some people run an electric vehicle with minimal solar assist and actually finish on time (though scoring poorly), while the top end competitors try to either (1) carry many people, like Stella, or (2) minimise charging.

      • One of the biggest surprises for me is the very narrow arrival window. The average speed required seems very generous at 38 to 41 mph(assuming that teams manage to schedule their re-charges for overnight) . No doubt this is to try and ensure a bigger number of genuine finishers but it does nothing to help the image of the cars. Presumably this speed requirement will be increased in future years but for now it will do nothing to convince the public that solar cars are a viable prospect, they will believe that they are too slow.

      • Then again, the Dutch have been slowed down in the Cruiser class by having a smaller panel, and other teams have been sped up by allowing more charges, so greater clustering would have happened anyway. Tactically, I guess fast Cruisers will just skip a charge, so I can see the need for some interesting graphs in the 2017 race.

  2. Read in haste, repent at leisure – as they almost say.
    If I had read more carefully I would have seen the words “right rectangular” instead of just “prism”
    so disregards my comments about the size of the cars.
    I did say IF I understood correctly – obviously I didn’t 🙂

    • Sometimes I think the real BWSC contest is a reading comprehension test. One where most of the contestants are non-native English speakers.

  3. Pingback: Preparing for the 2017 World Solar Challenge | Scientific Gems

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