Effects of Maintenance on Performance of Grid Connected Rooftop Solar PV Module System

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1 Effects of Maintenance on Performance of Grid Connected Rooftop Solar PV Module System Sumit Sharma 1, Devendra Kumar Vishwakarma 2, Prateek Bhardwaj 3, Ritesh Mathur 4 1,2,3,4 Department of Mechanical Engineering, ACEIT, Jaipur, Abstract Solar power plant is dependent on the transformation of sunlight into electricity, either directly using photovoltaic (PV), or indirectly using concentrated solar power. Photovoltaic s a simple and elegant method of harnessing the sun's energy. PV modules (solar cells) are unique in that they directly convert the incident solar radiation into electricity, with no noise or pollution making them robust, reliable and long lasting. In this analysis, an attempt has been made for evaluating effect of maintenance on energy efficiency, CUF and PR and performance evaluation by annual CUF and PR of 62 KWp Grid-connected rooftop solar PV plant. Applying the first law of thermodynamics, energy analysis was accomplished.the operating and electrical parameters of a PV array comprise PV module temperature, open-circuit voltage, short-circuit current, fill factor, etc. were experimentally determined and tabulated for two days (1 Dec and 5 Dec. 2016) at Jaipur. The performance and efficiency parameters have been studied and compared for both the days i.e. before and after maintenance. Results showed that the performance parameters can be improved by removing the dust and dirt or by cleaning the modules at regular interval. Keywords Photovoltaic s, energy, CUF, PR I. INTRODUCTION Solar energy has huge potential and its use is growing fast, yet in many quarters it is still viewed with concern about costs and doubts over efficacy. The research and development efforts have also helped in better efficiency, affordability and quality of the products. Over the years, renewable energy sector in India has emerged as a significant player in grid connected power generation capacity [1]. India is endowed with a very vast solar energy potential as it is located in the equatorial sun belt of the earth, thereby receiving abundant radiant energy from the sun [2]. Solar energy due to its intermittent nature is not available for a long time during the day. Solar Photovoltaic is a key technology option to realize the shift to a decarbonized energy supply and is projected to emerge as an attractive alternate electricity source in the future. The solar energy can be utilized through solar photovoltaic technology which enables direct conversion of sunlight into energy. India is having fourth largest electricity generation capacity in the world after US, China and Russia. As on June 2016 renewable based capacity became 43,727 MW in the total installed capacity of 303,100 MW [3]. The Ministry of New and Renewable Energy (MNRE), Government of India has announced an ambitious solar target of 100,000 megawatts (MW) installed capacity by 2022, of which 40,000 MW of solar photovoltaic (PV) systems are to be installed on rooftops [4]. Solar energy reaching to the surface of the earth can be utilized directly in two ways viz. directly converting the solar radiation to the electricity for useful purposes by the means of solar photovoltaic (SPV) modules or by heating the medium source for low temperature heating applications. PV, the technology which converts sunlight directly into electricity, is among the fastest growing segments of the renewable energy industry. Some of the factors driving the growth of this segment are: concerns towards carbon emissions, energy security and the rising prices of fossil fuels [5]. DOI: /IJRTER ZWJZV 190

2 The solar radiation reaching the earth s surface has two components: direct or beam radiation, which comes directly from the sun's disk; and diffuse radiation, which comes indirectly. The most common measurements of solar radiation is total radiation on a horizontal surface often referred as GHI (global horizontal irradiance) on the surface which is the sum of the direct and diffuse components. It is measured by pyranometer. When the PV modules are exposed to sunlight, they generate direct current DC electricity. An inverter then converts the DC into AC electricity, so that it can feed into one of the building s AC distribution boards ( ACDB ) without affecting the quality of power supply. PV systems usually require an inverter, which transforms the direct current (DC) of the PV modules into alternate current (AC), most usages being run on AC [6][7]. II. LITERATURE REVIEW The performance of solar power plants is best defined by the Capacity Utilization Factor (CUF), which is the ratio of the actual electricity output from the plant, to the maximum possible output during the year. The performance ratio is the other most important variable for evaluating the efficiency of a PV plant. It is the ratio of actual energy yield to nominal energy yield or theoretically possible energy outputs. Since there are several variables which contribute to the final output from a plant, the CUF varies over a wide range. These could be on account of poor selection /quality of panels, derating of modules at higher temperatures, other design parameters like ohmic loss, atmospheric factors such as prolonged cloud cover and mist. R. Khatri [8] investigated about design and assessment of solar PV plant and environmental aspect related with the energy generated with PV plant i.e. reduction in carbon emission and carbon credits earned was also considered. The capacity utilization factor of the proposed plant is nearly The carbon credits that can be earned from the plant was results as ton CO 2. S. A. Sulaiman et al. [9] analyzed the effects of dust on the performance of PV panels by using artificial dust (mud and talcum) particles on solar panels. The reduction in the peak power generated can be up to 18%. The accumulated dust on the surface of photovoltaic solar panel can reduce the system s efficiency by up to 50%. F. Mejia et al. [10] conducted experiment on the effect of dust on solar photovoltaic systems. Soiling losses have their largest impact during the long dry summers. The losses caused by accumulation of dust were estimated to be per day in relative solar conversion efficiency. After the rain event in the fall the efficiency increased to 7.1% a similar value to that observed in the spring further suggesting that dust had accumulated on the site. D.S. Rajput et al. [11] studied experimentally the electrical performances of photo-voltaic panels for the effect of deposited dust particles. Result shows that the maximum efficiency 6.38%, minimum 2.29% without dust & maximum efficiency 0.64%, minimum 0.33% with dust. The result shows that dust considerably reduces the power production by 92.11% and efficiency as 89% and recommended essential provision of auto cleaning mechanism to remove the dust particles from the surface of the panel in order to ensure high performance. M.S. Vasisht et al. [12] conducted experiment to determine the effect of seasonal variations on performance of 20 kwp solar PV installation. It produces an average daily yield of approximately 80 kwh for the past two years which translates to an annual yield of 28.9 MWh. The Capacity Utilization Factor (CUF) of the SPV system is 16.5%, and average Performance Ratio (PR) is around 85%. PR of the SPV system is correlated with the behaviour of SPV modules in different seasons, with module temperature (Tmod) as the key factor of comparison. T. Srivastava et al. [13] conducted experiment on energy analysis of 36 W solar photovoltaic module and observed that the PV module temperature has a great effect on the exergy efficiency, and it can be improved if the heat can be removed from the PV module surface. The PV exergy efficiency decreases as the ambient temperature increases due to increasing cell temperature and irreversibility while the output electricity All Rights Reserved 191

3 III. EXPERIMENTAL SETUP In the present study an experimental investigation was carried out for performance analysis of 62 kw Grid-connected Rooftop Solar Photovoltaic module arrays system. Initially all the parameters like intensity of solar radiation I s, ambient temperature Ta, cell temperature T c, wind speed v, V oc, I sc, V m, I m were noted from 9am to 5pm with difference of 15 min. Then by using these parameters, calculate fill factor, max. power produced, energy efficiency for each noted readings. In the same way all the parameters were noted again after the maintenance of the system in which dusting and water cleaning of plates occurs, calculate the efficiencies of the system. Based on the performance & output parameters, the effect of maintenance is evaluated by plotting various curves between irradiance & efficiencies. For this study, the rooftop solar PV module system mounted on VISHWAKARMA BLOCK Mechanical Engg. Dept. SKIT, Jaipur (26 55 N latitude, E longitude) has been chosen. This SPV system was commissioned in Sep and has been performing optimally to date. The system consists of 200 polycrystalline silicon PV modules of 310 Wp each. In order to achieve optimal system voltage, these modules are connect in series and forming an array. Each array contains 10 module of 310 W. so an array having 3100 W and total 20 arrays mount on vishwakarma block having the generation capacity of 6200 W or 62 KW. Each module consists of 72 cells and has an area of 1.94 m 2. Since the plant is on the roof of the mechanical building, the SPV system had to be installed with tinkering with the rooftop surface to avoid water leakage in the building during monsoon season. The module mounting structures are made up of galvanized mild steel. The SPV system is being protected by a lightning arrester, super-earth kits and isolator switches to avoid voltage surges. A remote monitoring system called SCADA has been installed in the inverter room of the SPV plant which records the real-time data and maintains the database of the previous data. The GHI and power output data are being collected at an intervals of 15 min. The power generation patterns from the SPV system during different days corresponding to changes in weather conditions are studied. Fig. 1 Detailed dimensional drawing of module. Fig. 2 Photographic view of a part of the installed PV setup A SR20-D2 secondary standard pyranometer are installed and connected in series with the modules, used to measure solar irradiance. The performance analysis of an SPV system involves evaluation of various instantaneous parameters that are recorded by the data acquisition system incorporated in All Rights Reserved 192

4 SPV system. However, the effective period of generation (EPG) is the period during which the instantaneous power output is at least 25% of the installed capacity, which is in the period 09:00 17:00 hour. Table 1. SPECIFICATIONS OF PHOTOVOLTAIC MODULE AND INVERTER Description Specifications Cell Type Virtus II (Polycrystalline), 156*156 mm, 72 (6*12) Pcs in series Module Efficiency 16% Electrical Characteristics : At STC* At NOCT** Max. Power (P max.) 310 W 230 W Max. Power current (I mp ) 8.38 A 6.80 A Max. Power voltage (V mp ) 37.0 V 33.8 V Short circuit current (I sc ) 8.80 A 7.10 A Open circuit voltage (Voc) 45.0 V 42.1 V Normal Operating Cell Temperature C Max. Operating Temperature Rating Max. PV Input Power of inverter Max. PV Input Voltage of inverter Nominal AC output Power of inverter Max. AC output apparent Power Max. AC output current 45 C + 2 C -40 C~ +85 C 52000W 1000 V 50000W VA 80 A Operating Ambient Temperature Range Operating -40 C to 60 C Grid frequency range 47~53Hz Max. Efficiency 98.9 % *Values at Standard Test Conditions (Solar Irradiance 1000 W/m 2, AM 1.5, Cell Temp. 25 C) **Values at Normal Operating Cell Temperature (Solar Irradiance 800 W/m 2, AM 1.5, Ambient Temp. 20 C, Wind speed 1 m/s) IV. CALCULATIONS These are some formulas which are used during calculations work. (i) The Energy Efficiency: [14-16] Where Annual yield = Total Energy generation (kwh) in one year (365 days) And Nominal energy yield =GHI Rated module efficiency Total PV area (in m 2 ) Where GHI is Global Horizontal Irradiation (in kwh/m 2 All Rights Reserved 193

5 V. DESIGN PARAMETERS FOR MULTI-CRYSTALLINE SPV MODULE (BEFORE AND AFTER MAINTENANCE) 5.1 Intensity of Solar irradiation Is : Fig. 3 shows the variation of intensity of solar radiation and ambient temperature w.r.t time on 1 Dec.2016 and 5 Dec The maximum and minimum solar radiation intensities were found to vary between (at pm.) and W/m 2 (5.00 pm.) The ambient temp. is K at 9.00 am and it increase upto K at 1.30 pm and after variations it reaches on K at 5.00 pm. After dusting and cleaning of panels with water, all the parameters are noted on 5 Dec. from 9 am to 5 pm. The climate or weather conditions on the site is completely same as before maintenance day as not much variation shows in the readings of ambient temperature and wind speed so it can say that the change occurs in energy and performance of the plant due to the maintenance effect. (a) (b) Fig. 3 Variation of intensity of solar irradiation& ambient temp. w.r.t time on 1 Dec.2016 and 5 Dec The increase in overall production of the day shows the impact of maintenance and its desirability. The maximum and minimum solar radiation intensities were found to vary between (at pm.) and 98.3 W/m 2 (5.00 pm.) The ambient temp. is K at 9.00 am and it increase upto K at 2.45 pm and after variations it reaches on K at 5.00 pm. Before maintenance, the cell temperature is K at 9.00 am and it increase upto K at 1.30 pm and after variations it reaches on K at 5.00 pm. The wind speed was found to vary between 1.24 m/s and 3.13 m/s with an average wind speed of 2.4 m/s whereas after maintenance the cell temperature is K at 9.00 am and it increase upto K at 1.00 pm and after variations it reaches on K at 5.00 pm. The wind speed was found to vary between 1.52 m/s and 3.71 m/s with an average wind speed of 2.38 m/s. This affects the convective heat transfer coefficient between the PV array surface & the ambient air. 5.2 Energy Efficiency The variations of energy efficiency with respect to time are plotted in Fig. 4 The energy efficiency of the PV module is maximum at morning am and also at 1.45 pm. PV module temperature should be kept near the cell operating or in other words, PV module temperature should be controlled by surface cleaning of the panel using water. In order to have maximum energy efficiency, PV module temperature should be kept near the cell All Rights Reserved 194

6 Fig. 4 variations of energy efficiency w.r.t time VI. CUF & PR CALCULATION The total yield of the system from the commencement on 20 th October, 2016 is KWh and the net annual yield, (1 Dec to 30 Nov. 2016) Ynet (annual) during this period was kwh. and the annual average daily yield over the study period is 269 kwh. The nominal energy yield is obtained by the product of Annual GHI of Jaipur is 5.3 kwh/m 2 /day, rated module efficiency (16%) and total PV area (1.94*200) m 2. Hence the annual CUF and the annual performance ratio of the plant is = % = % The CUF and PR of the plant on 01Dec All Rights Reserved 195

7 Volume 02, Issue 0X; Month [ISSN: ] = 32.88% =49.57% Similarly the CUF and PR of the plant on 05 Dec = 45.36% =68.38% VII. CONCLUSIONS From this research work we conclude the followings: (a) Before maintenance, the average energy efficiency between 9 am. to 5 pm. is 8.24 % and peak energy efficiency is % at 10.00am. After maintenance average energy efficiency is increasing upto 8.44 %and peak energy efficiency is % at am. (b) The Plant Performance parameters are also observed on annual and daily basis. The annual energy yield is kwh upto 1 Dec and calculated nominal energy yield is kwh. Hence the calculated annual CUF of the system is which lies within the range of CUF of well performing solar plants. The calculated PR of the system is 74.06% which shows that plant operates as per estimated performance from metered data and operating condition of system. (c) The comparison or improvement in plant performance shows by obtaining CUF and PR values before and after maintenance on both the experiment days. The CUF of the system is 32.88% before maintenance and 45.36% after maintenance. The PR obtained before and after maintenance is and respectively. REFERENCES I. An Annual Report, Ministry of New & Renewable Energy, Govt. of India II. Solar Radiation Hand Book, Solar Energy Centre, MNRE and Indian Metrological Department. III. M. Goel, Solar rooftop in India: Policies, challenges and outlook, Green Energy and Environment 2016, pp. 1-9 IV. Best Practices Guide National Solar Mission Implementation of State-Level Solar Rooftop Photovoltaic Programs in India, June 2016 V. Solar energy corporation of India ltd, VI. M. V. Hoeven, Solar Energy Perspectives, ISBN , Renewable energy division, International Energy Agency, November 2011 VII. D. Tan and A. K. Seng, Handbook for Solar Photovoltaic (PV) Systems, ISBN: , Energy Market Authority, Singapore VIII. Rahul Khatri, Design and assessment of solar PV plant for girls hostel (GARGI) of MNIT University, Jaipur city: A case study, Energy Reports 2 (2016) IX. Shaharin A. Sulaiman, H. H. Hussain, N. H. Nik Leh, Mohd S. I. Razali, Effects of dust on the performance of PV panels, International Journal of Mechanical, Aerospace, Industrial, Mechatronic and Manufacturing Engineering Vol:5, No:10, 2011 X. F. Mejia, J. Kleissl, J. L. Bosch, The effect of dust on solar photovoltaic systems, Energy Procedia 49 (2014 ) XI. D.S. Rajput, K. Sudhakar, Effect of dust on the performance of solar PV panel, International Journal of Chem Tech Research CODEN (USA): IJCRGG ISSN : ,Vol.5, No.2, pp , April-June 2013 XII. M. S. Vasisht, J. Srinivasan, S. K. Ramasesha, Performance of solar photovoltaic installations: Effect of seasonal variations, Solar Energy 131 (2016) XIII. T. Srivastava, K. Sudhakar, Energy and exergy analysis of 36 W solar photovoltaic module, International Journal of Ambient Energy, 2013 XIV. A. K. Pandey, P.C. Pant, O. S. sastry, A. Kumar, S. K. Tyagi, Energy and exergy performance evaluation of a typical solar photovoltaic module, Thermal Science, vol. 19, pp. S625-S636, 2015 XV. A.K. Pandey, Exergy analysis and exergoeconomic evaluation of renewable energy conversion systems, A PhD. Thesis, Shri Mata Vaishno Devi University, Katra, India, pp , 2013 XVI. V. Deepika, K. V. Reddy, N. Ramchander, Effect of seasonal variations on 100 kwp solar PV power plant installed at BVRIT, IJAREEIE, Vol. 5, Special Issue 8, Nov. 2016, ISSN (Print) : ISSN (Online): 2278 All Rights Reserved 196