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Research Papers

Simulation Model of Photovoltaic and Photovoltaic/Thermal Module/String Under Nonuniform Distribution of Irradiance and Temperature

[+] Author and Article Information
Giuseppe Marco Tina

Dipartimento di Ingegneria Elettrica
Elettronica e dei Sistemi,
Università di Catania,
Viale Andrea Doria 6,
Catania 95125, Italy
e-mail: giuseppe.tina@dieei.unict.it

Contributed by the Solar Energy Division of ASME for publication in the JOURNAL OF SOLAR ENERGY ENGINEERING: INCLUDING WIND ENERGY AND BUILDING ENERGY CONSERVATION. Manuscript received June 6, 2016; final manuscript received November 1, 2016; published online December 22, 2016. Assoc. Editor: Carlos F. M. Coimbra.

J. Sol. Energy Eng 139(2), 021013 (Dec 22, 2016) (12 pages) Paper No: SOL-16-1263; doi: 10.1115/1.4035152 History: Received June 06, 2016; Revised November 01, 2016

The modern concepts of sustainable cities and smart grids have caused an increase in the installation of solar systems in urban and suburban areas, where, due to the presence of many obstacles or design constraints, photovoltaic (PV) modules can operate in operating conditions that are very different from the optimal ones (e.g., standard test conditions, STC). Shading and reflection are the main phenomena that cause uneven distribution of irradiance on PV cells; in turn, they create a nonuniform distribution of PV cell temperatures. The latter problem can also be caused by different ventilation regimes in various parts of the PV array. On the other hand, due to the need to exploit different solar technologies (solar thermal and photovoltaic), problems related to the availability of a useful surface can arise. In this context, there is a technology that produces heat end electrical energy at the same time, such a technology is referred to as a solar hybrid photovoltaic/thermal (PV/T). Here, the uneven distribution of temperature is a design input and its effect depends on both path of the water flow and the PV cell connections. To study the electrical behavior of a PV array under mismatching conditions, a suitable matlab/simulink model has been developed. The model has been tested both numerically and experimentally. Finally, an application of this model in the electrical analysis of a PV/T module is reported, and the results are discussed.

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Figures

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Fig. 1

Shading and reflection phenomena of solar radiation in the urban context

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Fig. 2

Equivalent circuit for one-diode electrical PV module

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Fig. 3

Variation of I–V and P–V curves with PV cell temperature (Irr = 1 kW/m2, Voc = 38.82 V, Isc = 8.2 A, Vmp = 31.71 V, Imp = 7.52 A, ki = 0.0531%/ °C and kv = −0.3143%/ °C)

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Fig. 4

Variation of I–V and P–V curves with irradiance (Tc = 25 °C, Voc = 38.82 V, Isc = 8.2 A, Vmp = 31.71 V, Imp = 7.52 A, ki = 0.0531%/ °C, and kv = −0.3143%/ °C)

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Fig. 5

Electric model: (a) for PV module divided in three sections and (b) for temperature mismatch inside a PV string

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Fig. 6

simulink block diagram for a PV system

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Fig. 7

simulink block diagram of a PV cell

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Fig. 8

PLPB method: (a) linearization of I–V diode curve and (b) equivalent circuit of the diode

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Fig. 9

Equivalent circuit of the PV module using PLPB method

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Fig. 10

Modified PLPB method: R1–T curve (solid line) and E1–T curve (dashed line)

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Fig. 11

Block diagram of the modified PLPB method

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Fig. 12

Comparison between the measured (dashed lines) andsimulated (solid lines) I–V and P–V curves: Irr = 830 W/m2 and T = 53 °C, and Irr = 610 W/m2 and T = 48 °C

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Fig. 13

simulink model used for the simulations under nonuniform irradiance conditions

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Fig. 14

Comparison between the measured (dashed line) and simulated (solid line) P–V curves: (a) Irr mean = 980 W/m2 and T mean = 50 °C, percentage of irradiance on substrings 86.98%–100%–100% and (b) Irr mean = 800 W/m2 and T mean = 48 °C, percentage of irradiance on substrings 73.96–86.98–100%

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Fig. 15

simulink model of a PV system with two strings connected in parallel

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Fig. 16

Comparison between the measured (solid line) and simulated (dashed line) I–V and P–V curves under uniform irradiance condition

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Fig. 17

Comparison between the measured (markers) and simulated (solid line) I–V (a) and P–V (b) curves when one module of string II is shaded: (A) I–V (P–V) curve of the parallel of the two strings; (B) string I with no shading; and (C) string II with one module shaded

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Fig. 18

Comparison between P–V curves under normal (dashed line) and nonuniform irradiance conditions (solid line)

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Fig. 19

System used for experimental tests and thermal image of the model under an uneven temperature distribution

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Fig. 20

simulink models used for the simulations: (a) substrings in series and (b) substrings in parallel

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Fig. 21

P–V curves of a PV module with substring connected in series: (a) measured (solid line) and simulated (dotted line) P–V curves of two substrings of the PV module under nonuniform temperature condition (Irr = 695 W/m2, Thot = 55 °C, Tcold = 45 °C), and (b) simulated P–V curves of the module under normal and nonuniform temperature conditions

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Fig. 22

Substring connected in parallel—comparison between P–V curves: (a) of the three substring under nonuniform temperature condition, and (b) simulated P-V curves of the module under normal (upper line) and nonuniform (lower line) temperature conditions (Irr = 695 W/m2, Thot = 55 °C, Tcold = 45 °C)

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Fig. 23

Thermal image of the module under an uneven temperature distribution

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Fig. 24

simulink models used for the simulation: (a) substrings in series and (b) substrings in parallel

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Fig. 25

Substring connected in series—comparison between P–V curves: (a) three substrings under nonuniform temperature condition and (b) module under normal and nonuniform temperature conditions (Irr = 775 W/m2, Thot = 55 °C, Tcold = 45.5 °C)

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Fig. 26

Distribution of PV cell temperatures in a PVT module with substrings in series: (a) vertical water flow pattern, (b) horizontal water flow pattern, and (c) P–V curve for the PV module at 1000 W/m2 (solid curves), with 30% of the module, i.e., the third substring, shaded (dashed curves)

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Fig. 27

Distribution of PV cell temperatures in a PV/T module with substrings connected in parallel: (a) vertical water flow pattern, (b) horizontal water flow pattern, (c) P–V curves at 1000 W/m2 (solid curves) and with 30% of the module, i.e., the third substring, shaded (dashed curves)

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