Efficiency evaluation of gas fuelled and electric driven buses in the public transport sector

The following report evaluates the efficiency of gas fuelled and electric driven buses in the public transport sector on a theoretical basis. The results indicate that the combination of CHP power plants and electric driven buses reach an overall efficiency of about 51% throughout the production chain (Well-to-Wheel), including heat distribution losses. The overall Well-to-Wheel efficiency for conventional gas turbines without heat recovery decreases to around 28%. For gas fuelled buses the Well-to-Wheel efficiency is about 30%. The CO2-emissions are evaluated based on the example of a “Volvo B10L CNG” gas bus and the electric driven “Eurabus 600”. The low energy consumption of the electric driven bus results in CO2-emissions of only 181.4 gCO2/km (Grid-to-Wheel). Depending on the utilised power plant technology the overall CO2-emissions (Well-to-Wheel) amount to 307.5 gCO2/km for a CHP power plant and 553.5 gCO2/km for a conventional gas turbine. On the other hand, gas fuelled buses emit about 1.25 kgCO2/km (Tank-to-Wheel), which is eightfold the emissions of an electrical bus. The Well-to-Tank emissions further increase to about 1.32 kgCO2/km. The emission calculation is based on real gas consumption data from a Norwegian public transport utility. The results indicate that the combination of CHP plants and electrical buses provide a much higher efficiency while reducing CO2-emissions.