Publications by Daniel Favrat | EPFL Graph Search

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Structural reliability and durability is a hurdle for the large-scale commercialisation of solid oxide fuel cell (SOFC). Because of the multiphysics nature of the problem, modelling is required to first gain knowledge and then alleviate mechanical failures. This chapter places the emphasis on stress analysis at the SOFC stack scale. A brief overview on the mechanical behaviour of the cell, sealing and gas diffusion layer materials is provided, along with a discussion on their implementation in finite-elemen

Understanding of mechanisms affecting degradation, durability and performance of solid oxide fuel cell (SOFC) stacks and integrated systems has become important due to increasing worldwide deployment. A novel simulation approach accounting for state-of-the ...

Aim of this work is to model and study the behavior of thermocouples as they are used in the measurement of gas temperatures in solid oxide fuel cell systems. Due to the high temperature regime in such systems, the effect of radiation and conduction from surrounding solids may bias the measurements with important consequences on control, performance, and cell durability. In order to study these effects a mathematical model of a working thermocouple was developed and it was integrated in that of a heat excha

The World is facing major challenges regarding environmental threats, resource constraints and the large unbalance of wealth among developing and developed countries. Energy engineering is at the core of the actions to be undertaken to meet these challenge ...

The implementation of integrated energy systems within urban areas is a promising CO?2 emissions abatement measure. In this paper on-site heating, cooling and power generation based on a solid oxide fuel cell and gas turbine (SOFC-GT) combined cycle unit associated with a compression chiller and additional boilers has been considered from the viewpoints of cost and CO?2 emissions. Physical and costing modelling of such a unit has been integrated withn a new multi-criteria evolutionary algorithm for an asses

The characteristics of the 'Green Heating System', synonymous with 'Environmentally Friendly Heating System', is academically defined from the total energy systems' point of view, using the concept of 'reversible mode of heating' under the current and future technical, economic and environmental protection context. The exergy-based Specific Consumption Analysis Approach is used to quantitatively evaluate the influence of subsystems' exergy efficiencies on the overall performance of a heating system. Through

A CFD model was developed to predict with accuracy the local electrochemical performance in an operating solid oxide fuel cell. A particular focus was given on the study of performance limitations and degradation sources caused by the design of the fuel cell, by the choice of materials and components, or by improper operating points. The model is used to understand typical degradation effects observed on stacks tested in collaboration with HTCeramix - SOFCpower. The model is able to predict several degradat

Intube flow boiling experiments for refrigerant R-134a mixed with a lubricating oil are reported for a plain, horizontal tube. The tests were run at a nominal inlet pressure of 3.4 bar over a wide range of vapor qualities at mass velocities of 100, 200, and 300 kg/m2s (73.5, 147 and 220.5 thousands of lb/h ft2) for inlet oil concentrations from 0-5 wt.% oil. At low to intermediate vapor qualities (0.2

Fluid machines like compressors and expanders handling vapor or two-phase flows are required in many energy systems. Using a historical perspective the paper aims at highlighting key features of common technologies like scroll and twin-screw among the volumetric family and radial or axial among the dynamic family. One example of mechanical vapor recompression is cited to illustrate how some of the features considered can help practical decision making when operation deviate from expected nominal conditions.

For the most part, district heating demands can be met by an appropriate integration of cogeneration and heat pumps units provided that advantage is taken of the fact that many urban regions are concentrated around surface waters. Such an integration results in a substantial decrease in environmental impact. Several district heating concepts using centralized and sometimes decentralized heat pumps are currently under study at the EPFL [1]. Despite the fact that the economics at the moment are unfavourable,

The locally-resolved degradation behavior was studied during 1900 hours in an SOFC repeat-element. In-situ measurements of local electrochemical performance were made on 18 locations over a segmented anode-supported cell. The evolution of local current densities, overpotentials and area-specific resistances was studied, showing a reorganization of the electrochemical reaction with time. The extent and the spatial distribution of degradation were established for different electrochemical reactions steps usin

Although heat pump based district heating is often an obvious solution, adapting the delivery temperature to the most exigent users is detrimental to overall system performance. This pitfall can be avoided with a centralized plant of heat pumps, cogeneration and an auxiliary furnace, supplemented by decentralized heat pumps. However, the problem of mixed energy production and delivery which this poses is complex and presents for the engineer the dauting if not impossible task of adequately, much less optima

From the standpoint of an energetically and economically efficient waste elimination, the design and operation of optimized incineration power plants with the cogeneration of electricity and heat has become today an important issue. Decision models developed to minimize the total costs associated with such systems only partially respond to the problems associated with the choice of configuration (synthesis), component design, and the operation of the waste incineration / cogeneration unit. In fact, the time

An optimization tool to identify optimum structure/parameters of hybrid electric vehicles (hereafter abbreviated as HEV) is proposed, which can take account of various criteria regarding environmental impacts, cost minimization, or minimum fuel consumption. The scope of hybrid vehicles is extended to include normal ICE to dual mode vehicles using electric power train. In the paper, general framework and concepts of the study, namely framework of simulation model and optimization algorithm, are introduced br

The consumption of primary energy is often used to compare energy systems from a sustainability viewpoint at regional, national or even world level. For such comparisons to be “fair” and meaningful, this implies however to define primary energies in a cohe ...

Structural stability issues in planar solid oxide fuel cells arise from the mismatch between the coefficients of thermal expansion of the components. The stress state at operating temperature is the superposition of several contributions, which differ depe ...

This paper introduces a methodology for the heat integration of industrial batch processes. Based on Pinch Analysis principles, this methodology resorts to intermediate heat storage to prevent adverse effects on the operating flexibility. A systematic procedure, backed with a graphical representation, allows the determination of the minimum number of heat storage units and their range of feasible operation as a function of the amount of heat recovery. Understanding the cause and the bottleneck effect of the

Large scale power production benefits from the high efficiency of gas-steam combined cycles. In the lower power range, fuel cells are a good candidate to combine with gas turbines. Such systems can achieve efficiencies exceeding 60%. High temperature Solid ...

Experimental test results for flow boiling of pure ammonia inside horizontal tubes were obtained for a plain stainless steel tube. Tests were run at a nominal saturation temperature of 4°C, nine mass velocities from 20- 140 kg/m2s, vapor qualities from 1-99% and heat fluxes from 5-58 kW/m2. Two-phase flow observations showed that the current test data covered the following regimes: fully stratified, stratified-wavy, intermittent, annular and annular with partial dryout. The Kattan-Thome-Favrat flow boiling

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Current State of Models for the Prediction of Mechanical Failures in Solid Oxide Fuel Cells

The Effects of Dynamic Dispatch on the Degradation and Lifetime of Solid Oxide Fuel Cell Systems

The Error in Gas Temperature Measurements with Thermocouples: Application on an SOFC System Heat Exchanger

Environomics: An integrated vision of energy, environment and economics

Multi-Criteria Optimization of On-Site Heating, Cooling and Power Generation with Solid Oxide Fuel Cell - Gas Turbine Combined Cycle Units

Green heating system: characteristics and illustration with multi-criteria optimization of an integrated energy system

Modeling of Local Cell Degradation in Solid Oxide Fuel Cells: Cumulative Effect of Critical Operating Points

Flow Boiling and Pressure Drop Measurements for R134a/Oil Mixtures Part 2: Evaporating in a Plain Tube.

Review of Key Features of Selected Fluid Machines for Energy Systems

Réseaux de chauffage urbain alimentés par cogénération et pompe à chaleur. (Reti urbane di riscaldamento con cogenerazione e pompa di calore).

Locally-Resolved Study of Degradation in a SOFC Repeat- Element

An Environomic Approach for the Life Cycle Modeling and Optimization of a District Heating Network Based on Centralized and Decentralized Heat Pumps (Part II: Application)

An Approach for the Time-Dependent Thermoeconomic Modeling and Optimization of Energy System Synthesis, Design and Operation (Part I : Methodology and Results)

An Optimization Tool of Hybrid Type EV Systems

Methodological Aspects of the Definition of a 2kW Society

Simulation of thermal stresses in anode-supported solid oxide fuel cell stacks. Part II: Loss of gas-tightness, electrical contact and thermal buckling

Indirect and Mixed Direct-Indirect Heat Integration of Batch Processes Based on Pinch Analysis

Indirect and mixed direct-indirect heat integration of batch processes based on Pinch Analysis.

Thermo-economic Optimization of a Solid Oxide Fuel Cell, Gas Turbine Hybrid System

Evaporation of Ammonia in a Smooth Horizontal Tube : Heat Transfer Measurements and Predictions