Tuesday, October 13, 2009

The World Solar Challenge -- Coming Up Fast

In 1982, Australian Hans Tholstrup drove the first solar-powered car ("Quiet Achiever") almost 2,800 miles between Sydney and Perth in 20 days -- 10 days faster than the first gasoline-powered car to do so. Following his dusty "roll about," Tholstrup founded the World Solar Challenge, which has become the world championship of solar car racing. The event has also is one of many pivotal points in the history of solar energy.

You'll be reading more about the World Solar Challenge in the coming weeks (10/25 - 10/31) as I follow the University of Michigan Solar Car team, which turned 20 in 2009. The team has built 10 cars in that time. Five have won national championships; three placed third in world competition. And none of those races was inconsequential.

Crossing the Australian outback, from Darwin to Adelaide (north to south), on the Stuart Highway, powered only by sunlight, is a monumental undertaking. Here are some basics. If you compare a solar car with the cars that we drive daily, think of the battery as if it were the gas tank, and solar array as if it were the gas pump -- except the gas pump that sucks the money out of your wallet doesn't have an infinite supply of energy, as the sun does. An "optimizer" gets the energy from the array to the battery. You might think of an optimizer as an oil refinery that's small enough and light enough to have on board the car.

At some point in every race, the team must ask a question: Do you put the array power output directly into the motor, or do you put some of it in the battery? The weatherman figures mightily into the answer -- if it’s cloudy, then a solar car's dependent on its battery, and driving too fast in cloudy conditions can drain the battery quickly, leaving you with the aggravating task of punching up roadside assistance, which is never close by in the Outback. So the sophistication of the battery is critical.

However, as you might expect, the solar cells are the primary technology. In the University of Michigan's 2009 car, Infinium, the team has connected more than 40 individual cells to get the necessary voltage (140V) and power (5+ kilowatt hours). Previous cars had many more cells, but as photovoltaic technology advanced, the power density increased, enabling fewer cells to produce as much or more power than cells in earlier arrays.

The car also needs a mastermind in its circuitry. Here's another car analogy. Think of the solar cells as the number of gallons in your tank. Each battery cell has a small printed circuit that reports minimum and maximum voltage, temperature and current. An on-board system monitors all of the cells about every 100 milliseconds to control the function of the battery. So the car’s "brain" has to be at the top of its game.

Having said all of that, I must identify the most important element for each solar car in the event: its team. They take care of all logistics that get them from Point A to Point B. That includes feeding and housing everyone and keeping the caravan of accompanying vehicles gassed and on-the-move -- the Michigan team's convoy consists of a semi-trailer and its tractor, a weather van outfitted with high-tech instrumentation and students who know how to use it, the "lead" and "chase" vans with flashing yellow lights that protect the solar car from crazy or curious drivers, and a pickup with an array manipulator for media stops and after-race charging. Each of these vehicles has its own energy problems because of the need to operate computers, radios and cell phones.

The team also engineers PR, sponsorship, media relations, Internet support and business management.

If you want a look at what goes into a team's effort in the World Solar Challenge, check out "Continuum: Against All Odds," which won Best Short Documentary at the All Sports Los Angeles Film Festival, held July 10-11 in Hollywood. The documentary film is about the Continuum, the 2007 Michigan Solar Car and the team's dramatic showing in that year's World Solar Challenge. The movie chronicles the story of the team as it bounced back from a crippling crash. With its promising solar concentrator system, the team started off with high hopes. The car collided with a support vehicle and was sidelined just after the race began. The team worked through the night to get Continuum up and running again, and they managed to finish the 2007 World Solar Challenge in 7th place.

Read more about the University of Michigan Solar Car team at http://solarcar.engin.umich.edu.