It’s Time to Amp Up Bus Electrification

If the goal of moving to electric vehicles (EVs) is to reduce harm to the environment, then getting people out of individual cars and on electrified public transit should be a premier destination as well.

While they may not look as sleek as the latest Tesla, electric buses are going places, too, despite similar range anxiety and their own set of infrastructure challenges. Research shows we’re moving in the right direction, with adoption of electric buses expected to triple worldwide by 2025; this would mean just under half of the world’s buses will be powered by electricity within five years.

If you’ll excuse the pun, China is leading the charge, but many other jurisdictions are getting on board, too. But just like cars for the average consumer, a widely available fast charging infrastructure is essential if public transit organizations and riders are to have enough confidence in electric buses.

An uneven landscape for electric bus adoption

Many public transit organizations around the world are committed to quitting fossil fuels.

In the United States, the move toward different propulsion systems has been driven by concerns that diesel-powered buses cause poor air quality, although cheaper natural gas is a speed bump on the road to electrification. Another alternative is a flavor of electric bus that uses hydrogen fuel cells, which are designed to improve performance by generating on-board power from hydrogen to recharge the batteries. Trolley buses that draw power from dual overhead wires using spring-loaded trolley poles are still used in some municipalities, such as Vancouver, Canada.

There’s also been a rise in the use of hybrid buses. Rather than being solely powered by batteries, these vehicles also contain either a gasoline or diesel engine that activates after the bus has traveled a certain distance. By the end of 2019, Toronto’s goal was to have a bus fleet comprised of three different eco-friendly technologies that would include clean diesel, hybrid electric, and battery electric while continuing to trial a variety of bus models that operate on green technologies.

Research firm Wood Mackenzie sees China as the engine for driving the adoption of electric buses, fueled by the clean transportation targets of both government and transit agencies. Its 2019 report found that China accounted for about 98% of the world’s electric bus fleet and will hit the 1 million mark by 2023. The firm also forecasts that about 40,000 heavy-duty electric vehicles, including electric buses, will be on the roads in Europe and the U.S. by 2025. Widespread rollout of EV charging infrastructure, meanwhile, will mean that Europe, China, and the U.S. will have about 108,000 charge points in place by 2025.

Overall, electric bus adoption to date has been extremely uneven, according to WRI Ross Center for Sustainable Cities, despite the benefits of lower long-term operating costs and reduced air pollution. Among its recommendations are that public officials first take into account the scale of their electric bus projects and start with what’s feasible, such as structured yet flexible pilot programs. But they also need to think long term and put plans in place for infrastructure and procurement.

For electric buses to see more widespread, consistent adoption worldwide, fast charging infrastructure and on-board charging capabilities must be easily deployed and cost-effective.

Electric buses must be ready for the long haul

Electric buses have similar challenges and requirements to that of cars and trucks, but they also have some of their own unique characteristics.

Like any other electric vehicle, buses must overcome range anxiety in that they must be able to travel a minimal distance without needing to be charged. They also must be able to find a charging station with reasonable distances and be able to charge quickly. Electrified or not, public transit must always be convenient. In an urban setting, range anxiety is less of a factor, but any operator would prefer that an electric bus run the length of a typical driver’s shift without needing to be charged until it’s back in the garage. Rural and long-haul buses, however, face the same worries as families going on a road trip — travelling from one major center to another without fear of running out of power.

But even in electric-friendly jurisdictions, challenges remain for building out a charging infrastructure as well as making sure buses have the right on-board technology. Mirroring the convenience and dependability of traditional gas-fueled vehicles is table stakes when it comes to meeting the expectations of several affected parties, which include the municipalities that generally run the public transit system and local utilities. They must weigh the impact of charging infrastructure on the power grid, which tends to be a mix of aging equipment and newer systems.

Any infrastructure to support electric buses must be fast-charging. Municipalities want designs that are rugged, connected, and flexible, as well as robust enough for dirty and wet environments and ready for any weather conditions from around the world. Furthermore, these municipalities will want to leverage the fast charging infrastructure being put in place for cars to support electric public transit. We don’t have different gas stations for buses and cars, do we?

Municipalities and public transit agencies also are in it for the long haul in that these major, capital investments, like any other infrastructure, are expected to last decades. They don’t want to put time, effort, and money into infrastructure that will have to be replaced in a few years’ time. Any fast charging infrastructure for electric buses, or any electric vehicle, must be futureproof as to accommodate bidirectional capability and e-commerce capabilities — so, too, must the charging technology on the buses themselves as they continue to evolve.

Any fast charging infrastructure, whether deployed in urban or rural environments, must be complemented by charging capabilities of the vehicles themselves. As all vehicles become equipped with lighter, high-power-density batteries that can increase their range, there’s a shift toward bidirectional on-board chargers (OBCs) with additional intelligence that can address the challenges faced by electric buses and the power grids they drive on.

An OBC is not as powerful as a fast charger, which can charge a passenger vehicle in less than an hour. Traditionally, most OBCs are uni-directional, meaning power only flows from the charger into the battery. However, as the electric vehicle fleet grows worldwide, so does the capacity and the flexibility needs of the power grid. Many new OBC designs are incorporating bidirectional power flow that allows the vehicle fleet to be used to balance the load on the grid. This, alongside renewable energy power generation, can be a key factor in building a highly-efficient worldwide electrified energy infrastructure; something that all humankind and our planet need.

For an electric bus or other commercial vehicle in an urban environment, this shouldn’t be necessary — fast charging infrastructure should be enough to accelerate the electrification of buses.

Just as they do for cars and other personal vehicles, silicon carbide (SiC)-based solutions are the best option for meeting the design needs of all stakeholders to create the fast charging infrastructure that will accelerate the electrification of buses. A SiC-based solution satisfies a wide variety of customers and needs, including the municipalities and transit authorities looking to evolve to a fully electrified fleet.

China’s lead in bus electrification has been an opportunity for companies such as Shinry Technologies, which is the leading EV power converter company in the country. All of Shinry’s power systems require devices that enable the greatest possible efficiencies for power conversion, so they used Wolfspeed SiC MOSFETs to enable a 96% DC-to-DC power conversion efficiency rate. The SiC MOSFETs can enable more than 3× the power density versus designs based on traditional silicon technology.

Additionally, Zhengzhou Yutong Group Co., a large-scale industrial Chinese manufacturer of commercial vehicles that specializes in electric buses, is using Wolfspeed’s 1200V silicon carbide devices in a Starpower power module for its new, industry-leading, high-efficiency powertrain system for electric buses. When rolled out, Yutong Group will deliver their first electric bus in China to use silicon carbide in its powertrain, representing a significant advancement in providing an even more efficient e-bus to the market.

Conclusion

Silicon carbide-based solutions are not only ready today to support the electrification of buses but are futureproofed to support the fast charging infrastructures of tomorrow. The technology to deliver the most power, quickly, in the smallest form factor and at the lowest cost not only makes electric buses feasible but preferred. In addition, SiC-based solutions support bidirectionality that enables inevitable smart grid applications and e-commerce capabilities.

SiC-based solutions offer flexibility and adaptability to more people riding the bus — an electric bus — without worrying about running out of charge before they get where they’re going.