Or, did you ever ask you self: what is the fuel consumption of a hybrid bus?
The ElecTrip App has the answer.
The general answer to the initial questions is not satisfactory: “it depends on which route you think of”. The speed and topography are important. So are the stops. A stop directly after a downhill drive is really bad for the fuel consumption while an up-hill stop hardly has any negative impact. We clearly need to measure each route to give the answer.
So my colleague Ulf Gustafsson and I discussed if we could use a smart phone with GPS to analyze any bus route in the world with the objective to calculate the expected CO2 emissions and energy use for different bus technologies. After logging some routes it was not too hard to say yes, it is possible but the GPS signal is very noisy, in particular in altitude, causing random errors and too high energy use for all technologies.
With the help of e.g. colleague Jonas Hellgren at Volvo research division we made the ElecTrip APP for iPhones ®. The result was so unique that we filed a patent application that is pending. Still we have been able to make it available for the public and it is free.
The APP is pretty self-explanatory but the results may deserve some comments.
The first result display an overview of the logging:
Date: of the logging.
Distance: is the total distance from the start to the end of the route. My recommendation is to logg routes in two directions. Mostly routes are asymmetric and the result will depend on the direction. Logging in two directions allows a more precise forecast.
Duration: is the time measured from the start to the end of the logging.
Departure address: indicate the postal address closest to the start point of the route.
Arrival address: indicate the postal address closest to the start point of the route.
Next the calculated results of the logging are presented in a bar graph.
My screen dumps are unfortunately not very easy to read. To clarify the order in which the technologies are presented it’s always the same:
Diesel Bus Euro VI: Standard diesel fuel is assumed.
Gas Bus Euro VI: Compressed fossil CNG is assumed.
Volvo 7900 Hybrid Bus: The energy efficiency is calculated based on the real engine calibration of the Volvo Hybrid bus. For the CO2 emission data standard diesel fuel is assumed although Volvo Engines can use Hydrogenated Vegetable Oils.
Volvo 7900 Electric Hybrid Bus: The energy efficiency is calculated based on the real engine calibration of the Volvo Electric Hybrid bus. We have assumed a distance of 10 km between the charging stations, since many trips are not from terminus to terminus. For the CO2 emission data again standard diesel fuel is assumed although Volvo Engines can use Hydrogenated Vegetable Oils.
Volvo 7900 Electric Bus: The electric bus is assumed to use sustainable and renewable electricity.
The bars display the total fuel consumption in diesel liter equivalents, meaning that the data for the gas bus has been converted to the corresponding heat value of diesel to enable comparison. And the Electric Hybrid and the Electric Bus displays the corresponding electricity use.
We have confirmed the results for route speeds from 10 km/h to 30 km/h. Results from faster and slower routes are not reliable.
The blue bars below display the carbon dioxide emissions for the route:
In the first version we:
– don’t compensate for local hot or cold climate. The figures represent yearly average central European climate.
– the speed calculation is not sufficiently precise to differentiate harsh breaking and similar driver behavior induced effects on the emissions
– road quality and friction due to sharp curves is not included
– when logging short routes the error can be rather large
– routes with average speed less than 10 km/h or more than 30 km/h have not been validated experimentally and should be regarded as uncertain data.