Dr. Raymond M. Wright, Contributor
Dr. Raymond Wright, group managing director of the Petroleum Corporation of Jamaica. - ANDREW SMITH/PHOTOGRAPHY EDITOR
OVER THE longer term, we urge Jamaican motorists to switch to diesel-engined vehicles when they are considering their next purchase. Diesel vehicles are significantly more efficient than gasolene engines and, importantly, from the environmental point of view, they emit far less CO2 into the atmosphere. Also, diesel fuel is cheaper than gasolene. Modern diesel engines are quiet, powerful, with high specifications and are a pleasure to drive.
Diesel's status as the world's most efficient internal combustion engine - producing more power and utilising less fuel than other comparatively sized engines has been recognised by widespread application throughout the world.
In the United States, 95 per cent of all freight is transported by diesel power. In Europe, where fuel prices put energy conservation at a premium, diesel powers approximately 50 per cent of all new passenger vehicles.
The advantages of diesel include:
More power. Diesels produce more drive force at lower engine speeds. This is because of 'compression ignition' in the diesel engine combustion process. This in turn provides more power or 'torque'.
Better fuel efficiency. Light duty diesels such as cars and SUVs use between 30 per cent and 45 per cent less fuel than similarly sized gasolene engine, depending on the type of vehicle and the driving conditions. Diesel's compression ignition process results in greater thermal efficiency - more of the fuel's energy is harnessed. This improves fuel economy. A diesel's fuel efficiency is also as a result of the higher energy content of diesel fuel. One litre of diesel fuel contains about 10 per cent more energy than a litre of gasolene.
Diesel engines are more durable than spark ignition gasolene engines. Diesels run many more kilometres before needing rebuilding and also are more easily rebuilt to original specifications. Light duty diesel engines can last between 300,000 and 500,000 kilometres compared to 150,000 and 300,000 kilometres for comparable gasolene engines. Maintenance intervals are also longer for diesels.
Safer. Diesel fuel is less volatile than gasolene - that is, the fuel does not readily vaporise in the atmosphere. Further, diesel fuel ignites at a much higher temperature than gasolene. For these reasons, diesel fuel is less likely to ignite if released or spilled as the result of an accident.
ENVIRONMENTAL ADVANTAGES
The five major vehicle source emissions are carbon monoxide, hydrocarbon, carbon dioxide, nitrogen oxides, and particulate matter. Diesels produce only a small proportion of the first three, when compared to gasolene engines. However, diesels produce more nitrogen oxides and particulate matter than gasolene engines.
The high heat associated with diesel's compression combustion process generates more nitrogen oxides than less efficient, cooler burning gasolene engines. Also, the low level of oxygen in the combustion zone may prevent complete combustion of the diesel fuel, which contributes to the production of some soot, also known as particulate matter. The emission of particulate matter has been significantly reduced in the new common rail diesels.
European taxi operators have recognised the advantages of diesel and have allowed new diesel vehicles to prove themselves as efficient, quiet and powerful alternatives to gasolene engines. Largely as a result of embracing diesel, as well as smaller vehicles, Europe's cars get on average about 50 per cent better mileage than U.S. automobiles.
Engineers and policy makers would like a silver bullet technology that reduces air pollution in the transport sector. Hydrogen cars which would burn no fossil fuels and emit only water vapour, are not expected to compete in the market for another 20 years.
In the meantime, diesel, gasolene/ electric, and diesel/ electric hybrids will power cleaner cars.
Dr. Raymond M. Wright is group managing director of the Petroleum Corporation of Jamaica.
