Analyse des Betriebsverhaltens von Hochtemperatur-Polymerelektrolyt-Brennstoffzellen

A promising application for high temperature polymer electrolyte fuel cells is the efficient electrical onboard power supply of commercial vehicles. By combining the fuel cell with a fuel processing system the same fuel as for the main engine can be used. In this case the fuel cell will be supplied with reformate gas consisting mainly of hydrogen, nitrogen, carbon dioxide, water and carbon monoxide. In such an environment the use of high temperature polymer electrolyte fuel cells is favorable because of their high tolerance to carbon monoxide. Under these conditions it is a challenge to optimize the operation of fuel cell stacks regarding power density, efficiency and longevity. The chosen approach is the combined analysis of the local and global operating characteristics of the fuel cells. By the combined analysis interrelationships are revealed, which would otherwise remain concealed. For local analysis the current density distribution across the active cell area was measured by introducing a tailor made measuring board into the stack assembly. With the developed method the influence of fuel composition, stoichiometry, flow and thermal management on the operating characteristics is evaluated. This covers the direct influence on power and efficiency as well as the influence on the development of power and efficiency over time. The latter is usually addressed as degradation of fuel cells. The improved understanding of reformate supplied high temperature polymer electrolytefuel cell stacks leads to optimized operating strategies. One major conclusion is that the longevity of the fuel cell stacks can be increased by a homogenization of the current density distribution over the active cell area

Setup and experimental validation of a 5 kW HT-PEFC stack

This paper presents a performance analysis of a 5 kWel high temperature polymer electrolyte fuel cell (HT-PEFC) stack. Stack design and sizing is adapted to auxiliary power unit (APU) applications assuming the use of middle distillates. The parameter study comprises the variation of the fuel type (reformate, with pure hydrogen as a reference), the stoichiometry on the anode (1.3–2.7) and cathode (1.25–4.0) sides and the carbon monoxide (CO) concentration (0.9–3.5%) in the reformate. At 0.5 A cm−2, a coolant inlet temperature of 160 °C, stoichiometric factors of 1.3 on the anode and 2 on the cathode side and reformate operation, two interconnected full stacks produced 5 kW of electric power. The focus of the present work is an examination of the robustness of the full stacks through an analysis of the 70 single cell voltages. By comparison to other published operational parameter studies, this paper makes a significant contribution to the application of the methodology not to single cells or short stacks, but to a stack with technical relevance in the high power class

Absence of haematozoa in a wild chinstrap penguin Pygoscelis antarctica population

No haematoza were detected in 40 adult and 58 nestling wild chinstrap penguins (Pygoscelis antarctica) from Antarctica examined by blood smearThe present study was supported by grant ANT940036 from the Spanish Comisión Interministerial de Ciencia y Tecnología a (Plan Nacional Antártico).Peer reviewe

The use of Grounded theory in palliative care: methodological challenges and strategies

Background: The need for research methods that are suited to evaluate important issues and phenomena in palliative care has established different qualitative research approaches during the last years. This article describes the use and adaptation of a qualitative research methodology in a palliative care setting. Research process: The wish for hastened death of terminally ill patients is an important end-of-life issue. Proponents of palliative care have argued that good palliative care would prevent the wish for hastened death. However, this wish is stated by a few patients receiving palliative care, raising a challenging dilemma for patients, relatives and caregivers involved. In order to investigate the motivations of the patients asking for hastened death, we conducted a qualitative study using Grounded theory (GT). This article aims to illustrate the use of a flexible, less burdening qualitative research method and the adaptation of the research process of GT in a palliative care research setting. This is based on experiences and illustrated by examples from the qualitative study on the wish for hastened death in patients receiving palliative care. Conclusions: GT allowed a systematic understanding of patients' experiences and attitudes and careful in-depth exploration of this vulnerable population. Conducting a GT study needs high staff resources, a great catchment area for participant recruitment and realistic inclusion and exclusion criteria to allow for theoretical sampling. The use of GT should be facilitated by an experienced researcher familiar with this method because of high methodological requirements and rather complex analysis procedures