Durable hydrogen fuel cells
The EU-funded project SAPPHIRE (System automation of PEMFCs with prognostics and health management for improved reliability and economy) was initiated to address the relatively short life expectancy of PEMFCs. Extending service life can be achieved in several ways – one of these is prognostics and health management. Researchers reviewed existing models of PEMFC stacks, employed for state-of-health assessment and even operation control. The model fitting most of the needs of prognostics and health management was a combination of a static and a dynamic model. This hybrid approach was tested to estimate the global trend of voltage evolution through time and predict remaining useful life. Project partners also developed several controllers to efficiently counteract common factors that can cause degradation such as poisoning, dry-out and fuel starvation. Carbon oxide (CO) poisoning is usually compensated by bleed air, which is often set to high values to handle the worst expected poisoning level. A third partner implemented a feedback routine exploiting the poisoning's asymmetric dynamics, reducing bleed air by an order of magnitude, while maintaining the stack CO-free. An unexpected discovery in the project was due to a misconfiguration in the long-term testing equipment: the tested systems were often restarted over several thousand hours, and the restart procedure steadily improved their efficiency. Realising the importance of the finding, the consortium verified the phenomenon in additional experiments, and confirmed that most long-term degradation can be recovered. This effect had been observed before, but was thought to be temporary and never proven to last for thousands of hours. SAPPHIRE generated two patent applications, one for the controller system and another for the data-driven prognostic system. While focused on the current generation of PEMFCs, it will be possible to apply the same diagnostic and prognostic techniques to the next generation of fuel cells. By ensuring sufficient durability for transport and stationary applications, SAPPHIRE work promises to accelerate market uptake of fuel cell technologies and promote Europe’s energy independence.
Keywords
Hydrogen, fuel cells, PEMFCs, SAPPHIRE, system automation
