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Kulikovsky A.A.,Institute for Energy Research of Germany | Kulikovsky A.A.,Moscow State University
Journal of the Electrochemical Society | Year: 2014

An analytical polarization curve of the cathode side of a PEM fuel cell is derived. The curve results from approximate solution of the system of equations for the cathode catalyst layer (CCL) performance and it takes into account the oxygen and proton transport losses in the CCL, and the oxygen transport loss in the GDL. Fitting of the model equation to recently published polarization data is performed and the parameters resulted from fitting are discussed. Processing of accelerated stress testing results using the model equation is demonstrated. © 2013 The Electrochemical Society. All rights reserved. Source

Sliz-Szkliniarz B.,Institute for Energy Research of Germany
Land Use Policy | Year: 2013

Renewable energy sources (RES) can undoubtedly contribute to protecting the environment and conserving fossil fuels, as well as enhancing regional and rural development opportunities. However, every energy production process affects the environment and involves the use of land resources. The risks linked to intensified RES use should be adequately taken into consideration in any planning process, as ill-conceived energy policies may adversely impact land and local ecosystems, and lead to increases in public spending. Therefore, before designing any instruments for the regulation of both RES and land-use, the most essential step is to explore investment possibilities in different contexts. This paper intends to locate and quantify the potentials of biomass, wind and solar as well as to explore some of the potential planning issues associated with their development. The methods and findings presented in this paper may help to build a vision for the development of an optimal RES portfolio and to highlight emerging problems associated with RES deployment. © 2013 Elsevier Ltd. Source

Kulikovsky A.A.,Institute for Energy Research of Germany
Electrochimica Acta | Year: 2014

Using the variational technique we show that in PEM fuel cells, an exponential shape of the local current density along the oxygen channel provides the best cell performance. A simple method for checking the quality of the local current density distribution by comparison of two polarization curves measured at different oxygen stoichiometries is suggested. Aging processes running non-uniformly along the channel distort the optimal shape of the local current and affect the cell polarization curve. Non-uniform aging of the cathode catalyst (agglomeration) increases the activation and transport overpotentials, not changing the limiting current density. Local lowering of the GDL oxygen diffusivity decreases the cell limiting current, not affecting the activation overpotential. A combined effect of the two aforementioned processes increases the slope of the polarization curve, which may be misinterpreted as the growth of the cell ohmic resistivity. An equation for reconstruction of the local current, exchange current density and GDL oxygen diffusivity shapes from the cell polarization curve is discussed. © 2014 Elsevier Ltd. Source

Sieber J.,Institute for Energy Research of Germany
Climatic Change | Year: 2013

Extreme weather events and changed climate parameters have impacts on power plants and their connected infrastructures. Therefore, adaptation, especially in the context of a changing climate and a resulting shift in the intensity and frequency of extreme events, is necessary. Thermal power plants are subject to a diversity of extreme weather impacts, making them vulnerable if not adapted. In this paper, the impacts of extreme weather events on thermal power plants are first identified and structured. Then selected adaptation options for thermal power plants are presented. Three major types of adaptation option are identified: adaptation of cooling, infrastructure, and sites. The Supplementary Material introduces a GIS-based (Geographic Information System) decision-support tool for power plant adaptation and planning. © 2013 Springer Science+Business Media Dordrecht. Source

Loffler M.K.,Institute for Energy Research of Germany
International Journal of Refrigeration | Year: 2014

Trapezoid Cycles are thermodynamic cycles, mainly vapour compression cycles, which simply spoken adapt to the heat source curve and the heat sink curve in the temperature - entropy - diagram (T-S-diagram). The name of the cycles refers to the case of sensible heat, where the shapes of these cycles is similar to trapezoids. It was shown before that trapezoid cycles are feasible by adding storage devices to the cycle setup. In this article exact and simplified theoretic equations for the calculation of the COP of different cases of Trapezoid Cycles both with and without influence of dissipation are presented. These equations allow a mathematically simple prediction of the COP with very small error. Further the use of Trapezoid Cycles in the well-known Pinch Analysis is derived on a graphical basis (T-S-diagram). Heat which is usually lost in the Pinch Analysis will become usable with the highest thermodynamic possible efficiency. © 2014 Elsevier Ltd and IIR. All Right Reserved. Source

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