EXPERIMENTAL AND NUMERICAL INVESTIGATION OF PHOTO-VOLTAIC MODULE PERFORMANCE VIA CONTINUOUS AND INTERMITTENT WATER COOLING TECHNIQUES

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1 International Journal of Mechanical Engineering and Technology (IJMET) Volume 6, Issue 7, July 2015, pp , Article ID: Available online at ISSN Print: and ISSN Online: IAEME Publication EXPERIMENTAL AND NUMERICAL INVESTIGATION OF PHOTO-VOLTAIC MODULE PERFORMANCE VIA CONTINUOUS AND INTERMITTENT WATER COOLING TECHNIQUES Ali M. Rasham, Hussein K. Jobair, Akram A and Abood Alkhazzar Department of Energy Engineering / College of Engineering University of Baghdad ABSTRACT Experimental and numerical investigation of photovoltaic solar modules (PVSMs) performance via continuous water cooling technique (CCT) and intermittent water cooling techniques (ICT) has been investigated in present work. A New cooling technique had submitted for the (PVSM) as compared to previous works. In addition to analyze the enhancement for (PVSMs) temperature, cooling rate, output power, output energy, fill factor, and electrical efficiency. Experimental data were tabulated of (PVSMs) for both cooling techniques. A mathematical model for (PVSMs) were formulated. MATLAB code has been developed and written to solve mathematical model. Numerical integration of (1/3) Simpson's rule was used to estimate the energy enhancement. The average values of cooling rate for (ICT), and (CCT) were ( min ) and ( min ) respectively, than for non-cooling (PVSM). the enhancement of the output power, fill factor, electrical efficiency for (ICT), and (CCT) were (7.349 %) and (5.587 %), (6.313 %) and (2.630 %), (8.389 %) and (6.826 %) respectively, than for non-cooling (PVSM). The energy enhancement for (ICT) was ( %) for current work. By contrast, there were losses in energy for (CCT). Consequently, According to the obtained results, the enhancement for all parameters mentioned above were the better for (ICT) than for (CCT). Keywords: Optimisation of Solar Cells, Film Cooling, Cooling System of Solar Cells, Increasing Efficiency of Photovoltaic, Performance Enhancement of PV Solar Cells editor@iaeme.com

2 Ali M. Rasham, Hussein K. Jobair, Akram A and Abood Alkhazzar Cite this Article: Ali M. Rasham, Hussein K. Jobair, Akram A and Abood Alkhazzar, Experimental and Numerical Investigation of Photo-Voltaic Module Performance Via Continuous and Intermittent Water Cooling Techniques. International Journal of Mechanical Engineering and Technology, 6(7), 2015, pp INTRODUCTION Iraq was began to use renewable energy resources especially, with the successive depletion of conventional resources. The burning of conventional fossil fuels leads to atmosphere Pollution. In Iraq, abundance of land and sunny weather made it a good resource for solar energy applications. Consequently, renewable energy systems has become a good alternative way to facing this crisis. Solar photovoltaic systems have solution for the energy demand, which converts solar radiation into direct current electricity using semiconductors that display the Photovoltaic effect. Obviously, in order to decrease the cost of photovoltaic production, increasing the efficiency and collecting more energy had been focused. For that, the emphatic efforts are being made in this field. Even though, the efficiency of the photovoltaic system is low and is affected by solar radiation, temperature, dust, wind velocity, and humidity, the solar photovoltaic market grows a rapid rate. The majority of a previous researches used the (CCT) cooling system. In this paper, a comparison between the (CCT) and (ICT) has been investigated. The main aims were to submit a new cooling technique for the (PVSM), enhance output power, output energy, Fill factor, and efficiency. Indeed, the water used as a practical coolant for solar panels. Salih Mohammed Salih, etc., [1] presented experimentally the Performance enhancement of PV array based on water spraying technique. The economical results were achieved as result of the power saving increases 7w/degree at midday. Jothi Prakash k, etc., [2] analyzed the optimisation of solar PV panel output: a viable and cost effective solution. The cooling rate for the solar cells is 2.3 /min based on the concerned operating conditions, which means that the cooling system will be operated each time for 10 min, in order to decrease the module temperature by 7. Abdelrahman, M, etc., [3] offered the experimental investigation of different cooling methods for photovoltaic module. The results show that the daily output power of the PV cooling module increased up to 22 %, 29.8% and 35% for film cooling, back cooling and combined film back cooling module, respectively compared to non-cooling module. L. Dorobanțu, etc., [4] investigated the experimental assessment of PV Panels front water cooling strategy. The open voltage of the panels is increasing when its temperature decreasing and due to the lower operating temperature, its life cycle could be increased. Loredana Dorobanţu, etc., [5] studied the Increasing the efficiency of photovoltaic panels through cooling water film. For mono-crystalline silicon cells, the reduced power is (0.4% / C). Due to the front water cooling of the panel, the electrical yield has return a plus of about 9.5%. Ana-Maria Croitoru, etc., [6] reviewed the water cooling of photovoltaic panels from passive house located inside the university Politehnica of Bucharest. This article has attempted to present a way to increase the efficiency of photovoltaic panels. It is a water cooling system, which functions as a heat exchanger. With this system the panel's temperature decreases, so the electricity production is increased. T. Chinamhora, [7] introduced the PV Panel Cooling System for Malaysia Climate Conditions. During clear days, the cooling 86 editor@iaeme.com

3 Experimental and Numerical Investigation of Photo-Voltaic Module Performance Via Continuous And Intermittent Water Cooling Techniques system increases the electrical efficiency by around 10-22% whereas during cloudy days, the cooling system decreases the electrical efficiency by 3-20%. K.A. Moharram, etc., [8] researched the Enhancing the performance of photovoltaic panels by water cooling. Based on the heating and cooling rate models, it is found that the PV panels yield the highest output energy if cooling of the panels starts when the temperature of the PV panels reaches a (MAT) of 45. The (MAT) is a compromise temperature between the output energy from the PV panels and the energy needed for cooling. Stefan Krauter, [9] showed experimentally the Increased electrical yield via water flow over the front of photovoltaic panels. Water help keeping the surface clean, and reduces reflection by 2 3.6%, decreases cell temperatures up to 22 and the electrical yield can return a surplus of 10.3%; a net-gain of 8 9% can be achieved even when accounting for power needed to run the pump. Efstratios Chaniotakis, [10] proposed Modelling and Analysis of Water Cooled Photovoltaic. The former uses water in order to cool the panel while the latter uses air as the coolant. The results of the project showed that the most efficient and promising system is the water cooled photovoltaic. 2. METHODOLOGY The increasing in the ambient temperature at which PV systems work, had adversely effect on the PV module efficiency. Nowadays, the PV cooling is the common method to reduce the PV temperatures and to enhance the PV performance. In this paper, the (CCT) and (ICT) are shown below as follows: 2.1. Experimental Equipment Two identical Mono-crystalline solar photovoltaic modules were used with same orientation (facing south and tilted with 45 o from the horizon). One of them was connected to the close loop hydration cooling system, and the second stayed without water cooling, as shown in Fig. (1). The (PVSM) specifications were mentioned in table (1). (a) (b) Figure 1 PVSMs: (a) with water film cooling and (b) without water film cooling. Table 1 Technical specifications of Mono-crystalline (PVSM). Area V I V I P () 3.25 () 17.2 () 2.9 () 50 () The cooling system consist of a submersible pump (8W) used to pump the water, a perforated pipe with equally distance holes connected on the top end of PV solar module, used to distribute a thin water layers over a front face of (PVSM) and, a storage tank used to collect the falling water. The discharge hot water is very useful for domestic applications, buildings, and other applications, especially in the remote areas. On clear day of May 24, 2015 the tests were done under the outdoor exposure 87 editor@iaeme.com

4 Ali M. Rasham, Hussein K. Jobair, Akram A and Abood Alkhazzar (a) (b) (c) in Baghdad city with latitude of and longitude of , Beside the Laboratory of Energy Engineering department for University of Baghdad. The (PVSMs) were connected to Solar Module Analyzer PROVA 200A used to test the characteristics (V, I, P ), Solar Power Meter TES1333R used to measure the total incident solar radiation, and finally, a pump used to pump thin layers of water over a front face of PV solar module, as shown in Fig. (2). The temperatures of the (PVSMs) and ambient temperature were measured by a digital thermometer (TPM- 10) attached firmly to the back of the module. Figure 2 (a) Solar Module Analyzer PROVA 200A, (b) Solar Power Meter TES1333R, (c): A submersible pump Experimental Procedure (CCT) and (ICT) were used in this work to identify the best technique of (PVSMs). Two identical (PVSMs) were used, the film water spraying over a front face of the first (PVSM), from perforated pipe connected on the top end of (PVSMs) for both techniques. While, the second (PVSMs) remained without cooling. Incident solar radiation, temperatures of ambient and of both (PVSMs), open circuit voltage, short circuit current, and finally the output power, were measured. For both cooling techniques, one of the (PVSMs) was sprayed by thin water layers for (10 min) before the beginning of experiment. The (CCT) had begun from 10:10 am to 10:45 am, in this test the pump kept on continuous work for (35 minute), and the above parameters were measured every (5 minutes). After (10 minutes), the (ICT) was began from 10:55 am to 11:30 am, in this test the pump was turned on for (0.5 minute) and turned off for (3 minutes). At the end of each cooling period the measurements previously mentioned were tabulated in table (1) and (2) respectively. 3. MATHEMATICALAL MODEL The quality of (PVSM) can be predicted by the fill factor (FF), whichh is affected by the module surface temperature. It represents the ratio of maximum output power to the multiplication of the short circuit current (! " ) and the open circuit voltage ) [11, p.478].! " )# (1) The electrical output power ( ) to the solar input power representss the efficiency $) of (PVSMs), it is formulated as follows [11, p.480] : $ %& '( ) (2) $! " ) 4) (3) The net output power and enhancement of cooling (PVSM) can be expressed in Eqs. (4) and (5) respectively. Δ +,- +,-./) (W) (4) 88 editor@iaeme.com

5 Experimental and Numerical Investigation of Photo-Voltaic Module Performance Via Continuous And Intermittent Water Cooling Techniques 6 % Δ +,-. +,-8 ) +,-8 ) 100 (5) The energy of (PVSMs) and the pump energy can be written as in Eqs. (6) and (7) respectively. ; +,- <=><?@A>= Bh> D?=E> FG>=.BH>)# (J) (6) ;/ I J B) J) (7) Also, the pump energy was considered from the pump power multiplied by operation time for both cooling techniques. The net energy of cooling (PVSM) was represented the difference between the energy of cooling (PVSM) and pump energy, which can be written as: Δ; +,- ; +,-.;/) J) (8) The enhancement in energy, fill factor, and electrical efficiency for both (PVSMs) can be written as respectively: ; 6 % Δ; +,-.; +,-8 ) ; +,-8 ) 100 (9) 6 % +,-. +,-8 ) +,-8 ) 100 (10) $ 6 % $ +,-.$ +,-8 $ +,-8 ) 100 (11) Finally, the cooling rate of cooling (PVSM) is represents the rate of the temperature difference between both (PVSMs) with and without water cooling, and it can be formulated as: L M AN B ) min ) (12) 4. NUMERICAL ANALYSIS The numerical technique used to simulate the behavior of (PVSMs). Computer code for MATLAB software has been developed and written to solve mathematical model. The electrical output energy can be estimated from the power-time curve, which was represented the area under the curve. A numerical integration of 1/3) Simpson's rule was used to estimate the energy of (PVSMs). The least-squares regression of curve fitting was used in this analysis which is the most common technique of finding the best fit to experimental data. 5. RESULTS AND DISCUSSION Experimental and numerical investigation of Mono-crystalline (PVSMs) via (CCT) and (ICT) at Baghdad climate conditions has been analyzed in this work. At both techniques, one of the (PVSMs) was sprayed by thin film water layers which was used as antireflection material in addition to using it as coolant fluid and as cleaning material from dust and others, while the second (PVSM) was remained without cooling. A comparison was made between cooling and non-cooling (PVSM) at both techniques, in order to knowledge whether the best performance had. As renewable energy resources are stochastic quantities. Consequently, they are fluctuated randomly with time. The behavior of (PVSMs) temperature, cooling rate, output power, Fill factor, and electrical efficiency will be discussed in this section. In general, the enhancement of cooling (PVSM) parameters mentioned above was pluperfect in current work. Figs. 1 and 2 illustrates the decreasing of cooling (PVSM) temperatures and behavior of cooling rate respectively for (CCT) and (ICT), compared to the noncooling (PVSM). The enhancement of cooling (PVSM) cooling rate of (ICT) was better than the (CCT). It is worth mentioning, that the cooling effect is based on the evaporation process more than the flowing of the water. Also, in Fig. 1 the behavior 89 editor@iaeme.com

6 Ali M. Rasham, Hussein K. Jobair, Akram A and Abood Alkhazzar of ambient temperature was close to almost form the cooling (PVSM) temperature. The average values of cooling rate for (CCT) and (ICT) were ( min ) and ( min ) respectively, as shown in table (4). Consequently, the cooling rate of cooling (PVSM) at (ICT) was the best. Figs. 3a and 3b illustrate the enhancement of cooling (PVSM) output power for (CCT) and (ICT) respectively. The output power of the cooling (PVSM) increases with decreasing of its temperatures as a result of the sharp increase in the voltage and decrease of the output current. Table (5) showed that the cooling (PVSM) output power enhancement for both cooling techniques. Observably, that the output power enhancement of (ICT) and (CCT) were (7.349 %) and (5.587 %) respectively, than for non-cooling (PVSM). Accordingly, the enhancement of output power for (ICT) was the best. Also, the energy enhancement of cooling (PVSM) was just for the (ICT) than for (CCT). The energy enhancement for (ICT) was ( %) for current work of pump power (8 W), in addition to others value for energy enhancement were tabulated in table (6) for various values of pump power. By contrast, there was losses in energy for (CCT) due to use a pump for full time. Figs. 4a and 4b illustrates the enhancement of cooling (PVSM) fill factor for both cooling techniques. As in the above results, the enhancement of cooling (PVSM) fill factor was the better for (ICT) than for (CCT). The average fill factor enhancement for (ICT) and (CCT) were (6.313 %) and (2.630 %) respectively, than for non-cooling (PVSM) as shown in table (8). Indeed, Fill factor considers the effect of internal resistances of the (PVSM). The resistances are series resistance and shunt resistance, the series resistance tends to reduce the output voltage while the shunt resistance affect the output current. The resistances increases with temperature which reduces the maximum power output. This decreasing is accompanied by decreasing in open circuit voltage. Therefore the effect of cooling technique was to enhance the (PVSM) fill factor. Figs. 5a and 5b illustrates the enhancement of cooling (PVSM) efficiency for both cooling techniques. In the same manner, the enhancement of cooling (PVSM) efficiency was the better for (ICT) than for (CCT). The average efficiency enhancement for (ICT) and (CCT) were (8.389 %) and (6.826 %) respectively, than for non-cooling (PVSM) as shown in table (7). In spite of that the test conditions for (ICT) and (CCT) were taken at different periods. Also, because the data of both techniques were recorded in the same time for the cooling and noncooling (PVSM) and it was close to some extent. Nevertheless, a comparison between a cooling (PVSMs) at both cooling techniques was possible. As a result, determine whether which best performers has been possible. Finally, the Fig. 6 illustrates a comparison between the efficiency behaviors for both cooling techniques. Apparently, the performance of cooling (PVSM) for (ICT) was the better than for (CCT) editor@iaeme.com

7 Experimental and Numerical Investigation of Photo-Voltaic Module Performance Via Continuous And Intermittent Water Cooling Techniques 54 ( Bahavior of ambient and PV modules temperatures for continuous coolin 54 ( Bahvior of ambient and PV module temperaturesfor intermittent cooling tech Temperature ( o C) PV module temperature without cooling Fitting of PV module temperature without cooling PV module temperature with cooling Fitting of PV module temperature with cooling Ambient temperature Fitting of ambient temperature Temperature ( o C) PV module temperature without cooling Fitting of PV module temperature without cooling PV module temperature with cooling Fitting of PV module temperature with cooling Ambient temperature Fitting of Ambient temperature Time ( min ) Time (min ) Figure. 1 Variation of ambient and PV solar modules temperatures with time at a) (CCT). b) (ICT). Figure 2 Cooling rate of cooling PV solar module at a) (CCT). b) (ICT). 46 ( Enhancement of PV module output power by continuous water cooling 48 ( Enhancement of PV module output power by intermittent water cool PV module output power (W) Pout without cooling Fitting of Pout without cooling Pout with cooling Fitting of Pout with cooling PV module output power ( W) Pout without Fitting of Pou Pout with co Fitting of Pou Time (min) Time ( min ) Figure.3. Variation of PV solar modules output power with time at a) (CCT). b) (ICT) editor@iaeme.com

8 Ali M. Rasham, Hussein K. Jobair, Akram A and Abood Alkhazzar (Enhancement of PV module fill factor by continuous cooling) FF without cooling Fitting of FF without cooling FF with cooling Fitting of FF with cooling ( Enhancement of PV module FF by intermittent water cooling ) FF without cooling Fitting of FF without cooling FF with cooling Fitting of FF with cooling Fill factor of PV m odule ( FF % ) P V m odule Fill Factor ( FF % ) Time (min) Time ( min ) Figure.4.Variation of PV solar modules fill factor with time at a) (CCT). b) (ICT). Efficiency ( η % ) ( Enhancement of PV module efficiency by continuous water cooling ) η without cooling Fitting of η without cooling η with cooling Fitting of η with cooling E f f i c i e n c y ( η % ) ( Enhancement of PV module efficiency by intermittent water cooling η without cooling Fitting of η without cooling η with cooling Fitting of η with cooling Time ( min ) Time ( min ) Figure 5 Variation of PV solar modules efficiency with time at a) (CCT). b) (ICT) ( Comparison of PV module efficiency at continuous and intermittent cooling ) η at continuous cooling Fitting of η at continuous cooling η at intermittent cooling Fitting of η at intermittent cooling PV module efficiency ( η % ) Time ( min ) Figure 6 Efficiency comparison for cooling PV module at both cooling techniques editor@iaeme.com

9 Experimental and Numerical Investigation of Photo-Voltaic Module Performance Via Continuous And Intermittent Water Cooling Techniques Table 2 Data of (PVSMs) without and with (CCT). Time (min) N ( ) N 8 ( ) N ( ) 8 (W) (W)! "8 (A)! " (A) 8 (V) (V) G ( ) Table 3 Data of (PVSMs) without and with (ICT). Time (min) N ( ) N 8 ( ) N ( ) 8 (W) (W)! "8 (A)! " (A) 8 (V) (V) G ( ) editor@iaeme.com

10 Ali M. Rasham, Hussein K. Jobair, Akram A and Abood Alkhazzar Table 4 Cooling rate of PV modules at (CCT) and (CCT). Technique Continuous cooling Intermittent cooling Average of cooling rate ( min ) Table 5 Percentage of PV module power enhancement for (CCT) and (ICT). No. Pump power (W). Power enhancement for (CCT) Power enhancement for (ICT) % % % % % % % % % % % % % % % % Table 6 Percentage of PV module energy enhancement for (ICT) according to pump power. No. Pump power (W). Energy enhancement % % % % % % % % % Table 7 Enhancement of PV module fill factor and efficiency for (CCT) and (ICT) Cooling techniques PV module Fill factor PV module efficiency Continuous cooling % % Intermittent cooling % % 94 editor@iaeme.com

11 Experimental and Numerical Investigation of Photo-Voltaic Module Performance Via Continuous And Intermittent Water Cooling Techniques NOMENCLATURE Symbols Description T Temperature ) out output P Power (W) in input I Current (Ampere) p Pump V Voltage (Volt) e Enhancement G Irradiance ) m Measuring time A Area ( ) r rate E Energy (Joule) PVM Photovoltaic module t Time (sec.) C Cooling Greek symbols $ Efficiency Subscripts Description Difference for cooling module photovoltaic. a Ambient 1 PV Solar Module without cooling. Abbreviations 2 PV Solar Module with cooling. FF Fill Factor sc Short circuit PVSM Photovoltaic solar module oc Open circuit CCT Continuous cooling technique max Maximum value ICT Intermittent cooling technique 6 CONCLUSIONS The results of the present study lead to the following conclusions: 1. In current work, a new cooling technique it is (ICT) was submitted to enhancing the (PVSM) efficiency compared to a previous works. 2. Generally, the results show that the cooling (PVSM) enhancement of (ICT) was the best than from the (CCT). 3. It is worth mentioning, that there is an energy enhancement for (ICT). By contrast, there was a losses in (CCT) because a large amount of energy pump which used continuously was subtracted from energy of cooling (PVSM). 4. The cooling (PVSM) temperature, cooling rate, output power, fill factor, and electrical efficiency were enhanced as compared to (PVSM) without cooling. REFERENCES [1] Salih Mohammed Salih, Osama Ibrahim Abd, Kaleid Waleed Abid, [Performance enhancement of PV array based on water spraying technique], International Journal of Sustainable and Green Energy 2015; 4(3-14): [2] Jothi prakash k & Gopinath.N, Dr.V.Kirubakaran, [Optimisation of solar PV panel output: a viable and cost effective solution], International Journal of Advanced Technology & Engineering Research (IJATER), National 95 editor@iaeme.com

12 Ali M. Rasham, Hussein K. Jobair, Akram A and Abood Alkhazzar Conference on "Renewable Energy Innovations for Rural Development", ISSN No: , [3] Abdelrahman, M, Eliwa, A, Abdellatif, O.E, [Experimental Investigation of Different Cooling Methods for Photovoltaic Module], Joint Propulsion Conferences, July 14-17, 2013, San Jose, CA, 11th International Energy Conversion Engineering Conference. [4] L. Dorobanțu, M. O. Popescu, C. L. Popescu, and A. Crăciunescu, [Experimental Assessment of PV Panels Front Water Cooling Strategy], International Conference on Renewable Energies and Power Quality (ICREPQ 13), Bilbao (Spain), 20th to 22th March, 2013, ISSN X, No.11, March [5] Loredana Dorobanţu, Mihai Octavian Popescu, [Increasing the efficiency of photovoltaic panels through cooling water film], U.P.B. Sci. Bull., Series C, Vol. 75, Iss. 4, ISSN [6] Ana-Maria CROITORU, Adrian BADEA, [water cooling of photovoltaic panels from passive house located inside the university Politehnica of Bucharest], U.P.B. Sci. Bull., Series C, Vol. 75, Iss. 3, 2013, ISSN [7] T. Chinamhora, G. Cheng, Y. Tham, W. Irshad, [ PV Panel Cooling System for Malaysia Climate Conditions], Proceeding of international Conference on Energy and sustainability 2013, NED University of Engineering & Technology, Karachi, Pakistan. [8] K.A. Moharram, M.S. Abd-Elhady, H.A. Kandil, H. El-Sherif, [Enhancing the performance of photovoltaic panels by water cooling], Ain Shams Engineering Journal (2013) 4, [9] Stefan Krauter, [Increased electrical yield via water flow over the front of photovoltaic panels], Solar Energy Materials & Solar Cells 82 (2004) [10] Efstratios Chaniotakis, [Modelling and Analysis of Water Cooled Photovoltaic], Thesis, MSc Energy Systems and the Environment Department of Mechanical Engineering, University of Strathclyde. [11] Soteris A. Kalogirou, [Solar Energy Engineering Processes and Systems], Copyright 2009, Elsevier editor@iaeme.com