EEBC Method:
Analysis. Problem Definition. Solution

Simulation Process Sample-City


Data Base and Scope of Simulation

Amongst other information precise route data and passenger capacities of Sample-City are evaluated during the analysis, already previous to the actual simulation. The exemplary route Line M including all bus-stops and traffic-related stopping positions is tracked as a GPS profile to be used as a data base for the simulation later-on. Evidently speed limits and any special characteristics are taken into account as well.

Map of Model City and route plan Bus line M

Map of Model City and route plan Bus line M

In the present example start and return of the line differ from each other. Per circulation of the 13.4 km line 34 bus-stops are called at. During the day 14 rides are performed summing up in a total driving distance of 188 km per day in line-service.

In addition to the driven distances the overcome of differences in height is of major influence on energy consumption. In order to achieve a sufficient data base a precise height-profile of the entire line is established out of the GPS data.

Altitude profile of the Model Bus line M

Altitude profile of the Model Bus line M

In this example the customer requests the consideration of Line M exclusively. As a boundary condition any charging infrastructure apart from the bus depot must be avoided. The concept draft of a battery-electric vehicle with Battery-Extender is subject of simulation. Of course, other concepts such as inductive or conductive recharging at certain bus-stops can be simulated likewise. For this purpose route data and simulation parameters are adapted to match the particular concept.

 

Simulation and Energy Consumption Calculation

Amongst many other aspects, the use of the EEBC simulation method makes it possible to calculate energy consumption, to evaluate different (re)charging concepts, to find the optimal battery and drive-train set up per bus-line and even to quantify the influence of diver behavior on the energy consumption. This example only shows the fundamental principle very simplistically.

Based on the gathered information, route data and height profile are programmed in the simulator software as a motion profile. Obviously, alongside speed limits, bus-stops and traffic-related stopping positions, the connection between bus-depot and route is taken into account as well. Parameters such as the passenger volume (additional load) or the vehicle empty weight, which is strongly depending of the installed battery capacity, are included as variables. As a part of the simulation the resulting speed pattern over the entire bus-line is calculated exactly. The following diagram shows the speed pattern (blue curve) in contrast to the height profile.

Velocity profile of the Model Bus line M

Velocity profile of the Model Bus line M

The vehicle's energy consumption and the associated battery state of charge are calculated and visualized throughout all 14 daily circulations of Line M in passenger service. The speed pattern is repeatedly performed until the installed battery capacity reaches its minimal level (here: 5%). In this example the simulation starts with fully a charged battery (95%) when beginning line-service.

The simulation parameters "installed battery capacity" (vehicle and Battery-Extender) and in dependence the "vehicle empty weight" are iteratively optimized until the entire daily driven distance can be performed with the planned concept.

The following diagram shows speed pattern (blue), battery state of charge (green) and battery temperature (red). Due to the adequately dimensioned battery capacity the temperature hardly varies throughout the daily routine.

State of charge of the battery of the Model Bus-line M

State of charge of the battery of the Model Bus-line M

Simulation Result

Regarding Sample-City bus-service on Line M can be performed electrically without any charging infrastructure apart from the bus depot. The electrically driven reach of more than 200 km (daily driven distance and reserve) with sufficient passenger capacity can be reached by the Battery-Extender. The present exemplary 12m e-bus with 138 kWh of installed battery capacity is supplemented with a 207 kWh Battery Extender (ca. 18t). Any battery charging is limited to the bus depot (overnight charging).

Based on the gathered data and system concept EEBC establishes a cost prognosis for the overall e bus system (purchase and operation) subsequently to the simulation. In consultation with the customer alternative concepts are calculated and simulated likewise. This allows to compare and rate different concepts amongst each other in terms of cost, effort and benefit. For instant, concepts with recharging infrastructure on certain bus-stops could be simulated and evaluated in contrast to the Battery Extender concept.

Do you desire a simulation adapted to your service lines? Simply contact us!