Researchers at the Queen’s College-University of London last year could not hide their amusement at the sight of a tricycle with 10 people on board in one of my presentation slides. Tricycles are living testaments to Filipino ingenuity and have become an indispensable figure in day-to-day life for most of us. For a long time, two-stroke engines dominated the tricycle sector for their superior muscle and simplicity compared to their four-stroke counterparts. These engines, however, are designed to allow 15 to 40 percent of the fuel charge pumped to the cylinder to escape to the exhaust port, thus their significantly higher and toxic emissions. This phenomenon is more commonly referred to as “short-circuiting” and is the major culprit behind their poor fuel economy.
Efforts in recent years have focused on re-fleeting these vehicles to four-stroke systems. While the efficiency and environmental superiority of four strokes over two strokes is well recognized, they are far from being the cleanest technology for tricycles. My research visit to the Institute of International Combustion Engines and Thermodynamics of Graz University of Technology in Austria introduced me to a wide range of cutting-edge technology in small engine systems. While a number of these technologies are still in the pipeline, most of them have already been commercialized and adopted not only in Europe but also in Asia. Some of these technologies that may be feasibly adopted locally in the near term include the low-pressure direct injection, air-assisted direct injection, and optimized carbureted two-stroke systems, among others. Emissions may also be further reduced through the adoption of catalytic converters and LPG fuel. The concept of “leapfrogging” our tricycles to these technologies should thus be strongly considered. A more stringent emission standard for new vehicles, however, is required to catalyze the entry of these systems to the local industry. The accelerated re-fleeting of the remaining two-stroke tricycles to four strokes could possibly delay the adoption of these newer technologies, thus this should be carefully evaluated.
Do we allow then the remaining two-stroke tricycles to pollute our air while waiting for them to be completely retired? A number of technologies are available locally to clean up two-stroke tricycle emissions. The most notable of these technologies are the direct injection and LPG fuel retrofit technologies. Retrofitting carbureted two strokes to direct injection means that the fuel will be injected only when both the inlet and exhaust ports are close, thus eliminating fuel “short-circuiting.” LPG is considered a promising energy source to meet high environmental concerns on photochemical smog and greenhouse effect. Coupled with its lower cost, these environmental benefits made LPG one of most attractive alternative fuels locally and in other countries. A similar environmental benefit, however, may not be expected from LPG fuel carbureted two-stroke vehicles. It can be recalled that the two-stroke emissions issue is basically an engine design and not a fuel problem. Inasmuch as it could provide fuel cost savings, it will not address fuel short-circuiting, thus would provide very minimal in-use emissions benefits. LPG-run four strokes and direct injection two-stroke technologies, on the other hand, are expected to considerably contribute to cleaning our air and should be seriously considered. Soft solutions such as traffic calming interventions and vehicle load regulations may also play a role in reducing impact from remaining two-stroke tricycles.
In the long term, there are reasons to be optimistic about the possibility of much cleaner electric tricycles running on our streets. The inaugural trip, however, might still take some time and will greatly depend on developments in battery technology. Currently, most electric vehicles operate on lead acid batteries with lower energy densities, longer charging times and less charging cycle life. The current cost of the more efficient nickel metal hydride and lithium ion batteries cannot be outbalanced by their technical advantages. The Argonne National Laboratory, a premiere research institution in the United States, projected that battery technology developments would eventually change this and open the doors for a more viable electric vehicle technology by 2020. The electric tricycle unveiled in Puerto Princesa recently is thus a very interesting piece of work. I cannot help, however, but be curious about its rated power, system efficiency, and battery technology parameters such as type, energy density and charging cycle life, among others. Should it live up to its promised viability and performance, I strongly believe that this is something that we Filipinos should be proud of considering the technology constraints cited earlier.
As we seek better ways to reduce emissions from tricycles, we should not forget that the best way is not to burn any fuel at all. We would do ourselves and the environment a big favor by walking as much as we can instead of riding motorized vehicles. While walking strengthens our body, it would also clean the air we breathe and contribute in ensuring a brighter future for the next generation.
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Dr. J.B. Manuel M. Biona is a faculty member of the Mechanical Engineering Department of Don Bosco Technical College-Mandaluyong. He is also a researcher at the Center for Engineering and Sustainable Development Research (CESDR) of De La Salle University-Manila in the area of transport, energy and environmental modeling and has published a number of works in international research journals. E-mail him at bionaj@dlsu.edu.ph.