太阳能板在不同温度和倾斜角下的功率输出研究

9 1. Introduction Pakistan is facing a serious energy crisis since the last decade. Despite strong economic growth during the past decade and consequent rising demand for energy, no worthwhile steps have been taken to install new capacity for generation of the required energy sources. Now, the demand exceeds supply and hence load-shedding is a common phenomenon through frequent power shutdowns. Pakistan needs about 14000-15000MW electricity per day, and the demand is likely to rise to approximately 20,000 MW per day by 2013. Presently, it can produce about 11,500 MW per day and thus there is a shortfall of about 3000-4000MW per day. This shortage is badly affecting industry, commerce and the daily life of people [1]. With the power shortfall in Pakistan hovering between 2,000 to 4,000 Megawatts, the energy crises in this country are not going to disappear anytime soon. Due to increasing prices of fossil fuels in the country, it is dif- ficult to concentrate on these conservative energy re- sources for production of electricity. Hence, the only way is to get benefit from renewable energy resources like solar, wind and biomass [2, 3]. The most plentiful power source we have in Pakistan is solar. The sun is upon us almost 365 days a year and that too with harsh intensity which is almost 700 w.m-2.hr-1 [4]. To overcome the crises of electric energy, people in Pakistan are installing solar panels for electric power generation from solar energy. Solar panels comprise the technology to convert sunlight directly into electricity. Most solar panels in use today are made of silicon and other semiconductor materials are expected to surpass silicon solar cells in performance and cost and become viable competitors in the PV marketplace. This technology has a high initial cost but has a good market all over the Abstract An experiment was con-ducted on PV (Photo- voltaic) solar panels to- wards achieving maximum power output. The power output of PV solar panels is examined with different tilt angles (0°, 20°, 35°, 50° and 90°) and different tem- peratures (15°C to 45°C) of the PV solar panels. The PV solar panels showed maximum power output at a tilt angle of 35° and low temperature of 15°C. The power output of PV solar panels decreases when the tilt angle increased from 35° to 90° or when the tilt angle decreased from 35° to 0°. It was concluded that PV solar panels must be installed at 35° tilt angle (equal to the latitude of Jamrud, Khyber Agency, Pakistan) to get maximum power output. Also PV so- lar panels must be installed at a place where they re- ceive more air currents so that the temperature re- mains lower and the out- put remains high. Keywords: PV Solar Panel, Tilt angles, Temperature, Current, Voltage, Power Output. Studying Power Output of PV Solar Panels at Different Temperatures and Tilt Angles 1Hanif M.*, 2M. Ramzan, 2M. Rahman, 3M. Khan, 2M. Amin, and 1M. Aamir 1Lecturers and 2Assistant Professors in the Department of Agricultural Mechanization, Faculty of Crop Production Sciences, Khyber Pakhtunkhwa Agricultural University Peshawar, Pakistan 3Principle Engineer in Nuclear Institute for Food and Agriculture (NIFA) Peshawar, Pakistan *Email: calm_tiger_hanif@yahoo.com Tel: +923339049552 V o l u m e 8 - N u m b e r 1 4 - N o v e m b e r 2 0 1 2 ( 9 - 1 2 ) ISESCO JOURNAL of Science and Technology Hanif… 9/11/12 8:48 Page 9 country. If installed and maintained properly, they can be a good competitor for solving our energy crises in homes, industries and educational institutions [5]. After installing the solar panel it is very much neces- sary to get maximum performance from them. The ob- jective of the present work is to study different Tilt angles and different Temperatures of the solar panels that affect performance of roof integrated solar panel system in the year 2011. 2. Materials and Methods 2.1 Site Selection The data were recorded in the Jamrud, Khyber Agency, Pakistan. It is located within the Latitude of 34°01 N and Longitude of 71°35 E. The site was made perfect for receiving maximum solar radiation and there was no shading of any structure or any object in the path of solar rays falling on the Pyranometer from dawn to dusk. 2.2 Solar Panel Orientations and Tilting The solar panels were oriented facing South axis, having five different tilt angle of 0°, 20°, 34°, 50° and 90° with the horizontal as shown in Figure 1. It was done to see the effect of tilt angle on the performance of panels. 2.3 Recording Solar Irradiance The solar irradiance (Si) data were recorded with the help of Pyranometer. The data recorded by Pyranometer was in kwh.m-2.day-1 [9,10]. 2.4 Temperature of the Solar Panel The temperature of the solar panel was determined by the help of thermometers installed on the gazing of each panel [6]. 2.5 Calculating Power Output Generation of electrical power under constant solar Irradiance was achieved by the capability of the solar panel to produce voltage over an external load and current through the load at the same time. When the cell was short circuited under constant solar irradiance then the maximum current (IMpp) and the short circuit current (ISC) are generated, while under open circuit conditions no current can flow and the voltage is at its maximum, called the open circuit voltage (VOC). The point in the IV-curve yielding maximum product of current and voltage, i.e. power, is called the maximum power point (MPP). Another important characteristic of the solar cell performance is the fill factor (Ff), defined as the ratio of the products of current voltage at maximum power point to short circuited point [7]. Mathematically Ff = VMPP x IMPP / VOC x ISC (1) Using the fill factor, the maximum power output of the solar cell can be written as [6, 8] PMax = VOC x ISC x Ff (2) 2.6 Determining Current and Voltage Current of the solar panel is determined by the help of ampere meter connected in series while voltage is determined by connecting a volt meter in parallel to the output wiring system of the solar panel [11, 12]. 3. Results and Discussions 3.1. Solar Irradiance Solar irradiance was recorded with the help of a Pyra- nometer at Five different tilting levels. The data recorded at different tilt angles for the year 2011 is given in Figure 2. It is clear from the graph that solar irradiance is higher all over the year at a tilt angle of 34° which equal to the latitude of Peshawar as compared to other tilt angles. These results of solar irradiance are in accor- dance with results of Feroz, 1989 [2] and Boyle and God- frey, 1996 [7]. Hanif, Ramzan, Rahman, Khan, Amin, & Aamir / ISESCO Journal of Science and Technology - Volume 8, Number 14 (November 2012) (9-12) 10 Figure 1. Different Tilt Angles of Solar Panel Tilt Angle Hanif… 7/11/12 11:24 Page 10 3.2 Power Output Vs Tilt Angle of Panel Power output was correlated with different tilting angles of Solar panel. The data of power output recorded at different tilt angles for the year 2011 is given in Figure 3. At 34° tilt angle the graph has a chi-squared value of 0.97 and R-square 0.99 showed the best corre- lation between power output and tilt angle throughout the year. The graph at 0° horizontal level with chi-squared value of 0.93 and R-square 0.96 showing that power output is lower on 0° tilt angle throughout the year as compared to that of 34° tilt angle. Similarly the graph data for 90° tilt angle or vertical level with a chi-square value of 0.675 and R-square 0.83 showing poor corre- lation between power output and tilt angle throughout the year. These results are in accordance with the findings of Ubertini and Desideri, 2003 [13] and Kollins, 2008 [14]. The chi-square goodness of fit test showed that there is a significant (P > 0.001) increase of power output if we increase the tilt angle of solar panel from 0° to 34°. Also there is a significant (P > 0.003) increase shown if we decrease the tilt angle from 90° to 34°.These results are in agreement with the findings of Meillaud. 2001 [1] and Olivia, 1998 [5]. 3.3 Power Output VS Panel Temperature Effect of temperature on the performance of solar panel is given in Figure 3. It is clear from the graph that cell temperature significantly (P > 0.000) decreases the power output of the solar panel. Also voltage and current was significantly (P > 0.001) decreased with increase in panel temperature. These result are also in accordance with the findings of Mahar, 2004 [9] and Salman et al., 2012 [10]. Hanif, Ramzan, Rahman, Khan, Amin, & Aamir / ISESCO Journal of Science and Technology - Volume 8, Number 14 (November 2012) (9-12) 11 Figure 2. Solar irradiance for the year 2011 Figure 3. Solar Panel Outputs Vs Temperature Conclusion It was concluded that: l Solar panel gives maximum power output throughout the year if installed at 34o tilt angle which is equal to the latitude of Peshawar, Pakistan. l Solar panels must be installed at 20° tilt angle in the months of May to August to get maximum power in summer while they must be installed at 50° tilt angle to get maximum power in the months of December to February. l In hot summer days, solar panel must be installed in a place where it receives maximum air currents so that its temperature remains low and power output remains high. Hanif… 7/11/12 11:24 Page 11 Hanif, Ramzan, Rahman, Khan, Amin, & Aamir / ISESCO Journal of Science and Technology - Volume 8, Number 14 (November 2012) (9-12) 12 [1] F. Meillaud, A. Feltring, M. Despeisse, F.-J. Haug, D. Dominé, M. Python, T. Söderström, P. Cuony, M. Boccard, S. Nicolay, and C. 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U.K. 1996. [8] C. Philibert, “The present and future use of solar thermal energy as a primary source of energy”, International Energy Agency, Pairs, France. 2005. [9] F. Mahar, “Model of Commercialization of Solar Photovoltaic Systems”, J. Science Vision. Vol. 9 (1-2) .2004. [10] K. A. Salman., Z. Hassan, and K. Omar, “Effect of Silicon Porosity on Solar Cell Efficiency”, Int. J. Electro. che. Sci., 7. 376 - 386. 2012. [11] T. Geoffrey, Klise and S. S. Joshua, “Models Used to Assess the Perfor- mance of Photovoltaic Systems”, SANDIA Report. Sandia National Laboratories Albuquerque, New Mexico. USA. 2009. [12] H. S. Jung, Y. S. Jung, G. J. Yu, J. Y. Choi and J. H. Choi, “Performance results and analysis of 3 kW grid-connected PV systems”. J. Renewable Energy. 32. 1858-1872. 2007. [13] S. Ubertini and U. Desideri, “Performance estimation and experimental measurements of a photovoltaic roof”, J. Renewable Energy. 28.1833- 1850. 2003. [14] K. 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