A Hybrid Vehicle is ....:
"A vehicle with more than one power source such as a small internal combustion engine and an electric motor."
There are several major technologies that can, potentially, be used in a Hybrid Vehicle .. or more correctly put .. define a Hybrid Vehicle according to the above definition.
It is therefore the specific combination of "power unit" technology and "traction engine" technology that can be used to categorize Hybrid Vehicles.
First we need to discuss ICE - the
Internal Combustion Engine.
ICE has been the primary power source for automobiles and trucks since the beginning of the 20. century. When inexpensive fuels and new production methods made electric and steam propulsion less economical for the mainstream.
Electric vehicles did however survive the race have had their nice in several special applications (more on EV's...later..).
steam engine however only survived in trains and Naval application well into the latter part of last century.
Steam trains are very rarely seen to day and have only a few have survived the technological development. Those left can for example be seen in mining applications in third world countries and as tourist attractions.
ICE can be categorized according the fuel used for combustion i.e. into:
Other engine technologies like:
...have been used successfully in a number of applications.
What practically sets them apart and defines their practicality for a given situation is that the Fuel Cells are usually dependent on high quality fuels while Turbines can be made to burn almost anything from fish oil to coal dust. A Turbine and corresponding generator can be made somewhat smaller and lighter than a Fuel Cell delivering the corresponding power levels.
The traction engines, I currently know off, are either:
There are several different electrical tranction engines (or motors). They can be AC motors, DC motors, free of the hub or hub/wheel mounted.
E-Traction is developing a line of both hub mounted and free standing motors for different vehicle categories and have show example solutions for Buses and SUV's.
Hydraulic "tractions engines" are also found in a greate variety and as hub/wheel motors as well. Hydraulic motors have mainly been used in the heavy vehicle applications - because of the weight of the hydraulic motors. Yamaha has changed that, lately, as you see discussed below an may well have started an new trend in ultralight hub mounted hydraulic motors.
The Liquid Drive technology from Power Curve is also interesting in this context and may well be applicable to Cars and SUV's in the near future.
If you know off manufacturers producing hydraulic "traction engines" suitable for use in light automotive applications please send me a line.
ICE - Electric
This is the most common Hybrid Vehicle concept. It was the concept used in the first Hybrid Vehicle and is also the most used in new applications today.
ICE - electric can broadly be categorized into:
ICE - Hydraulic
ICE - Hydraulic technology has, as mentioned above, been widely used heavy vehicle applications like large trucks, mining trucks, bulldozers and such.
The large and heavy hydraulic motors have had limited appeal in lighter applications.
The big manufacturers have in recent years explored diesel-hydraulic technology in various applications. I have for example seen som material on a UPS Truck project (more on that and similar applications later...).
A demonstration on how compact a hydraulic drive can be made was recently done by Yamaha. As Yamaha developed a lightweight hydraulic drive for a motorcycle.
The diesel-hydraulic principle may well be the correct option where the operational environment is not in favor of electrics.
My own family outings include river crossings and driving in snow blizzards where snow and water ingress everywhere.
I would probably trust an hydraulic drive better than an electric one in situations like that
-at least until proven wrong!