Gasoline-powered vehicles are the largest source of air pollution, accounting for about half the air pollution nationwide, according to the U.S. Environmental Protection Agency.

Engineers and technology buffs around the world are working on the sleek, energy-savvy cars of the future.

Recently, Y-Press interviewed two sophomores at Rose-Hulman Institute of Technology -- James FioRito, a mechanical engineering major, and Ryan Kingsbury, a computer engineering major -- about their work on the school's solar-powered car.

We also talked with Clinton Husted, managing director of the General Motors Advanced Technology Vehicles division in Indianapolis, to see what GM is doing to develop more fuel-efficient vehicles.

FioRito and Kingsbury have been working on the latest version of the Solar Phantom, an $80,000, 750-pound solar-powered car.

"The car looks like a teardrop or an airplane wing, and it's pretty much based on an idea for aerodynamics, able to go down the road and kind of get a streamlined effect," FioRito said.

Other differences are that the Solar Phantom is made with a lightweight material called Nomax and has only three wheels to maintain its aerodynamic shape.

"That's a little interesting, when you start looking at how the car handles and problems that you have when you have a tire blowout," said Kingsbury, who added that the Solar Phantom has no air conditioning, radio or seat padding.

"Our car right now is capable of driving about 72 miles per hour. Past Solar Phantoms have gone around 85 miles an hour, I think, but we generally don't run them that fast because they're highly inefficient at those speeds. We usually average around 30 miles an hour during a race."

The biggest advancement in solar-car technology has been in the energy efficiency of solar cells -- they now produce almost double the energy they did 10 years ago, according to the students.

But while the Solar Phantom uses no gas, it's not practical for everyday life.

"What I see right now for any solar-powered vehicle would be probably something more along the lines of the hybrid vehicles that are starting to come out now," said FioRito. "The difference would be, the solar panels would be on your garage or at a gas station or something like that, and then you'd plug your car into it to charge it up."

Putting solar panels on a car is impractical, he added: "They're so fragile, any hail, any major dents in the car would cause the solar panels to break."

General Motors started working on a realistic hybrid-powered car around 1990. The Indianapolis facility employs 65 engineers, designers and technicians.

A hybrid vehicle uses two or more sources of power. GM is working on a combination gasoline-electric car, similar to models now sold by Toyota and Honda.

The electric motor and combustion engine take turns. When the car is on city streets, the electric motor is in charge, while on the highway, the combustion engine takes over.

"We've blended the two motors together, so you can't feel the difference between an electrical motor and the internal combustion motor," said Husted.

Inside the car is a computer controlling the change from an electric motor to a conventional internal-combustion engine.

"If the customer is driving along, hitting stoplight after stoplight, then the car registers and recognizes that it's not into a mode of continuous driving or cruising and will keep it in electrical mode," Husted said.

"Customers today want a car that has a capability to carry four passengers, and they want to improve their fuel economy. A hybrid car can do that."

But there are still some limitations. The biggest is not making the engine too large.

"What you want to do is try to downsize the internal combustion engine and make it smaller than what it has been in the past and get a higher utilization of the electric motor," said Husted.

In addition, work is being done to extend the electrical charge that powers the car. Right now, in the electric mode, the hybrid can go 70 to 100 miles between charges, depending on driving habits.

Husted sees further potential in hybrid cars. The next step, he said, is developing hydrogen fuel cells to operate the electrical motors and electronics of the hybrid car.

"There's a natural progression," said Husted. "Ten years from now, we should have hydrogen-powered cars out there."

Indeed, last year, GM announced the development of a hydrogen-powered pickup truck. BMW also is working on a hydrogen-powered car -- the 750hl -- which has been exhibited in several cities.

In a hybrid hydrogen-gasoline vehicle, the internal combustion engine is designed to use either gasoline or liquid hydrogen.

The latter is preferable, because the exhaust consists of only water vapor. But the technology to make liquid hydrogen is still expensive and can result in harmful waste products, except when it is processed by solar power.

In addition, refueling stations will have to be widely established before hydrogen-powered vehicles are viable alternatives.

The future of car technology still depends on what consumers want and what they're willing to pay for efficiency.

"A lot of it has to do with the size of vehicles and the price of gas," Husted said.

ASSISTANT EDITORS: Emerson Barnett, 17; Andrea Zeek, 14.

REPORTERS: Robin Wetherill, 12; Chad Dyar, 13.