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Green is clean PDF Print E-mail

The global motor industry has long been attempting to find a viable alternative to the internal combustion engine.  Fuel cells appear to be one answer, a hydrogen unit that produces electricity, but they are some way off being perfected despite a number of prototypes already existing from DaimlerChrysler and Ford. 

Ballard Systems of Vancouver, in which both companies have a stake, is the world leader in fuel cell technology but it is unlikely to reach production in the foreseeable future.

Hydrogen powered, reciprocating engines exist and it is possible to order a BMW 7-series with just such an engine, but lack of refuelling infrastructure effectively rules out the essentially green propulsion system.  Trucks and buses operate successfully on compressed natural gas (CNG) but a large storage tank is necessary to provide adequate range and is therefore not suitable to passenger cars.  Hong Kong taxis have switched to liquefied petroleum gas (LPG) but power losses and, again, an unrealistic number of refuelling outlets make this an unlikely alternative to the conventional petrol engine.

 Two Japanese manufacturers, Honda and Toyota, have adopted a different approach to the conundrum and have introduced so-called hybrids: vehicles that are able to operate with either electric or petrol motors.  The Honda Insight is currently only available in the United States, but the Toyota Prius is now sold in a number of countries, including Hong Kong and Secretary for Environment, Transport and Works, Dr Sarah Liao has one.

Dr Liao obviously believes that as she is responsible for improvement of our air quality, she should set an example.  A small but welcome gesture.

The Prius, originally designed at Toyota’s studio in California, features a small, permanent magnet electric motor, but the key to the whole system is the 1.5 litre petrol engine.  This delivers part of the power output to the wheels and part to a generator.  The electricity from the generator may be directed to the motor to drive the car, or may go through an inverter to be converted into direct current and stored in batteries.

It works in a number of ways, depending on speed, demand and battery life.  When starting out, moving slowly or descending hills the engine is inefficient, so is turned off and the electric motor used.  During normal driving the engine’s power is split with some used to generate electricity and the remainder driving the vehicle.  However, if full acceleration is required, both the petrol engine and the electric motor come into play. Under deceleration or braking the motor acts as a generator transforming the kinetic energy of the wheels into electricity – which in turn is transmitted to the batteries.

A useful side-effect to this part of the operation is the regenerative braking system which also slows the car in combination with the conventional disc/drum brakes.

If this all sounds a little confusing, in reality it is very simple with little waste of spare energy.  And when the car comes to a halt, the engine automatically switches off, restarting as soon as the throttle is re-applied.

 Image Apart from this innovative power system in the Prius, it is a solid, safe little car capable of transporting four adults in reasonable comfort.  Its long wheelbase and short front and rear overhangs contribute to an excellent ride. Electric power steering is fitted which  alters the amount of assistance added according to speed, while also reducing fuel consumption by up to three per cent over an engine-driven hydraulic system.

Toyota claims the Prius is environmentally friendly on a number of levels.  Its fuel economy is an outstanding 28 km per litre and the exhaust emissions are significantly lower than those of similar conventional vehicles.  Even the tyres are of a special, low  rolling resistance design and the wheels are lightweight aluminium.

Continuing the green theme, the Prius’ air conditioner uses a refrigerant which does not harm the ozone layer and lead has been eliminated throughout the vehicle, including the wiring harness and the fuel tank, which in this case is electro-plated with aluminium.

In other respects the Prius is a conventional Toyota, with the latest active and passive safety systems, including front and rear crumple zones, impact bars within the doors, pre-tensioners and force limiters on the front seat belts, and dual airbags.  

The dashboard is uncluttered but features a large digital readout in the centre which advises the driver whether it is electric or gasoline in operation, or both, as well as speed and the gear selected.  The shifty lever is column mounted and the parking brake foot operated, leaving a clear floor area between the driver and front seat passenger.  Overall the level of equipment is surprisingly high for such a small car, but as the Prius is significantly more expensive than any comparable vehicle Toyota has to compensate with extra gadgets and information.  In addition, there are numerous boxes, trays and pockets dotted around the interior, in which to store those essential items we all carry about in our cars.

The Prius is never going to be a big seller, partly because of its initial cost, but also because fossil fuels remain plentiful and relatively cheap.  It is estimated that the world can survive on available resources for at least another century and if this is the case, why do we need to investigate alternative propulsion systems such as this Hybrid, let alone fuel cell vehicles?  Arguments for the environment do not make a lot of sense either, as petrol – and diesel – engines are ever increasingly cleaner and more efficient.  Although diesel passenger cars are not permitted in Hong Kong, in Europe they are one of the most popular sellers, in part due to the higher mileage undertaken and the lower cost of diesel compared to petrol.

Dr Liao is to be commended for taking the initiative however.  Perhaps the Environmental Protection Department can persuade its colleagues in government to follow suit and, if not exactly plumping for green vehicles, at least going for cars which are more economical, more environmentally friendly and perhaps of greater importance in these lean economic times, cost less to purchase in the beginning.


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© 2019 Jeff Heselwood. All rights reserved.
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