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.