today I had a talk with an integrator who wanted to know when to apply which scenario in the context of the CEN emission calculation (aka EN16258_2012). Here's a little overview with some stories describing the different approaches. (Here's also a more generic article about emissions).
| Story | Approach |
|---|---|
| ACTUAL_FUEL_CONSUMPTION - The actual fuel consumption for this route in [l] for liquid fuel types or [kg] for gaseous fuel types like COMPRESSED_NATURAL_GAS. | Imagine you start a journey with a full tank, during the trip you fill up and once you arrived at your destination you fill up again. In this case you know the exact consumption of the specific vehicle on that trip. Most precise scenario! |
| VEHICLE_SPECIFIC_AVERAGE_FUEL_CONSUMPTION - The calculation of emissions is based on the current vehicle profile. | This approach is valid if you determine a specific vehicles total consumption and distance over a long period and then you simply compute the average. Not as precise as #1 but still focused on an individual vehicle's consumption. |
| FLEET_SPECIFIC_AVERAGE_FUEL_CONSUMPTION - The average fuel consumption for a fleet in [l/100km] for liquid fuel types or [kg/100km] for gaseous fuel types like COMPRESSED_NATURAL_GAS. | This is valid if you know the total kilometers and fuel consuption of the fleet as a whole. No longer focussed on an individual vehicle, therefore les precise than 1 and 2. |
| ROUTE_SPECIFIC_AVERAGE_FUEL_CONSUMPTION - The average fuel consumption for a specific type of route in [l/100km] for liquid fuel types or [kg/100km] for gaseous fuel types like COMPRESSED_NATURAL_GAS. | Imagine the distance and fuel consumption are determined on the basis of a recurring route, e.g. you know that the busses 1,2,5 drive the route A-B-C-D-A several times a day, each time with the same geometry but different vehicles. Again the consumption is rounded but in the focus of a specific track. This means "when we drive this route we consume an average of NN liters...". |
| HBEFA_BASED_FUEL_CONSUMPTION - The emissions based on the fuel consumption as it was calculated by HBEFA 3.2. | If you have no clue about existing consumptions based on #1-#4 you need to derive it from an abstract model such as HBEFA. Then we first apply HBEFA 3.2, gather the fuel consumption and forward it to the CEN as input factor. This is completely theoretical and has no reference to your drivers behaviour. |
"Does CEN consider elevations?" - According to the categories mentioned above the consideration of elevations is bound to "how close is the relation between the route in charge and the choosen approach?" Look at approach #1 which obviously determines the used amount of fuel in an exact way. Obviously this reflects the real consumption and therefore also the elevations on that specific route. With this approach the answer is "YES, CEN does consider elevations when you apply ACTUAL_FUEL_CONSUMPTION." The answer is also positive with the HBEFA approach because HBEFA 3.2 considers elevations.
But how about the other approaches? From my perspective the three other approaches are based on "use some average determined over a long time" and in these cases the route in charge does not necessarily match the base of the average. Here my response would be "no". Long story short:
ACTUAL_FUEL_CONSUMPTION and HBEFA_BASED_FUEL_CONSUMPTION consider elevation.
VEHICLE_SPECIFIC_AVERAGE_FUEL_CONSUMPTION, FLEET_SPECIFIC_AVERAGE_FUEL_CONSUMPTION and ROUTE_SPECIFIC_AVERAGE_FUEL_CONSUMPTION do consider elevations on an approximated level.
OK with that? I hope this little overview enables you to have a better understanding of the scenarios and to choose the proper one for you!
Best regards,
Bernd
PS: Here are the conversion factors for the different values:
| Substance | EnergyUseTank2Wheel [MJ/l] | energyUseWell2Wheel [MJ/l] | co2eTank2Wheel [kgCO2e/l] | co2eWell2Wheel [kgCO2e/l] | Density [kg/l] |
|---|---|---|---|---|---|
| Benzin | 32,2 | 37,7 | 2,42 | 2,88 | 0,745 |
| Diesel | 35,9 | 42,7 | 2,67 | 3,24 | 0,832 |
| LPG | 25,3 | 28,3 | 1,70 | 1,90 | 0,550 |
| CNG | 45,1 | 50,5 | 2,68 | 3,07 | 1,000 |
| Biobenzin (Ethanol) | 21,3 | 52,1 | 0,00 | 1,24 | 0,794 |
| Biodiesel | 32,8 | 68,5 | 0,00 | 1,92 | 0,890 |
