Drivetrain Basics

• Hybrid technology comes in two basic varieties: parallel and series. Parallel hybrids, such as the Toyota Prius, can motivate the vehicle using either an internal combustion engine, an electric motor and battery or a combination of both. Series hybrids don't use the gas engine to drive the wheels; rather, the engine acts as a generator to recharge the car's batteries. Hydrogen fuel cell vehicles are essentially electric cars with an on-board power generation station: The hydrogen fuel combines with oxygen in a fuel cell, producing water and electricity as a byproduct.
  
  

Problems With Hybrids

• Aside from their cost, complexity and initial environmental impact, hybrids don't have too many problems. Modern magnet and material technologies help to keep weight down and motors light, but the car's battery pack still makes it heavier than a non-hybrid car. Lithium-ion and lithium polymer battery packs can reduce weight, but they're still very expensive compared to lead-acid and nickel-cadmium batteries. One aspect to consider is that lithium -- which was once almost worthless -- tends to come from developing nations, where money in the ground tends to equal blood in the sand.
  
  

Problems With Hydrogen Fuel Cell Vehicles

• In a word: infrastructure. Hydrogen, fairly cheap to produce, is the most abundant element in the universe and produces no harmful emission. However, it's also highly explosive (think Hindenburg) and requires a whole network of specialized distribution and storage facilities in order to be used safely. Most gas stations just aren't equipped to handle a widespread demand for pressurized liquid hydrogen. Infrastructure changes like this tend to be either self-sustaining or entropic in nature. If America buys enough hydrogen fuel cell cars, more gas stations will carry hydrogen. If we stop buying them, hydrogen goes away.
  
  

Solutions

• Time and patience are the two primary solutions to both the hybrid and hydrogen vehicle's primary issues. Supply and demand cycles will eventually catch up to meet production demands for hybrid drivetrains and batteries. High-capacity lithium-air batteries are the next step in battery technology -- once they hit mass-production status, they'll help to reduce lithium requirements and battery weight and cost. If hydrogen vehicle sales continue to grow, then hydrogen filling station locations will probably expand outward from places like southern California and New York. Fuel companies aren't going to gamble by retro-fitting existing stations without a guaranteed return, so customers will either drive the demand for hydrogen infrastructure expansion or they won't.