What Are the Basic Structures of E-Buses?

This article will discuss the different types of E-Buses and their essential components, structure, and energy supply.

Different types of E-Buses.

• Trolleybus
• Fuel Cell Electric Bus
• Battery Electric Bus.

Course Mascot. PEM Motion (2023)

As discussed in the previous lecture, an E-Bus is a bus whose traction power can be supplied entirely by an electric motor. The energy used for its batteries is obtained from an external source and/or from regenerative braking.

Its main components are: battery, Battery Management System (BMS), electric motor (central & in-wheel), regulator, charging port, and inverter.

Basic Structure

The following diagrams, provide an insightful glimpse into the basic design and layout of an E-Bus, highlighting the crucial components and their arrangements.

Click to expand. Schematic of an E-Bus. Electric Buses in India (2016)

Click to expand. Electric motor (in wheel). TUMI E-Bus Mission (2022)

Energy Supply

When starting, E-Buses operate by sending a signal to the powertrain system controller. This drives the high-voltage battery, where chemical energy is stored and converted into electrical energy. The electrical energy is then distributed to all the different components that accelerate the bus, such as the electric motor and the thermal control system.

AC stands for alternating current, where electrons switch back and forth in cycles. It can be generated from renewable sources like wind or hydropower. DC stands for direct current, with electrons flowing steadily in one direction. It can be produced, for example, from solar panels and is used for energy storage.

Click to expand AC and DC Power. PEM Motion (2023)

The process involves drawing AC power from the grid, converting it into DC power, and then storing and utilizing it in high-voltage batteries, as the diagram below. This conversion process is also applied in numerous other electronic applications. For instance, when charging a laptop, the charger converts AC power from the grid into DC power, facilitating the charging of the laptop’s battery.

Click to expand. Different ways of supplying energy. TUMI E-Bus Mission (2022)

Trolleybus

A Trolleybus is similar to a normal bus, but it includes a mechanical arm that powers it, and provides a continuous power supply through overhead wires.

It has several benefits, such as no release of pollutant emissions as well as quiet operations. However, its popularity has suffered due to its reliance on overhead wires and its difficulty deviating from its original route.

Some advantages of this technology are the possibility of uninterrupted operation, due to the continuous power supply. Moreover, the long durability makes the trolleybus very reliable public transport. Accordingly, this type of e-bus is mainly interesting for cities with an existing trolleybus network or BRT routes with high capacity and fixed corridors. In the next diagram, the trolleybus structure is shown.

Click to expand. Trolleybus – Structure. TUMI E-Bus Mission (2022)

Fuel Cell Electric Bus – FCEB

The Fuel Cell Electric Bus incorporates a hydrogen fuel cell and batteries, creating a hybrid architecture. The fuel cell supplies the necessary energy to operate the vehicle, while the batteries contribute to maximum engine power. All energy is generated through the conversion of hydrogen into electricity.

Fuel Cell Electric Buses are equipped with an electric motor that utilizes a blend of compressed hydrogen and oxygen from the air, with water being the only by product of this process.

H2 consumption

• Single bus: approx. 8-16 kg/100km
• Articulated bus: approx. 12-24 kg/100km

Range

• Long daily distances may not pose a problem, but it is essential to differentiate between the installed and actual usable capacity for H2 storage. Additionally, adjustments to the current storage capacities might be necessary.

Requirements for IT systems

• Prediction and monitoring of the range, including the state of charge (SOC) for both energy storages, for example, battery and H2.
• Planning and scheduling of refueling will depend on the availability of refueling infrastructure and can be modeled accordingly.
• Monitoring and evaluating vehicle data, possibly extending to additional data and log data.

Click to expand. Fuel Cell Electric Bus – Structure. TUMI E-Bus Mission (2022)

Battery Electric Bus – BEB

The Battery Electric Bus, often described as purely electric, runs on electricity stored in an onboard battery and, thus, does not include any mechanical engine configuration. To charge the battery, the BEB utilizes two operational forms: opportunity charging and overnight charging.

The differences between the two types are based on range and charging time. Buses using opportunity charging have a smaller battery package offering a limited range (20–30 miles) and can be fully charged (80–100%) within 5–10 minutes. On the other hand, buses using overnight charging contain a larger battery package with a range of up to 200 miles and require a much longer charging time (2–4 hours). In the following diagram, the structure of a battery electric bus is shown.

Click to expand, Battery Electric Bus – Structure. TUMI E-Bus Mission (2022)

You can also define these two different types of E-Buses as follows:

Standard charger:

• charging overnight in the depot or during longer stopping times
• equipped with a high-energy battery.

Fast charger:

• opportunity charging along the route
• equipped with either a high-power or high-energy battery.

High-power and high-energy batteries are two distinct types of rechargeable batteries designed for specific applications. They differ in terms of their performance characteristics and the tasks they are best suited for. The choice between high-power and high-energy batteries depends on the specific requirements of the application. High-power batteries are used when rapid bursts of power are needed, while high-energy batteries are employed when longer runtime and energy storage capacity are essential.

Although fast charging in a depot can also be a viable solution, in most cases, only a few stops at the terminal are needed as charging locations. The advantages of this technology include its adaptability to specific requirements and its high overall efficiency. Furthermore, it provides the ability to utilize regeneratively produced electricity directly, with no tailpipe emissions and only minimal overall emissions when using renewable energy sources. Because of these, this emerging technology is showing significant potential in the current markets.

Conclusion

E-Buses, including Trolleybuses, Fuel Cell Electric Buses (FCEBs), and Battery Electric Buses (BEBs), offer promising solutions for sustainable urban transportation. With their electric motors, essential components, and various charging options, these buses contribute to cleaner cities and a greener future. Embracing E-Bus technologies is crucial for reducing emissions and creating more eco-friendly public transportation networks, especially in urban areas. In the next activity, we will learn more about the exciting world of user experiences with E-Buses. Get ready to explore how people interact with and enjoy the benefits of these cutting-edge innovations.

References

• Pleško, J., & Sullivan, H. (2021). Ev charging: The difference between AC and DC. EVBox. Retrieved from: Link
• HISOUR (n.d.).Electric bus. Retrieved from: Link
• MRCagney. (2017). Electric Bus Technology. Transport Research Report. Retrieved from: Link
• Sanguesa, J., Torres Sanz, V., Garrido, P., Martinez, F., & Marquez Barja, J. (2021). A Review on Electric Vehicles: Technologies and Challenges. MDPI – Smart Cities. Retrieved from: Link
• Sinhuber, P., & Wasiluk, K. (2022). Mobility Academy. Retrieved from: Link