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How the GM Sunraycer Worked

        Auto | Hybrid Cars

Sunraycer Design: The Rolling Cockroach
Energy Secretary John Herrington, left, points to a component of the solar-powered GM Sunraycer while co-driver Molly Brennan of Waterford, Mich., sits in the cockpit in Washington, D.C., Nov. 18, 1987.
Energy Secretary John Herrington, left, points to a component of the solar-powered GM Sunraycer while co-driver Molly Brennan of Waterford, Mich., sits in the cockpit in Washington, D.C., Nov. 18, 1987.
AP Photo/Charles Tasnadi

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It goes without saying -- the Sunraycer is a rather peculiar looking vehicle. Resembling a cross between a squashed bullet and a cockroach, the Sunraycer is long and sleek. In order for the car to be able to run on solar energy, more than 7,000 solar cells are installed on the skin of the vehicle covering an area of about 90 square feet (8.4 square meters). The solar cells charge a large silver-cell battery pack which is installed behind the driver's compartment. The driver sits almost as if driving a Formula One or Indy Car and the entire vehicle (minus the driver) weighed less than 400 pounds (181.4 kilograms).

Along with its large battery pack, the Sunraycer contains a smaller silver-zinc battery used primarily for accelerating past slow traffic and up hills. Both batteries power a lightweight direct-drive electric motor that powers the rear wheels. At 8.1 pounds (3.7 kilograms), the electric motor produces just two horsepower.

The Sunraycer's slung-back design eliminates as much as drag as engineers could ca­lculate. At a paltry .125 drag coefficient (Cd), the Sunraycer was more aerodynamic than a McLaren F1 at .32 Cd. In fact, most production cars rarely dip below .30 Cd. The GM (Impact) EV-1, which we'll learn about in the next section, had a very low drag coefficient, too.

The solar cells on the Sunraycer are similar to those found on satellites. MacCready pulled on his aerospace engineering background to design a comfortable cockpit for the driver. Because of the excessive heat in the Australian Outback and the lack of climate control devices and outside ventilation, the sealed cockpit had to be well-insulated. Engineers solved the heat issue by applying a thin gold film over the cockpit. The film blocked 90 percent of visible light and 98 percent of the Sun's infrared radiation.

In the next section you'll learn how GM went from solar-power pioneer to the brink of bankruptcy. Believe it or not, the Sunraycer played a major role. Read on to find out.


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