Photovoltaic Remote Monitoring System Based on GSM

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1 Photovoltaic Remote Monitoring System Based on GSM Farihah Shariff, Nasrudin Abd Rahim, Hew Wooi Ping UM Power Energy Dedicated Advanced Centre (UMPEDAC) Level 4, Wisma R&D UM, Jalan Pantai Baharu, Kuala Lumpur, Malaysia Abstract In remote area, the need for monitoring PV system is crucial to ensure stable PV power delivery. This paper describes the hardware and software design for PV monitoring system in remote area. The monitoring system is equipped with voltage, current, temperature and irradiation and GSM modem for data transmission. Real time clock chip is used for real time recording. The designed system is built and has been applied on field and satisfactory results are obtained. Index Terms Photovoltaic; Solar energy; Remote monitoring; GSM. I. INTRODUCTION Energy is one of the important resources to human life, but non-renewable resources are depleted every year. Nowadays, solar energy is widely used all over the world. The growth of solar photovoltaic products in market showed the importance of conserving energy and awareness of renewable energy. Photovoltaic (PV) solar cells are reliable, environmentally safe and produce clean energy [1, 2]. In order to ensure PV modules in good performance and enhance knowledge on local solar radiation and natural environment, PV system must be monitored and built [3, 4]. Traditional monitoring method requires close maintenance from staff for continuously monitoring. Results are taken directly from equipment. Normally, solar power system is placed in remote area. The environment factor can degrade PV power performance [4]. Various methods are used to monitor solar modules. Wireless transmission is one of the alternatives to monitor PV. Wireless medium has the flexibility function which does not require staff to be in actual area where the solar panels are located to control and monitor the system. Previous work shows that photovoltaic modules can be monitored using wireless networks [5]. There are many drawbacks when using wireless network to transmit data. Wireless network consume more energy to operate. Besides that, wireless network has higher risk of malicious intrusion and attack [6]. These drawbacks made it less reliable for data transmission. Many transmission techniques can be used for monitoring such as Ethernet network, RF module and zigbee wireless network. Ethernet uses network cable to transmit data. Hence, it is affected by geographical environment [7, 8]. While transmission bit error rate of RF module is high and less reliable [9, 10]. Zigbee wireless network is more costly compared to other module. Furthermore, Zigbee is complex and hard to develop. Besides that, it has limited signal range [11, 12]. In order to overcome these problems, monitoring system using Global System for Mobile Communication (GSM) is used. GSM technology contains essential intelligent functions to support of personal mobility [13]. GSM network has low error rate, low costs and wide signal coverage. Users can communicate easily using GSM to perform monitoring anytime and anywhere [14]. Hence, provides higher reliability in data transmission. In this project, a stable and reliable system is built using microcontroller and GSM to monitor performance of solar modules. Attention (AT) commands are used to control functionality of GSM modem. Two modes can be implemented to give commands to GSM modem like Protocol Description Unit (PDU) and text mode. These modes are based on AT command sets [15]. In this project, GSM modems are set to work in text mode because text mode is easier to understand and implement compared to PDU mode. There are only a few commands used for this project. Table 1 shows the command used for this project [16]. TABLE I. LIST OF AT COMMANDS Command AT AT+ECHO AT+CNMI AT+CMGF=1 AT+CMGS AT+CMGL AT+CMGD Function Initialize modem Turns echo on/off New message indicator Send message Read message Delete message /13/$ IEEE 379

2 II. SYSTEM ARCHITECTURE The projects architecture consists of two parts. The first part is the monitoring end while the second part is the remote pc end. The monitoring end composed of PV module; data acquisition device and GSM modem 1 while the remote pc end composed of GSM modem 2 and remote pc. PV module is monitored using data acquisition device. Data acquisition device consists of s, Real Time Clock (RTC) chip, and Liquid Crystal Display (LCD) and microcontroller unit. Microcontroller will collect all the data from s in five minutes interval time. GSM modem 1 will stored the received data and transmit it in short messages (SMS) to GSM modem 2. The second modem is connected to remote pc. The received data will be filtered and categorized before saved to excel file. The overall architecture of the system is shown in Fig. 1. III. HARDWARE DESIGN In hardware development, data acquisition device is built. In Fig. 2, it shown that the module composed of s, microcontroller, RTC and LCD. Several of s used in this project. Voltage measurement used in this project is range from 0 to 100V while current ranges from 0 to 25A. Voltage (LV25) and current (LA25) from LEM will be used in this project. In this project, two units of temperature s (LM35) are used to measure ambience temperature and PV panel temperature. Irradiation is used to identify amount of light density received by PV module. Li-200 from LI-COR was chosen PIC18F4550 from Microchip is chosen for the controller part as it can support up to five and more Analog to Digital Converter channel (ADC) which is needed for the monitoring operation [17]. RTC (DS1307) is used to indicate actual time of the operation. RTC also functions as timer for the microcontroller [18]. After certain interval, RTC notifies microcontroller to send collected data to GSM modem 1. GSM modem 1 will send the data in form of text message to another GSM modem in remote pc end. In this project, functionality of LCD is to display microcontroller activities and acknowledge user the status of PV power system. GSM modems model MOD 9001D were used in this project. It supports baud rate per second. It supports 900MHZ, 1800MHz and 1900 MHz frequency for better signal quality. It has one serial port which equips with 3.3V TTL voltage level to RS232 voltage level. Besides that, it also support AT command set [19]. Voltage Current Temperature s Irradiation PV module Data Acquisition Device GSM modem1 GSM modem2 Remote PC Fig. 1. System architecture. Real time clock (RTC) Microcontroller LCD display Fig. 2. Data acquisition device design Monitoring end Remote pc end GSM modem 1 IV. SOFTWARE DESIGN One of the key factors of monitoring is software design. In this project, it composed of algorithm for microcontroller and pc interface. A. Microcontroller Algorithm From Fig. 3, it shows that the first stage is initialization. Initialization of microcontroller, LCD display, GSM modem 1 and RTC were done. Next, AT command were used to switch off echo function in GSM modem to easily identify feedback from modem. AT+CMGF=1 command is sent to enable modem 1 to operates in text mode. Then, interrupts is enabled if any text received. After that, microcontroller will wait for command from GSM modem 2 which will be sent from pc. If GSM modem 1 received text message, microcontroller will start logging data. If not, microcontroller will continue waiting /13/$ IEEE 380

3 until it receives command. Microcontroller will log data in one minute time interval for 5 minutes and send data in short messages form to GSM modem 2. Then, it will check for any unread messages. If it receives stop logging command from GSM modem 2, it will exit the system and keep in standby mode. If not it will continue monitoring until it receives stop command. B. PC Interface In this session, graphical user interface (GUI) for PC interface is designed. The first stage of PC interface design is initialization of GSM modem. In order to operate modem in text mode, AT+CMGF=1 command was utilized. Next, modem was cleared. All data in sim messages will be deleted to make sure it is ready to receive data from GSM modem 1. Next, by clicking a button; start logging command will be sent to GSM modem 1 to activate microcontroller system monitoring. After that, program will be idle for 5 minutes before GSM modem 2 checks for any unread messages. Then, unread message is opened and data will be organized and classify according to format. Next, data will be saved in csv format. The algorithm was shown in Figure 4. Initialization Clear GSM modem Send start logging command Open unread messages Organizing data according to format Save in csv format Fig. 4. PC interface algorithm. Initialization Off echo in GSM modem Enable interrupts Wait for command SMS mode = 1 Logging data Send data Check for unread message Receive stop logging command Exit Yes Yes No No V. EXPERIMENTAL RESULTS AND ANALYSIS Data will be saved in csv format. It can be viewed using Microsoft Excel. Figure 5, 6 and 7 show data collected on remote pc. Data on open circuit voltage (Voc), short circuit current (Isc), ambience temperature (Tamb), panel temperature (Tpv) and solar irradiation (G) were collected. Open circuit voltage was obtained from ADC pin RA0 while short circuit current was obtained from ADC pin RA1. Ambience temperature was calculated from pin RA5 and panel temperature was calculated from pin RE0. Pin RE1 was used to measure irradiation. The system was set to start monitoring from am and end at pm. Hence, figures below shows collected data from am to pm. Figure 5 shows daily variations of solar irradiation and ambience temperature. Solar irradiation varies rapidly because Malaysia s atmosphere is cloudy while temperature was high as Malaysia was closed to the equator line. From Fig. 6, daily variations of short circuit current and open circuit voltage with panel temperature were plotted. The highest short circuit current value is 3.75A while the open circuit voltage mainly constant throughout the day. Open circuit voltage started to rise at 7 am and dropped at 7 pm coherently related to sunrise and sunset time. As the panel temperature increases, the open circuit voltage rapidly decreased while the short circuit current slightly increased [20]. Figure 7 shows relations between maximum power and ambience temperature. Maximum power was calculated from: Pmax = Isc*Voc*FF (1) Fig. 3. Microcontroller algorithm /13/$ IEEE 381

Where FF is the solar cell fill factor and it can be calculated using Eq. 2 by assuming both Rs and Rsh have negligible effect upon cell performance [21]. FF = [Voc - ln(voc+0.

4 Where FF is the solar cell fill factor and it can be calculated using Eq. 2 by assuming both Rs and Rsh have negligible effect upon cell performance [21]. FF = [Voc - ln(voc+0.72)]/(voc+1) (2) Figure 7 shows maximum power was high when ambience temperature was low and dropped when ambience temperature increased. VI. CONCLUSIONS In previous section, the need for monitoring is addressed and a remote photovoltaic monitoring system is designed and built. This system ease user in monitoring photovoltaic system placed at remote area. Furthermore, monitoring using GSM increased the efficiency of data transmission. The system eliminates risks of malicious intrusion and attack; the drawbacks of using wireless transmission. Hence, it could be conclude that the system is another alternative for monitoring photovoltaic system and provide higher reliability and efficiency. ACKNOWLEDGMENT This work was supported and funded by Institut Pengurusan & Pemantauan Penyelidikan (IPPP), University of Malaya under PV A grant. Fig. 5. Daily variations of solar irradiation and ambience temperature Fig. 6. Daily variations of short circuit current, open circuit voltage and panel temperature Fig. 7. Daily variations of maximum power and ambience temperature REFERENCES [1] Y. Tsur, and A. Zemel, Long-term perspective on the development of solar energy, Solar Energy, vol. 68, pp , January [2] D.Y. Goswami, New and emerging developments in solar energy, Solar Energy, vol. 76, pp , January [3] Q. Wu, and X. Sun, The data acquisition and communication system based on LabVIEW for pv power station, Micro computer information, vol. 18, pp , [4] J. Xiao et al., Design of pv power station remote monitoring system data acquisition device, Proceedings of the 2011 International Conference on Advanced Mechatronic Systems, Zhengzhou, China, pp , August [5] C. Ranhotigamage, and S. C. Mukhopadhyay, Field trials and performance monitoring of distributed solar panels using a low-cost wireless network for domestic application, IEEE Sensors Journal, vol. 11, pp , October [6] W. Dargie, and C. Poellabauer, Fundamentals of Wireless Networks: Theory and Practise. Wiley, NJ, USA, [7] Z.W. Zhu, and C.M. Wang, Remote electric network monitoring system based on MCU web server, High Voltage Engineering, pp , February [8] J. Sun, and Z.Y. Wang, Design of remote temperature monitoring and controlling system base on ethernet, Control & Automation, pp , September [9] Y.C. Ding, J.H. Wei, and G.Z. Liu, Distributed temperature test system based on nrf2401, Electronic Measurement Technology, pp , December [10] Y.K. Sun, B. Wang, and Y.H. Huang, Design of wireless monitoring system for fermentation process based on ARM, Application of Electronic Technique, pp , July [11] H. Liu, Development of farmland soil moisture and temperature monitoring system based on wireless network, Journal of Jilin University (Engineering and Technology Edition), pp , March [12] G.J. Zhang, Forest fire detection system based on Zigbee wireless network, Journal of Beijing Forestry University, pp , October [13] J.J. Thomsen, Vibrations and Stability. Advanced Theory, Analysis, and Tools. Springer-Verlag, Berlin, [14] J. Ding, Remote monitoring system of temperature and humidity based on GSM, Proceedings of the 2nd International Congress on Image and Signal Processing, Tianjin, China, pp , October [15] D.D. Vyas, and H.N. Pandya, Design of GSM based autoresponder for educational institute, Proceedings of the 2011 International Conference on Advances in computing, /13/$ IEEE 382

5 communication and control, Mumbai, India, pp , January [16] SIM300_ATC_V1.03, SIMCOM, pdf, [17] PIC18F2455/2550/4455/4550 Data Sheet, Microchip, ww1.microchip.com/downloads/en/devicedoc/39632c.pdf, [18] DS x 8, Serial, I C Real-Time Clock - Maxim, Maxim Integrated, datasheets.maximintegrated.com/en/ds/ds1307.pdf, [19] MOD 9001D RS232 GSM/GPRS modem user manual, Cytron, %20RS232%20GSMGPRS%20Modem%20User%20Manual.pdf, [20] J.-C. Wang, Y.-L. Su, J.-C. Shieh, and J.-A. Jiang, Highaccuracy maximum power point estimation for photovoltaic arrays, Solar Energy Materials & Solar Cells, vol. 95, pp , November [21] M. A. Green, Solar cell fill factors: general graph and empirical expressions, Solid-State Electronics, vol. 24, pp , /13/$ IEEE 383

Telemetry Monitoring of Solar Panels Using GSM

Student Research Paper Conference Vol-2, No-59, July 2015 Telemetry Monitoring of Solar Panels Using GSM 1 Hafiz Muhammad Zubair, 2 Syed Mutahir Ahmed Electrical Engineering Department Institute of Space