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Nuna 3 wins World Solar Cup for the 3rd Time
jberends writes "The Dutch TU Delft team wins for the third time in a row the World Solar Challenge in Australia. The average speed of Nuna 3 was 102.75 km/h over the 3021 km strech which is the first time that an average speed above 100 km/h is achieved in the Challenge. It is also the first time in the history of the race that a team wins 3 times in a row."
Well, not only did the Dutch set a new record...the record they beat was their own! According to their official webpage, though, the Nuna 3 has a top speed of about 160 km/h!
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Having worked on a solar car in the past (1996), I would say that the improvements have been incremental, but across a large number of components. Some major ones off the top of my head:
1. The 'best' shell back in my days were the ones that sort of looked like a fish. A round front that tapered to a flat (mammallian-like) tail. These days the best shell is a flat rectangle with a little bubble for the drivers head. Not only is this aerodynamically more efficient, but it exposes a greater portion of the cars solar cells to the sun at any given time, and a more uniform power output across all sun conditions.
2. Solar cells are better. Maybe from about 20% efficiency to 25-30% efficiency for the best cells.
3. Weight reduction: fiberglass monococ shells now made with carbon fiber; replacement of metal components with composites where possible. Aluminum wiring instead of copper.
4. Efficienct DC hub motors: These have come a long way in the past 15 years.
5. Battery technology: Hasn't advance too far, but still lighter more enegy dense packs are always being developed. I don't know what is state-of-the art these days...
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In case anyone didn't know, the true reason for yet another record-breaking win comes down to a single factor: solar array power. The Nuna cars, ever since 2001, have all had first quality satellite grade solar arrays. They have also been the only car with a sponsor (ESA) that could afford these incredibly expensive cells, which have a list price on the order of 2 million dollars. Every other team has settled for "factory second" solar cells with 25-40% less power at less than 1/10th the cost. While Nuna's array power is likely in excess of 2500 watts, the rest of the top 3 have less than 1900W. Nuna has yet to innovate in aerodynamics, vehicle dynamics, or construction techniques. This is just another example of a good business plan and the right contacts prevailing over true engineering excellence. Nuna has done a great job in getting their whole country behind them with tremendous media coverage. To see some excellent designs, check out the next top 3 teams: Aurora, Michigan, and TIGA. Aurora has placed 2nd in the last 3 challenges, usually only an hour behind Nuna but with 30% less array power. They boast an incredibly light car, very good aerodynamics, and a unique carbon fiber tubular suspension/frame that is truly unique. Tiga is the top Japanese team and is the best solar car around a closed track. At under 550lbs (with driver) they are the lightest car in the race. The car handles like a BMW and runs just as fast. Michigan is the top American car and boasts arguably the best aerodynamics of all the cars. Their car is only 10" thick at the midsection and uses sweeping wheel covers to sail through crosswinds. They were also the 3rd best car on the track during the race qualifier, an engineering feat in itself, as a thin car presents a number of suspension/frame and dynamic challenges.