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Solar
Odyssey 2001 is going to be a tough race. Driving from Darwin to Adelaide
at the end of November involves crossing 3010 km of Australian desert
during the hottest season. It will be a four-day battle against the
elements. And yet 40 teams are keen to enter the competition.
Testing Nuna on the DAF test circuit at St. Oedenrode
Place your bets on Nuna as the winner - it is much more than an ordinary solar powered racing car. Nuna is partly fitted with solar cells which have actually been in outer space, as part of the Hubble Space Telescope. The Alpha Centauri Team, which built Nuna, is supported by Dutch astronaut and Delft University of Technology (TUD) Professor Wubbo Ockels.
If
Nuna does win, it will be due in part to the use of space technology. The
solar cells used all over the top of the car have never before been used
in the race, and they have a very high efficiency. They are dual junction
and triple junction gallium arsenide cells, with two or three layers. The
sunlight that passes through the top layer, which would normally be
wasted, is now used by the second or even third layer. The solar cells are
such a recent development that the European Space Agency (ESA) has yet to
use them in space.
Their
first space application will be at the end of next year when the SMART-1
lunar mission is launched. One of the jobs of SMART-1 is to test a solar
powered ion engine. “No team has ever used such efficient solar cells on
their car” says Ramon Martinez, a mechanical engineering student at TUD
and leader of the Alpha Centauri Team, which also includes another five
TUD students and two students from Amsterdam University. “Nuna is fitted with 36 solar panels” explained Martinez, “their output is optimised by Maximum Power Point Trackers.” Maximum Power Point Trackers (MPPT) have been used in satellites for years. They optimise the output of the solar panels when they are in the shade, for example when the attitude of the satellite changes relative to the sun. ESA's Rosetta mission to comet Wirtanen, to be launched in January 2003, will also be equipped with MPPTs.
Martinez
continued “Nuna will also occasionally be in the shade, which reduces
the efficiency of solar cells. But the MPPTs will ensure that the solar
cells supply a lot of power and will also stabilise the power. A chip
measures the voltage supplied by a solar panel, compares it with the fixed
battery voltage, and then determines the best voltage to charge the
battery. In this way we can get an efficiency of no less than 97%. Of
course, we also need a high-performance battery to operate effectively in
poor weather conditions. Depending on the speed, we will be able to travel
250 to 500 km on a full battery.” Delft
University - Nuna II
“I
think the whole car could easily be launched into space.” jokes Koen
Boorsma, who studies aerospace engineering at TUD. He was responsible for
the construction of the aluminium frame around the driver, as well as
Nuna’s bodywork. “The whole car has to be light and strong. That’s
why we built the bodywork in carbon fibre, reinforced on the outside with
Kevlar. The Kevlar layer will protect Nuna against the impact of gravel
during the race.” Kevlar is extremely strong and is used not only in
bullet-proof vests but also in spacesuits, for protection against
micrometeorites. Some walls of the International Space Station (ISS) are
also reinforced with Kevlar to protect the astronauts.
The Alpha Centauri Team even considered the use of real space suits. Air cooling would adversely affect the aerodynamics of the racing car. As the temperature in the cockpit can be as high as 70°C, a space suit might help. However, in the small cockpit it would be too restrictive. Instead, the pilot will wear a cooling vest with ice cubes.
Another
key factor in the race is good communications. From a support vehicle the
team will collect data about the temperature and electrical current
generated by the solar panels. This information will help the pilot to
determine the strategy. “Should you try to drive away quickly from under
cloud cover? Or should you try to save energy in that situation? Selecting
the best racing strategy should help us to gain an advantage over the
other teams.” said Martinez. “Will we win? With this car we stand a pretty good chance.” concluded Martinez. “In theory, we should be able to reach a speed of 190 km/h. In practice it will probably be around 160 km/h, which would still be a record for a solar powered racing car. However, we will only reach that speed on a special test circuit, before the race. During the race itself on public roads the normal Australian speed limits will apply. Greatest competition is expected from the Australian Aurora 101 that won the 1999 World Solar Challenge and the car of the Japanese Honda team that has won twice before. We also have to beat the University of Michigan’s solar car that won the solar car race down Route 66 in July.”
Last
year the average speed of the winner was slightly more than 90 km/h. The
Alpha Centauri Team hopes to cross the 100 km/h boundary. If it meets this
target, it would then also complete the race within a magical four days
instead of five.
In
the Land-Down-Under, between October 20-24 2003 the Nuna II solar-powered
car raced from Darwin to Adelaide, a distance of over 3000 km in a record
30 hours and 54 minutes. In doing so she beat her own 2001 record by
better than a hour and half. The estimated average speed over the course
was 97 kph, again more than five kph faster than its earlier record.
The
secret of the Nuon Solar Team from Delft University is the Nuna II's
improved aerodynamics, its use of space-age carbon fibers that helped cut
its weight, and new triple-junction gallium-arsenide solar cells. The
cells capture 20% more energy than those used by Nuna II's predecessor.
The
second and third place finishers were the Aurora 101 from Melbourne,
Australia and MIT's "Tesseract", respectively. Event organizers
say that this year's 22 entrants are of a higher standard than previous
events.
Congratulations
to the team for a job well done and for advancing the cause of clean,
sustainable, electric transportation. For
further information about ESA’s contribution to the Nuna, please
contact: ESA's Communications Office at ESTEC in Noordwijk Alpha
Centauri Team World
Solar Challenge Virtual
Solar Challenge Hubble
Scientific & Technical SMART-1
ESA
Technology Transfer
SOLAR CAR EVENTS
American World Solar Challenge - Formula Sun Australian World Solar Challenge Canadian Solar Discovery Challenge Dream Cup Solar Car Race Suzuka 2003 - Japan Japanese World Solar Car Rallye North American Solar Challenge Solar Express - Solar Bike Race
A taste for adventure Solar Cola - a healthier alternative.
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