This paper presents the heat transfer characteristics of a stationary PV system and a dual-axis tracking PV system installed in the Upper Midwest, U.S. Because past solar research has focused on the warmer, sunnier Southwest, a need exists for solar research that focuses on this more-populated and colder Upper Midwest region. Meteorological and PV experimental data were collected and analyzed for the two systems over a one-year period. At solar irradiance levels larger than 120 W/m2, the array temperatures of the dual-axis tracking PV system were found to be lower than those of the stationary system by 1.8 °C, which is a strong evidence of the different heat transfer trends for both systems. The hourly averaged heat transfer coefficients for the experiment year were found to be 20.8 and 29.4 W/m2 °C for the stationary and tracking systems, respectively. The larger heat transfer coefficient of the dual-axis tracking system can be explained by the larger area per unit PV module exposed to the ambient compared to the stationary system. The experimental temperature coefficients for power at a solar irradiance level of 1000 W/m2 were −0.30% and −0.38%/ °C for the stationary and dual-axis tracking systems, respectively. These values are lower than the manufacturer's specified value −0.5/ °C. Simulations suggest that annual conversion efficiencies could potentially be increased by approximately 4.3% and 4.6%, respectively, if they were operated at lower temperatures.

References

References
1.
Quintana
,
M.
,
King
,
D.
,
McMahon
,
T.
, and
Osterwald
,
C.
,
2002
, “
Commonly Observed Degradation in Field-Aged Photovoltaic Modules
,”
Photovoltaic Specialists Conference, Conference Record of the 29th
IEEE
, May 19–24, pp.
1436
1439
.
2.
Goetzberger
,
A.
, and
Hoffmann
,
V. U.
,
2005
,
Photovoltaic Solar Energy Generation
,
Springer Science & Business Media
,
New York
.
3.
Vázquez López
,
M.
, and
Rey-Stolle
Prado
, I
.
,
2008
, “
Photovoltaic Module Reliability Model Based on Field Degradation Studies
,”
Prog. Photovoltaics Res. Appl.
,
16
(
5
), pp.
419
433
.
4.
Kurtz
,
S.
,
Whitfield
,
K.
,
TamizhMani
,
G.
,
Koehl
,
M.
,
Miller
,
D.
,
Joyce
,
J.
,
Wohlgemuth
,
J.
,
Bosco
,
N.
,
Kempe
,
M.
, and
Zgonena
,
T.
,
2011
, “
Evaluation of High-Temperature Exposure of Photovoltaic Modules
,”
Prog. Photovoltaics Res. Appl.
,
19
(
8
), pp.
954
965
.
5.
Kurtz
,
S.
,
Whitfield
,
K.
,
Miller
,
D.
,
Joyce
,
J.
,
Wohlgemuth
,
J.
,
Kempe
,
M.
,
Dhere
,
N.
,
Bosco
,
N.
, and
Zgonena
,
T.
,
2009
, “
Evaluation of High-Temperature Exposure of Rack-Mounted Photovoltaic Modules
,”
34th IEEE Photovoltaic Specialists Conference
(
PVSC
), Philadelphia, PA, June 7–12, pp.
2399
2404
.
6.
Luque
,
A.
, and
Hegedus
,
S.
,
2011
,
Handbook of Photovoltaic Science and Engineering
,
Wiley
,
Chichester, UK
.
7.
Del Cueto
,
J. A.
,
2002
, “
Comparison of Energy Production and Performance From Flat Plate Photovoltaic Module Technologies Deployed at Fixed Tilt
,” 29th
IEEE
Photovoltaic Specialists Conference
, May 19–24, pp.
1523
1526
.
8.
Gottschalg
,
R.
,
Betts
,
T.
,
Williams
,
S.
,
Sauter
,
D.
,
Infield
,
D.
, and
Kearney
,
M.
,
2004
, “
A Critical Appraisal of the Factors Affecting Energy Production From Amorphous Silicon Photovoltaic Arrays in a Maritime Climate
,”
Sol. Energy
,
77
(
6
), pp.
909
916
.
9.
Rehman
,
S.
, and
El-Amin
,
I.
,
2012
, “
Performance Evaluation of an Off-Grid Photovoltaic System in Saudi Arabia
,”
Energy
,
46
(
1
), pp.
451
458
.
10.
Warren
,
R. D.
,
Pate
,
M. B.
, and
Nelson
,
R. M.
,
2008
, “
A Feasibility Study of Stationary and Dual-Axis Tracking Connected Photovoltaic Systems in the Upper Midwest
,” Technical Report No. 065-03.
11.
King
,
D. L.
, and
Eckert
,
P. E.
,
1996
, “
Characterizing (Rating) the Performance of Large Photovoltaic Arrays for all Operating Conditions
,” 25th
PVSC
, Washington, DC, May 13–17, pp.
1385
1388
.
12.
Myers
,
D. R.
,
Reda
,
I.
,
Wilcox
,
S.
, and
Andreas
,
A.
,
2004
, “
Optical Radiation Measurements for Photovoltaic Applications: Instrumentation Uncertainty and Performance
,”
Proc. SPIE
,
142
, pp.
142
153
.
13.
National Weather Service Forecast Office
,
2008
, “
Observed Weather
,” Washington, DC.
14.
National Climatic Data Center
,
2015
, “
NOAA's 1981–2010 Climate Normals
,” http://www.ncdc.noaa.gov/oa/climate/normals/usnormals.html
15.
Duffie
,
J. A.
, and
Beckman
,
W. A.
,
1991
,
Solar Engineering of Thermal Processes
,
Wiley
,
New York
.
16.
Sharples
,
S.
, and
Charlesworth
,
P.
,
1998
, “
Full-Scale Measurements of Wind-Induced Convective Heat Transfer From a Roof-Mounted Flat Plate Solar Collector
,”
Sol. Energy
,
62
(
2
), pp.
69
77
.
17.
Sartori
,
E.
,
2006
, “
Convection Coefficient Equations for Forced Air Flow Over Flat Surfaces
,”
Sol. Energy
,
80
(
9
), pp.
1063
1071
.
18.
Bergman
,
T. L.
,
Incropera
,
F. P.
, and
Lavine
,
A. S.
,
2011
,
Fundamentals of Heat and Mass Transfer
,
Wiley
,
New York
.
19.
Lee
,
B.
,
Liu
,
J.
,
Sun
,
B.
,
Shen
,
C.
, and
Dai
,
G.
,
2008
, “
Thermally Conductive and Electrically Insulating EVA Composite Encapsulants for Solar Photovoltaic (PV) Cell
,”
Express Polym. Lett.
,
2
(
5
), pp.
357
363
.
20.
Whitaker
,
C.
,
Townsend
,
T.
,
Wenger
,
H.
,
Iliceto
,
A.
,
Chimento
,
G.
, and
Paletta
,
F.
,
1991
, “
Effects of Irradiance and Other Factors on PV Temperature Coefficients
,”
22nd Photovoltaic Specialists Conference
, Las Vegas, NV, Oct. 7–11, pp.
608
613
.
You do not currently have access to this content.