Fuel cells for mobile application such as passenger cars, commercial vehicles (for lifts, delivery vans, trucks, buses) and train applications require an air supply with a compressor. Due to the dynamic market and technology development there is no clear standardization in the compressor specifications yet. This project targets to solve this problem by a smart combination of compressor system building blocks for different specifications. This allows for compressor systems with lower cost and lower validation effort than fully application specific compressor systems, and higher efficiency than existing, but non-optimal compressor systems. The research results from this project allow the fuel research and development community to improve efficiency and reduce cost, and with this strengthen the fuel cell technology and market acceptance.
Main findings
Specifications in the fuel cell industry will stay dynamic, standardization concerning power classes, voltage levels, pressure/flow requirements, ambient conditions and many more requirements is coming, but more slowly than expected and forecasted. Fuel cell components, specifically a compressor system based on building blocks that can be adapted for different specifications, are mandatory for the next years to allow for the fuel cell market to evolve. For the H2-community it is important to assess which fuel cell system requirements have become a standard, and therefore also component requirements can be fixed, and which fuel cell system requirements are still evolving and therefore have to be covered with flexible designs such as building blocks and/or modular approaches.
This project shows that the maximum range of fuel cell power classes that can be covered with only modifying building blocks in a baseline compressor, and limiting the compressor efficiency reduction to 5%, is around 40-100%, i.e. with the investigated baseline compressor as of this project a range in fuel cell power class from 25 to 60 kW. A baseline compressor for the next size fuel cell power class according to this finding can cover a range of fuel cell power class from 60 to 150 kW. This is important for the H2-community, specifically for fuel cell system integrators and stack manufacturers, to define their power classes, i.e. such that they can plan to cover a 60-150 kW fuel cell stack/system product line with the same baseline compressor. Since no standardization in pressure ratio and mass flow requirements are present for the different fuel cell power classes, the fuel cell system integrators and stack manufacturers either a) use standard compressors and accept the disadvantages in efficiency and operating range or the compressor, or b) invest into a custom design, or c) now according to this project choose a building block design (with smaller efficiency and operating point range disadvantages than with a), or d) invest (with much smaller duration and cost than with b) into a new building block design.
The input voltage can be adapted without impact on the efficiency, however it requires significant design adaptions and validation. This is in line with the standardization that is happening at fuel cell system integrators in the high-voltage range (with HV2 and HV3 voltage levels), but not yet in line with the still evolving low voltage requirements between 36 and 80 Vdc.
Somewhat surprisingly, a building block design has minimal impact onto the piece price in serial production, therefore, for single applications with large quantities custom designs will remain. However, the design and validation of two such building block system variants further shows that the design and validation effort and therefore cost and time to market is reduced significantly by 46% (for adaption of the input voltage) and up to 91% (for adaption of the aerodynamic building block) when using building block versus full customized compressors systems. Therefore, building block compressor systems therefore give the H2 community a powerful measure to allow for shorter time to market than with full customized compressors systems, especially important for the upcoming years and projects with small to medium quantities.
The main findings of this project can be rolled out to other compressor and fuel cell power levels by Celeroton or other compressor manufacturers, and with adaptions also to other fuel cell components.
