Electric thermal management in e-buses: the future is now

Busworld Europe in Brussels represents more than just a leading industry trade show: It’s a window into technological innovation in the transportation sector. Sometimes, it’s the overlooked elements whose value we recognize only when they falter. A prime example is the air conditioning in electric buses. Often taken for granted as a given comfort, its crucial role only truly stands out when it becomes inefficient or stops working altogether.

In electric buses, air conditioning presents a unique challenge as it’s directly powered by the battery. Inefficient thermal management can significantly impair battery performance, subsequently shortening the bus’s range. For a vehicle whose primary power source is the battery, it’s not just about preserving comfort but also about operational costs and the bus’s availability.

This year at Busworld, Webasto is seizing the opportunity to raise awareness about this underestimated technology while offering a detailed glimpse into the future of thermal management in electric buses. On display is our eTM showcase. The standout feature? All components of the futuristic electric thermal management are clearly visible under glass, including a heat pump, a high-voltage heater, an eight-centimeter-thin air conditioner, and fans. “In our showcase, we aim to display what the future of electronic thermal management solutions looks like. Everything, from interior climate control to the temperature management of batteries and power electronics, is precisely designed for efficiency and performance,” emphasizes Martin Arzberger, System Expert for Thermal Management at Webasto.

Especially smaller e-buses need efficient thermal management

It might seem obvious, but for e-buses, efficient air conditioning isn’t a luxury; it’s a necessity. Arzberger explains, “The second largest power consumer in an e-bus is the air conditioning. The more efficiently it runs, the less the battery is taxed. This reduces the entire vehicle’s energy consumption.” This also means that if up to 50% of the required energy goes solely to heating and cooling the e-bus, buses with efficient thermal management can stay on the road longer and spend less time charging – directly impacting revenue. After all, in the bus industry, profits are only made when the wheels are turning.

For larger electric buses, there’s the luxury of simply increasing energy capacity by adding more batteries. But what if space is limited? Especially in compact buses, engineers and designers face constraints. “The smaller the bus, the more critical space and weight limitations become. In an E-mini bus, available space is maxed out after a battery capacity of 70 to 100 kilowatt-hours,” notes Arzberger.

Smart use of excess and waste heat

Webasto’s electric thermal management system (eTM) represents a radical departure from conventional approaches. While traditional systems tend to discard generated waste heat, viewing it as merely waste to be vented out, Webasto sees this perceived waste as a valuable resource. “Instead of unnecessary energy loss by simply venting out the waste heat, we capture and reintegrate it into the vehicle’s thermal cycle,” Arzberger elaborates. The smart integration of residual heat facilitates innovative applications. Even the waste heat produced by the water-cooled power electronics and the batteries can be recaptured and used to warm the passenger compartment. An integral player in this is the electric battery thermal management (eBTM): Temperature-regulated batteries can charge faster and more efficiently, thereby shortening charging times.

This meticulous and detailed approach to thermal management directly affects range, which is vital for bus operators. “Thanks to enhanced efficiency in utilizing waste heat, our calculations show that an electric bus’s range can be increased by up to 40% year-round,” says Arzberger. This marks a significant advantage over the latest heat pump systems on the market, which are about 20 to 30% less efficient. Another noteworthy feature of the eTM system is its ecological sustainability: the optimized cycle of heat significantly reduces refrigerant use, which not only protects the environment but also lowers operating costs.

Modular approach for customized requirements

The eTM showcased at Busworld is much more than a technical feasibility study. Everything is already set up for the near future. Webasto is actively collaborating with customers on implementing eTM systems into prototypes. The modular design expedites the integration process. “The flexibility of our approach allows us to design the optimal heating and cooling solution based on each bus’s specific requirements,” Arzberger clarifies. This includes the heating and cooling needs of various engines, batteries, and vehicle cooling systems. Furthermore, the bus’s regional use is specially considered. After all, an electric bus in Northern Sweden faces different thermal challenges compared to a similar vehicle in Southern Italy.

How long until the future of electric thermal management becomes standard in e-bus manufacturing? “We anticipate that most electric bus manufacturers will start mass production around 2025. However, Webasto is already poised for this evolution, aiming to be a cornerstone in the burgeoning e-mobility landscape,” opines Arzberger.

At Busworld, one can marvel at the future of thermal management for electric buses under glass. Once the system seamlessly integrates into everyday technology, drivers and passengers will barely notice the presence of an eTM. But that’s precisely the point: The subtlety of the technology will lie in its effectiveness and reliability, making it an indispensable element for the next generation of electric buses.