Photo: Tokai University
Just came across a piece
in IEEE Spectrum about Tokai's winning solar car in this year's event, and was amazed at the stats:
- 3000 kilometers
- four days
- average speed of 100 kilometers per hour (~62 mph)
That's an
average speed! That's seriously impressive. Even moreso when you learn that the car has just a 1.8 kilowatt array.
How did they do it?
- satellite grade solar cells with a conversion efficiency of 30 percent, "considerably higher than the 20 percent efficiency level typical of even advanced crystalline-silicon solar cells"
Quote:
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More than 2000 of the current compound cells were mounted over the surface of the one-man three-wheeled vehicle; they produced a peak output of 1.8 kilowatts at noon. "By contrast, silicon cells have an output of 1.2 kW," says Kimura. And even when factoring in aerodynamic drag, which increases rapidly as the speed rises, Kimura says that a car using silicon solar cells would be able to achieve an average speed of only 86 km/h compared with the Tokai Challenger's 100 km/h.
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- Lithium batteries (25 kg pack limit) with the best available specs: largest storage capacity (at 5.6 kWh), best energy density on a watt-hour per kilogram basis.
- modified brushless DC direct-drive motor with an efficiency of 97 percent and an output of 2 kW
- Oh, and they were lucky too: "only one puncture, and one power-tracking circuit needed replacing."
Source:
IEEE Spectrum: The Tech Behind the Winning Solar Car