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Types of E-Buses & Charging Infrastructure

Through the analysis of a case, you will learn and distinguish each charging method.
E-Bus being charged in a charging point.

Charging Strategy of Madrid, Spain

In the previous lecture, we explained various charging strategies. In this article, we will present an actual example of a charging strategy employed in Madrid, Spain. Recently, Madrid initiated the installation of wireless charging pads on its streets. This form of opportunity charging offers multiple advantages that bolster E-Bus operations.

Case Study: Madrid

Over the last few years, several cities have begun integrating E-Buses into their public transit networks. The city of Madrid, Spain, has joined this trend, with the local government planning to deploy 331 E-Buses in 2023. Implementing such an E-Bus project also requires Madrid to establish a suitable charging strategy that aligns with the E-Bus and its operations, taking into consideration factors such as the size of the E-Bus battery, the length of daily routes, and other critical operational parameters.

Photo of a bus stop in a sidewalk outside a building Bus Stop in Madrid. EMT Madrid (2023)

Using plugs to charge the E-Bus overnight is a charging strategy that many cities have implemented. However, Madrid has opted for a charging strategy that enables E-Buses with smaller batteries to charge throughout the day, which is less conspicuous than other charging methods. This type of charging is known as wireless charging and presents a form of opportunity charging where E-Buses are charged via an inductive power charging system using wireless charging pads embedded in the streets.

Fast Induction Charging

Wireless charging stations are placed along the E-Bus route and therefore help exceed the state of charge (SOC) percentage throughout a day’s operation. Therefore, an E-Bus with a smaller battery (e.g., 60 kWh) can undergo a whole day of driving.

Inductive charging utilizes two magnetic coils, one underneath the bus and the other embedded in the street. The charging station is activated electrically. This only occurs when a bus equipped with a magnetic coil is detected above the recessed magnetic coil. All these components are fully isolated to ensure the total safety of the system (Grupo ETRA, n.d.)

Electric bus wireless charging station Fast Induction Charging Station. MDPI and ACS Style (2022)

For the use of these pads, there are several technologies where the placement of the charging station is variable. In general, there are two different ways to set up the charging station, either as a road charger or as a footpath charger.

Road Charger

Diagram representing charging station components.Click to expand. Charging station components. PEM Motion (2023)

Course mascot explaining components of a road charger.Click to expand. Couse mascot. PEM Motion (2023)

Footpath Charger

Diagram representing four different political factors to be consideres in E-Bus deployment.Click to expand. Diagram representing a footpath charger. PEM Motion (2023)

Mascot with the dialogue "The footpath charger has the track supply embedded into the footpath, providing easier access to the track supply for maintenance works when needed." Click to expand. Course Mascot. PEM Motion (2023)

Charging Time

The charging process typically occurs during scheduled breaks or stops. When an E-Bus is parked or stopped at a designated charging point, that’s when the charging happens. Like when the passengers are boarding or alighting from the bus, while the bus is being charged in the meantime.

The time it takes to charge the bus using fast induction charging can differ based on specifics like the battery size or the charging setup. Generally, fast induction charging systems can provide the bus with a solid charge in a short time. Sometimes, it might only take about 5 to 10 minutes to add a good amount of charge. This allows the bus to keep going on its route with more battery capacity. The exact charging time can change depending on specific technical details and operational influences.

Conclusion

The conversion of hybrid buses to electric was perceived as an opportunity to explore new wireless charging technologies. Following the successful implementation of wireless charging in Madrid, other countries and cities are now contemplating the adoption of this charging strategy in their respective cities. Naturally, the specific technology required will depend on each city’s unique requirements and the type of E-Bus utilized.

‘The Empresa Municipal de Transportes’ (responsible authority for public bus transit in Madrid) has opted for the inductive system, which is more efficient, sustainable, and possibly safer. Its efficiency stems from the fact that this charging system provides an increased range for E-Buses and could eliminate the need to use cables and other chargers utilized for opportunity charging. In addition, the visual impact was considered since this system does not require catenaries or pantographs. (Sawilla & Swenja, n.d.).

In the words of Joseph Ma, Deputy General Manager of Shenzhen Bus Group: “Buying the buses is one thing, but electrification requires you to change your entire business model and network” (Lopez et al., 2022).

Throughout the upcoming activities, we will explore the strengths and weaknesses of this innovative technology.

References

  • Grupo ETRA. (n.d.) Inductive Charging System. Retrieved from: Link
  • Lopez, I. et al. (2022) Different Approaches for a Goal: The Electrical Bus-EMT. Retrieved from: Link
  • Sawilla, & Swenja. (n.d.) Wireless Opportunity Charging buses in Madrid IPT Technology. Retrieved from: Link
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