With the rapid increase in Building Integrated Photovoltaic (BIPV) systems and the popularity of photovoltaic (PV) applications, a simple but accurate model to calculate the power output of PV modules is crucial for evaluating systems. In addition, in the analysis of energy payback, two factors, the power output (maximum power output) model of PV modules and the representative local weather data, affect calculations of the energy savings and the payback time of BIPV systems. Most studies take the efficiency of PV modules as constant when calculating the energy payback time of PV systems, and ignore the influence of solar radiation and temperature on the results of the calculation. This study tries to develop one simple, practical, yet more accurate model for describing the characteristics of the power output of PV modules. It develops a model for describing the $I-V$ characteristics of PV modules according to the equivalent circuits of solar cells, by which an accurate but complicated model of the maximum power output (MPO) can be achieved. Taking this MPO model as a benchmark, two other application models from other studies are evaluated and examined. One simplified application model for describing the maximum power output of PV modules is then derived from the results of the simulation. Once the solar radiation on PV panels and the ambient temperature are known, the power output of BIPV systems or PV systems can be calculated accurately and easily.

1.
Overstraeten, R. J. Van, and Mertens, R. P., 1986, Physics, Technology and Use of Photovoltaics, Adam Hilger Ltd, Bristol and Boston, pp. 187–191.
2.
Zheng, G. F., 1996, “High Efficiency Thin-film Silicon Solar Cells,” Ph.D. Dissertation, University of New South Wales, Sydney, Australia.
3.
Wenham, Stuart R., Green, Martin A., and Muriel, E. Watt, 1994, “Applied Photovoltaics, Center for Photovoltaic Devices and Systems,” University of New South Wales, Sydney, Australia.
4.
Akbaba
,
M.
, and
Alattawi
,
Mohammed A. A.
,
1995
, “
A New Model for I-V Characteristic of Solar Cell Generators and its Applications
,”
Solar Energy Materials and Solar Cells
,
37
, pp.
123
132
.
5.
Wilson
,
R.
, and
Young
,
A.
,
1996
, “
The Embodied Energy Payback Period of Photovoltaic Installations Applied to Buildings in the U.K.
,”
Build. Environ.
,
31
(
4
), pp.
299
305
.
6.
Alsema
,
E. A.
,
2000
, “
Energy Payback Time and CO2 Emissions of PV Systems
,”
Prog. Photovoltaics
,
8
, pp.
17
25
.
7.
Knapp
,
K.
, and
Jester
,
T.
,
2001
, “
Empirical Investigation of the Energy Payback Time for Photovoltaic Modules
,”
Sol. Energy
,
71
(
3
), pp.
165
172
.
8.
Yang, H. X., Lu, L., and Chen, T. Y., 2003, “Embodied Energy and Energy Payback Time Analysis of Building Integrated Photovoltaics in Hong Kong,” submitted.
9.
Lu, L., and Yang, H. X., 2003, “The Effect of Temperature and Solar Radiation on the Maximum Power Output and Efficiency of Photovoltaic Modules,” submitted.
10.
Jones
,
A. D.
, and
Underwood
,
C. P.
,
2002
, “
A Modeling Method for Building-integrated Photovoltaic Power Supply
,”
Build. Services Eng. Res. Technol.
,
23
(
3
), pp.
167
177
.
11.
Lu, L., 2004, “Investigation on Characteristics and Application of Hybrid Solar-Wind Power Generation Systems,” Ph.D. Dissertation, The Hong Kong Polytechnic University.
12.
Borowy
,
B. S.
, and
Salameh
,
Z. M.
,
1996
, “
Methodology for Optimally Sizing the Combination of a Battery Bank and PV Array
,”
IEEE Trans. Energy Convers.
,
11
(
2
), pp.
367
375
.
13.
Jones
,
A. D.
, and
Underwood
,
C. P.
,
2001
, “
A Thermal Model for Photovoltaic Systems
,”
Sol. Energy
,
70
(
4
), pp.
349
359
.
14.
Chen
,
T. Y.
,
Burnett
,
J.
, and
Chau
,
C. K.
,
2001
, “
Analysis of Embodied Energy Use in the Residential Building of Hong Kong
,”
Energy (Oxford)
,
26
, pp.
323
340
.
15.
Markvart, T., 1994, Solar Electricity, John Wiley & Sons Ltd, Chichester, England.
16.
Nelder
,
J. A.
, and
,
R.
,
1965
, “
A Simplex Method for Function Minimization
,”
Comput. J.
,
7
, pp.
308
313
.
17.
BP Solar Ltd, BP Solar Specifications.