The efficiency of the coupled electrode-membrane processes in hydrogen fuel cell: Thermodynamic analysis

Transcription

1 The efficiency of the coupled electrode-membrane processes in hydrogen fuel cell: Thermodynamic analysis F. Maršík T. Němec Institute of Thermomechanics ASCR, v. v. i. Czech Hydrogen Day,

2 Outline 1 Structure of the Academy of Sciences of the Czech Republic Mission of Institute of Thermomechanics ASCR v.v.i. and today s activities 2 Up-to date state of Polymer Electrolyte Membrane FC technology 3 The enhancement of fuel cell efficiency, especially under load 4 The estimate of the efficiency. Application of non-equilibrium thermodynamics

3 Mission of Institute of Thermomechanics ASCR v.v.i. and today s ac Stránka č. 1 z 1

4 Institute of Thermomechanics ASCR v.v.i Mission of Institute of Thermomechanics ASCR v.v.i. and today s ac Institute of Thermomechanics Academy of Sciences of the Czech Republic Brief Information

5 Institute of Thermomechanics ASCR v.v.i Mission of Institute of Thermomechanics ASCR v.v.i. and today s ac History of the Institute 1953 founded as the Laboratory of Mechanical Engineering 1962 renamed to the Institute of Thermomechanics 1964 Laboratory of Aerodynamics in Nový Knín (high-speed wind tunnels) 1986 new building and laboratories in the Academic Campus Mazanka Mission The Institute - deals with the fundamental research in fields of applied physics with focusing to the fluid dynamics, thermodynamics, dynamics of mechanical systems, solid mechanics, material diagnostics, biomechanics, and to the interaction between solid and fluid phases; - contributes to the improvement of the standard of knowledge and the application of results of research in practice; - organises conferences and other meetings, publishes periodicals and proceedings; - provides doctoral study programmes in co-operation with universities.

6 Institute of Thermomechanics ASCR v.v.i Structure of R&D Groups Research Departments Detached Branch Offices Mission of Institute of Thermomechanics ASCR v.v.i. and today s ac Dept. Fluid Dynamics Centre of Material Diagnostics (establ. 1997, Plze ) Dept. Thermodynamics Centre of Mechatronics (establ. 1997, FME TU Brno) Dept. Dynamics and Vibrations Centre of Power Engineering (establ. 1998, FME CTU Prague 6) Dept. Impact and Waves in Solids Dept. Environmental Aerodynamics Supporting Groups Laboratory of Aerodynamics (Nový Knín) Laboratory of Modelling of Physical and Chemical Processes in Atmosphere

7 Institute of Thermomechanics ASCR v.v.i Mission of Institute of Thermomechanics ASCR v.v.i. and today s ac Laboratory of Turbulent Shear Flows Experimental investigation of turbulent shear flows, laminar/turbulent transition, interaction of turbulent flows, active flow-control, advanced experimental techniques Laboratory of Internal Flows Complex shear flows, transonic flows in blade cascades and in narrow channels, flow/body interaction Modular wind tunnel with radial inlet turbine cascade

8 Institute of Thermomechanics ASCR v.v.i Mission of Institute of Thermomechanics ASCR v.v.i. and today s ac Laboratory of Thermophysical Properties of Fluids Accurate measurements of pvt relations of fluids and thermal conductivity measurements of electrically non-conducting fluids Laboratory of Phase Transition Kinetics Investigation of nucleation and growth of droplets and bubbles from a supersaturated mother phase, study of the effects of phase transition on fluid flow Laboratory of High/Low Temperature Stability Laminar/turbulent transition in a thermal plasma plume and stability of free/confined jets Laboratory of Biomechanics Modelling of chemo-mechanical conversion in the heart, blood flow in blood vessels and operating reliability, hydrodynamics of the cerebrospinal fluid Von Kármán vortex street

9 Institute of Thermomechanics ASCR v.v.i Mission of Institute of Thermomechanics ASCR v.v.i. and today s ac Laboratory of Modelling and Identification of Dynamical Systems Identification and tuning of complicated and mechatronic dynamical systems, optimisation of dynamical systems Laboratory of Vibrodiagnostics and Nonlinear Dynamics Monitoring of vibrations and dynamic loadings of machine elements under rotation, vibrodiagnostics of rotating machines, vibro-acoustic properties of mechanical systems with dissipative layers Laboratory of Fluidelasticity Modelling of fluid-structure interaction problems including acoustical aspects, modelling of aeroelastic and fluid-structure interaction phenomena in biomechanics 4th eigenmode of vibration of the tram wheel at f=1291 Hz

10 Institute of Thermomechanics ASCR v.v.i Mission of Institute of Thermomechanics ASCR v.v.i. and today s ac Laboratory of Computational Solid Mechanics Continuum mechanics, computational mechanics, finite element method, molecular dynamics simulations Laboratory of Ultrasonic Methods Ultrasonic methods for testing of metals, ceramics, composites, characterization of material structure and damage, signal and image processing Laboratory of Acoustic Emission Acoustic emission, non-destructive testing of materials and structures incl. biomaterials, advanced signal analysis, artificial neural networks Laboratory of Experimental Stress Analysis Experimental investigations of stress wave propagation in solids Residual stress field measured by ultrasonic signal

11 Institute of Thermomechanics ASCR v.v.i Mission of Institute of Thermomechanics ASCR v.v.i. and today s ac Laboratory of Wave Modelling in Solids Numerical and experimental modelling of stress wave propagation in solid bodies, complex analysis of non-stationary stress state of shells and plane bodies under the influence of geometrical discontinuities (notches, cracks, cavities) Laboratory of Fatigue Damage Experimental and numerical study of fatigue damage of materials, fatigue life and crack propagation (various harmonic and random modes of loading processes) Steel tube-shape specimen notched by a laterally drilled hole

12 Institute of Thermomechanics ASCR v.v.i Mission of Institute of Thermomechanics ASCR v.v.i. and today s ac Laboratory of Environmental Aerodynamics Mathematical and physical modelling of processes related to atmospheric flows, dispersion and environmental and wind engineering problems Equipments Environmental wind tunnel Visualisation system for qualitative assessment of flow characteristics LDA (Laser Doppler Anemometer) for measurement of turbulence characteristics FID (Flame Ionisation Detector) for mean concentration measurement Model of Podbielski Strasse, Hannover

13 Institute of Thermomechanics ASCR v.v.i Mission of Institute of Thermomechanics ASCR v.v.i. and today s ac Joint group of the Institute of Thermomechanics and the Faculty of Mechanical Engineering, University of Technology in Brno Laboratory of Mechatronics and Robotics Intelligent quality control based on machine learning, local data approximation methods used in robotics, artificial intelligence methods used for control Laboratory of Biomechanics Cardiac cell biomechanics (processes involved in electrical and mechanical cellular activity of cardiac cells), hip and elbow endoprostheses reliability (experimental and numerical investigation of stress and deformation) FEM model of elbow joint

14 Hydrogenics PEM Fuel Cell Applications

15 Hydrogenics (Canada) Backup PEMFC Solution

16 Hydrogenics (Canada) Automotive PEMFC Solution

17 Ballard (Canada) Multipurpose PEMFC

18 Ballard (Canada) Residental/Cogeneration PEMFC

19 Ballard (Canada) Automotive PEMFC

20 Nuvera (Italy) Automotive PEMFC

21 Siemens Submarine PEMFC Power: kw

22 Siemens SOFC Cogeneration Plant Power output: 125 kwe net AC Thermal output: up to 100 kwt Electrical Efficiency: Overall fuel effectiveness: 80 Expected availability: > 98 Height: 11.6 ft (3.7 m) Depth: 9.5 ft (2.9 m) Length: 37.5 ft (11.4 m) System Weight: 25,000 kg

23 UTC (USA) Space Program AFC Apollo 1.5 kw, 28 V, 130 kg Orbiter 12 kw, 28 V, 140 kg 70 % efficiency

24 The enhancement of fuel cell efficiency, especially under load.

25 Basic Assumptions and Balance Laws. Mass balance equations Chemical reactions at electrodes and transport equations of H + and H 2 O formulated by non-equilibrium thermodynamics. Minimum entropy production principle-coupling of irreversible processes.

26 Basic Assumptions and Balance Laws. Mass balance equations Chemical reactions at electrodes and transport equations of H + and H 2 O formulated by non-equilibrium thermodynamics. Minimum entropy production principle-coupling of irreversible processes.

27 Basic Assumptions and Balance Laws. Mass balance equations Chemical reactions at electrodes and transport equations of H + and H 2 O formulated by non-equilibrium thermodynamics. Minimum entropy production principle-coupling of irreversible processes.

28 The estimate of the efficiency. Application of non-equilibrium thermodynamics Maximum voltage efficiency of the fuel cell. The voltage efficiency η volt gives the ratio of the cell electric work W to the Gibbs free energy difference G for the given electroosmotic drag coefficient n d [1], η volt. = W G = j H+ F φ j H2O µ H2O, η volt, max = ( ) q 2 tr q tr Maximum voltage efficiency Electroosmotic Drag Coefficient Water Content Water Content

29 Maximum thermodynamic efficiency. The estimate of the efficiency. Application of non-equilibrium thermodynamics The maximum thermodynamic efficiency is a maximum of the ratio of electric power Ẇ = j H +F φ and enthalpy change Ḣ for the given electroosmotic drag coefficient n d [1] η T,max = ẆḢ = j H + F φ = q 2 (1 tr 1 q 2 ). tr Ġ P = 4 ρ=1 rρaρ j D RT (ln c H2 O H 2 O) j DH + F φ q 2 tr Maximum thermodynamic efficiency Water Content Electroosmotic Drag Coefficient Water Content

30 The estimate of the efficiency. Application of non-equilibrium thermodynamics The estimated an optimum thickness of membranes. The optimal thickness L M of catalyst layers and PEM can be calculated from the stability conditions of the above transport equations of H + and H 2 O of the respective layer. When t char is a characteristic time of a power fluctuation, we found that for the PEM a realistic estimate is πtchar D H2 O(1 n d /λ) L M = 8

31 The estimate of the efficiency. Application of non-equilibrium thermodynamics Application of non-equilibrium thermodynamics The second law of thermodynamics is formulated on the base of balance laws 4 T σ(s) = r ρ A ρ + j Dα ( µ α T ) 0. ρ=1 α=1 The coupling coefficients evaluate the following cross-effect between chemicals reaction rates and fluxes of protons and water q chem def = l a1a2 la1a1 l a2a2 and q tr def = Chemical reaction rates: r a1 = l a1a1 A 1 + l a1a2 A 2, r a2 = l a2a1 A 1 + l a2a2 A 2 L 12 L11 L 22 ( 1, 1). Diffusion fluxes: j H2 O = L 11 µ H2 O L 12 (Fφ) Marsik, j Nemec + = Fuel L cell efficiency µ L (F φ)

32 The maximum voltage and thermodynamic efficiencies was calculated for the given material properties of Polymer Electrolyte Membrane(PEM)- Nafion. Relation between membrane thickness and operational stability of Fuel Cell (FC) was found. Outlook To analyze sequence of electrochemical reactions in anode and cathode Catalyst Layers. To find closer relation between geometry and surface of electrodes and Gibbs free energies of oxidation of H 2 at the anode and reduction of O 2 at the cathode.

33 Appendix For Further Reading For Further Reading I Nemec T., Marsik F., Mican O. The Characteristic Thickness of Polymer Electrolyte Membrane and the Efficiency of Fuel Cell. Heat Transfer Engineering, accepted for publication., 2008.