Abstract
M.Ing. (Electrical Engineering)
Proton exchange Membrane Fuel stack systems have developed over the last fifty years into a technology that is more widely accepted in specialized applications than ever before. It has become lighter, more efficient and although affordable, is still expensive.
The use of hydrogen as a fuel seems obvious and the implementation of PEMFC and other fuel cells based on the most common element on earth, hydrogen, intuitive. Yet, in practice there are fewer fuel cell companies today than a decade ago. The hydrogen economy growth is stifled by perceptions, rightly so, that PEMFC stacks are not dependable for general use. Further that the production of hydrogen as fuel other than in hydrocarbon combinations is expensive and impractical.
PEMFC stacks cannot be serviced by the user and are often discarded as dormant or unserviceable. The purpose of this study is to understand the operation of PEMFC stacks and the PEMFC system and to search for answers to the causes of lowered PEMFC performance and dormancy.
As the study progressed, operational protocols were established by experimentation to improve the operational parameters of the PEMFC in high efficiency applications. Operational protocols and parameters were found to be the major contributing factors of PEMFC performance.
Proton Exchange Membrane technology has developed over the last fifty years into efficient and lightweight devices which can be used in many environments where standard equipment could not be used purely because of the high energy density of a PEMFC stack and the clean power that it produces with only water as a by-product.
Deficiencies in the performance of the PEMFC stack became known when even new PEMFC stacks could not deliver the performance specified by the manufactures of the PEMFC stacks. The new PEMFC stacks had been dormant in storage for some time and could not deliver the power required even after careful operation.
This study is aimed at finding the reasons for PEMFC stack dormancy and the possible factors to consider for dormancy recovery. Specific attention was drawn to the effect of Purging on the PEMFC stack and the resultant improvement in performance of the PEMFC stack with dynamic purging. The application of the research allowed for the use of the iterative scientific method to gain insight into the operation of the PEMFC stack system.
The testing protocol applied to the testing of the PEMFC stacks are focused on the operational use of the PEMFC stack. Operational parameters can be derived from activation curves, load testing for extremum and the operational characteristic curves for the PEMFC stack current and voltage.
Adaptive control and differentiating between the requirements of the PEMFC stack under start-up and shut-down conditions are focused on the purging requirements to operate a PEMFC stack properly. Experimental work is based on fundamental principles of operation and operational testing. The experimental work on PEMFC stacks smaller than 5 kW allows for the practical implementation of the results in small and domestic PEMFC stacks of water or air-cooled design.