Eager buyers are waiting up to a year for a new Toyota Prius, the hot hybrid sedan that gets around 50 mpg and has negligible emissions. Imagine, then, the excitement that could be generated by our proposed GreenCar, an eco-mobile that’s bigger than the Prius but gets more than twice the mileage–without emitting a single milligram of air pollution. “It’s all about resistance and aerodynamics,” says Catherine Greener of the Rocky Mountain Institute, a nonprofit energy-policy think tank. Improvements in composite materials will be critical, as will computerized aerodynamic modeling. But it all hinges on fuel cells, which won’t proliferate until their cost comes down and their capacity goes up. When that
happens, the impact will be tremendous. With electronic mobility possibly more important than physical mobility in a fuel-constrained future, the electricity-generating GreenCar will be perfect for powering homes. Blackouts? No sweat.
Extreme fuel efficiency is largely a matter of reducing weight and drag. Less power will be needed to push cars down the road, bringing triple-digit fuel economy within reach. Making the GreenCar lighter will require a transition to structural carbon composites, which will be used to make both frame and body. Significant advances in production techniques and technology will be necessary. Composites have already appeared in a few car parts, but making an entire body out of them is currently too expensive for a mass-market vehicle. Aerodynamic improvements will come out of computerized wind tunnels, which will squeeze out drag.
A Proton Exchange Membrane (PEM) fuel cell powers the GreenCar and all its systems. Compressed hydrogen gas reacts with oxygen to form water, generating electricity in the process. When the car is parked, it doubles as a generator. Electricity produced by the fuel cell and regenerative braking is shunted to ultracapacitors, which collect charge and, with their faster release capabilities, make high-demand activities such as starting the car much easier than with a standard battery. The energy is stored by building up an electrostatic charge between the two plates and then transferred to the vehicle system through conduits.
Fuel cells replace conventional engine and powertrain, freeing space
for storage or
Windshield is highly sloped and the tail end tapered to create a low-pressure zone behind the car, reducing turbulent (drag-inducing) airflow
Low-rolling-resistance tires reduce friction but not traction
Plastic windows on sides and rear weigh less than glass and help block ultraviolet radiation
Most accessories–vent fans, radios–are powered by solar panels on roof
Wheel covers, a panel on the car’s belly that makes air flow more smoothly across the underbody, and the use of cameras instead of side-view mirrors further improve aerodynamics.