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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - Giantleap (Giantleap Improves Automation of Non-polluting Transportation with Lifetime Extension of Automotive PEM fuel cells)

Teaser

Summary

Zero-emission buses are today very interesting for many municipalities and authorities in light of the increasing scepticism towards diesel\'s emissions of local pollution and greenhouse gases.
While battery buses are being deployed in several cities across Europe, the cost of batteries and their limited range pose serious economical and technical limits.
Fuel-cell buses running on hydrogen have in fact been tested in Europe for more than a decade, and are able to store 10 to 20 times more energy in hydrogen tanks than in the same weight of batteries. However, fuel cells are still more expensive than batteries per installed kW, and the more complicated balance-of-plant system required in such buses (valves, compressors, humidifiers, etc.) has proven to be unreliable in previous demonstrations.
The Giantleap project aims to improve the availability and reliability of fuel-cell systems for buses by developing diagnostic and prognostic systems for automotive fuel cells and their ancillary components, integrating this knowledge in an advanced control system, and testing and evaluating the improvement in performance.
Since it is expected that the largest reduction in fuel-cell cost will occur in the car-sized segment, due to the larger size of the market compared to buses, Giantleap assumes that buses will use car-derived fuel cells, which are significantly cheaper but have a shorter life: therefore, it will be necessary to change fuel cells at least once during the life of the bus.
This is easily done if the fuel cell system is not integrated within the bus, but rather in its own range extender, which is mounted on the back of the bus. This approach fits well with a fleet of battery buses, which can be equipped with range extenders when required and thereby have their range increased. The ability to rapidly swap a malfunctioning fuel-cell system is another advantage, and the battery of the bus provides a redundant power source that can at least bring the bus back to the depot so a new range extender can be attached in case of malfunctions.
The Giantleap project shall build such a range extender and test it in a relevant environment, and assess its effect on the reliability of hydrogen-battery buses.
The higher reliability of the complete system, its flexibility and (as fuel cells become mass produced) its competitive price will allow the bus and coach sector to transition to zero-emission operation, improving air quality in our cities and reducing greenhouse gas emissions.

Work performed

In the first three years of the project, we developed and tested multiple diagnostic, prognostic and control methods that have been integrated in the recently completed prototype.
We developed a dynamic diagnostic method that exploits control theory\'s relay feedback to measure key parameters to estimate the state of health of a fuel cell without any additional expensive equipment, and tested on full-size stacks. We studied the previously observed phenomenon of rejuvenation, where some degradation can be recovered when shutting down the cell in a particular way; we have now a much better understanding of how this phenomenon behaves and under which conditions it occurs.
We developed model-based prognostic methods that allowed us to estimate with confidence the lifetime of fuel cell stacks, based on the method of Energetic Macroscopic Representation.
Fuel-cell stacks were produced in both laboratory scale and in full size; the overall system was first extensively tested first in a laboratory and then implemented in a trailer prototype.
We noticed that it was especially difficult to find data on balance-of-plant components of a fuel-cell system, such as compressors, humidifiers etc. At the same time these components are the most common cause of failures in FC systems, whereas fuel cells themselves are quite reliable. We decided therefore to generate this data ourselves, and make it available for the public; the experimental campaign was concluded and the data will be made available before the end of the project.
Through close cooperation among the industrial partners, the hydrogen range extender was designed and built, and will be soon ready for demonstration. Instead of just testing it in a laboratory, we decided to extend the work so that we may test it on the road.

Final results

\"The focus of Giantleap in advancing the state of the art is availability and reliability: previous projects such as CHIC reported 70%, whereas contemporary projects such as HyTransit report numbers closer to 85%. Giantleap aims to bring the availability of the range-extender setup to 98%, i.e. the same availability that operators expect of diesel buses.
The choice of car-derived fuel cells means that lifetime will not be very high for a bus application: the target is 12,000 operating hours, but with a system cost of just 500 â‚¬/kW, and a cost for the whole bus of 650,000 â‚¬.

We also investigated fuel-cell rejuvenation methods, to recover the performance of degraded fuel cells and increase their lives. It was found advantageous to implement some prognostic methods \"\"in the cloud\"\", as the computational power in automotive control units is typically very limited; instead, data will be gathered during operation and uploaded automatically at the end of the day to a server for processing.
The final 6 months of the project will be dedicated to demonstration of the range extender and to validation of the performance of the diagnostic, prognostic and control systems.

The main impact of the Giantleap project will be the ability to deploy zero-emission buses also on longer routes or in situations where charging would not be an option, improving air and life quality in cities. As hydrogen stations are deployed thanks to a reliable customer base of buses, they can start absorbing peaks of renewable energy (especially wind) that would otherwise be wasted, and improve the penetration of renewables in the energy market.
The diagnostic, prognostic and control methods developed in Giantleap are tailored for a car-derived stacks, and can therefore very easily be adapted for use on fuel-cell passenger cars.\"