Innovations in e-compressors and e-turbos for fuel cell engines

Innovation in commercial mobility is driving sustainable transportation. As technologies like battery electric vehicles (BEVs) and fuel cell electric vehicles (FCEVs) advance, the demand for optimized components that balance efficiency, power, cost, and durability grows.

Cummins Inc. along with Accelera™ by Cummins – the zero-emissions business segment of Cummins - are at the forefront of supplying and integrating zero-emissions technologies to decarbonize the world’s hardest-working industries. Cummins is actively working with Accelera™ on innovative technologies for transportation and heavy-duty operations.

E-compressors vs. e-turbos in fuel cell engines

E-compressors and e-turbos play vital roles in fuel cell engines by compressing air for the chemical reactions powering the engine. This process increases power density and efficiency. Cummins is currently working on integrating e-compressors as part of the integrated powertrain solution and is continuing to innovate on e-turbos to provide the right solutions for any application.

E-Compressors: Electric compressors, or e-compressors, are powered directly by electricity. In fuel cell engines, e-compressors provide instant pressurized airflow by compressing air and sending it into the fuel cell engine's cathode. The electricity required to drive the e-compressor is taken from the fuel cell, making the e-compressor the largest parasitic load on the system. However, higher fuel cell power density and efficiency can be achieved by pressurizing the air intake.

E-Turbos: Electric turbochargers, or e-turbos on the other hand, combine the functionality of e-compressors with a turbine. While an e-compressor relies on the fuel cell engine's electrical supply to power the motor and supply the compressed air, an e-turbo adds a turbine to assist the electric motor. This reduces the parasitic load on the fuel cell engine by recovering some of the waste energy, thus further increasing system efficiency.

In summary, the critical difference between e-compressors and e-turbos lies in their operation and impact on fuel cell engine performance. E-compressors provide a simpler solution, making them ideal for immediate performance enhancement over low-pressure blowers. E-turbos, however, are more complex to design and integrate, but will further enhance system efficiency over an e-compressor.

Another important concept is the two-stage e-compressors, a cutting-edge fuel cell engine air supply technology. In Internal Combustion Engine (ICE) applications, two-stage compression increases the pressure ratio by compounding compression across multiple compressors. In fuel cell engines, its primary purpose is to lower rotor speed for a given aerodynamic power demand, simplifying motor requirements. A secondary benefit is balancing the thrust load on the system. This is achieved by positioning compressor wheels at each end of the motor shaft, which reduces the net thrust load and simplifies the bearing design.

Given the benefits, why are e-turbos not the current architecture of choice?

E-turbos harness energy from exhaust gases that would otherwise be wasted, presenting significant potential for enhancing fuel cell performance. However, several challenges must be overcome. Let us explore these in detail:

The Challenge of Thrust Loading

A key technical challenge for e-turbos is managing thrust loading, the force along the turbocharger's axis. This force must be balanced to prevent wear. Two-stage e-compressors, with their symmetrical design, handle these forces more effectively. However, innovative engineering can also address this issue in e-turbos.

High-Speed Motor Technology Limitations

E-turbos push high-speed motors to their limits, especially at peak power and high altitudes. Higher power output requires lower speeds, which reduces aerodynamic efficiency. Advanced engineering is needed to maximize power while maintaining target speeds.

Corrosion and Erosion Concerns

Fuel cell engines have moisture in their exhaust, which can cause corrosion and erosion in turbocharger parts—unlike traditional Internal Combustion Engines (ICE). Durable materials are essential to ensure e-turbos perform reliably in these conditions. This issue, however, does not affect e-compressors.

How will e-turbos evolve?

Despite these challenges, e-turbos show great potential for fuel cell engines. Their ability to boost efficiency and power density makes them a strong candidate for future clean energy solutions. As these challenges are resolved, e-turbos will evolve to become the air-handling architecture of choice and represent another innovative technology for fuel cell engine air supply.

Cummins' components business collaborates with Accelera to advance fuel cell technology, focusing on longer ranges and robust performance for heavy-duty transportation. Cummins also delivers innovative, integrated powertrain solutions, offering complete systems—from engines to axles—with seamless component integration. This approach drives sustainability while empowering customers with reliable, high-performance options.