Integrated Photovoltaic System (BIPV) in Malaysia. Simulation was implemented using MATLAB/SIMULINK and results are compared with the actual monitored ...
2010 IEEE International Conference on Power and Energy (PECon2010), Nov 29 - Dec 1, 2010, Kuala Lumpur, Malaysia
Modeling and Simulation of Grid Connected Photovoltaic System for Malaysian Climate Using Matlab/Simulink H.A.Rahman*, K.M.Nor*, M.Y.Hassan*, S.Thanakodi**, M.S. Majid* , F.Hussin* * Center of Electrical Energy Systems, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor, Malaysia ** Dept of Electrical and Electronics, Universiti Pertahanan Nasional Malaysia, 57000 K.Lumpur, Malaysia
temperature. Hence, a 100Wp PV would only produce a maximum of 80Wd.c at times. Obviously, the energy produced depend on the site where the system to be installed [3]. Besides, the PV system has different seasonal pattern behavior depending on the temperature as well as the solar irradiation. Due to the different temperature coefficient of voltage and current the PV system has different output. Photovoltaic modules are rated at STC (standard test conditions) of solar irradiation as 1000 Wm-2, and sun-spectrum at air mass of 1.5 (AM = 1.5). The STC temperature operating for the PV cell is at 25oC which does not relate to the practical world especially to Malaysia. This paper presents the effect on the energy output by changing the clearness index for the Building Integrated Photovoltaic System (BIPV) in Malaysia simulated using MATLAB/SIMULINK. The simulated values are than compared with the actual monitored data for a system with installed capacity of 45.36 kW using actual ambient temperature and solar radiation data.
Abstract—The impact of solar irradiance, ambient temperature and clearness index on the outdoor performance of poly-crystalline (poly-Si) PV modules is considered. This paper highlights the effect on the energy output by changing the clearness index for the Building Integrated Photovoltaic System (BIPV) in Malaysia. Simulation was implemented using MATLAB/SIMULINK and results are compared with the actual monitored data. A case study was presented for a 45.36 kWh system using poly-crystalline module and results show that the energy output differs from 7.23% to 8.52% with clearness index of 0.55 and hence clearness index also influenced the energy output besides solar irradiance and temperature. Keywords—Photovoltaic module; Solar irradiance, Energy output; Clearness index.
I. INTRODUCTION Photovoltaic System (PV) is getting popular by day as the crude oil price increases and unstable in the global market. Furthermore with green peace movement, and the consciousness of mankind has heightened up green energy which photovoltaic is one of the solution for better as well cleaner energy as it is naturally harness from the Sun energy. Although the technology is mainly well known in the space mission, yet it’s still an alien for domestic usage in Malaysia. This is due to the high initial cost, generation efficiency and reliability [1]. Currently, more than 3500MW of photovoltaic system have been installed all over the world [2]. Referring to the results from Earth Policy Institute (EPI), the world production of solar PV cells increased to 32% in 2003, compared to the most recent 5-year average of 27% a year. Production increased to 742 MW, with cumulative global production at 3145 MW at the end of year 2003, sufficient to meet the electricity niche of one million homes. Referring to the EPI, this extraordinary growth is driven to some degree by improvements in materials and technology, but primarily by market introduction programs and government incentives [2]. Currently, renewable energy account for about 5% of the country energy demand in Malaysia which is equal to between 500 and 600 MW of installed capacity. In a tropical climate country, such as in Malaysia, the maximum solar radiation is typically between 800W/m2 to 1000W/m2 but the ambient temperature could be as high as 40oC at noon, resulting in a 60oC PV cell
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II.
METHODOLOGY
A. Modelling of PV Cells The basic criteria for modeling a PV device are its electrical characteristics, i.e., the current and voltagecurrent relationship of a PV cell for varying weather conditions [4, 5]. Fig. 1 shows the equivalent circuit of a PV cell [6]. The values of currents and voltages are dependent on the solar irradiance and the ambient temperature [5, 7, 8]. The electrical performance models which include cell temperature model require parameters that describe the important of panel characteristics. The parameters required which can be obtained from the manufacturer’s module specifications include short-circuit current and open-circuit voltage temperature coefficients. Io or reverse current saturation is given by equation 1 [9].
e
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I
,
V
,
V
K I ∆T K ∆T
. 1
1
TABLE I.
PHOTOVOLTAIC (PV) MODULE CHARACTERISTICS FOR STANDARD LOGIES TECHNOL
PV module
ηr (%)
o
type
The light generated current, Ipv of thee photovoltaic cell which depends linearly on the influennce of temperature and solar radiation is given by equation 2 [9]. I
K I ∆T
,
G . G
2
I
e
V R I V
1 .
βp
( C)
(% / oC)
Mono-Si
13.0
45
0.40
Poly-Si
11.0
45
0.4
a-Si
5.0
50
0.11
CdTe
7.0
46
0.24
CIS
7.5
47
0.46
M C. Matlab / Simulink Circuit Modeling Figure 2 shows the modeliing of the PV system with load using Matlab/Simulink platform. p The diode in the system is to block the reverse current while the isolation transformer is to smooth andd isolate the load directly from universal bridge which acts as an inverter. Pulse block is a PWM (pulse widthh modulation) generator to drive the inverter into the circuuit.
And the model current, Im is given by equation 3 [9].
I
NOCT
3
The cell temperature, Tc is calculatedd as in equation (4) [10] using the actual ambient temperatture data obtained from the Malaysia Metrological Departm ment. Tc
T
219
832 Kt
NOCT 20 8 800
4
B. Energy Output Modeling Table 1.0 shows the PV module characteristics for standard technologies. The efficiency of o the solar module and solar types are considered in moodeling the energy output. The energy output is determinedd by the following equations. The array efficiency, ηp is inffluenced by cell temperature, module efficiency and module m temperature coefficient [11]. ηp is written as follows;; (5)
ηp = ηr x [1 – βp (Tc – Tr)/100]
The energy delivered by PV array, Ep is calculated using the equation below [12]. E
η A
G
6
The energy delivered to grid, Egrid is [12]; E
E 1
λ
1
λ
η
7
Therefore the actual energy, Edlvd delivered can be determined as follows [12]; E
E
η
.
Figure 2. PV System Model Using Matlab/Simulink
8
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III. RESULTS AND DISCUSSION The temperature and solar irradiance characteristics of single junction solar cell MSX-60 is simulated and verified with the theoretical manufacture’s datasheet. The effect on the energy output by changing the clearness index for Building Integrated Photovoltaic System (BIPV) in Malaysia is also simulated. The simulation results were compared with the monitored data gathered from an installed PV system of 45.36 kW using actual ambient temperature and solar radiation. The variation of temperature from 0°C to 75°C in step of 25 with solar irradiance fixed at 1 kW/m2 is simulated and the result shows that when the solar radiation (G) is constant, the open circuit voltage decreases as depicted in Fig. 4 to Fig. 7. This resulted in the change of the maximum power point operation. On the other hand, when the cell temperature (Tc) is fixed at Tc = 25 ºC and the solar radiation is varied from 0.4kW/m2 to 1kW/m2, the current generated by the cell increases accordingly as in Figure 8 to Figure 11. Figure 4. Simulation Output at Tc = 0 ºC and G = 1kW/m2
Figure 3. The I-V Curve from BP Solar MSX-60 datasheet
Figure 5. Simulation Output at Tc = 25 ºC and G = 1kW/m2
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Figure 6. Simulation Output at Tc = 50 ºC and G = 1kW/m2
Figure 9. Simulation Output at Tc = 25 ºC and G = 0.6kW/m2
Figure 10. Simulation Output at Tc = 25 ºC and G = 0.8kW/m2
Figure 7. Simulation Output at Tc = 75 ºC and G = 1kW/m2
Figure 8. Simulation Output at Tc = 25 ºC and G = 0.4kW/m2
Figure 11. Simulation Output at Tc = 25 ºC and G = 1kW/m2
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The monitored energy output from Pusat Tenaga Malaysia (PTM), Bangi, Selangor has been b chosen for the case study to compare with that of thee simulated value. The installed capacity of the system in PTM is 45.36 kW with efficiency of 94.3%. The photovoltaic technology is poly-Si with 12% module efficiency. Figure 12, Figure 13 and Figuure 14 show the comparison of the energy output for the t year 2008 for clearness index at 0.45, 0.5 and 0.55 resppectively. It is observed that, with the clearness index 0.55, the simulation result obtained is nearest to the actual monitored output with a difference between b 7.23% to 8.52%. The differences are due too some practical constraints such as the beam radiance, diffuse radiance, the zenith angle of the sun and the inncidence angle of beam irradiance on the array. Hence, clearness index is also an impportant indicator in determining the energy output besidees solar irradiance and temperature.
Figure 14. Energy Output O with K = 0.55
IV. CONC CLUSION The impact of solar irradiaance, ambient temperature and clearness index on the outtdoor performance of polycrystalline (poly-Si) PV moduule was studied. The study show that variation of clearness index has an impact on t temperature and solar the energy output. Besides, the irradiance characteristics of single junction solar cell MSX-60 is also being simulaated and verified with the theoretical from manufacturee’s datasheet. Hence in selecting the best PV technologgy actually depends on the usage and also niche area on where w the PV system would be applied. For more modeling accuraccy, beam radiance, diffuse radiance, the zenith angle of thhe sun, the incidence angle of beam irradiance on the arrray and the ratio of beam radiation on the PV array to thhat on the horizontal should be taken into account while modeling instead of solar radiation and cell temperature. This T will help in estimating the energy output accurately while designing the PV system.
Figure 12. Energy Output with K = 0.45
DGMENT ACKNOWLED
The authors wish to ackknowledge the Ministry of Higher Education under Funndamental Research Grant Scheme; Vote No: 78459 for thhe financial funding of this project.
Nomenclature the short circuit currennt (A) I ,
Figure 13. Energy Output with K = 0.50
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KI K a Vt ∆T
current co-efficient voltage co-efficient diode ideality constant the array’s thermal voltage (V) the differences between the actual and nominal temperature values (°C) I , the light generated current at nominal conditions when T = 20ºC and Gn = 800 W/m2 (A) G nominal solar irradiation at STC (W/m2) G solar irradiation on the surface (W/m2) cell temperature (°C) Tc Ta ambient temperature (°C) monthly average clearness Index Kt NOCT Normal Operating Cell Temperature (°C) 800 solar irradiation at NOCT (W/m2) 20 cell ambient temperature at NOCT (°C) module efficiency at reference ηr temperature (Tr = 25 oC) temperature coefficient (% / oC) βp Tc cell temperature reference temperature (25 oC) Tr PV array average efficiency ηp A PV array area (m2) miscellaneous PV array losses λp other power conditioning losses λc ηinv inverter efficiency ηabs PV energy absorption rate REFERENCES [1]
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