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Solar Raycers

Across America without a drop of gas

Hybrid drivers, eat your hearts out. While a gas/electric hybrid may get phenomenal mileage compared to a conventional car or SUV, there is a new type of car that can go clear across the continent without using any fuel at all. No gasoline, no diesel, no gasohol, no propane, no BioWillie, no nothing! These sleek racing cars derive all their power from the sun, and they compete in a grueling, long-distance enduro every two years. Called solar Raycers (so named for the rays of the sun), their big event is the North American Solar Challenge.

Natural Attraction

The United States Department of Energy and Natural Resources Canada put on the event, which is centered on solar-powered vehicles (although there is a demonstration-only class for other energy-efficient powerplants). Entry is open to anyone, but all the teams competing in the 2005 event represent (officially or unofficially) colleges and universities. Students design the Raycers using computer simulation and design programs, then build the vehicles themselves.

Early electric vehicles were based on golf-kart principles, with conventional lead-acid batteries and simple speed controllers. These had a short range and long recharge times. By adding solar arrays to the top of the vehicle's body, the power supply on modern solar Raycers can be recharged without stopping. In addition, solar Raycers employ state-of-the art technology in their batteries, electric motors and carbon-fiber body construction. However, as with other types of racing cars, all the technology in the world will not help if the vehicle is sitting broken beside the road. Dependability, simplicity of construction and controllability are as important to sun Raycers as they are to Formula 1 or NASCAR competitors. The race is not always to the swiftest, but usually to the team with the least mechanical grief and the best teamwork. The route for the biannual event varies, but the 2005 event streaked 2500 miles from Austin, Texas to Calgary, Alberta. The cars run at highway speeds through all types of weather—yes, even when it's cloudy!

Qualifying

Before a Raycer can compete, it has to pass a rigorous safety inspection and survive a 120-mile qualifying race. This year, 21 teams qualified to take part. The cars set off with two support vehicles (one at each end), as they do not have lights or extensive crash protection (however, many of them are fully street legal in their home states).

From Austin, the teams made a relatively short three-hour run north across Texas then stopped at the small town of Weatherford for the night. This initial leg allowed the teams to sort out any problems that cropped up. From North Texas, the teams set off for Canada, with media stops along the way to give the curious a chance to see these ingenious creations up close.

The teams race from 8:00 a.m. to 6:00 p.m., at which time they must stop where they are and camp out until the next morning when they can speed off again. The winner is determined by the lowest elapsed time on the journey, but there are other awards for teamwork, technical innovation, engineering excellence, safety and sportsmanship.

Rules

The rules allow lots of freedom in design, but some ideas have been found to work better than others. Although any electric motor can be used, most of the top teams use a small, round motor made by New Generation Motors. It is mounted inside the driven wheel and has no transmission. This makes it highly efficient at highway speeds, but not so efficient when starting or climbing a steep hill.

Batteries are a critical factor for Sun Raycers. The regulations stipulate different weights for each type of battery, allowing for the fact that new technology batteries are lighter (and more expensive) than old-tech lead-acid batteries. Many top teams are employing lithium polymer batteries, although others use lithium-ion or lead-acid batteries.

The bodies are mostly made from carbon fiber, a light, strong fiberglass-like material. Attached to the top of the broad, flat bodies are hundreds of solar cells that provide power to run the motor and recharge the batteries. There are different Raycing classes based on the use of commercially available cells or much more expensive experimental ones.

The slim bodies are styled for aerodynamic efficiency and low drag. The tops of the bodies are easily removable, so they can be set on stands and oriented toward the sun for optimum recharging when the cars are stopped along the route. To prevent any 'stray' current from giving an entrant an advantage, Rayce officials impound the batteries after 8:00 p.m.

Chassis design is one area where there is no clear-cut winner. Some cars have three wheels, others four. Some teams prefer chrome moly steel or aluminum-tube space frames, while others fabricate a monocoque chassis from carbon fiber. All are light, with typical weights of 385 to 880 pounds. Most cars hold one driver, although some two-seaters have been built as well.

All their high-tech components don't come cheap. A complete vehicle costs anywhere from $100,000 to $300,000. This means that the students also learn about landing sponsors and raising funds as well as constructing exotic vehicles.

So how well do they run? Solar Raycers have been clocked at over 100 mph, although most top out at about 70 mph. They can cruise at 65 mph, although steep hills can take a toll on top speed and they are not allowed to exceed the posted speed limit.

Under the Weather

Drivers lay on their backs to allow the cars to have a low profile (for less wind resistance), and a bubble or aircraft-style canopy usually covers the driver's head. Once inside, the driver snuggles in for a miserable ride. A helmet is required and there is no air conditioning. Minimal ventilation is provided, but the drivers (mostly college students) don't seem to mind.

Once on the road, the Raycers fall in behind a lead vehicle and are followed by a chase vehicle. In addition to crewmembers, each convoy has a race official aboard to enforce rules and provide help if needed. The driver is kept busy monitoring battery condition and other systems via an instrument array. Steering can be provided by a multitude of arrangements, including conventional steering wheels, levers or handgrips. Drivers must be changed every six hours.

Learning Curve

So why do they do it? The opportunity to work with cutting edge materials and systems on a project of potentially global importance is a major factor. Like all racers, the competitors intend to win, but also enjoy the camaraderie of being with like-minded competitors from other schools as well.

Solar racing has been going on for 18 years, but the North American Solar Challenge started in its current format in 2001. It's held every two years and the enthusiasm and entry lists are growing. Maybe the starter of the future will say, 'Ladies and Gentlemen, plug in your batteries!'