Paris, 25 August 2003
On 19 October 50 racing cars will be in Darwin, Australia warming up for the start of the 7th World Solar Challenge; among them, a slick student-built machine that profits from space technology supplied by ESA. The Dutch Nuon Solar Team and their car Nuna II is among the favourites and ready to defend the title won by their predecessor Nuna in 2001.
In the 2001 World Solar Challenge Nuna, the first Dutch solar car to use European space technology, crossed the finishing line first after a grueling 3010 km race across Australia. Nuna won in a record-breaking time of 32 h 39 m, beating the previous record set by the Honda team in 1996 of 33 h 32 m. Another new record was set by Nuna's average speed of 91.81 km/hour compared to the Honda team record of 89.76 km/h. Nuna also pushed the limits by finishing in just under 4 days.
"Of course we will try to be first again" says Koen Koster of the student's team. "We aim for an average speed of 100 km/h and to finish within 30 hours. It will be tough though as we will be strongly challenged by the 2001 runner-up, Aurora 101, one of the eight Australian teams and the 1999 winner. Other high-budget teams vying for the lead are US Principia College, Queens University from Canada and the Japanese team."
"If we win, in part it will be due to the use of space technology," explains Diederik Kinds, an aerospace engineering student at the Delft University of Technology and leader of the Nuon Solar Team. "Our car uses the most advanced space technology, provided to the team via ESA's Technology Transfer Programme. This should enable the car to reach a theoretical top speed of 175 km/h compared to Nuna's top speed of 160 km/h.
"We strongly improved the aerodynamics by lowering the canopy and reducing the car's bodyweight by using lightweight space-plastics. The main body is made from carbon fibre, reinforced on the upper side and on the wheel's mudguards with aramide, better known under the prodict name of Kevlar."
Carbon fibre is commonly used in the space industry for constructions that have to be both lightweight and strong. One use of Kevlar is in spacesuits to protect against micrometeorites. On Nuna II Kevlar is used to shield against the impact of gravel during the race.
"Most important are the solar cells," continues Kinds, "we use solar cells that harvest up to 20% more energy than those used on Nuna for the 2001 race."
"The solar cells used on the top and the sides of the car are triple-junction gallium-arsenide cells made in three layers. Sunlight passing through the top layer is captured by the second and the third layer. These solar cells are such a recent development that not even ESA has used them yet. Their first space application will be when the SMART-1 lunar mission is launched in September.
"Nuna II is fitted with 3000 solar cells" continues Kinds. and their output is optimised by 10 Maximum Power Point Trackers." These have been used in satellites for years as they optimise the output of the solar panels when satellites pass into the shade due to their position in relation to the sun.
Nuna II will also occasionally be in the shade, due to clouds, buildings and overtaking trucks which reduce the efficiency of solar cells. Maximum Power Point Trackers will ensure that energy from the solar cells remains high and constant. A chip will measure the voltage supplied by the solar cells, compare it with the fixed battery voltage and then determines the best voltage to charge the battery. In this way more than 95% effiency can be attained.
"In poor weather high-performance batteries are needed and these are also based on space technology. Those on board Nuna II have 46 large Li-ion cells connected in series to supply 5 kw/h of electrical energy. Again these were originally developed for use in satellites where high reliability is essential. Their first space application will also be on the SMART-1 lunar mission.
"Last but not least, our captain of communications is astronaut Wubbo Ockels" adds Koster with pride. Ockels, ex-ESA astronaut now head of ESA's Education Office and Professor of Manned Spaceflight at the Technical University of Delft, led the first Nuna team to victory in 2001.
"Will Nuna II win? I think the team has a very good chance," says Ockels, "It will be a tough race as driving from Darwin to Adelaide in October means traversing 3010 km of Australian desert during the start of the hot season. It will be a four-day battle against the elements. As in 2001 we will send a car in advance to warn of any obstacles on the road. The rest of the team and I will follow Nuna II in a support vehicle collecting data about the temperature and current from the solar cells.
"This information will help the pilot to determine strategy, such as whether it is better to drive quickly to escape cloud cover or to drive slowly to save energy. Also we will study the very latest images from weather satellites and meteo bulletins. Selecting the best racing strategy should help us to gain on the other teams."
After crossing Australia in 2001 Nuna then toured Europe visiting schools and museums in 35 cities in 12 European countries. This educational programme emphasized the value of space technology for a more sustainable world and showed, in a tangible way, how the dreams of youngsters can become reality.
In May 2004 Nuna II will ride again, this time in Greece in the Phaeton 2004 rally for solar cars, an initiative of the Cultural Olympiad 2001-2004. For the first time during an Olympics solar cars, made by young scientists from all over the world, will take part in a rally. The rally, which starts and ends in Athens, will visit historic sites such as Olympia and Delphi, sending a clear message that human activities should be exercised in respect of nature.
"Most important," adds Ockels, "is that the cars are designed and driven by young scientists who are inspired and motivated by such events. In Australia the Nuna II team will demonstrate this inspiration and motivation. No wonder we are again one of the favourites to win the race."