This document summarizes research on modeling the thermal and electrical performance of a densely packed concentrating photovoltaic receiver. A numerical model was developed to simulate the spectral response, electrical output, and thermal behavior of the receiver. Both 2D and 3D finite element analysis were conducted in COMSOL Multiphysics to predict the cell surface temperature under varying ambient conditions and convective heat transfer coefficients. The results showed passive cooling is not sufficient to dissipate heat from a densely packed configuration, and an effective cooling system with a heat transfer coefficient over 2.5 kW/m2K would be required.

1. 3D Thermal Numerical Analysis of a
Densely Packed Concentrating Receiver
Marios Theristis, Michail E. Arnaoutakis, Nabin Sarmah, Tapas K. Mallick
and Tadhg S O’Donovan
4th ICAER
10-12th December 2013
IIT Bomday, Mumbai, India

2. Research Aim
Spectral
response
Electrical
CPV
Performance
500x
Thermal
GaInP
GaInAs
Ge
Vtot=Vtop+Vmid+Vbot
Itot=min(Itop, Imid, Ibot)

3. Approach
•
NREL SMARTS model (AM1.5D) multiplied by a CR of 500x assuming uniform
concentration per nm
•
EQE data for (Ga0.35In0.65P/Ga0.63In0.17As/Ge) III-V cells (from literature)
•
Simulation of IV characteristics of each sub-cell and total electrical power output
estimation
 2D and 3D Finite Element Analysis (FEA) of the thermal behaviour in COMSOL
Multiphysics
 Thermal power as calculated from the electrical model is used as an input
 Prediction of the cell’s surface temperature using a parametric study to vary the
ambient temperature and the convective heat transfer coefficient

4. EQE and AM1.5D

5. Theoritical Model
(Losses Mechanisms)
Front losses due to radiation
and convection
Electrical energy
Back losses due
to radiation and
convection
Conduction

6. Current density

7. IV Curves (500x)
Pelec,max=18.55W
Pheat=26.45W
Vtot=Vtop+Vmid+Vbot
Itot=min(Itop, Imid, Ibot)

8. Boundary Conditions of 2D single cell
model
No
1
2
3
4
Region
Back side of cell
Air gap
Cell’s surface
Sides of cell
5
6
Back plate
Air gap
InGaP
InGaAs
Ge
Adhesive
Material
Copper
Alumina
Copper
Boundary condition
Inflow heat flux as found from electrical model
Open boundary conditions with no shear stress
Surface to ambient radiation and natural convection
Perfect thermal insulation was assumed on the sides of the cell
and a no slip boundary condition was considered on the wall
Surface to ambient radiation and convection
Ambient temperature of 20-45oC
Air

9. Parametric Study

10. Temperature Distribution
(a)
(b)
Temperature distribution for hconv = 6kW/m2K and (a) Tamb = 25oC; (b) Tamb = 45oC

11. Real meteo data
Heat transfer coefficient
needed for a maximum cell
surface temperature of 80oC
Validation of hconv = 6kW/m2K
Temperature (oC)

12. Configuration of the HWU Solar Collector

13. Geometry & Boundary Conditions of 3D
Densely Packed Receiver
No
Region
Boundary condition
1
On top of cells
Inflow heat flux as found from numerical model
2
Ambient
Ambient temperature of 20-45oC
3
Cell’s surface
Surface to ambient radiation and natural convection
4
Sides of cell
5
Heat Sink
PV receiver components
1: Frame
2: Cover glass
3: Al2O3 ceramic
4: Solar cells
5: Copper plate
6: Aluminium heat sink
Heat is conducted through the layers
Surface to ambient radiation and convection
2
3
1
2
1
4
4
5
3
5
6

14. Results of 3D Model
(with an extensive surface – aluminium heat sink)
Tcell(hnat.conv)
5<=hconv<=25W/m2K
C=500x
Tcell(Tamb)
15<=Tamb<=45oC
C=500x
Tcell(C)
50<=C<=500 suns
hnat.conv=15W/m2K
C=500x
Tamb =15oC
hnat.conv=15W/m2K

15. Results of 3D Model
(without an extensive surface)
C=500x
Tamb =25oC
hf.conv=3.5kW/m2K
Tcell(hnat.conv)
0.5<=hf.conv<=7.5kW/m2K
C=500x

16. Results of 3D Single Cell Model
C=500x
Tamb =25oC
hconv=700kW/m2K
nopt(λ)=1 (will be added later on)
Unrealistic Scenario – NO current mismatch
Realistic Scenario - Current mismatch

17. Spectral irradiance within
various solar spectra*
*B. S. Richards, "Enhancing the performance of silicon solar cells via the
application of passive luminescence conversion layers," Solar Energy Materials
and Solar Cells, vol. 90, pp. 2329-2337, Sep 22 2006.

18. Discussion & Conclusions
A detailed integrated solar spectrum dependent thermal-electrical model was
described for a HCPV cell. This model can lead to the accurate quantification
of the thermal power which is needed to be dissipated, including the excess
thermal output due to current mismatch.
Passive cooling cannot dissipate enough heat from the densely packed
configuration since a minimum convective heat transfer coefficient of
2.5kW/m2K is needed from the candidate cooling system.
Passive cooling with (Rth<1.2K/W) is feasible for single cell geometries
however, the atmospheric conditions of the location (wind speed, ambient
temperature, etc) must be taken into careful consideration when designing a
receiver.
This study validates the results of our previous work, where real
meteorological data were used to predict the temperature distribution across
a solar cell and was suggested that a hconv of around 6kW/m2K should be
required from the cooling system in order for the cell to withstand the harsh
ambient conditions.

19. Thank you!!!
Questions Please ???