Effect of hot-spotted cell on PV module performance

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In this paper, the effects of the hot-spotted cell on PV module were evaluated. The experimental observation was based on 100 kW PV array composed of 20 PV modules. It was found that an increasing number of hot-spotted solar cells in a PV module would likely increase its output power loss.

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Nội dung Text: Effect of hot-spotted cell on PV module performance

International Journal of Mechanical Engineering and Technology (IJMET) Volume 10, Issue 03, March 2019, pp. 994-1000. Article ID: IJMET_10_03_100 Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=3 ISSN Print: 0976-6340 and ISSN Online: 0976-6359 © IAEME Publication Scopus Indexed EFFECT OF HOT-SPOTTED CELL ON PV MODULE PERFORMANCE Najib Hamisu Umar* Sharda University, Greater Noida (NCR, Delhi) - 201306, India Birinchi Bora and Chandan Banerjee National Institute of Solar Energy, Gurugram, India *corresponding author ABSTRACT In this paper, the effects of the hot-spotted cell on PV module were evaluated. The experimental observation was based on 100 kW PV array composed of 20 PV modules. It was found that an increasing number of hot-spotted solar cells in a PV module would likely increase its output power loss. It was also noticed that most of the PV modules affected by hot-spotted PV string are relatively affected by high-temperature levels, dust, and Partial shading due to trees or tall vegetation. Furthermore, the average performance ratio (PR) and degradation rate (DR) of all examined PV modules were analyzed. PR was observed to have a higher value of 0.78 in a non-hot-spotted PV array, whereas low PR of 0.65 was observed in a hot-spotted PV array. High DR of 3.13/year was observed in hot-spotted PV array; while low DR of 1.48/year was found in a module with no hot-spot. It was evident that the mean PR is significantly reduced due to the existence of hot-spots in the PV modules. DR was also increased due to hot-spot in the PV array. Hence, it is important to select materials that have the highest thermal stability to avoid mild hot spot situations that will lead to immediate damage of the panel. Hot-spot study analysis will help increase PV lifetime power output by detecting and preventing hot spotting before it permanently damages the PV panel. Keyword: Photovoltaic system, Hot-spot, Performance ratio, Degradation rate, Module defects, PV module Cite this Article Najib Hamisu Umar, Birinchi Bora and Chandan Banerjee, Effect of Hot-Spotted Cell on Pv Module Performance, International Journal of Mechanical Engineering and Technology, 10(3), 2019, pp. 994-1000. http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=10&IType=3 1. INTRODUCTION In recent years, the deployment of photovoltaic (PV) system has increased significantly due to its availability and cleanliness. Hence it is essential to conduct accurate studies on degradation http://www.iaeme.com/IJMET/index.asp 994 editor@iaeme.com
Najib Hamisu Umar, Birinchi Bora and Chandan Banerjee and performance analysis of the PV system. The aging and degradation of PV modules significantly depend on climatic and environmental conditions such as ambient temperature, relative humidity, solar radiation and dust [1-4]. Hot-spot heating occurs when a cell in a string of series connected cells is negatively biased and dissipates power in the form of heat instead of producing electrical power. This happens when the current generated by a given cell is lower than the string current [5, 6]. Hot-spots may occur in a PV module when the solar cells are mismatched or have certain defects, or when one or more cells in the module are partially shaded or damage [7-9]. The concept of current mismatch refers to any mechanism that can cause a reduction in the short- circuit current of a cell compared to other cells in the series string [10]. The power dissipation for any given faulty or shaded cell depends on the series-parallel configuration of cells in a module. In general, increasing the number of cells in series increases the power dissipation and increasing the number of cells in parallel decreases the power dissipation of the faulty cell [9, 11]. The main aim of this paper is to analyze the impact of hot-spots on the performance of PV modules. 2. METHODOLOGY In In this paper, 100kW PV array composed of 20 solar modules underwent inspection to identify modules with hot-spot. The Infra-red (IR) images were used to enable us to detect hot- spot in the module. The module terminals were short-circuited, and the IR image is taken from the back site. The FLIR E-60 IR camera was used to take the IR images. The temperature at different points of each PV modules is extracted from IR images. The FLIR E-60 IR camera and module with hot-spot are presented in Fig. 1 and 2 respectively. The temperatures were normalized to the reference condition of 1000 W/m2 and 40°C, using the relation [11, 12]: (𝑇𝑚𝑒𝑎𝑠𝑢𝑟𝑒𝑑 − 𝑇𝑎𝑚𝑏𝑖𝑒𝑛𝑡 ) × 1000 𝑇𝑛𝑜𝑟𝑚𝑎𝑙𝑖𝑧𝑒𝑑 = 40 + 𝐼𝑟𝑟𝑎𝑑𝑖𝑎𝑛𝑐𝑒 Where 𝑇𝑛𝑜𝑟𝑚𝑎𝑙𝑖𝑧𝑒𝑑 = 𝑛𝑜𝑟𝑚𝑎𝑙𝑖𝑧𝑒𝑑 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 (℃) 𝑇𝑚𝑒𝑎𝑠𝑢𝑟𝑒𝑑 = 𝑚𝑜𝑑𝑢𝑙𝑒 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑜𝑏𝑡𝑎𝑖𝑛𝑒𝑑 𝑓𝑟𝑜𝑚 𝐼𝑅 𝑖𝑚𝑎𝑔𝑒(℃) 𝑇𝑎𝑚𝑏𝑖𝑒𝑛𝑡 = 𝑎𝑚𝑏𝑖𝑒𝑛𝑡 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑚𝑒𝑎𝑠𝑢𝑟𝑒𝑑 𝑎𝑡 𝑠𝑖𝑡𝑒 (℃) Also 𝑀𝑜𝑑𝑢𝑙𝑒 ∆𝑇 = (𝑇max 𝑐𝑒𝑙𝑙,𝑛𝑜𝑟𝑚 − 𝑇𝑚𝑜𝑑𝑢𝑙𝑒,𝑛𝑜𝑟𝑚 ) Where 𝑇max 𝑐𝑒𝑙𝑙,𝑛𝑜𝑟𝑚 = 𝑛𝑜𝑟𝑚𝑎𝑙𝑖𝑧𝑒𝑑 𝑚𝑎𝑥𝑖𝑚𝑢𝑚 𝑐𝑒𝑙𝑙 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑚𝑜𝑑𝑢𝑙𝑒𝑠 𝑇𝑚𝑜𝑑𝑢𝑙𝑒,𝑛𝑜𝑟𝑚 = 𝑛𝑜𝑟𝑚𝑎𝑙𝑖𝑧𝑒𝑑 𝑚𝑜𝑑𝑒𝑙 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑚𝑜𝑑𝑢𝑙𝑒 The mean monthly temperature of the site is greater than 27℃ http://www.iaeme.com/IJMET/index.asp 995 editor@iaeme.com
Effect of Hot-Spotted Cell on Pv Module Performance Figure. 1: FLIR E-60 IR camera Figure. 2: Module IR image The PV modules are allowed to operate for three months period (from February to April 2018). The daily electricity generation in kWh was extracted using a SCADA system. Meanwhile, another 100kW PV array of the same number of modules but with no hot-spot ware also analyzed. Average performance ratio (PR) and average degradation rate (DR) was calculated for both hot-spot and non-hot-spot modules, using the following relations [13, 14]: 𝑌𝑓 𝑃𝑅 = 𝑌𝑟 Where 𝑓𝑖𝑛𝑎𝑙 𝑒𝑛𝑒𝑟𝑔𝑦 𝑜𝑢𝑡𝑝𝑢𝑡 (𝑘𝑊ℎ) 𝑌𝑓 = 𝑛𝑜𝑟𝑚𝑖𝑛𝑎𝑙 𝐷𝐶 𝑝𝑜𝑤𝑒𝑟 (𝑘𝑊) 𝑡𝑜𝑡𝑎𝑙 𝑖𝑛𝑝𝑙𝑎𝑛𝑒 𝑖𝑟𝑟𝑎𝑑𝑖𝑎𝑛𝑐𝑒 (𝑘𝑊ℎ/𝑚2 ) 𝑌𝑟 = 𝑃𝑉 𝑟𝑒𝑓𝑒𝑟𝑒𝑛𝑐𝑒 𝑖𝑟𝑟𝑎𝑑𝑖𝑎𝑛𝑐𝑒 (𝑘𝑊/𝑚2 ) 𝑖𝑛𝑖𝑡𝑖𝑎𝑙 𝑃𝑅 − 𝑓𝑖𝑛𝑎𝑙 𝑃𝑅 𝐷𝑅 = × 100 𝑖𝑛𝑖𝑡𝑖𝑎𝑙 𝑃𝑅 Furthermore, PR Comparison was made between hot-spot and non-hot-spot modules, and lastly, DR for hot-spot modules and non-hot-spot was compared. The PV module and inverter specifications were presented in Table 1 and 2 respectively. Table 1: PV module specifications 1.2 kW Inverter Specifications Maximum DC input voltage (Vmax) 600V Rated DC input voltage (Vdcr) 185V Rated DC input power (Pdcr) 1500W Maximum input short circuit current 12.5A Rated AC power (Pacr) 1200 W Maximum AC output power (Pacmax) 1200 W Rated AC grid voltage (Vac,r) 230V AC voltage range 180..264 V Rated output frequency (fr) 50 Hz / 60 Hz Maximum efficiency (ηmax) 94.8% http://www.iaeme.com/IJMET/index.asp 996 editor@iaeme.com
Najib Hamisu Umar, Birinchi Bora and Chandan Banerjee Table 2: inverter specifications Polycrystalline Module Specifications Power output Pmax W 100 Module efficiency ηm % 13.09 Voltage at Pmax Vmpp V 29.5 Current at Pmax Impp A 7.20 Open-circuit voltage Voc V 36.0 Short-circuit current Isc A 7.80 Nominal operating cell temperature NOCT °C 46 +/- 2 Temperature coefficient of Pmax γ %/°C -0.45 Temperature coefficient of Voc βVoc %/°C -0.37 Temperature coefficient of Isc αIsc %/°C 0.06 3. RESULTS AND DISCUSSION In this paper, the 100kW PV array composed of 20 PV modules was analyzed. The defectives modules were identified by visual and IR inspection. The plant has been in operation since 2010. 3.1. PV array without hot-spot The module cell temperature was found to be less than 80℃. The low temperature is due to the absence of the defective module in the PV array. There is high energy production in the PV array with no hot-spot defect. The average PR and DR was found to be 0.78 and 1.48/year respectively. 3.2. PV array with hot-spot It was observed that, out of 20 PV modules, only three modules were found to be defective with hot-spot. The module cell temperature was found to be higher than 120℃. The sharp increase in temperature of hot cells is attributable to the combined effect of the two parts, dissipated power and heat converted from radiation. The average PR and DR was found to be 0.65 and 3.13/year respectively. In general, the increasing number of hot-spots in PV modules, it is more likely to have a more significant drop in output power. On the other hand, the PV modules with a whole hot- spotted PV string are caused due to faulty bypass diodes. Therefore, there is more chance to have less output power produced by these particular PV modules, since bypass diodes is used to overcome the issue of the partial shading conditions which usually PV modules suffer from. As presented in Fig. 3, high electricity generation is noticed in a module with no hot-spot, whereas low electricity produced observed in a module with hot-spot. Performance ratio for hot-spotted and non-hot-spotted PV module was presented in Fig. 4. Performance ratio was observed to have a higher value of 0.78 in a non-hot-spotted PV array, whereas a low-performance ratio of 0.65 was found in the hot-spotted PV array. The high degradation rate of 3.13/year was seen in hot-spotted PV array; while PV array with no hot- spot has the low degradation rate of 1.48/year. The analysis of the results exhibits that the hot- spotted cell in PV module increases module temperature leading to accelerated aging of the PV module, and gradually reduces the system efficiency. http://www.iaeme.com/IJMET/index.asp 997 editor@iaeme.com
Effect of Hot-Spotted Cell on Pv Module Performance Table 3: performance parameters for hot-spotted and non-hot-spotted PV module Average parameter Module without hot-spot Module with hot-spot Performance ratio, PR 0.78 0.65 Degradation rate, DR (%/year) 1.48 3.13 Normalized module temp. (℃) 13.3 33.4 Max. Module cell temp. (℃) 74.6 126.2 Figure. 3: Electricity generation comparison Figure. 4: Performance ratio comparison 4. CONCLUSION In this paper, the effects of the hot-spotted cell on PV module performance were evaluated. The experimental observation was based on 100 kW PV array composed of 20 PV modules. It was found that an increasing number of hot-spotted solar cells in a PV module would likely increase its output power loss. It was also noticed that most of the PV modules affected by hot-spotted PV string are relatively affected by high-temperature levels, dust, and Partial shading due to trees or tall vegetation. Furthermore, the PR and DR of all examined PV modules were http://www.iaeme.com/IJMET/index.asp 998 editor@iaeme.com
Najib Hamisu Umar, Birinchi Bora and Chandan Banerjee analyzed. PR was observed to have a higher value of 0.78 in a non-hot-spotted PV array, whereas low PR of 0.65 was observed in a hot-spotted PV array. High DR of 3.13/year was observed in hot-spotted PV array; while low DR of 1.48/year was found in a module with no hot-spot. It was evident that the mean PR is significantly reduced due to the existence of hot-spots in the PV modules. DR was also increased due to hot-spot in the PV array. Hence, it is important to select materials that have the highest thermal stability. As a result, mild hot spot situations should not lead to immediate damage of the panel. Hot-spot study analysis will help increase PV lifetime power output by detecting and preventing hot spotting before it permanently damages the PV panel. ACKNOWLEDGMENT The authors are grateful to National Institute of Solar Energy, India for their support and guidance. REFERENCES [1] A.M. Syed, et al., “The effect of environmental factors and dust accumulation on photovoltaic modules and dust-accumulation mitigation strategies,” Renewable and Sustainable Energy Reviews, vol. 82, pp. 743-760, 2018. [2] T. C. Miqdam and A. K. Hussein, “Generating Electricity Using Photovoltaic Solar Plants in Iraq,” springer publisher, 2018. [3] S. Anu, at al., “Environmental Effects on Performance of Solar Photovoltaic Module,” IEEE Conference on Power and Energy Systems towards Sustainable Energy (PESTSE), pp. 1-6, 2016. [4] F. A. Ehsan, “Impact of the Environment on the Performance of the Photovoltaic Cell,” American Journal of Energy Engineering, vol. 4, pp. 1-7, 2016. [5] K.A. Kim and P.T. Krein, “Hot Spotting and Second Breakdown Effects on Reverse I-V Characteristics for Mono-Crystalline Si Photovoltaics,” Proceedings of the IEEE Energy Conversion Congress and Exposition, ECCE’13, Denver, CO, USA, pp. 1007-1014, 15-19 September 2013. [6] K.A. Kim and P.T. Krein, “Reexamination of Photovoltaic Hot Spotting to Show Inadequacy of the Bypass Diode, IEEE Journal of Photovoltaic, vol. 5, pp. 1435-1441, 2015. [7] J. Solórzano, M. Egido, Hot-spot mitigation in PV arrays with distributed MPPT (DMPPT), Sol. Energy 101 (2014) 131–137. [8] K.A. Kim, at al., “Photovoltaic hot-spot detection for solar panel substrings using AC parameter characterization,” IEEE Transection of Power Electronics, vol. 31, pp. 1121- 1130, 2016. [9] N. Kaushika and A.K. Rai, “An investigation of mismatch losses in solar photovoltaic cell networks,” Energy, vol. 32, pp. 755-759, 2007. [10] P. Manganiello, at al., “A survey on mismatching and aging of PV modules: the closed loop,” IEEE Tran. Ind. Electronics, vol. 62, pp. 7276-7286, 2015. [11] R. Moreton, at al., "Dealing in Practice with Hot Spots," 29th European Photovoltaic Solar Energy Conference and Exhibition, Amsterdam, pp. 2722-2727, 2014. [12] J. Oh and G. TamizhMani, "Temperature Testing and Analysis of PV modules per ANSI/UL 1703 and IEC 61730 standards," 35th IEEE Photovoltaic Specialist Conference, Honolulu, pp. 984-988, 2010. [13] M. Drif, at al., “A grid connected photovoltaic system of at Jaén University Overview and performance analysis,” Solar Energy Material Solar Cells, vol. 91 (8), pp. 670–683, 2007. http://www.iaeme.com/IJMET/index.asp 999 editor@iaeme.com
Effect of Hot-Spotted Cell on Pv Module Performance [14] L.M. Ayompe, at al., “Measured performance of a 1.72 kW rooftop grid connected photovoltaic system in Ireland. Energy Conversion and Management, vol. 52 (2), pp. 816- 825, 2011. [15] K.A. Kim and P.T. Krein, “Reexamination of Photovoltaic Hot Spotting to Show Inadequacy of the Bypass Diode. IEEE Journal of Photovoltaic, vol. 5, pp. 1435–1441, 2015. BIOGRAPHIES OF AUTHORS Najib Hamisu Umaris Ph.D Reserch Scholar at Sharda Univerdity, Greater Noida. Dlhi NCR. India. He is currenty working in Module Reliablity and Renewable Energy Conversion. Email: umarnajibhamisu@gmail.com. Birinchi Bora is a Senior Research Scientist at National Institute of Solar Energy, Gurugram. India. He Specialized in Reliability of Photovoltaic System, Energy Modeling and Solar Cell Characterization. Email: birinchibora09@gmail.com. Dr. Chandan Banerjee is a Scientist and Deputy Director General at National Institute of Solar Energy, Gurugram. India. He was the former Post Doctorate Fellow at Tokyo Institute of Technology, Japan. He is currently research interest is Photovoltaic System, Thin Film Technology. Email: chandanbanerjee74@gmail.com. http://www.iaeme.com/IJMET/index.asp 1000 editor@iaeme.com