{"id":8834,"date":"2024-10-21T04:12:58","date_gmt":"2024-10-21T08:12:58","guid":{"rendered":"https:\/\/blogs.sw.siemens.com\/simcenter\/?p=8834"},"modified":"2026-03-26T06:51:32","modified_gmt":"2026-03-26T10:51:32","slug":"aiming-for-zero-emission-buses","status":"publish","type":"post","link":"https:\/\/blogs.sw.siemens.com\/simcenter\/aiming-for-zero-emission-buses\/","title":{"rendered":"Aiming for zero-emission buses"},"content":{"rendered":"\n

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When considering switching to zero-emission buses, the transition can sound very expensive at first. Bus and coach manufacturer VDL discovered that shifting to an electric bus is even cheaper per kilometer than a diesel one!<\/strong> We met with Anouk Hol, aerodynamics and energy specialist at VDL,<\/a> and discussed this new trend and its challenges. <\/strong><\/p>\n\n\n\n

Interestingly, there are a lot of similarities between the automotive and bus industries. \u201cWe can learn from car manufacturers, for example by using the same battery cells and packs\u201d, she said. However, they have to make them bigger because they obviously need a bigger capacity. Buses are driving whole day long, they drive easily 300 to 500 kilometers a day. Besides, a city bus behaves very differently from a car: driving at a low velocity, stopping and opening the door every minute \u2026 The huge cabin and the passenger’ flow are also additional reasons why the components have different duty cycles and requirements. <\/p>\n\n\n\n

Challenges of designing zero-emission buses! <\/h2>\n\n\n\n

With this new orientation, VDL had to suddenly strengthen software and control knowledge because they had to supply the full infrastructure. \u201cWhen switching to zero-emission buses, we also switched from supplying a bus to supplying a system including charging infrastructure, helping customers with timetables…\u201d says Hol. <\/p>\n\n\n\n

Indeed, cities don\u2019t\nhave all the same bus and charging infrastructure: from a 24\/7 service needing\nfast charging at bus stops, to a lighter service which can rely on bigger\nbatteries and slow charging once or twice a day.<\/p>\n\n\n\n

\u201cWe are really looking at what is the best solution for our customer: what is the best battery chemistry, fast charging, low charging, what is the best charging rate, how do we use it in the system climate\u2026\u201d Hol reports. But without the real bus available, there were so many options that it was not possible to just buy and test.  <\/p>\n\n\n\n

Use of modeling in the development process<\/strong><\/h2>\n\n\n\n

This is where the need for modeling and simulation tools started to grow. Indeed, it was essential to know very early what the best configuration was to select suppliers before getting to the engineering and prototyping phases. This allowed them to make the bus as efficient as possible and propose to the customers a specific offer that best suits them. <\/p>\n\n\n

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Total cost of ownership of buses<\/figcaption><\/figure><\/div>\n\n\n

On electric buses, the driver becomes the most expensive part, and that\u2019s why optimization is so important: \u201cIt\u2019s essential to optimize the battery size and reduce charging time as much as possible,\u201d states Hol.<\/p>\n\n\n\n

The simulation tool Simcenter\u2122 Amesim\u2122 software was used for several purposes. Before prototyping and measuring, VDL’s starting point was modeling. Using models, they could map energy flow in the vehicle, model and optimize component behavior, and optimize range and vehicle energy management.<\/p>\n\n\n\n

Detailed battery cell and pack modeling<\/h2>\n\n\n\n

First, they made detailed models of the battery’s cell and pack and ran simulations to see what the behavior of this system was, how to control it, and how to optimize suppliers\u2019 selection. \u201cWe have nice components models we can use to select suppliers and components, but then we want to optimize the whole system,\u201d says Hol. Combining all the components of one bus, including a vehicle control unit, and filling it with data like, for example, ambient temperature and route, they could run an analysis and accurately predict a lot of behaviors. These analyses also provided information on how all these components were interacting. \u201cWe can easily run analysis with only 5% error rate\u201d, Hol says. Those models were also used for control design.<\/p>\n\n\n

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Combined vehicle model<\/figcaption><\/figure><\/div>\n\n\n

Mapping energy flows<\/h2>\n\n\n\n

Second, simulation was\nalso used for mapping energy flows in the vehicle, by coupling Simcenter Amesim\nwith Simcenter\u2122 STAR-CCM+\u2122 software to import 3D information. For example, for\nthe battery cooling, a fan is blowing air around the cells and this behavior\ncannot be included in a 1D model. \u201cWe got very great help with the Siemens\ncolleagues here. We made a very simplified model which was easy to understand,\nand we could make a lookup table out of it which can include the 3D behavior in\nour 1D model\u201d, concludes Hol. \u201cFor us, the integration between 1D Simcenter Amesim\nmodels and 3D Simcenter STAR-CCM+ models was very simple, and the run time is\nvery good now\u201d, Hol ads.<\/p>\n\n\n\n

Battery management systems<\/h2>\n\n\n\n

Next, Simcenter tools are used to validate battery control strategies: a model of the battery and its cooling system, including electrical and thermal calculation, is connected to a model of the BMS to validate strategies and calibrate control parameters.<\/p>\n\n\n\n

\"Simcenter
The battery and its cooling system are represented by a Simcenter Amesim model, which includes electrical and thermal calculations and the cooling loop control strategy.<\/figcaption><\/figure>\n\n\n\n

Modeling component behavior as well as mapping energy flows are both aimed at improving range estimation and optimizing range and vehicle energy management.<\/p>\n\n\n\n

\u201cThe simulation models\nhelp us to easily do some analysis based on different usage profiles of our\ncustomers: different temperatures, different velocities, slopes, wind speeds\u2026\u201d\nsays Anouk Hol. The customer was then able to clearly identify the reasons\nbehind VDL\u2019s selection.<\/p>\n\n\n\n

More information about zero-emission buses and vehicles?<\/h2>\n\n\n\n

Whether for cars or buses, energy management optimization is a topic of interest. If you are willing to know more about this, check our selection below :<\/p>\n\n\n\n