This type includes those hybrids where the primary source of on-board electrical power is a generator mated to a mechanical engine. There are principally three types of mechanical engines: Piston, rotary and turbine.

These are by far the most common type of mechanical engines, being used in all conventional and most hybrid vehicles. Called “internal combustion” engines (as the burning of the fuel occurs within enclosed cylinders) they run most commonly on gasoline, diesel oil or natural gas, although some have been designed to run on more exotic fare, like coal dust or alcohol.

The main advantage to a hybrid vehicle that incorporates a piston engine is that it is utilizing a readily available, proven technology for its primary on-board power source. (The secondary electrical power source, as always, is regenerative braking, discussed previously in the Overview section.)

The disadvantage to such a hybrid vehicle is that its piston engine has all the drawbacks of the engines in conventional vehicles: Noise, pollution (unless powered by compressed or liquid natural gas [C/LNG] or propane [LPG]) high moving parts count and poor reliability with age. The degree of mechanical complexity is certainly not improved when the electric motor is, itself, connected directly to the piston engine/generator (in an arrangement previously described in the Overview as a “hybrid engine”).

Both of these engines employ rotating rather than reciprocating action, resulting in smoother operation, especially at higher speeds, with fewer moving parts and greater reliability. Trouble is, rotary engines are not terribly fuel-efficient and turbine engines are radically expensive and tend to run at temperatures too hot to use in and around people and property. As of yet, no one has produced a commercially viable turbine or rotary engine for use in a hybrid electric vehicle, although some of each have powered a handful of otherwise conventional vehicles.

Fuel cells are devices that produce electricity via chemical activity as opposed to mechanical activity. Instead of spinning a mechanical generator to produce electrical power, the fuel cell produces electricity by capturing the electrical discharges produced when certain chemicals are combined (or, as is often the case, re-combined).

A separate section in this site is devoted to the technology involved in utilizing fuel cells to power vehicles. Fuel cells are also discussed to a lesser degree in the Overview. Suffice it to say, for the purposes of this section on hybrids, that the fuel cell holds great promise for producing on-board power in the areas of reliability and maintenance but provides us virtually no means for current evaluation in terms of safety, cost or expected availability.

Our hands-down favourite hybrid vehicle would be one covered with solar panels and sporting a back-up primary power source, be it a mechanical system or a fuel cell. Take a moment to think about all the vehicles baking for hours in the hot sun each day while their owners are at work. Certainly the power that could be harnessed on most days would be enough to get those cars home using battery power alone. Once home, an overnight charge could easily get the car back to work again the next day. An added plus would be that the interior of the car would stay much cooler during the day, with most of the sun’s energy absorbed by the solar panels.

Of course, should the trip home require several detours, or an out and out journey, the back-up primary power system (be it mechanical or fuel cell) would be there to ensure a worry-free trip.

As it stands, however, we know of no one that has mated a solar panel to an otherwise perfectly capable hybrid vehicle. That being the case, we are left with only solar “experiments” rather than functional solar vehicles. In fact, as close as we have seen the world come to building an all-in-one solar/hybrid electric vehicle would be the planned final design configuration of that indomitable unmanned aircraft, the Helios.

And so, while Australia’s “Solar Challenge” brings out many highly-efficient one-person solar-powered designs from the top schools around the world everyone still drives home from the annual event with the sun beating down on their own vehicle’s bonnet, boot and top, to no avail.