Water transport study in high temperature fuel cell stack

This work presents analysis of water transport phenomena in the 120 Wel high temperature PEM fuel cell stack. Phosphoric acid doped PBI membranes are known for their abilities to work with dry gases; however water in the electrolyte still plays an integral role in the proton conduction mechanism. The presence of water in the membrane increases proton conductivity, however at high operating temperatures in the anhydrous environment phosphoric acid can dehydrate consequently lowering its conductivity. Therefore, understanding of water transport in the PBI- H3PO4 membranes is important as it can explain certain phenomena inside the cell. Tests have shown that water transport from cathode to anode due to water accumulation rises almost linearly with current density while decreases with cathode stoichiometry. Water transport seems to be independent of operating temperature. Also, in some cases, reverse flow water transport (from anode to cathode) appears to take place near the outlet. Ohmic resistance was also found to decrease slightly with an increase in current density and lower stoichiometries.Peer ReviewedPostprint (author’s final draft

Techno-economic analysis of PEM fuel cells role in photovoltaic-based systems for the remote base stations

Expansion of telecommunication networks even to the most remote areas where connection to the utility grid could never be justified, especially in touristic regions, has led to the increasing need for stand-alone power systems. In Adriatic coastal area employment of hybrid photovoltaic-based systems is straightforward due to high sun potential. Inherent intermittent nature of renewable sources is especially not compatible with telecommunication system who require uninterrupted power supply. This leads to the need of not only energy storage, but also a "back up" solution in the case of primary system failure. Emphasis is put on the system reliability and simplicity while system price is not necessarily top priority. Usual approach of using diesel generators as a "back up" has been challenged by the introduction of PEM fuel cells. Even with hydrogen technologies market development still lagging behind some comparable advantages such as high energy conversion efficiency, silent operation and no emissions make PEM fuel cells a legitimate candidate for replacing traditional oil burning generators. Technoeconomic analysis of various stand-alone power systems for the remote base station on an Adriatic island is made. At the moment, levelized cost of electricity point of view still gives slight advantage to the diesel generators. Long term reliability of PEM fuel cells system still needs to be examined in practice, as this combined with pro-environmental characteristics of fuel cells can make the difference especially in pristine and protected areas. Furthermore, uncertain petroleum market and fast developing hydrogen technology market could reverse this trend in the near future.Peer ReviewedPostprint (author’s final draft

Water transport study in high temperature proton exchange membrane fuel cell stack

A study of water transport in a high temperature phosphoric acid doped polybenzimidazole (PBI) membrane fuel cell stack is reported. Tests with different stoichiometries of dry cathode and different humidity levels of anode are performed. It is found that water transport across the membrane electrode assembly (MEA) is noteworthy and that water vapor partial pressure on the anode outlet is almost always higher than on the cathode outlet, even when using dry hydrogen. The water transport is a strong function of current density but it also depends on stoichiometry and humidity level. In a series of tests with dry nitrogen on one side and humid nitrogen on the other side, the membrane's water permeability coefficient is determined to be 2.4 × 10-13 mol s-1 cm-1 Pa-1 at 160 °C which is more than an order of magnitude higher than the values previously reported in the literature. Also, the results indicate that the permeability coefficient might be relative humidity dependent and could even be somewhat higher than the value reported here, but further investigation is needed. The experimental findings are reproduced and explained with a 2D steady state computational fluid dynamics (CFD) model. Internal water transport profiles across the membrane and along the gas flow channels are presented and discussed.Peer ReviewedPostprint (author’s final draft

Techno-economic analysis of PEM fuel cells role in photovoltaic-based systems for the remote base stations

Treball de recerca per a estudiants d'intercanviExpansion of telecommunication networks even to the most remote areas where connection to the utility grid could never be justified, especially in touristic regions, has led to the increasing need for stand-alone power systems. In Adriatic coastal area employment of hybrid photovoltaic-based systems is straightforward due to high sun potential. Inherent intermittent nature of renewable sources is especially not compatible with telecommunication system who require uninterrupted power supply. This leads to the need of not only energy storage, but also a "back up" solution in the case of primary system failure. Emphasis is put on the system reliability and simplicity while system price is not necessarily top priority. Usual approach of using diesel generators as a "back up" has been challenged by the introduction of PEM fuel cells. Even with hydrogen technologies market development still lagging behind some comparable advantages such as high energy conversion efficiency, silent operation and no emissions make PEM fuel cells a legitimate candidate for replacing traditional oil burning generators. Techno-economic analysis of various stand-alone power systems for the remote base station on an Adriatic island is made. At the moment, levelized cost of electricity point of view still gives slight advantage to the diesel generators. Long term reliability of PEM fuel cells system still needs to be examined in practice, as this combined with pro-environmental characteristics of fuel cells can make the difference especially in pristine and protected areas. Furthermore, uncertain petroleum market and fast developing hydrogen technology market could reverse this trend in the near future.Incomin

Techno-economic analysis of PEM fuel cells role in photovoltaic-based systems for the remote base stations

Treball de recerca per a estudiants d'intercanviExpansion of telecommunication networks even to the most remote areas where connection to the utility grid could never be justified, especially in touristic regions, has led to the increasing need for stand-alone power systems. In Adriatic coastal area employment of hybrid photovoltaic-based systems is straightforward due to high sun potential. Inherent intermittent nature of renewable sources is especially not compatible with telecommunication system who require uninterrupted power supply. This leads to the need of not only energy storage, but also a "back up" solution in the case of primary system failure. Emphasis is put on the system reliability and simplicity while system price is not necessarily top priority. Usual approach of using diesel generators as a "back up" has been challenged by the introduction of PEM fuel cells. Even with hydrogen technologies market development still lagging behind some comparable advantages such as high energy conversion efficiency, silent operation and no emissions make PEM fuel cells a legitimate candidate for replacing traditional oil burning generators. Techno-economic analysis of various stand-alone power systems for the remote base station on an Adriatic island is made. At the moment, levelized cost of electricity point of view still gives slight advantage to the diesel generators. Long term reliability of PEM fuel cells system still needs to be examined in practice, as this combined with pro-environmental characteristics of fuel cells can make the difference especially in pristine and protected areas. Furthermore, uncertain petroleum market and fast developing hydrogen technology market could reverse this trend in the near future.Incomin

Water transport study in high temperature fuel cell stack

This work presents analysis of water transport phenomena in the 120 Wel high temperature PEM fuel cell stack. Phosphoric acid doped PBI membranes are known for their abilities to work with dry gases; however water in the electrolyte still plays an integral role in the proton conduction mechanism. The presence of water in the membrane increases proton conductivity, however at high operating temperatures in the anhydrous environment phosphoric acid can dehydrate consequently lowering its conductivity. Therefore, understanding of water transport in the PBI- H3PO4 membranes is important as it can explain certain phenomena inside the cell. Tests have shown that water transport from cathode to anode due to water accumulation rises almost linearly with current density while decreases with cathode stoichiometry. Water transport seems to be independent of operating temperature. Also, in some cases, reverse flow water transport (from anode to cathode) appears to take place near the outlet. Ohmic resistance was also found to decrease slightly with an increase in current density and lower stoichiometries.Peer Reviewe

Water transport study in high temperature fuel cell stack

This work presents analysis of water transport phenomena in the 120 Wel high temperature PEM fuel cell stack. Phosphoric acid doped PBI membranes are known for their abilities to work with dry gases; however water in the electrolyte still plays an integral role in the proton conduction mechanism. The presence of water in the membrane increases proton conductivity, however at high operating temperatures in the anhydrous environment phosphoric acid can dehydrate consequently lowering its conductivity. Therefore, understanding of water transport in the PBI- H3PO4 membranes is important as it can explain certain phenomena inside the cell. Tests have shown that water transport from cathode to anode due to water accumulation rises almost linearly with current density while decreases with cathode stoichiometry. Water transport seems to be independent of operating temperature. Also, in some cases, reverse flow water transport (from anode to cathode) appears to take place near the outlet. Ohmic resistance was also found to decrease slightly with an increase in current density and lower stoichiometries.Peer Reviewe

Techno-economic analysis of PEM fuel cells role in photovoltaic-based systems for the remote base stations

Expansion of telecommunication networks even to the most remote areas where connection to the utility grid could never be justified, especially in touristic regions, has led to the increasing need for stand-alone power systems. In Adriatic coastal area employment of hybrid photovoltaic-based systems is straightforward due to high sun potential. Inherent intermittent nature of renewable sources is especially not compatible with telecommunication system who require uninterrupted power supply. This leads to the need of not only energy storage, but also a "back up" solution in the case of primary system failure. Emphasis is put on the system reliability and simplicity while system price is not necessarily top priority. Usual approach of using diesel generators as a "back up" has been challenged by the introduction of PEM fuel cells. Even with hydrogen technologies market development still lagging behind some comparable advantages such as high energy conversion efficiency, silent operation and no emissions make PEM fuel cells a legitimate candidate for replacing traditional oil burning generators. Technoeconomic analysis of various stand-alone power systems for the remote base station on an Adriatic island is made. At the moment, levelized cost of electricity point of view still gives slight advantage to the diesel generators. Long term reliability of PEM fuel cells system still needs to be examined in practice, as this combined with pro-environmental characteristics of fuel cells can make the difference especially in pristine and protected areas. Furthermore, uncertain petroleum market and fast developing hydrogen technology market could reverse this trend in the near future.Peer Reviewe

Defining innovation performance measurement criteria with a qualitative research: A research on it firms

YÖK Tez No: 417557Bu çalışmanın birinci amacı, işletmelerin inovasyon süreçlerinin performanslarının ölçümünde kullanılabilecek göstergeleri belirlemektir. Araştırmaya, TR42 Doğu Marmara Bölgesi'de yer alan teknopark ve teknokentlerde faaliyet gösteren bilişim işletmeleri dâhil edilmiştir. Çalışmada nitel araştırma yöntemi kullanılmıştır. Veriler, işletmelerin yöneticileri ile yüz yüze gerçekleştirilen görüşmelerle toplanmıştır. Elde edilen veriler betimsel analiz ve içerik analizi teknikleri birlikte kullanılarak analiz edilmiştir. Çalışmada, bilişim işletmelerinin inovasyon süreçleri "fikir üretme", "deneme sürüm ürün geliştirme", "tam sürüm ürün geliştirme" ve "satış" olmak üzere dört aşamaya bölünmüş ve her bir aşama için performans göstergeleri belirlenmiştir. Araştırmaya katılan bilişim işletmelerinin inovasyon süreçlerinin performansına genel olarak bakıldığında ise "fikir üretme aşaması"nın ciddi yürütülmediği, "deneme sürüm aşaması" ve "tam sürüm aşaması"nın performanslarının yüksek olduğu, "satış" aşamasının ise işletmeler tarafından ciddi analize tabi tutulması gerektiği sonucuna varılmıştır.The first aim of this study is to define innovation performance measurement criteria for IT firms. IT firms located in technoparks at TR42 East Marmara Region are included in the study and qualitative research method is used. Data are collected by the interviews made with managers of IT firms and are analyzed with descriptive analysis and content analysis techniques. The innovation process of IT firms is divided into four stages: "Idea Generation", "Beta Version Development", "Full Version Development" and "Sale". After the analysis, some performance measurement criteria are introduced to measure the performance of innovation processes of IT firms. Measurement results of innovation performance of participant firms show that "Idea Generation" stage is not taken seriously by these IT firms. Performances of "Beta Version Development" and "Full Version Development" are high. "Sale" stage has to be analyzed by firms carefully

Water transport study in high temperature proton exchange membrane fuel cell stack

A study of water transport in a high temperature phosphoric acid doped polybenzimidazole (PBI) membrane fuel cell stack is reported. Tests with different stoichiometries of dry cathode and different humidity levels of anode are performed. It is found that water transport across the membrane electrode assembly (MEA) is noteworthy and that water vapor partial pressure on the anode outlet is almost always higher than on the cathode outlet, even when using dry hydrogen. The water transport is a strong function of current density but it also depends on stoichiometry and humidity level. In a series of tests with dry nitrogen on one side and humid nitrogen on the other side, the membrane's water permeability coefficient is determined to be 2.4 × 10-13 mol s-1 cm-1 Pa-1 at 160 °C which is more than an order of magnitude higher than the values previously reported in the literature. Also, the results indicate that the permeability coefficient might be relative humidity dependent and could even be somewhat higher than the value reported here, but further investigation is needed. The experimental findings are reproduced and explained with a 2D steady state computational fluid dynamics (CFD) model. Internal water transport profiles across the membrane and along the gas flow channels are presented and discussed.Peer Reviewe