7th PVPMC Energy Rating and Module Performance Modeling Workshop, 30-31 March, 2017 in Lugano, Switzerland

1. 30.03.2017 7th
PVPMC Workshop, Lugano, Switzerland
Modeling of PV module temperature using
steady-state models: analysis for different
climates
Elena Barykina, CvO University Oldenburg, Energy Meteorology Group

2. Outline
1. Motivation
2. Steady-state models
3. IEC 61853 part 2: Faiman model
4. Faiman parameters: sensitivity analysis for sites
with different climates
5. Model comparison
6. Conclusions
30.03.2017 7th
PVPMC Workshop, Lugano, Switzerland

3. 30.03.2017 7th
PVPMC Workshop, Lugano, Switzerland
Motivation
PV performance modeling step
Solar Irradiance
Ambient Temperature Wind Speed
Module Temperature
Mounting, module physical properties

4. 30.03.2017 7th
PVPMC Workshop, Lugano, Switzerland
Motivation
PV module temperature models
Steady-state Dynamic
Thermal
response
Neglect t ~ 7-10 min
Math Simplified heat transfer equations Heat transfer equations
Easy to use Numerical solution is needed
Model parameters can be site
specific: measurements are
required
Module layers physical properties
are required
Input data Low resolution ( weather
prediction data, satellite images)
High resolution data

5. Motivation
30.03.2017 7th
PVPMC Workshop, Lugano, Switzerland
Steady-state model: Faiman (IEC 61853-2)
Parameters of the model can be found in literature
or fitted from data
How suitable are the parameters for a particular
location and module technology?
PV performance modeling with input data from weather
prediction models and satellite retrieved irradiance

6. Data
30.03.2017 7th
PVPMC Workshop, Lugano, Switzerland
5 sites with different climate (PVKLIMA project)
Site
Tilt <Tmod>, °C <Gpoa>,
W/m²
Cologne, DE 35° 21 297
Ancona, IT 35° 25 382
Tempe, US 33.5° 39 565
Thuwal, SA 25° 33 522
Chennai, IN 15° 33 440
Estimation of model parameters: 30-sec data (2 weeks, 6 months)
Model validation: 15-min averages (1 year)
Parameters are defined for 4 technologies: polySi, CdTe, CIGS, aSi

7. Data
30.03.2017 7th
PVPMC Workshop, Lugano, Switzerland
Fig.1. Frequency distribution of the module temperature for one year data.

8. 30.03.2017 7th
PVPMC Workshop, Lugano, Switzerland
Data
Fig.2. Frequency distribution of the wind speed for one year data.

9. 30.03.2017 7th
PVPMC Workshop, Lugano, Switzerland
Steady-state models
Standard/NOCT model
Skoplaki model
Tmod=Tamb +
GPOA
GNOCT
(TNOCT−Ta, NOCT).
Tmod=Tamb +
GPOA
GNOCT
(TNOCT−Ta, NOCT)
hw , NOCT
hw
[1−
nSTC
ta
(1−ßSTC TSTC )],
hw=5.7+2.8Vwind .
(1)
(2)
(2a)

10. 30.03.2017 7th
PVPMC Workshop, Lugano, Switzerland
Steady-state models
Mattei model
Sandia model
Tmod=
U PV Tamb +GPOA (ta−nSTC TSTC )
U PV + ßSTC nSTC GPOA
,
U PV=26.6+2.3V wind ,
U PV=24.1+2.9Vwind .
Tmod=Tamb +GPOA exp(a+bV wind).
(3)
(3a)
(3b)
(4)

11. 30.03.2017 7th
PVPMC Workshop, Lugano, Switzerland
IEC 61853-2: Faiman model
Faiman model Tmod=Tamb +
GPOA
u0+u1V wind
.
Fig.3. Gpoa/(Tmod-Tamb) plotted against the wind speed for two weeks of
measurements and corresponding linear fit to the data for polySi module

12. 30.03.2017 7th
PVPMC Workshop, Lugano, Switzerland
IEC 61853-2: Faiman model
Data filters
It is recommended to use 5-sec temporal resolution
measurements and at least 10 days of data
- Low irradiance filter
Irradiance values below 400 W/m²
- Irradiance fluctuations filter
Irradiance values in 10 min after the irradiance varies by more than
±10% from the maximum to minimum value during the preceding 10 min
- Wind fluctuations and gusts filter
Wind speed values in a 10-min interval after and including deviations
below 0.25 m/s and gusts larger than +200% from a 5-min running
average
- Low and high wind speed filter
Wind speed data when the 5-min running average is less than 1 m/s and
greater than 8 m/s

13. 30.03.2017 7th
PVPMC Workshop, Lugano, Switzerland
Note: we used 30-sec measurements
Irradiance fluctuations filter was modified:
reject G(i) and next 10 minutes if
IEC 61853-2: Faiman model
where ∆G(i) = G (i) − G (i − 1) – irradiance increments,
∆G = Gmax − Gmin – is the difference between maximum and minimum values
within the preceding 10 minutes
|∆G(i) | > max(5 W/m² , 0.1 * ∆G ),

14. 30.03.2017 7th
PVPMC Workshop, Lugano, Switzerland
Faiman parameters
After filtering we can define the Faiman
parameters using linear fits
The Faiman parameters defined from two weeks (April) and six months of
measurements for polySi module.
Site u0, W/°C m²
two weeks
u0, W/°C m²
six months
u1, Ws/°C m³
two weeks
u1, Ws/°C m³
six months
Colgone, DE 34.7 35.7 7.78 8.22
Ancona, IT 41.2 41.9 3.20 3.95
Tempe, US 36.4 32.1 4.51 6.08
Thuwal, SA 31.8 39.7 5.61 3.06
Chennai, IN 28.6 30.1 4.45 4.75
mean 34.5 35.9 4.44 4.46
std 4.8 5.0 1.0 1.28
std, % 14 14 22.5 29

15. 30.03.2017 7th
PVPMC Workshop, Lugano, Switzerland
Faiman parameters
Fig.4. Contour plots for rmse and mbe of the modeled module temperature for polySi module at site
Cologne and the Faiman parameters.
- two weeks
- six months
- average over all sites
- literature values

16. 30.03.2017 7th
PVPMC Workshop, Lugano, Switzerland
Faiman parameters
Fig.5. Contour plots for rmse and mbe of the modeled module temperature for CIGS module at site
Tempe and the Faiman parameters.
- two weeks
- six months
- average over all sites
- literature values

17. 30.03.2017 7th
PVPMC Workshop, Lugano, Switzerland
Faiman parameters
1. The similar behaviour is observed for all sites and
modules: 'best performance ellipse' 2-2.5 °C rmse
2. Exact values of the Faiman parameters are not
crucial for the accuracy of the modeled module
temperature
3. Although the values derived from 2 weeks and 6
months differ from each other they give the same
accuracy of the modeled module temperature for the
whole year

18. 30.03.2017 7th
PVPMC Workshop, Lugano, Switzerland
Model comparison
Fig.6. Rmse (left) and mbe (right) of the modeled module temperature using different
steady state models: Standard (NOCT), Skoplaki (SK), Mattei (M1, M2), Sandia (SA),
Faiman (FA)

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PVPMC Workshop, Lugano, Switzerland
Model comparison

20. 30.03.2017 7th
PVPMC Workshop, Lugano, Switzerland
Model comparison

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PVPMC Workshop, Lugano, Switzerland
Conclusions
1. Faiman parameters are site specific
2. Representative dataset for a given site
results in reliable values of parameters
3. The steady-state models have similar
performance

22. 30.03.2017 7th
PVPMC Workshop, Lugano, Switzerland
Acknowledgements
The work is funded by the German Federal Ministry for Economic
Affairs and Energy (BMWi FKZ 0325517A).
TÜV Rheinland, Markus Schweiger and Werner Herrmann
Literature
The results are published: Barykina, E., Hammer, A., 2017. Modeling of
photovoltaic module temperature using Faiman model: Sensitivity analysis
for different climates. Sol. Energy 146, 401-416.
Literature values of Faiman parameters: Koehl, M., Heck, M., Wiesmeier,
S., Wirth, J., 2011. Modeling of the nominal operating cell temperature
based on outdoor weathering. Sol. Energy Mater. Sol. Cells 95, 1638-
1646.

23. Thank you for
your attention!
30.03.2017 7th
PVPMC Workshop, Lugano, Switzerland

24. Supplementary materials