Performance enhancement of photovoltaic grid-connected system using PVT panels with nanofluid

Solar Energy 150 (2017) 38–48

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Performance enhancement of photovoltaic grid-connected system using PVT panels with nanofluid Ali Najah Al-Shamani a,b,⇑, K. Sopian a,⇑, Sohif Mat a, Azher M. Abed a,c a

Solar Energy Research Institute (SERI), Universiti Kebangsaan Malaysia, 43600 Bangi, Malaysia Al-Musaib Technical College, Al-Furat Al-Awsat Technical University, 51009 Babylon, Iraq c Department of Air conditioning and Refrigeration, Al-Mustaqbal University College, Babylon, Iraq b

a r t i c l e

i n f o

Article history: Received 12 August 2016 Received in revised form 7 January 2017 Accepted 3 April 2017

Keywords: GCPVT system Rectangular absorber tube Nanofluid Performance ratio (Efficiencies – PV array, inverter, system)

a b s t r a c t A 1.2 kWp roof top grid-connected photovoltaic thermal system (GCPVT) with SiC nanofluid that supply both electricity and hot water has been designed, fabricated, and evaluated under the tropical climate conditions. The performance was compared to a conventional photovoltaic grid connected system (GCPV). The photovoltaic thermal (PVT) collectors consist of specially designed rectangular tube absorbers with a height of 15 mm and a width of 25 mm, and attached under an array of 10 pieces of photovoltaic modules. The results indicated that the GCPVT SiC nanofluid system has better performance ratio, array, final and reference yield, and (PV, inverter, and system) efficiencies compared to the gridconnected photovoltaic (GCPV) system. In the month of March, the GCPV indicated PV array efficiency of 8.77%, performance ratio (PR) of 77.14%, monthly array yield of 105.70 kWh/kWp and final yield of 100.53 kWh/kWp. Similarly, the GCPVT with nanofluid indicated a PV array efficiency of 13.52%, PR of 95.72%. The highest values for monthly array yield and final yield were obtained in March, were at 157.32 and 152.71 kWh/kWp, at flow rate of 0.17 kg/s, respectively. Ó 2017 Elsevier Ltd. All rights reserved.

1. Introduction A grid-connected system is made up of PV modules and an inverter. The inverter converts the direct current (DC) electricity generated by the PV modules into alternating current (AC) electricity, which is synchronized with the main electrical source so that excess electricity will be fed into the grid. The relatively high solar irradiance condition in equatorial climate regions is suitable for use with solar photovoltaic (PV) systems, despite its relatively higher ambient temperature and humidity. Nanofluid is a pure base fluid with suspended metallic nanoparticles. Nanofluids contain very tiny particles suspended in its base fluid. The convective heat transfer characteristic of nanofluids relies on the thermophysical properties of the base fluid and the ultra-fine particles. 1.1. Grid connected photovoltaic system (GCPV) The performance of GCPV systems can be evaluated by investigating the performance ratio (PR) (Blaesser and Munro, 1995), ⇑ Corresponding author at: Solar Energy Research Institute, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia. E-mail addresses: [email protected] (A.N. Al-Shamani), ksopian@ukm. edu.my (K. Sopian). http://dx.doi.org/10.1016/j.solener.2017.04.005 0038-092X/Ó 2017 Elsevier Ltd. All rights reserved.

which is defined by the ratio of the system efficiency and the nominal efficiency of PV modules under STC (Devices—Part, 2008). The average values of PR were found to be 66% rooftop mounted PV in Germany (Kiefer et al., 1995), 55–70% for eight GCPV systems in Europe (Van Schalkwijk et al., 1995), while it was 63–76% in the Netherlands (Boumans et al., 1995). These values apply to systems using solar cells made of poly-and monocrystalline silicon. The major components of a GCPV system are shown in Fig. 1. The inverter may simply fix the voltage at which the array operates, or use a maximum power point tracking function to identify the best operating voltage for the array. The inverter operates in phase with the grid, and generally delivers as much power as it can to the electric power grid as per available sunlight and temperature conditions (Newmiller et al., 2007). Pietruszko and Gradzki (2003) summarized a year of monitoring of a roof-mounted 1-kWp grid-connected system in Warsaw. The results showed that the annual system energy yield was
830 kWh, and the performance ratio ranges from 60% to 80%. The efficiency of the PV system was within 4–5%. 1.2. Water based Photovoltaic Thermal (PVT) collector To increase the collection efficacy, the photovoltaic and thermal collectors can be combined. This type of collector is also known as

A.N. Al-Shamani et al. / Solar Energy 150 (2017) 38–48

39

Nomenclature Ac I(t) FF _ m Tp YA EDC PPV,rated FiT GCPV SiC

collector area (m2) solar irradiance (W/m2) fill factor of PV module mass flow rate (kg/s) PV plate temperature (°C) array yield (kWh/kWp) net DC energy output (kWh) PV array rated power (kWp) Feed-in Tariff Grid-Connected Photovoltaic Silicon Carbide Nanofluid

k

l q Ti To YF EAC Ht PVT GCPVT ST

photovoltaic thermal (PV/T) collector system. The efficiency of photovoltaic collectors decreased when ambient temperature increases, and vice versa. The performance of the PVT collector also depends upon various design parameters, such as absorber design configurations (Zondag et al., 2003), collector length (Koech et al., 2012), collector depth (Tonui and Tripanagnostopoulos, 2008), and PV module types (Agrawal and Tiwari, 2010). The existing thermal absorbers for PVT were made from metals with sheet and tube, roll bond, and box channel types. Generally, the most adopted configurations were the sheet and tube, due to its simple manufacturing processes and low thickness requirements. Besides simulation studies, experimental studies on the performance evaluation of PVT collectors have been also carried out by many researchers (Al-Shamani et al., 2015, 2014; Charalambous et al., 2007; Hussien et al., 2015; Lin et al., 2014; Singh et al., 2016; Sobhnamayan et al., 2014; Su et al., 2016; Sultan et al., 2014).

thermal conductivity (W/m K) viscosity (mPa s) density (g/mL) inlet fluid temperature (°C) outlet fluid temperature (°C) final yield (kWh/kWp) net AC energy output (kWh) Plane-of-Array (POA) irradiance (kWh/m2) Photovoltaic Thermal Collector Grid-Connected Photovoltaic Thermal Solar Thermal Collector

There is no study in literature on the use GCPVT system using nanofluid. GCPV system has an inherent drawback of producing lower efficiencies and performance ratio. Meanwhile, GCPVT system with water still does not improve the efficiencies and system performance ratio, due to the lower absorption coefficient and the higher thermal resistance. Therefore, nanofluid with high heat transfer characteristics has motivated us to use it on GCPVT system. This paper presents an experimental study to determine the performance of a GCPVT using SiC nanofluid and comparison with a conventional GCPV system. The performance ratio (PR) and efficiencies of the PV array, inverter, and system will be determined. More, the system monthly and final yield will also be determined.

2. Experimental setup 2.1. The grid-connected photovoltaic thermal system

1.3. Nanofluid and nanoparticles The addition of small amounts of solid nanoparticles in convectional fluids enhance their thermo-physical properties vis-à-vis its base fluid. Some examples of There nanoparticles are SiO2, Al2O3, TiO2, and SiC. Examples of base fluids include pure water, ethylene glycols, and oil. Different types of nanofluids have different values of thermal conductivity and costs. Recently, the amount of experimental, theoretical, and numerical studies on the application of nanofluids in solar collectors have been extensive studied. These included direct absorption solar collector (Otanicar and Golden, 2009), concentrating parabolic solar collectors (Khullar et al., 2012), evacuated tube solar collectors (Liu et al., 2013), flat plate solar collectors (Yousefi et al., 2012), parabolic trough collectors (Nasrin et al., 2013), and concentration photovoltaic–thermal collectors (Xu and Kleinstreuer, 2014).

GCPVT is mainly composed of PV arrays and absorber collectors, an inverter device with the function of maximum power tracking, and a control system. 1.2 kWp GCPVT-SiC nanofluid system has been installed and tested in the National University of Malaysia (UKM) for performance analysis of its characteristics and efficiencies. The photograph of the set-up is shown in Fig. 2. The nominal power of GCPVT arrays ranged from 1.1 to 1.2 kWp, while the specifications and equipment of GCPVT system is shown in Fig. 3. A 1.2 kWp solar PV power system comprised of 10 Polycrystalline Silicon modules. Each module has a rated power of 120 Wp and a nominal voltage of 17.4 V and the parameters are given in Table 1. The modules were connected in a series string of five groups of two parallel connected modules for a nominal voltage of 87 V DC, as shown in Fig. 4. The installed GCPVT-SiC nanofluid system has been fully monitored, and its performance was then evaluated. The monitored results GCPVT-SiC nanofluid

Fig. 1. GCPV power system.

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A.N. Al-Shamani et al. / Solar Energy 150 (2017) 38–48

a function of the independent variables x1, x2, x3, . . ., xn and w1, w2, w3, . . ., wn and this represents uncertainties in the independent variables. Thus, uncertainty, R, is expressed as (Holman, 2001):

"
WR ¼

@R w1 @x1

2




@R þ w2 @x2

2




@R þ :::: þ wn @xn

2 #1=2 ð1Þ

The independent parameters measured in the experiments include solar irradiance, (PV module, PVT collector, inlet, outlet, and ambient), while temperatures represent experimental uncertainties, shown in Table 2. The maximum uncertainties in electrical efficiency and thermal efficiency were ±0.083% and ±1.092%, respectively. 2.4. Experimental procedures The measured data were ambient temperature, PVT module temperature, DC voltage, DC current, inverter output energy, and solar irradiance. The performance parameters were obtained in the context of DC power, energy produced by the PVT modules, solar irradiance, PV module, inverter and system efficiencies, final yield, and Performance Ratio (PR). These performance parameters would enable normalized comparisons with GCPV system. 3. Energy balance and performance analysis of GCPVT system The performance of GCPVT-SiC nanofluid system can be examined using the following performance parameters that include (in accordance with the IEC 61724 standard (Ayompe et al., 2011; Commission, 1998)) energy output, performance yields (array, final and reference), efficiencies (array, inverter and system), losses and the overall performance of the GCPVT system. 3.1. Energy output

Fig. 2. GCPVT system, (a) PV module outside system view, (b) absorber collector inside system view.

systems were collected in a 1-min sampling period. The measured data were recorded and averaged every 5 min and stored for analysis and evaluation. 2.2. Thermo-physical properties of nanofluid Nanofluid is a suspension of nanoparticles in a base fluid. The two-step method was used to prepare Silicon Carbide (SiC) nanofluid included suspension of the nanoparticles in the base fluid and its subsequent ultra-sonication. Fig. 5 shows the thermophysical properties of the nanofluid at multiple temperatures. The thermo-physical properties of nanofluid, such as thermal conductivity, density, and viscosity were also determined. The thermo-physical properties of nanofluid were required to determine the heat transfer coefficient of the nanofluid. A KD2-Pro thermal properties analyzer (made by Decagon, USA) was used to measure the thermal conductivity of nanofluid. DH-300L Leading Factory Liquid Density Tester was used to measure the density of nanofluid. A Brookfield (LVDV III ultra-programmable) viscometer was used in this experiment to measure the viscosity. 2.3. Experimental error and uncertainty analysis The experimental uncertainties were calculated by applying Gauss’ propagation law. The uncertainty R has been calculated as

The energy output is defined as the amount of alternating current (AC) power produced by the system over a set period of time. The total hourly, daily, and monthly energy produced are as follows (Ayompe et al., 2011; Commission, 1998):

EAC;h ¼

60 X EAC;t

ð2Þ

t¼1

EAC;d ¼

24 X EAC;h

ð3Þ

t¼1

EAC;m ¼

N X EAC;d

ð4Þ

t¼1

EAC,t is AC energy output at time (min); EAC,h is AC energy output at hour (hr); EAC,d is the daily AC energy output; EAC,m is the monthly AC energy output, and N is the number of days in a month. 3.2. System yields The system yields can be classified into three types, namely (a) array, (b) final, and (c) reference yields. The yields indicate the actual array operation relative to its rated capacity. The array yield is defined as the direct current (DC) energy output from the PV array over a given period of time normalized by the PV rated power. It represents the number of hours the PV array needs to operate at the rated PV capacity in order to produce similar amounts of energy, as was recorded. The system array yield is calculated using the following formula:

41

A.N. Al-Shamani et al. / Solar Energy 150 (2017) 38–48

C

Thermocouples Flow meter Pyranometer Anemometer kWh- pump

meter

kWh- heater

Fig. 3. The schematic diagram of the GCPVT experimental set-up.

The Performance Ratio (PR) is widely used to access the quality of PV system installations that are commonly reported on a daily, monthly, or yearly basis. PR can be expressed as a percentage by the following formula:

Table 1 Typical electrical characteristic of the PV module. Electrical performance under Standard Test Conditions (S.T.C) Model

STF – 120P6

Rated Power (Pmax) Open-circuit voltage (Voc) Short – circuit current (Isc) Voltage at Pmax (Vmp) Current at Pmax (Imp) Module area (m2) PV module electrical efficiency Nominal Operating Cell Temperature (NOCT)

120 ± 3% 21.5 V 7.63A 17.40 V 6.89A 0.85714 14% 42 °C

PR ¼

EDC PPV;rated

ð5Þ

The final yield is defined as the energy output from the inverter (AC energy), normalized by the PV system rated capacity. The final yield thus indicates how many hours a day the PV system must operate at its rated power in order to produce similar amounts of energy, as was recorded. The final yield is calculated using the following formula:

YF ¼

EAC PPV;rated

ð6Þ

The reference yield is the ratio of the total in-plane solar radiation to the array reference irradiance (usually taken as 1000 W/ m2). It is a measure of the theoretical energy available at a specific location over a specified period of time. The reference yield can be calculated using the following formula:

YR ¼

Ht IðtÞstc

ð8Þ

3.3. System efficiencies

*STC: Irradiance 1000 W/m2, AM 1.5 spectrum, module temperature 25 °C.

YA ¼

YF YR

ð7Þ

The efficiency of a GCPVT-SiC nanofluid system can be grouped into PV module, system, and inverter efficiencies. Depending on the available data and desired level of resolution, these efficiencies can be determined on instantaneous, hourly, daily, monthly, and annual bases. The module efficiency is based on the DC power output, while the system efficiency is a function of the AC power output. The PV module efficiency is determined using:

gPV ¼




EDC H t  Ac

  100 ð%Þ

ð9Þ

The system efficiency is given as:

gsys ¼




EAC H t  Ac

  100 ð%Þ

ð10Þ

The inverter efficiency is given as:

ginv ¼




EAC EDC

  100 ð%Þ

ð11Þ

4. Results and observations The performances of the GCPVT-SiC nanofluid system have been determined under tropical conditions. The Voc and Isc were

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A.N. Al-Shamani et al. / Solar Energy 150 (2017) 38–48

17.4V

17.4V

17.4V

17.4V

17.4V

6.89A

6.89A

6.89A

6.89A

6.89A

17.4V

17.4V

17.4V

17.4V

17.4V

6.89A

6.89A

6.89A

6.89A

6.89A

87V 6.89A

87V 6.89A

87V = 1.2 kWp

13.78A

1.1

2

ρ -Water ρ - SiC- 0.5wt.% ρ - SiC- 1wt.% ρ - SiC- 2wt.% μ - Water μ - SiC- 0.5wt.% μ - SiC- 1wt.% μ - SiC- 2wt.% κ - Water κ - SiC- 0.5wt.% κ - SiC- 1wt.% κ - SiC- 2wt.%

1.05 1 0.95 0.9 0.85

1.8 1.6 1.4 1.2 1

0.8

0.8

0.75 0.6

Viscosity (mPa.s)

Density (g/mL), Thermal condictivity (W/m.K)

Fig. 4. Schematic cable connection diagram of the 1.2 kWp CGPVT-SiC nanofluid system.

0.7 0.4 0.65 0.2 0.6 10

20

30

40

50

0

O

Temperature ( C) Fig. 5. Thermo-physical properties of Silicon Carbide (SiC) nanofluid with temperatures at different concentrations (0–2) wt.%

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A.N. Al-Shamani et al. / Solar Energy 150 (2017) 38–48

Equipment

Parameter

Experimental uncertainty

recorded. The temperatures (ambient, inlet, outlet, PV module and PVT collector) were also measured and recorded to determine the performance ratio and (PV, system and inverter) efficiencies of CGPVT nanofluid system.

Pyranometer Thermocouples

Irradiance Temperature (PV module, PVT collector, inlet, outlet, and ambient) Voltage Current

±3.2% ±1.09 °C

4.1. Weather data

Table 2 Uncertainties associated with the individual measurements of the PVT system.

±0.05% ±0.003%

The weather data such as the solar irradiance and ambient temperatures have been recorded at the site located at 2.9197°N,

7000

60 G T

6500

55

6000 5500

Ambient temperature ( C)

Solar radiation (W/m 2)

5000

Solar irradiance (W/m2)

4500 4000 3500 3000 2500 2000 30 1500 1000

25

500 0

0

50

100

150

200

250

300

20 400

350

Time (day) Fig. 6. Average daily solar irradiance and ambient temperature distributions during the year of 2015 for UKM, Bangi, Malaysia.

1100

200 Solar Irradiance PV Module Temp.

180

1000 900 2

160

Solar Irradiance (W/m )

o

PV Module Temperature ( C)

Multimeter Multimeter

800

140

700

120

600 100 500 80

400

60

300

40

200

20 0

100 7

8

9

10

11

12

13

14

15

16

17

18

0 19

Time (hr) Fig. 7. Hourly solar irradiance and PV module temperature over daytime.

44

A.N. Al-Shamani et al. / Solar Energy 150 (2017) 38–48

9 8

Current (A)

7

2

I-V, 1000W/m I-V, 800W/m2 2 I-V, 600W/m I-V, 400W/m2 2 P-V, 1000W/m P-V, 800W/m2 2 P-V, 600W/m P-V, 400W/m2

50

40

6 30 5 4

Power (W)

10

20 3 2

10

1 0

5

10

0 20

15

Voltage (V) Fig. 8. I-V and P-V curves for PV module under various solar irradiances.

Table 3 Characteristic of PV module under various solar irradiances. Solar irradiance (W/m2)

Isc (A)

Voc (V)

Pmax (W)

Fill factor (FF)

PV module temperature (°C)

Electrical eff. (gel)

400 600 800 1000

3.50 4.53 5.58 6.55

18.91 18.62 18.30 19.26

36.07 38.67 41.19 44.64

0.544 0.458 0.403 0.373

41.26 51.62 65.63 78.31

10.52 7.52 6.00 5.20

10 9

Current (A)

8

120

I-V, 1000 W/m2 2 I-V, 800 W/m 2 I-V, 600 W/m I-V, 400 W/m2 P-V, 1000 W/m2 P-V, 800 W/m2 P-V, 600 W/m2 P-V, 400 W/m2

110 100 90 80

7

70 6 60 5 50 4

40

3

30

2

20

1

10

0

5

10

15

20

Voltag (V) _ = 0.170 kg/s. Fig. 9. I-V and P-V curves PVT-SiC nanofluid, m

0

Power (W)

11

45

A.N. Al-Shamani et al. / Solar Energy 150 (2017) 38–48 Table 4 Characteristic of PVT-SiC module under various solar irradiances. Solar irradiance (w/m2)

Isc (A)

Voc (V)

Pmax (W)

Fill factor (FF)

PV module temperature (°C)

Electrical eff. (gel)

400 600 800 1000

2.99 4.30 5.76 7.35

20.23 20.36 20.44 20.52

47.93 69.92 92.31 114.92

0.793 0.798 0.783 0.761

34.62 39.61 45.61 50.62

13.88 13.67 13.57 13.53

4.2. Photovoltaic (PV) module (without the absorber and nanofluid) 100

The PV module without the absorber was experimentally tested, and the output power was logged at an interval of every 2 min. The data of the output power and the PV module temperature were recorded simultaneously. This enables the establishment of the PV power output, as well as its temperature. The PV module temperature and solar irradiance were recorded for an entire day, as shown in Fig. 7. The open circuit voltage Voc and short circuit current Isc were measured based on the test results. During experimental testing, the I-V curves referred to the modules under various solar irradiance ranges (400–1000) W/m2. Fig. 8 and Table 3 show the results of the PV module, where solar irradiance between (400–1000) W/m2 indicated changes in the Isc (3.50–6.55) A, while the PV module temperature increased from (41.26–78.31) °C.

GCPV System

80

o

Temperature ( C)

90

70 60 50 40 GCPVT NF System

30

4.3. I-V and P-V curves for PVT collector with nanofluid 600

700

800

900

1000

1100

1200

The electrical characteristics of the PV module can be represented by I-V, P-V plots. When measuring current-voltage characteristics, electrical losses become evident. The losses are indicated by decreased in the fill factor at high current, and a decrease in the open-circuit voltage at elevated PV module temperature. Fig. 9 and Table 4 show the I-V and P-V curves for the PVT-SiC nanofluid collector. The variation of the I-V and P-V for various solar irradiance were also shown for (400, 600, 800, 1000 W/m2) at a flow rate of 0.170 kg/s. The I-V curves can be sim-

Time(Minute) Fig. 10. GCPV and GCPVT nanofluid module temperatures over clear sunny day (7:00 AM- 7:00 PM).

101.7814°E, which is at The National University of Malaysia (UKM) - Bangi. Fig. 6 shows the average daily ambient temperature and solar irradiance distribution’s data for the year 2015.

1400

1000 Solar Irradiance GCPVT DC Voltage GCPV DC Voltage GCPV DC Power GCPVT Power

Power (W), DC Voltage (V)

1300 1200

900

1100

800

1000 900

700

800 700

600

600 500

500 400

400

300 200

2

500

Solar Irradiance (W/m )

20 400

300

100 0 400

500

600

700

800

900

1000

1100

200 1200

Time (Minute) Fig. 11. Power, DC voltage and solar irradiance over clear sunny day for GCPV and GCPVT-SiC nanofluid system.

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A.N. Al-Shamani et al. / Solar Energy 150 (2017) 38–48

plified so that the Isc increases linearly with the increase of solar irradiance (Lasnier, 1990). The Isc increased from 3.00 A at a solar irradiance of 400 W/m2, to 7.35 A at a solar irradiance 1000 W/m2, respectively. Meanwhile, Voc increased from 20.23 V to 20.52 V under similar solar irradiance condition. In fact, that the Voc decreased with increasing PV module temperature, but the Voc increased alongside the PV module temperature when nanofluid were used due to the enhancement in heat transfer. The Pmax increased from 47.94 W to 114.52 W. The electrical PVT-SiC nanofluid efficiencies were in the range of 13.33–13.88%, showing enhancement in the performance over the PV module only.

80

0

Temperature ( C)

70

rd

3 GCPV bottom rd 3 GCPVT front rd 3 GCPVT bottom Ambient Outlet fluid

65 60 55 50 45 40 35 30 25 400 7:00 AM

600

800

1000

1200 7:00 PM

Time (Minute)

Fig. 12. Ambient, water outlet, GCPV module and GCPVT-SiC nanofluid module temperature over clear sunny day from (7.00AM- 7.00 PM).

The 1.2 kWp GCPVT-SiC nanofluid system was built on the roof top of a prototype house. The data was recorded from 7:00 AM to 7:00 PM using data acquisition software. During field-testing, data was recorded every 1 min, which was later averaged for 5 min. Fig. 10 shows the GCPV and GCPVT nanofluid module temperatures data gathered from the test at the field. The temperature data comprised of T1 - T20, and it was evident that the GCPV module temperature was very high, reaching almost 78 °C at mid-afternoon compared to the GCPVT-SiC module temperature system. Fig. 11 shows the DC voltage and power difference between GCPV and GCPVT-SiC nanofluid systems. Moreover, the temperature of the GCPVT-SiC nanofluid module decreased hence, the power increased. Fig. 12 shows the ambient, water outlet, GCPV module and GCPVT-SiC nanofluid module temperatures over a clear sunny day, from 7.00 AM- 7.00 PM. The performance parameters of the GCPVT-SiC nanofluid system that were calculated were array yield, final yield, reference yield, performance ratio, PV module efficiency, system efficiency, and inverter efficiency. Fig. 13 shows the hourly energy production of the GCPV and GCPVT-SiC nanofluid system over a sunny day. It can be seen that the energy production from GCPVT-SiC nanofluid system exceeded the GCPV system due to the enhancement of heat transfer by the SiC nanofluid of the PVT module. The reason for this was due to the lower module’s temperature and thus increasing the electrical efficiency of the PV. Fig. 14 shows the average daily (array, final and reference) yield production. The monthly array and final yield values were 157.32 and 152.71 kWh/kWp respectively. Figs. 15 and 16 show the monthly energy yield, system performance ratio (PR), and (PV, system, inverter) efficiency for GCPV and GCPVT-SiC nanofluid, respectively. Fig. 15 observed that the values for monthly array yield and final yield obtained in March were 105.70 and 100.53 kWh/kWp, respectively. These values differ due to the PV module operating at higher temperatures. The monthly array and final yields of the GCPVT SiC nanofluid system, as shown in Fig. 16, observed that the highest values for monthly array yield and final yield were obtained in March, with values of (157.32) and (152.71) kWh/kWp, respectively. The lowest values

1

1 GCPV/T nanofluids

Total yeild (kWh)

0.9

0.9

GCPV

0.8

0.8

0.7

0.7

0.6

0.6

0.5

0.5

0.4

0.4

0.3

0.3

0.2

0.2

0.1

0.1

0

5

6

7

8

9

0 10 11 12 13 14 15 16 17 18 19 20 21 22

Time (hr) Fig. 13. GCPV and GCPVT-SiC nanofluid system total yield and power during one day.

Power (kW)

75

4.4. Performance of GCPVT-SiC nanofluid system

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A.N. Al-Shamani et al. / Solar Energy 150 (2017) 38–48

Array yield (kWh/kWp.d)

Final yield (kWh/kWp.d)

Reference yield (kWh/kWp.d)

7 6 5 4 3 2 1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Fig. 14. Array, final and reference yield for GCPVT-SiC nanofluid system.

120.000 100.000 80.000 60.000 40.000 20.000 0.000

Ya, Yf, kWh/kWp kWh/kWp

PR, %

PV eff., %

Sys. Eff., %

Inver. Eff., %

January

98.580

94.625

72.991

8.740

8.380

95.870

February

95.680

91.365

70.656

8.710

8.340

95.410

March

105.701

100.538

77.138

8.77

8.38

95.12

April

101.571

96.999

74.715

8.8

8.41

95.5

Fig. 15. The monthly energy yield, system performance ratio (PR), and (PV, system, inverter) efficiency for GCPV system.

for the monthly array yield and final yield were obtained in February with values of (145.11) and (140.71) kWh/kWp, respectively. The observed low yields during these months were due to lower solar irradiation and it reduced number of sun hours per day. The performance ratio (PR) of the GCPV system were in the range of 70.65–74.71%, while the performance ratio (PR) for GCPVT-SiC nanofluid system were in the range of 95.49–95.92%. The electrical efficiency of the GCPV was about 8.8%. In addition, the electrical efficiency of the GCPVT-SiC nanofluid was about 13.5%. The system efficiency for GCPV was at about 8.4%, while the system efficiency of the GCPVT-SiC nanofluid was at about 13.1%. 5. Conclusions Grid interconnection of PV power generation system has the advantage of increased effective utilization of the generated

power. However, the technical requirements from both the utility power system grid side and the PV system side need to be satisfied to ensure the safety of the PV installers and the reliability of the utility grid. Experimental studies on the performance of GCPV and GCPVT SiC nanofluid have been carried out. GCPV and GCPVT-SiC nanofluid system parameters, such as the mean PV module temperature, outlet temperature, (array, final and reference) yield, performance ratio, and (PV, inverter, and system) efficiencies have been evaluated. It can be seen that the performance ratio of the GCPVT-SiC nanofluid has been enhanced to an average of 30%. The highest values for monthly array yield and final yield were obtained in March, with values of (157.32) and (152.71) kWh/kWp, respectively. It is concluded that the GCPVT-SiC nanofluid system is more efficient to use, and resulted in the highest energy production compared to GCPV system only. For future work, the effect of different size and survive area of nanoparticles, as well as new nano particles can be studied. Also, use of phase

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A.N. Al-Shamani et al. / Solar Energy 150 (2017) 38–48

180 160 140 120 100 80 60 40 20 0

Ya, kWh/kWp

Yf, kWh/kWp

PR, %

PV eff., %

Sys. Eff., %

Inver. Eff., %

January

149.705

145.015

95.489

13.513

13.094

96.900

February

145.110

140.713

95.713

13.524

13.110

96.970

March

157.326

152.711

95.762

13.526

13.117

96.975

April

151.39

147.145

95.922

13.528

13.125

97.023

Fig. 16. The monthly energy yield, system performance ratio (PR), and (PV, system, inverter) efficiency for GCPVT-SiC nanofluid system.

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