The evolution of commercially viable electric and hybrid vehicles has been a long process, and from the sidelines it has been a sometimes painful process to watch.
For hybrid vehicles it has been clear that diesel hybrids make more sense than gasoline hybrids from an engineering standpoint, especially considering the efficiency of next generation diesel motors and generators. Unfortunately the traditional antipathy in the american marketplace towards diesel has led to a great deal of international work on standard gasoline hybrids and much less work on diesel hybrids except for industrial and commercial applications where the bias against diesel fuel is minimal or nonexistent. This is only just beginning to change.
Another key component for both electric and hybrid vehicles has been the disadvantages associated with battery based energy storage. Primarily the low energy density, slow recharge time, limited lifespans, and high costs. These issues are, however, being addressed as fundamental improvements to battery technologies like Li-ion and others are improving recharge time, energy density, lifespan, and addressing overall cost and recyclability issues. In addition, ultra capacitors address the problems associated with electrical energy storage from a different direction, and as both Li-ion batteries and ultracaps improve, storage systems using both elements are becoming more common in electrical and hybrid vehicle applications.
For electrical vehicles, it has also been clear that 'in wheel' motors provide a more efficient approach than a centralized drive train, but the technology required has just not been mature enough. This is also changing. One example of this technology is the wheel motors from PML which allow for the construction of a wide variety of very efficient electric vehicles.
Further, it has always been clear that the most efficient electric vehicles would be the lightest possible designs constructed using the best strength to weight ratio materials. In this sense, electric motorcycles and scooters seem an obvious first step toward a full range of efficient and effective electric vehicles. And, as it happens, the first electric motorcycles are just beginning to appear in the marketplace. An excellent example of a well thought out design and product support strategy is provided by Zero Motorcycles and the Zero X - their initial all terrain motorcycle currently available to customers. A street legal version motorcycle, the Zero S, should be available soon.
So, are commercially viable electric vehicles almost upon us after fifteen years of agonizing fits and starts? My money says yes, even though the specific players and technologies have yet to shake out.