Energy and exergy assessment with updated Reistad estimates: A case study in the transportation sector of Bangladesh

Transportation sector is one of the core parts of modern civilization. Proper utilization of energy and exergy in this sector is necessary to ensure energy loss and environmental sustainability. Increasing exergy efficiency will reduce carbon emissions from this sector. Since 1970, Reistad estimates have been widely used to determine the energy and exergy efficiencies of this sector. However, the modern transport sector has undergone significant changes in recent decades. Hence, it is necessary to apply new Reistad estimates in determining the energy and exergy efficiencies. This is the first study to apply updated Reistad estimates to explore the energy and exergy efficiencies in the transportation sector of Bangladesh based on the data from 2000 to 2017. The overall exergy efficiency is significantly lower than the energy efficiencies as it ranges from 27.7% to 30.0%. Efficiencies are lower as the maximum portion of input exergy is lost to the environment. The road subsector needs major improvements as it is responsible for major amount of exergy loss. A comparison is made between conventional and updated estimates which highlights that the updated estimates provide more accurate results. Thus, it is recommended to apply updated Reistad estimates in determining the energy and exergy efficiencies of the transport sector.