Time filter

Source Type

Engineering, Greece

Andreadis G.,University of ThessalyVolos | Tsiakaras P.,University of ThessalyVolos
EFC 2011 - Proceedings of the 4th European Fuel Cell Piero Lunghi Conference and Exhibition | Year: 2011

In the present work, a model-based parametric analysis of the performance of a direct ethanol polymer electrolyte membrane fuel cell (DE-PEMFC) is conducted with the purpose to investigate the effect of several parameters on the cell's operation. The analysis is based on a validated one-dimensional mathematical model that describes the operation of a DE-PEMFC in steady state. More precisely, the effect of several operational and structural parameters on (i) the ethanol crossover rate, (ii) the parasitic current generation and (iii) the total cell performance is investigated. According to the model predictions it was found that the increase of the ethanol feed concentration leads to higher ethanol crossover rates, higher parasitic currents and higher mixed potential values resulting in the decrease of the cell's power density. However there is an optimum ethanol feed concentration for which the cell power density reaches its highest value. Furthermore, the increase of the diffusion layers' porosity up to a certain extent, improves the cell power density despite the fact that the parasitic current increases. Moreover, the use of a thicker membrane leads to lower ethanol crossover rate, lower parasitic current and lower mixed potential values in comparison to the use of a thinner one. Finally, according to the model predictions when the cell operates at low current densities the use of a thick membrane is necessary to reduce the negative effect of the ethanol crossover. However, in the case where the cell operates at higher current densities (lower ethanol crossover rates) a thinner membrane reduces the ohmic overpotential leading to higher power density values. Source

Triantakonstantis D.,University of ThessalyVolos | Stathakis D.,University of ThessalyVolos
Geocarto International | Year: 2015

Urbanisation is a global phenomenon with an important impact on the quality of human life. Europe has been widely affected by urbanisation. One of the main characteristics of urban growth is sprawl, a negative form of urban expansion, which affects large cities and most types of urban landscapes. Spatial indicators are applied to CORINE Urban Morphological Zones (UMZ) changes in order to measure urban sprawl between 1990–2000 and 2000–2006 in 24 European countries. The indicators calculate urban morphological properties such as shape, aggregation, compactness and dispersion. The results revealed that the urban areas (UMZ) increased by 146% during 1990–2006 and the urbanisation becomes more circle-shaped and less complex where mostly sprawl occurs. Moreover, urban form becomes less clumped or aggregated. Therefore, due to accelerating rates of urban sprawl, European urban planning should intensify appropriate initiatives to avoid negative impacts on human life. © 2015 Taylor & Francis. Source

Andreadis G.,University of ThessalyVolos | Song S.,University of ThessalyVolos | Tsiakaras P.,University of ThessalyVolos
EFC 2011 - Proceedings of the 4th European Fuel Cell Piero Lunghi Conference and Exhibition | Year: 2011

In the present work the effect of both cell discharge current and operating temperature on (a) the ethanol conversion, (b) the reaction products distribution and (c) the reaction yield towards each released product, during a Direct Ethanol PEM fuel cell is examined. More precisely, the results of the continuous and on-line product analysis are presented and thoroughly discussed. The MEA of the fuel cell is comprised of a PtRu/C anode, a Nafion®-115 membrane and a Pt/C cathode. It is found that the increase of the cell current and the operating temperature lead to an increase of the ethanol conversion. The main products detected during the fuel cell operation are acetaldehyde (CH3CHO), acetic acid (CH3COOH) and small amounts of carbon dioxide (CO2). The selectivity of acetaldehyde ranges from 45% to 70%, the selectivity of acetic acid ranges from 25% to 45% and the selectivity of CO2 ranges from 5% to 15%. Moreover, as it concerns the reaction yield towards each product, it is found that the increase of the temperature results in an increase of the yield. Furthermore, from the Arrhenius plots based on the products formation rate, it is found that the acetaldehyde is favored over PtRu/C compared to the other products. Finally, based on the apparent activation energy of the COi formation rate, it is concluded, that the C-C bond breakage of the ethanol molecule is difficult to occur over the examined anode catalyst. Source

Discover hidden collaborations