| Summary: | Around 35% of gasoline combustion energy is wasted as heat in exhaust pipes of spark ignition engines. It represents not only energy losses but also thermal pollution and hazardous gas emission. Therefore utilizing this waste heat is strongly urged in order to minimize negative impacts of steadily increasing number of motorized vehicles. One of the possible methods is using a Thermoelectric Generator (TEG) to convert waste heat directly into electricity. The generated electricity can be used by the vehicles itself, and therefore contribute to improve engine efficiency, decrease fuel consumption and reduce gaseous emissions.
Thermoelectric Generator modules used in this research are TEG 127 - 40 A, made from Bismuth Telluride (Bi2Te.J which is most appropriate for lower temperatures, while the exhaust gas as the heat source is produced front one of the two investigated motorcycles, which have 110 cm3 and 150 cm3 displacement volumes, respectively. These modules are placed in three locations on the exhaust pipe. The first location is near the exhaust manifold, the second is between the exhaust manifold and the collector, while the third is close to the collector. Observations and measurements are carried out when the engine is idle (around 1500 rpm) and at 3000 rpm, both are on a test bed without load. Further data collections are conducted when the motorcycles run on the road with speeds of 20 km/hr, 25 km/hr 30 km/hr., respectively. Electrical power is obtained b)' serial connecting the three test points with a load of 1.4 Ohm from LED lamps.
The results showed that engine rotation speed and position of the TEG modules in the exhaust pipe affect the generated electrical energy. Likewise, power generation is influenced by cylinder capacity and running speed of the motorcycles. Maximum electrical power of the 110 cc engine at a speed of 30 km/li is 0.57 W, which is considerably smaller than that generated by the 150 cc engine at the same speed, where a power of 1.2 W is delivered. Actually the conversion efficiency is less satisfying, because the waste gas temperature is already relatively low (the maximum attainable is 230°C). Higher electrical power can be expected from larger engine capacities running at higher speed.
Keywords: Bismuth Telluride, Motorcycle exhaust pipe, Thermoelectric generators, Waste heat.
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