Japanese car Tokai Challenger leads World Solar Challenge

The leading cars in the World Solar Challenge have passed the halfway point in the race from Darwin to Adelaide.

Leading the way late on Monday was the Tokai University solar car entry Tokai Challenger.

At last report the car was 1,436km from Darwin. Race officials said it was expected to stop for the night just south of Alice Springs with about 1,540km covered.

In second position was Infinium from the University of Michigan, which was about 70km behind.

The leading cars are expected to reach the finish in Adelaide on Wednesday or Thursday, depending on weather conditions.

The Tokai Challenger is equipped with triple-junction compound solar cells that use indium gallium phosphide (InGaP), indium gallium arsenide (InGaAs) and germanium (Ge) for top, middle and bottom cells, respectively. They are originally space cells used on communication satellites and feature a cell conversion efficiency of 30% (conventional crystalline silicon solar cells typically have a little more than 15% efficiency).

A total of 2,176 cells, each of which measures 77 x 39mm, were installed on the top surface of the vehicle. When used as space cells, they are sealed with glass to make a module. This time, however, the cells are sealed with a film so that they can be mounted on a curved surface and the total weight of the solar car can be reduced.

The total area of the solar cells is 6m2, and the total output is 1.8kW. Generated electricity drives Mitsuba Corp's brushless DC direct drive motor (efficiency: 97%) after passing through Mishimaki Denshi Y.K.'s buck-boost type maximum-power-point tracking circuit (efficiency: 98%). Also, Panasonic Corp's Li-ion secondary battery (5.6kWh) is used to store electricity.

The car can reach a top speed of 150km/h but as the race is being held on open public roads they have to respect the speed limit of 130km/h.

Follow the race Live on Google Maps here

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