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Durability Analysis on Solar Energy Converters containing Polymeric Materials
Steffen Jack, Michael Köhl, Karl-Anders Weiß, Jochen Wirth
Fraunhofer Institute for Solar Energy Systems ISE, Freiburg, Germany
COMSOL ConferenceHannover, 4-6.11.2008
Presented at the COMSOL Conference 2008 Hannover
Jochen Wirth, Steffen Jack, Michael Köhl, Karl-Anders Weiß, Fraunhofer ISE, COMSOL Conference Hannover, 2008 2
Durability Analysis on Solar Energy Converters containing Polymeric Materials
Durability analysis
Accelerated testing to estimate degradation processes
Problem: Limits of acceleration, measurement of certain parameters
Simulation, Example: Mass transport of water within photovoltaic modules
Virtual product qualification
New approaches for product design
Problem: Performance of materials during operation conditions
Simulation, Example: Calculation of mechanical loads on polymeric collectors
Content
Jochen Wirth, Steffen Jack, Michael Köhl, Karl-Anders Weiß, Fraunhofer ISE, COMSOL Conference Hannover, 2008 3
Durability Analysis on Solar Energy Converters containing Polymeric Materials
Multiphysics Simulation Approach
Simulationof e.g. fluid flow
and temperature distribution
General Heat Transfer Module
Simulation ofstress distribution and
deformation
Structural Mechanics Module
Simulation ofconcentration of water
Chemical Engineering Module
Input ParametersGeometry
Material parametersMeasured weather data Input Parameters
Temperaturedistribution
Measured material parameters
Jochen Wirth, Steffen Jack, Michael Köhl, Karl-Anders Weiß, Fraunhofer ISE, COMSOL Conference Hannover, 2008 4
Durability Analysis on Solar Energy Converters containing Polymeric Materials
Mass transport of water is an essential reason for degradation of photovoltaic modules
Micro climate inside module has to be calculated
Given climates
Given materials and geometries
Mass transport of water within photovoltaic modules
Fläche nutzbar für Bild / Graphsolar cells (Si)
encapsulation (EVA)
back sheet (PVF-PET-PVF)
encapsulation (EVA)
front cover (glass)
Jochen Wirth, Steffen Jack, Michael Köhl, Karl-Anders Weiß, Fraunhofer ISE, COMSOL Conference Hannover, 2008 5
Durability Analysis on Solar Energy Converters containing Polymeric Materials
Cutout of two cells
Results of analysis of parameter sensitivity
Very high resolution of mesh required between cells
Finite stretching of elements possible
Geometry and Mesh of 2D-Model
x10^-3
Jochen Wirth, Steffen Jack, Michael Köhl, Karl-Anders Weiß, Fraunhofer ISE, COMSOL Conference Hannover, 2008 6
Durability Analysis on Solar Energy Converters containing Polymeric Materials
Results of the 2D simulations – Freiburg, Germany
Jochen Wirth, Steffen Jack, Michael Köhl, Karl-Anders Weiß, Fraunhofer ISE, COMSOL Conference Hannover, 2008 7
Durability Analysis on Solar Energy Converters containing Polymeric Materials
Fläche nutzbar für Tabelle oder breitformatige Darstellung
Results of the 2D simulations – Freiburg, Germany
between glass and cellbetween cell and back-sheet
1 year 5 years
time t / d time t / a summer winter s w s w s w s w s w
calc
ulat
ed c
once
ntra
tion
c / m
ol/m
³
time t / d time t / a summer
Jochen Wirth, Steffen Jack, Michael Köhl, Karl-Anders Weiß, Fraunhofer ISE, COMSOL Conference Hannover, 2008 8
Durability Analysis on Solar Energy Converters containing Polymeric Materials
Cost reduction
Substitution of materials
Integrated design
Triple wall-sheet
Integrated Design
Extrudable
Front cover
Back insulation
Holohedralabsorber
All polymeric flat plate collector - considered geometry
Fläche nutzbar für Bild / Graph
Jochen Wirth, Steffen Jack, Michael Köhl, Karl-Anders Weiß, Fraunhofer ISE, COMSOL Conference Hannover, 2008 9
Durability Analysis on Solar Energy Converters containing Polymeric Materials
High temperature gradient in wall with absorbing surface
Typical stagnation temperatures
Collector without stagnation protection calls for high performance polymers
Temperature distributions and levels
Fläche nutzbar für Bild / Graph
Jochen Wirth, Steffen Jack, Michael Köhl, Karl-Anders Weiß, Fraunhofer ISE, COMSOL Conference Hannover, 2008 10
Durability Analysis on Solar Energy Converters containing Polymeric Materials
Variation of wall thickness and material
Big influence of wall thickness and thermal conductivity of wall material
Still acceptable collector efficiency factor at wall thickness 3mm
Heat transfer capability of absorber
Fläche nutzbar für Bild / Graph
0,92
0,93
0,94
0,95
0,96
0,97
0,98
0,99
0 0,001 0,002 0,003
thickness of wall in m
colle
ctor
effi
cien
cy fa
ctor
F`
PMMA, top absorptionPMMA, absorption insidePPS, top absorption
Jochen Wirth, Steffen Jack, Michael Köhl, Karl-Anders Weiß, Fraunhofer ISE, COMSOL Conference Hannover, 2008 11
Durability Analysis on Solar Energy Converters containing Polymeric Materials
Variation of material and thickness in 3D model
Max. stresses at aobsorbing layer
Max. stresses below valid stresses for all considered configurations
Downwards bending of the collector due to uneven thermal expansion
Thermo-mechanical loads
Fläche nutzbar für Bild / Graph
Examples of stress distribution and deformation at 350K inlet temperature
Jochen Wirth, Steffen Jack, Michael Köhl, Karl-Anders Weiß, Fraunhofer ISE, COMSOL Conference Hannover, 2008 12
Durability Analysis on Solar Energy Converters containing Polymeric Materials
Calculated efficiency of polymer collectors can even be higher than of conventional solar thermal flat plate collectors
Deformation of integrated collector design has to be considered
Outlook: Inclusion of change of material parameters over time
More precise modeling of thermal losses
Development of concentration of water strongly depends on climate and materials
Long time periods are needed until max. water concentration is reached
Outlook: Inclusion of change of material parameters over time
Simulation over 25 years
Summary
Jochen Wirth, Steffen Jack, Michael Köhl, Karl-Anders Weiß, Fraunhofer ISE, COMSOL Conference Hannover, 2008 13
Durability Analysis on Solar Energy Converters containing Polymeric Materials
Thank you for your attention.
