Shine down on me: Solar cars

by Roland I. Maldonado

If you know anything about Superman, you know that his powers are fueled by Earth’s yellow sun. The brighter the day the more powerful he becomes.

While many scientists scramble to find cleaner, abundant fuel sources like hydrogen and biofuels, the possibility of solar power for transportation has become a reality. Iowa State University’s solar car club, Team PrISUm, continues to show why solar energy transportation has moved from the pages of comic books and onto the road.

How it works

A solar car uses 3 main components in order to work:

1. a solar array,
2. a battery,
3. a motor and motor controller.

The electrical component of the solar car works by using a solar array. It consists of hundreds or thousands of individual solar cells that convert sunlight into electricity and in turn run the car.

So for every 1,000 watts of sunlight that fall on the Earth’s surface during afternoon-peak hours, 1,250–2,250 watts of power can be used for the solar car. This is roughly the amount of power a hairdryer uses.

The battery also plays a pivotal role and is just as vital to the system. Most solar race cars use 25 kilograms of lithium ion batteries, which hold enough energy to drive the car 200 miles without sunlight. The battery can then be charged in about 3 hours using the solar array.

Both the solar array and battery would be useless without the motor and motor controller. An electric motor and motor controller is what Team PrISUm uses. It’s built into the wheel. And there's no transmission. For each rotation the wheel makes, the motor also makes a rotation. Finally, a motor controller converts DC power from the batteries and solar array into 3-phase AC electricity for the motor to get the solar car moving.

Although Team PrISUm has not measured the top speed of its current solar car, Sol Invictus, it can probably reach a top speed in the 70 mph range, says Evan Adkins, electrical director of the team.

Competing

Sol Invictus recently returned home after earning 8th place in the 2008 North American Solar Challenge.

Problems plagued the team before getting Sol Invictus to the race. According to project director Mike Steffens, they had to finish part of the car’s electrical system as it was on its way to Texas. “We had problems with the electrical and the brakes stopped working during the race which was a bit scary,” Steffens says.

Still the team did well finishing 8th. Placing well helps attract sponsorship participation, which offsets the costs involved with each project. While Iowa State University pays for some of the costs, sponsors like Boeing and the Iowa Energy Center cover the bulk of expenses incurred by the solar array and other necessary components.

The team plans to add some innovative and radical changes to the new project car, such as a split battery pack for the 2010 North American Solar Challenge. Another change involves the frame design. “We were the only car that had four wheels. Everyone else had three,” says Adkins.

Many students, many talents

Originally, Team PrISUm started as a project in 1989 for Tau Beta Pi, an honor society in the College of Engineering at Iowa State University. Today the team boasts a broad range of student involvement from a range of disciplines like graphic design, business, and engineering. Together they tackle the logistics, electrical, solar array, mechanical, aerodynamics, fundraising and outreach aspects of team PrISUm.

They're proud of the fact that their team is the only one to enter a new car into each of the Solar Car Challenges since the team first began competing. To date Team PrISUm has created 9 solar cars.     

Get involved

As project manager for the next two years, Mike Steffens isn’t just looking to improve the solar car design but increase outreach efforts too. “That’s where we get the bulk of our membership involvement and sponsors,” says Steffens.

If you would like to get involved with Team PrISUm or would like them come out for a visit, contact them via email at solarcar@prisum.org, or call their offices at (515) 294-0899. For more information visit their website at www.prisum.org.