1896 was a busy year: Queen Victoria became the nation's longest-serving monarch, X-rays were discovered, MDCCCXCVl occurred, and the Toyota Prius was pre-empted by a young electrician from the Black Country.
Whilst Ferdinand Porsche was dabbling with series hybrids, Mr H J Dowsing developed what was arguably the world's first parallel hybrid, when he fitted an Arnold car with a so-called dynamotor that served both as an electric starter and as a means of propulsion. And when it wasn't doing that, it charged the battery.
Despite Porsche's pioneering designs, series hybrids have yet to catch on, whereas parallel hybrids are now quite commonplace - notably the Toyota Prius and various Lexus cars. It is the advent of modern electronics combined with advances in materials technology that have enabled many of these early ideas to be dusted off and put to good use.
Before we go any further, I should perhaps explain the basic difference between series and parallel hybrids. Series hybrids are electric cars powered by traction motors that are fed current from a generator driven by a gasoline engine, which has no mechanical connection to the driven wheels. London's first-ever motorised fire engine used a Porsche 'Mixt' drivetrain working on that very principle.
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a button enables the driver to engage electric traction only |
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On the other hand, parallel hybrid cars are powered by a traction motor and gasoline engine working in tandem, both connected to the same drive shaft and one taking over from the other according to road-speed and load. That is the Toyota Prius.
A parallel hybrid takes advantage of the differing characteristics of electric motors and conventional gasoline engines. The former are highly efficient at low speeds and the latter work best at high speeds. Link the two via a common drive shaft and you have the best of both worlds - a high-torque, low-speed traction motor to power the car away from standstill, and a lean-burn gasoline engine to provide efficient tractive effort at cruising speeds. And when the gasoline engine needs a bit more grunt, the traction engine can be switched in to provide torque assist.
And the driver need do nothing: the system is entirely automatic. Moreover, surplus power from the engine is used to 'top up' the batteries that provide current for the traction motors, and this is supplemented by so-called regenerative braking in which waste kinetic energy is converted to electrical energy that also charges the batteries.
By way of a bonus, the latest Prius also has a button that enables the driver to engage electric traction only. The range is limited - about 1.25 miles - but nonetheless during that period, the Toyota is silent, emission-free, and no greater threat to the planet than a cucumber.
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