Kulikovsky A.,Institute for Energy Research of Germany
Journal of Electroanalytical Chemistry | Year: 2017
We report a physics-based model for impedance of the cathode catalyst layer (CCL) with nonuniform Nafion loading in a PEM fuel cell. The general system of equations for the perturbation amplitudes is derived and solved analytically for the cases of either fast oxygen transport, or fast proton transport in the CCL. The expressions for the respective CCL impedances are obtained. In the case of large cell current, we analyse the numerical solutions for the CCL impedance. © 2017 Elsevier B.V.
Kulikovsky A.,Institute for Energy Research of Germany
Journal of Electroanalytical Chemistry | Year: 2017
A model for impedance of the cathode catalyst layer (CCL) with poor electronic conductivity σe is developed. In the case of small cell current, an analytical expression for the CCL impedance is derived. At small currents, finite σe increases the static cell resistivity by the value 1/(3σe). In addition, the CCL exhibits a pure ohmic resistivity, which is equivalent to proton and electronic resistivities connected in parallel. Finite σe distorts the shape of the Nyquist spectrum in the HF domain; the CCL proton conductivity σp can no longer be determined simply as a projection of the straight HF line onto the real axis. However, σp and σe can be found by fitting the model equations to the experimental spectra. © 2017 Elsevier B.V.
Mirakyan A.,Institute for Energy Research of Germany
Renewable and Sustainable Energy Reviews | Year: 2013
Although the integrated energy and environmental planning processes of cities and territories with more than 50,000 inhabitants differ, previous studies suggest that long-term, model-based energy planning processes have a common scheme that can also be used as a framework for reviewing the methods and the tools that are used in the integrated energy planning of these cities and territories. This paper first presents a generic integrated energy planning procedure in which the planning activities are divided into four main phases. Second, the methods and the tools that are used for these diverse planning tasks are mapped to the suggested generic planning procedure tasks. Finally, the combined use of these methods and tools in the scope of integrated energy planning are briefly discussed from a mapping point of view. © 2013 Elsevier Ltd.
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.
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.
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.
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.
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.
Blasing M.,Institute for Energy Research of Germany |
Muller M.,Institute for Energy Research of Germany
Fuel Processing Technology | Year: 2013
The limitation of fossil fuel resources and the necessity of reducing CO2 emission require an increase of the efficiency of coal based power plants. The Integrated Gasification Combined Cycle (IGCC) is a potential concept to realise these objectives. In the IGCC a broad range of different coals can be used to produce a fuel gas for gas turbines or synthesis gas for chemical applications. The direct use of hot flue gas for driving a gas turbine requires a hot gas cleanup to achieve corrosion prevention of the turbine blades and prevention of catalysts from poisoning. Main problems are related to alkali metal, sulphur, and chlorine compounds released during the coal gasification process. High and low-rank coals differ in the amount, mode of occurrence and release mechanism of alkali metal, sulphur, and chlorine. Therefore, release experiments have been done with 8 different coals at 1400°C, 1 atm and a gas stream with 7.5% O2 and 2.5% water steam. Differences of the release mechanisms of high and low-rank coals were identified. The modes of occurrence of several inorganic coal constituents were shown to have a remarkable effect on the release, e.g., the results could distinguish between organic and inorganic bound sulphur. © 2012 Elsevier B.V.
Bachmann T.M.,Institute for Energy Research of Germany
International Journal of Life Cycle Assessment | Year: 2013
Purpose: In the European Union project New Energy Externalities Development for Sustainability (NEEDS), power generation technologies were ranked by means of two sustainability assessment approaches. The total costs approach, adding private and external costs, and a multi-criteria decision analysis (MCDA) were used, integrating social, economic and environmental criteria. Both approaches relied on environmental indicators based on life cycle assessment. This study aims to analyse the extent to which the development of life cycle sustainability assessment (LCSA) can draw on these ranking methods. Methods: The approaches to rank technologies in the NEEDS project are reviewed in terms of similarities and differences in concept, quantification and scope. Identified issues are discussed and set into perspective for the development of a potential future LCSA framework. Results and discussion: The NEEDS MCDA and total costs considerably overlap regarding issues covered, except for several social aspects. Beyond total costs being limited to private and external costs, most notable conceptual differences concern the coverage of pecuniary (i.e. price change-induced) external effects, and potential double-counting for instance of resource depletion or specific cost components. External costs take account of the specific utility changes of those affected, requiring a rather high level of spatial and temporal detail. This allows addressing intra- and inter-generational aspects. Differences between both ranking methods and current LCSA methods concern the way weighting is performed, the social aspects covered and the classification of indicators according to the three sustainability dimensions. The methods differ in the way waste, accidents or intended impacts are taken into account. An issue regarding the definition of truly comparable products has also been identified (e.g. power plants). Conclusions: For the development of LCSA, the study suggests that taking a consequential approach allows assessing pecuniary effects and repercussions of adaptation measures, relevant for a sustainability context, and that developing a life cycle impact assessment for life cycle costing would provide valuable information. The study concludes with raising a few questions and providing some suggestions regarding the development of a consistent framework for LCSA: whether the analyses in LCSA shall be distinguished into the three dimensions of sustainable development at the inventory or the impact level also with the aim to avoid double-counting, whether or not LCSA will address exceptional events, whether or not benefits shall be accounted for and how to deal with methodological and value choices (e.g. through sensitivity analyses). © 2012 Springer-Verlag Berlin Heidelberg.