Strategy more than anything might determine which of 15 entries wins the North American Solar Challenge race this year.
Drivers of the sleek, wing-shaped solar powered cars that flashed into Winnipeg yesterday and out again today en route to Calgary were complaining about a shortage of fuel --sunlight.
"If we don't have sunshine there's not a chance for us to recover our battery charge," said James Doell, captain of the Red River College team, one of four Canadian teams in the 15 entry field.
How does that affect strategy? In a myriad of ways.
First consider that these cars are covered with dark solar cells that convert sunlight into electricity to drive an electric motor. Since a car's solar array produces only a small amount of power (enough to run a hair dryer), the vehicles have to be lightweight and extremely energy efficient.
Over the past two decades of solar car racing, students have come up with innovative designs to help them go faster and further than the competition -- and the astonished drivers of the gas guzzlers they pass along the way.
Most solar cars are made from lightweight, ultrastrong materials such as carbon fiber, Kevlar and titanium -- all of which are commonly used to make high performance aircraft.
Compact suspension systems can handle the roughest roads, specially designed tires minimize road friction, and hydraulic disc brakes made for bicycles provide enough stopping power.
The use of advanced materials and simple components can keep the weight down to 300 kilograms - about a fifth of that of a conventional car.
Solar cars are shaped like wings to minimize air resistance. Only a small canopy for the driver's head breaks the streamlined top surface. Computer programs for designing aircraft are used to come up with the most aerodynamic shape, and some designs are tested in wind tunnels.
Solar cells on these cars convert between 14 per cent and 28 per cent of the sunlight falling on them into electricity (the best and most expensive ones were designed for satellites).
The electricity from the cells is stored in a battery pack and drawn off as needed to run the car.
Over the years, battery packs have evolved from simple and heavy lead-acid car batteries to more sophisticated lithium polymer systems like those in laptop computers. Some of the most efficient electric motors ever designed are used to run the cars.
Students can't win a race just because they've bought the best technology. They also need a race strategy.
A well designed car will run at the speed limit during the middle of the day while still having extra energy from the solar panel to store in the battery pack. This "banked" energy is used later in the day and the next morning when the sun is low in the sky and the panel is generating less electricity. It's also needed when clouds block the sun and cut down on the available power.
Winning a race hinges on careful energy management. Drive at an unsustainable speed and you might be stuck at the side of the road the next day recharging the batteries.
If a storm is rolling in, should you risk draining batteries by trying to outrace it to stay under clear skies?
Races have been won and lost on such decisions. Competitions can be as fierce as any NASCAR event.
The Australian outback was the scene of the first long-distance solar car race, the 1987 World Solar Challenge. The North American Solar Challenge (NASC) is the other big event in the solar racing circuit (it was called the American Solar Challenge before venturing north of the border for the first time in 2005) and it only has entries from colleges and universities.
Students develop practical engineering skills from these projects and they benefit from working with corporate sponsors. Some of today's solar car racers were first inspired by the educational outreach programs offered by many teams.
Are solar cars the way of the future? Probably not. They're too expensive and cramped to appeal to most people. However, like the space program, these vehicles provide an arena for demonstrating cutting-edge ideas. They show how better batteries, motors and advanced materials could be used in tomorrow's hybrid and electric vehicles.
The NASC vehicles, including Red River College's "Racer," have covered more than 2,600 kilometres since the race began in Texas on July 12.
Tom Simko is an engineer who has been a student member and alumni advisor with the Queen's University Solar Vehicle Team, which is in this summer's NASC.
PREVIOUS
