Think of concept cars as glimpses into crystal balls, through automakers' eyes. They are predictions of the future -- and also chances for vehicle manufacturers to test out their ideas and get feedback from the market before spending big bucks to roll out new designs and technologies on the streets.

This year, the concept cars at the North American International Auto Show make it clear that green is on manufacturers' minds. Plug-in hybrids, electric cars, fuel-cell cars and biofuel cars all are represented on the showroom floor.

That signifies that automakers think the future holds a greener path, but that they aren't yet in agreement about which technologies to take down that road. After all, while manufacturers say there's room for many different powertrain technologies, the truth is that they probably can't produce all of them -- and get the infrastructure in place for too many multiple technologies -- and still remain profitable.

Katie Hepler, a Chrysler spokesperson, said the company is relying on customer reaction from the showrooms to help decide which technologies to pursue.

"You can do the research and collaborate on all these things, but -- yeah -- you can't invest in everything," she said. "At the same time, I don't know how you pick a horse, necessarily, and they all are part of the pie. Nothing's going to be the only [technology] in the near term."

Here are some of the green concepts that illustrate automakers' green dreams:

fisker karma
Fisker Wants to Spread its Good Karma

With the drop of a white curtain, CEO Henrik Fisker on Monday unveiled Fisker Automotive's first production car, a plug-in hybrid called Karma. The debut was met with gasps and applause from the crowd.

Source: Fisker Automotive
fisker karma
Fisker Wants to Spread its Good Karma

Reporters crowd in to get a closer look at the sleek Fisker Karma, which can drive for 50 miles before using any gasoline. Kleiner Perkins Caufield & Byers invested an undisclosed amount in Fisker Automotive, the car company said.

Source: Jennifer Kho
fisker karma
Fisker Wants to Spread its Good Karma

The Karma comes with a hip brown-and-beige leather interior and a price tag starting at $80,000.

Source: Jennifer Kho
fisker karma
Fisker Wants to Spread its Good Karma

Fisker has equipped the Karma with asolarpanel on the roof, which recharges the batteries whenever the sports car is in the sun. Fisker believes it will be the first to market with the plug-in hybrid, expecting to enter production in the fourth quarter of next year. For more information, see Automakers Vie for Green Cred.

Source: Jennifer Kho
vue plug-in
A Plug with a Vue

Tom Stephens, vice president of GM North America, demonstrates how a plug-in hybrid version of the Saturn Vue Green Line could be recharged. The car, which can fully recharge in four to five hours, could go into production as early as 2010, he said.

Source: General Motors
flextreme
A Flextreme Future

Tom Stephens, vice president of GM North America, introduces the Flextreme concept. The Flextreme will be all-electric for up to 35 miles and will be paired with the ability to use different fuels, including diesel, he said.

Source: Jennifer Kho
flextreme
A Flextreme Future

The sleek Flextreme is the next technology step for Saturn, said Tom Stephens, vice president of GM North America. "Flextreme shows we can take this brand all the way, all the way to electric," he said.

Source: General Motors
dodge zeo
Light, Fast and Electric

With an all-aluminum body structure and a 64 kilowatt-hour lithium-ion battery pack, the sporty all-electric Dodge Zeo can go from 0 to 60 mph in less than six seconds.

Source: Chrysler
dodge zeo
Light, Fast and Electric

Photographers crowd in to get a good angle of the Dodge Zeo doors, which open upward. Lou Rhodes, president of Chrysler's Envi division, which is developing electric cars, said the four-passenger concept has more than 250 horsepower.

Source: Jennifer Kho
dodge zeo
Light, Fast and Electric

The Dodge Zeo is equipped with a clean console and features like built-in navigation. The concept car also has a 250-mile range, said Lou Rhodes, president of Chrysler's Envi division, which developed the Zeo.

Source: Jennifer Kho
jeep renegade
Renegade Fuels Diesel Hybrids

Chrysler's plug-in hybrid Jeep Renegade concept gets the equivalent of 110 miles per gallon with a 16 kilowatt-hour battery pack. The car has a 40-mile electric range, as well as a 115-horsepower diesel engine to take over after that.

Source: Chrysler
jeep renegade
Renegade Fuels Diesel Hybrids

The two-seat Jeep Renegade is propelled by two 268-horsepower electric motors at each axle and a diesel engine. Running primarily in electric-drive mode, the car gets up to 110 miles per gallon, according to Chrysler.

Source: Jennifer Kho
ecovoyager
Luxury Comes in Green

The four-door ecoVoyager has a 45-kilowatt fuel cell, lithium-ion batteries and a 268-horsepower electric motor and can drive up to 300 miles -- with the first 40 being all-electric -- before recharging or refueling.

Source: Chrysler
ecovoyager
Luxury Comes in Green

Chrysler said its ecoVoyager is a luxury concept aiming to mimic the experience of a Gulfstream jet, albeit on the ground. The plug-in fuel-cell hybrid goes 0 to 60 in 8.8 seconds, gets more than 110 miles per gallon and emits only water vapor, Chrysler says.

Source: Jennifer Kho
audi r8
Bringing the Race to the Roads

Audi, which has raced a diesel car in the American Le Mans Series the past two years -- winning both times -- unveiled a diesel-powered R8 concept road car at the Detroit show. The brand in July announced it was launching the "cleanest diesel in the world" with its ultra-low-emission TDI engines, scheduled to begin production this year.

Source: Jennifer Kho
ferrari
Ferrari Boosts Horsepower with Ethanol

Ferrari unveiled a Spider 450 concept that runs on E85, a blend of 85 percent ethanol and 15 percent gasoline. The company said it made the Spider prototype to show it could deliver just as much, or more, horsepower on ethanol as on gasoline. The concept has 500 horsepower, up from 490 on standard Spiders, and 5 percent better fuel economy.

Source: Jennifer Kho