Fuel Cell Diagnostics Team
Farid Golnaraghi, Professor, Simon Fraser University
Project: Development of the Next Generation of Heavy Duty (Bus) Fuel Cells with Integrated Diagnostics and Safety Systems.
1. Background and Motivation
Over the past decade governments and transit agencies world-wide are promoting measures to reduce airborne emissions and greenhouse gases (GHG) from motor vehicles, and fuel cell buses as zero emission vehicles can make an important contribution to this effort. In that regard, Ballard Power Systems in collaboration with coach supplier New Flyer Industries (Winnipeg) has built a fleet of 20 hydrogen fuel cell powered hybrid buses that were placed in regular revenue service by BC Transit in Whistler for the 2010 Winter Olympics and subsequent continuing service. These buses are powered by Ballard’s 6th generation FCvelocity™-HD6 Modules, which utilize two Mk1100 Proton Exchange Membrane (PEM) stacks. This fleet constitute the world’s largest fuel cell bus fleet, and represents an ongoing opportunity for Canada to both showcase and also continue to develop this world-class product.
While significant progress towards fully commercial fuel cell buses has been made over the past five years, this technology is still more expensive and less durable than conventional internal combustion (diesel) engine technology. For PEM fuel cell buses to become a preferred option for transit agencies, improvements in both fuel cell durability and reduced cost are essential. Once these are available, the market for larger fuel cell bus fleets will grow and this technology will begin to replace the incumbent, but more polluting, IC engine technologies. PEM is currently the life-limiting component in bus operation. As a result Ballard’s goal is to enhance the durability of the membrane elements of the fuel cell by
- Expanding the fundamental understanding of membrane degradation mechanisms and the linkages between chemical and mechanical degradation,
- Developing a membrane durability model that can predict membrane life as a function of operating conditions and load cycles, and
- Developing fundamental improvements in membrane durability towards prolonged service life of heavy duty fuel cell modules.
A key to success of this undertaking is development of a well-instrumented and comprehensive fuel cell test bed system that can be utilized to measure durability of the membrane elements of the fuel cell and by the application of state-of-the-art diagnostic sub-systems and diagnostic sensors for on-line operational monitoring of fuel cells, particularly in respect to fugitive hydrogen releases. In this respect, the goal of this project is to assist Ballard with the development of a test bed that leads to development of better fuel cells with improved durability, manufacturability, servicing and safety.
2. Proposed Research Activity
The flowchart in Figure 1 shows the proposed procedure in Ballard’s fuel cell development, where the process begins with a set of criteria and constraints, including power, energy, size, operating conditions, safety specifications, etc. In addition, knowledge of materials and processes is necessary to properly construct a fuel cell stack. Once the initial design phase is completed, modeling (mechanical, chemical, thermodynamics etc.) is performed to identify the successful design and to fabricate a prototype for performance testing. The tests performed on the prototype system can either result in a final product or result in an iteration of existing designs for improvement. Reliable diagnostics are needed not only to find the deficiencies of the existing design so that it can be improved, but also to calibrate and verify the models and assumptions used in developing them. Hence, accurate modeling has a critical role in shortening the design process and to help with developing durable fuel cell stacks more efficiently.
Using fuel cell modeling as a successful design tool requires the model to be robust, accurate, and able to provide usable answers quickly. In terms of robustness, the model should be able to predict fuel cell performance under a large range of operating conditions. For example, a PEM fuel cell can be operating at different temperature, humidity level, and fuel mixture However, enhancing model robustness and accuracy often trades off with computational efficiency. To provide answers quickly, the designer must select a model that balances robustness, accuracy, and computational effort.
Figure 1: Role of testing and diagnostics in the fuel cell design process.
The long-term goal of this research is to utilize the test and diagnostics phases to enhance the fuel cell design process by improving the accuracy of the model and by identifying what is wrong with the fuel cell and its possible causes.