GaAs cells power Dutch car to victory
A team of students from Delft University in The Netherlands won last month s Panasonic World Solar Challenge using a car covered with GaAs-based solar cells.
Nuon Solar s car, the Nuna4, completed the 3000 km race across Australia in 33 hours, beating its closest rival by 1 hour 36 minutes.
The vehicle s top speed was 137 km/h and its average speed over the whole race was more than 90 km/h. Along with other solar cars, Nuna4 had to compete under extreme weather conditions as well as navigate between other traffic on the road from Darwin to Adelaide, including kangaroos and Australia s notorious road trains.
"This race shows the public that not only can a car run on solar power, but also that it is fast," Tine Lavrysen, team spokesperson, told environmentalresearchweb.
"Most people believe that a solar car can get an average speed of about 50 km/h, but when I tell them ours did 3000 km on solar power with an average speed of more than 90 km/h, they are always surprised."
The car used triple junction solar cells with an efficiency of more than 26 percent. This year s car was covered in only 6 m2 of solar panels compared with the 9 m2 of previous models.
The reduction in solar panel area was one of the new entry criteria for the 2007 race. Organisers also stipulated that the cars must be equipped with roll bars and an upright seating angle for the driver, making the vehicles more like "real" cars.
Despite having a smaller area coverage of solar cells than its predecessor, the Nuna4 still managed to have an average speed comparable to the Nuna3.
"The most important aspect of the car is not that it s on solar power, but that it uses the power it gets through solar cells so efficiently," says Lavrysen.
"The car is so light and the motor is so efficient (88"“98%, in comparison to fossil-fuelled cars at 40"“60%) that the energy consumption of Nuna4 at 90 km/h is about the same as a normal vacuum cleaner."
Clearly, there is further room for improvement, since solar cell manufacturers including Emcore, Spectrolab and Azur Space have all pushed electro-optic efficiencies close to 40 percent for terrestrial concentrator systems (see related stories).
The team also used a genetic algorithm and adaptive cruise control to optimize the performance of the car. The car s optimal speed was constantly calculated for every set of circumstances (e.g. sunshine, inclination of the road, battery state of charge etc) and was then transmitted wirelessly to the car, which automatically adjusted itself.
The Nuon Solar Team, which was one of the smallest teams in the competition this year, comprised 12 students from various engineering departments of Delft University of Technology. Their disciplines included aerospace, mechanical, maritime and electrical engineering as well as industrial design engineering.
Nadya Anscombe is a contributing editor to environmentalresearchweb, a sister site of compoundsemiconductor.net.