What defines a Hybrid Vehicle ?
See the Definitions

Ford Espace Hybrid SUV

What sets this Ford Escape SUV apart from other Escape´s and SUV's?

It is a Hybrid Vehicle!

What constitutes a Hybrid vehicle?

Is a hybrid vehicle defined by the mix of technologies?

Are some technology or principle combinations more hybrid than others?

There are many different definitions out there.
I would like to embrace a definition that includes hydraulic drive. I like the definition from centrica.com, as it is simple and does not exclude technologies like hydraulics, springs and water wheels (a diesel driven water pump, pumping water on a water wheel driving the wheels of the vehicle is silly, except for a toy - but you get the point ).

So for now we can use the following definition.
A Hybrid vehicle is:

"A vehicle with more than one power source such as a small internal combustion engine and an electric motor."

If we apply this definition to a number of possible cases we can have:

Where ICE stands for Internal Combustion Engine.

Do we have more, relevant, drive trains than mechanical, electric and hydraulic? Please send me a note!

We can then carry on and find more permutations by replacing the primary power source (ICE) with a:

  • Steam engine (piston)
  • Steam engine (turbine)
  • Gas turbine where the pressure can be generated by burning different fossil fuels, chemical reaction etc. The small efficient engines used on modern day helicopters could probably be used to run big transport rigs.
  • Fuel Cell
    With an electric drive we can use a Fuel Cell as the primary power source.
  • Compressed Air. One of the vehicles of the day is the so called Air Car built round an interesting concept. One would think this is new technology, but as with so many technologies it has all been done before albeit wrapped in a different wrapper ... as can be seen here!.

As you see the possibilities are endless, but some are currently more economically viable than others at least at this point in time.