The Automotive X Prize, Part 2
Fewer passengers, less weight, fewer minimum wheels, and lower performance requirements for top speed, incline, and range. Three wheelers with two front wheels and one rear driving wheel are going to be all the rage. The reasons are because in the US they are legally considered to be motorcycles, and have far fewer regulatory hurdles to clear (airbags, bumpers, etc).
I’m hoping a few four wheelers will make it just to see if it can be done. But I’m convinced the Alternative class will see the bulk of the vehicles that can meet 100 MPGe.
The concepts behind building cars for any of these classes would likely be as follows:
Massive weight reduction. All vehicles will be very light, especially to climb and accelerate during city driving cycles.
Aerodynamic drag and rolling resistance will have to be minimized, so frontal area and drag coefficients will have to be low. But the rolling resistance will have to be high enough to provide adequate braking and cornering traction for the performance requirements. The necessity of these tradeoffs may result in active devices being used to expand the overall performance envelope.
In order to maximize energy efficiency the propulsion method will also use regenerative braking to recapture otherwise lost energy, and reduce the size of the conventional brakes. If an internal combustion engine is used there will be idle cut off and designs will strive to run at a near constant RPM.
The engine will provide only modest power, and will be assisted during acceleration by additional stored energy such as that saved from regenerative braking. Finally, energy captured from waste heat or solar sources will be used for accessory loads. Vehicles using solar sources would have to somehow hedge against extended dark or overcast periods to ensure adequate energy at all times – most likely using the vehicles fuel source directly as back up.