International Engineering Conference on Hot Arid Regions (IECHAR 2010) Al-Ahsa, KSA, March 1-2, 2010
Fabrication and Performance Test of a Solar Tracking Intelligence System Using Matlab Graphical User Interface Z. Hasib, T. Mahdi, A. Morshed, and M. Sarkar Abstract— This paper presents the fabrication and performance testing of a solar tracker using low cost locally available materials. An expert controller sensors and input/output interface are integrated with a tracking mechanism, to increase the energy generation efficiency of solar panel. Light sensing devices such as Light Emitting Diodes (LED) and Light Dependent Resistors (LDR) are used to track the path of the Sun at Dhaka. PC interfacing and microcontroller based hardware and software arrangement using MATLAB has been incorporated to ensure the highest efficiency of solar panels. Graphical User Interface (GUI) is incorporated in the MATLAB based software to make the software user friendly. The control system based on the MATLAB algorithm is designed and implemented on microcontroller based embedded system. The fabricated solar tracking system can track the sun light automatically. Experimental work has been carried out carefully. The result shows higher solar power conversion efficiency with the tracker.
power, wind power, biomass energy, terrestrial heat, temperature difference of sea, sea waves, morning and evening tides, etc. are the most important ones. Although storm is a common phenomenon in hot arid regions, but to use wind energy, a continuous wind flow is required, which is available only in limited region of the world. However hydropower and other sources of energy are also limited. This leads to the use of solar energy; which can be an excellent alternative solution of energy crisis. The sun is a giant nuclear fusion reactor and the energy it supplies is equivalent of about 27,000 times the total amount of energy presently produced from all other sources. This huge source of energy is especially suitable for Asian countries where a warm climate with no snow fall persists. Moreover 10-14 hours of day light thorough out the year in the hot arid regions such as Middle Eastern countries, have made this region most appropriate for the utilization of solar energy. But, as a result of the atmospheric phenomena involving reflection, scattering, and absorption of radiation, the quantity of solar energy that ultimately reaches the earth's surface is much reduced in intensity as it traverses the atmosphere. Finally, the total solar radiation received at ground level includes direct solar radiation and diffuse radiation [1]. But, due to diurnal rotation and annual motion of the earth, the sun rays does not fall with the same intensity in every direction and in every place all over the year. Day-time vs. solar intensity curve (Fig.1) shows that, higher intensity is available at noon time when the fixed solar panels face normal to sun. On the other hand the PV panels do not have the highest solar intensity on other time of the day. But to convert highest solar energy, the solar panels should always face the sun vertically to get the highest intensity.
Keywords— Solar, Solar tracker, conversion efficiency 1.
INTRODUCTION
F
rom the introduction of modern civilization, energy is the key requirement of all development. Till nineteenth century the fossil fuels were the only source of energy; e.g. coal, oil, natural gas. Still in twenty first century fossil fuel is the main resource of energy. It was estimated by the Energy Information Administration that in 2006 primary sources of energy consisted of petroleum 36.8%, coal 26.6%, and natural gas 22.9%, amounting to an 86% share for fossil fuels in primary energy production in the world. But the future of fossil fuel is uncertain. Based on present global economic growth rates, fossil fuel energy resources may last a generation or two at most, before they are exhausted. As a result, the current energy system will come to an end. The increase of the emissions of carbon-dioxide, responsible for the global warming and for the greenhouse effect, is an additional reason for the limited future of fossil fuel use. These concerns may force us to give up our present energy system before we physically exhaust extant fossil fuel energy resources. This phenomenon drives us to the use of renewable energy resources of which solar energy, water
Manuscript received December 30, 2009. This work was supported by department of Mechanical Engineering, Bangladesh University of Engineering and Technology (BUET), Dhaka1000. Bangladesh Z.M. Hasib, T.H. Mahdi and A. Morshed are final year student of Mechanical Engineering Department, Bangladesh University of Engineering and Technology (BUET). (e-mail:
[email protected] [email protected] ) M.A.R. Sarkar is the Dean, Faculty of Mechanical Engineering, Bangladesh University of Engineering and Technology (BUET), Dhaka-1000. Bangladesh. (e-mail:
[email protected])
Fig. 1 Day-time vs. solar intensity curve
So, a two axis tracker (Fig. 2) is important for tracking the changing position of the sun due to diurnal rotation and 85
annual motion of earth. A tracking system must be able to follow the sun with a certain degree of accuracy, return the collector to its original position at the end of the day and also track the seasonal position changing of the sun. The objective of our work is as follows1.1.1To design the detailed hardware and software for a two-axis solar tracker incorporated with solar panels 1.1.2Performance test of the solar tracking system
between the sun rays and panel. The positions of the Sun on its path along the year represent an input data in designing the solar trackers (Fig. 3). The annual rotational motion of the earth follows an elliptical path around the sun. The diurnal spinning of the earth around its own axis is a complete rotation. The variation of the altitude of the sun on the celestial sphere during one year is determined by the precession motion, responsible for a declination of the Earth axis in consideration with the plane of the elliptic yearly path; the value of this angle is 23.5º (Fig. 1); this motion generates the seasons because of the alternative exposure of the northern and southern hemisphere to the sunrays trajectory [5]. So, total difference in height of sun all around the year is 47°.
Fig. 3 Solar orientation all over the year
Fig. 2 Two-axis solar tracker model
3. HARDWAR ARRANGEMENT
2. WORKING PRINCIPLE
A model of two-axis solar tracking system, with two degrees of freedom, has been designed and implemented. The model was fabricated using wood and aluminum considering its placement in open corrosive environment. The tracking system is used for following the sun in both polar and seasonal directions, keeping the sun‘s rays normal to the platform surface. The daily motion is directly driven by a rotary motor that is able to develop an angular displacement up to 220°. Another rotary motor is provided to rotate the panels 360° to follow the seasonal motion of the sun. However many scholars proposed different methods for tracking the sun [6-7].
The efficiency of the solar system depends on the degree of use and conversion of the solar radiation. When performing the energy balance on the solar panel, reference is done to the surface that absorbs the incoming radiation and to the balance between energy inflow and energy outflow. The rate of useful energy leaving the absorber is given by the difference between the rate of optical (short wavelength) radiation incident on absorber and the rate of energy loss from the absorber [2]. In these terms, there are two ways for maximizing the rate of useful energy: optimizing the conversion to the absorber level, and decreasing the losses by properly choosing the absorber materials; increasing the incident radiation rate by using mechanical tracking systems (the maximum degree of collecting is obtained when the incident radiation is perpendicular on the active surface). Basically, the tracking systems are mechanical devices (i.e. mechanisms), driven by motors or actuators, which orient the panel in order to follow the sun path on the sky. The orientation of the solar panels may increase the efficiency of the conversion system up to 40% [3] [4]. The orientation principle is designed on the basis of the position of the sun on the sky. For extracting highest energy from the sun, the sun rays have to fall normal on the solar cells. So the system was designed such that its position is modified periodically in order to maintain a definite relation
3.1 Material and Design This work mainly emphasizes on the fabrication of low cost solar tracker with locally available materials. Solar panels with tracker are placed in open spaces so it is often subjected to heavy rain, storm, erosion, corrosion and other environment catastrophe. So, the materials used to fabricate the model is to ensure some important properties such that high strength, corrosion resistance, good machinability and overall the total system should be cost effective. The design consists of mainly three parts: 1) Wooden base: To hold the entire system. 2) Wooden frame: To incorporate 360° rotational motion to overcome the annual motion of earth around the sun.
86
3) Aluminum frame: To support the solar panels and incorporate about 220° rotation to overcome the diurnal rotation of earth on its own axis. The solar panels are always exposed to high temperature and corrosive environment. So selection of material is to be considered carefully. Wooden base has been chosen instead of metallic base, to avoid the risk of short circuit. Moreover wood has higher compressive strength and corrosion resistive properties.
been incorporated. The software automatically monitors all the panels individually. The operator from the control has also the option to set the rotational speed of each of the panels (Fig. 7) individually.
4. CONTROL AND SENSING UNIT
The control unit consists of sensors and actuators. In choosing sensors and actuators, locally available and low cost materials have been given priority. The sensors and actuators can be listed as below: 1) Gear motors. 2) LDR (Light dependent resistors). 3) Operational Amplifiers (OP-AMPs). 4) LED (Light Emitting Diodes). 5) DPDT relay switch. The control unit employs a rather simple logic of light intensity on sensing components (i.e. LDR and LED) to actuate the tracker rotation. Major electronic components included Light Dependent Resistors (LDR), Light Emitting Diodes (LED), simple comparators and DC gear motors. The basic working principle on the main horizontal axis rotation has been built on the change in sensitivity (namely resistance) of LDR with the change in light intensity impressed upon it. The sensor portion uses two LDRs put side by side, along the quotidian path of the sun with a physical barrier such as a cardboard in between them. Just when the sun is directly above the unit on perpendicular to the panel position, both of the two LDRs receive exactly same amount of light resulting in an equal resistance for both of them which keeps the whole system stationary. As the sun tilts to one side, one of the LDRs will still get the full intensity while the other one now will be under the shadow created by the physical barrier. This will in turn create a level of difference in resistance between the two LDRs, which is then amplified and sent to the central control. The control logic then starts the motor and rotates the frame until the light intensity is same again on the two LDRs thus effectively following the sun. [8-10] As the sun sets, both the LDRs are left in the dark. At this point the whole frame rotates back to the original position (east facing), ready for the next day. The maximum rotation of the frame is limited by using two limit switches, each on east and west, which when pressed, cuts the motor power and saves energy. The circuit (Fig. 4) for the control system of this horizontal axis rotation is designed with simplicity and cost effectiveness. The other rotation on the vertical axis uses same logic. However it should be noted that the sun moves laterally with respect to the horizon very little on a daily basis. The movement is rather year long and consequently the control circuit (Fig. 5) is very light, and should be used only when necessary. Here direct level of voltage difference is taken from the LEDs and the motor employs a H-BRIDGE circuit for its control (Fig. 6). The endeavor of our work was to develop an efficient solar power plant using the solar trackers (Fig. 7). Software has been developed to make the system user friendly. To develop the software, virtual instrumentation (Fig. 8) has
Fig. 4 Circuit diagram for horizontal movement of solar tracker.
Fig. 5 Circuit diagram for vertical movement of solar tracker.
Stepping motor (X-axis rotation)
Solar Panels
Stepping motor (Y-axis rotation)
Light Sensitive Resistors
Stepping Motor Driver Operational Amplifiers
DPDT relay Stepping Motor Driver
Fig. 6 Block Diagram of the solar tracking system
87
Table 1 shows that different tilting angle is suitable for different month. Moreover the increase in solar radiation on the panel having two-axial rotation over polar axis rotation is also significant (Table 1). Table 1 Monthly solar insolation availability (kWh/m2/day) on PV panels with trackers over the year in Dhaka.
Fig. 7 Sketch of the 2-axis array solar cells
Month
0°
10°
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
3.01 3.90 4.70 5.99 5.52 4.06 3.65 4.00 4.06 3.95 3.27 3.31 1503
3.40 4.29 4.92 6.11 5.47 3.99 3.60 3.99 4.20 4.32 3.66 3.81 1575
Tilt Angle 20° 30° 3.82 4.66 5.05 6.05 5.22 3.75 3.41 3.87 4.22 4.65 4.08 4.35 1616
3.93 4.72 4.96 5.86 4.87 3.54 3.19 3.68 4.11 4.70 4.19 4.57 1581
40° 4.08 4.81 4.92 5.61 4.62 3.29 3.02 3.52 4.02 4.74 4.33 4.72 1572
MOT 4.31 5.58 5.00 6.05 5.52 4.06 3.65 4.00 4.18 5.30 4.45 5.13 1740
Tracking Mode Double Single Axis Axis 4.49 4.73 5.70 5.81 5.92 5.92 7.30 7.38 6.36 6.62 4.42 4.63 3.95 4.13 4.48 4.56 5.07 5.08 6.10 6.15 4.89 5.10 5.19 5.50 1942 1997
An automatic solar tracking system with two-axial rotation was designed and fabricated to ensure the highest solar intensity on the panels all over the day and year and it was incorporated with a solar panel (Table 2) to observe the increase in output of the panel. Although the experiment was done in winter season, the result was very satisfactory with an increase of about (18%-23%) in power output from solar panels (Fig. 10 and Fig. 11). Table 2 Specification of solar panel
Company Name Model No. Maximum power
Fig. 8 Graphical User Interface for control unit
The software has the option to monitor the power generation of each PV panel (photo voltaic panel). The software records and shows the power generation of each PV panel by means of online update (Fig. 9). The software is made collaborated with the national grid. So the operator can easily transfer the generated power to the national grid or has the option to store that. However the software apprises the operator immediately, if a solar panel generates low power (Due to damage or interrupted). The software facilitates the operator to isolate that solar panel from the array of panels.
Micro 5125794 5W
Fig. 10 Power outputs of dual-axis solar tracking system (Date 28-12-2008)
Fig. 9 Graphical User Interface for monitoring 5. RESULT
The performance of the model was observed by providing the motion both manually and automatically. While moving the tracker manually the step size was chosen about 10° (data was taken at the tilting angels 0°, 10°, 20º, 30°, 40°).
Fig. 11 Power Outputs of dual-axis solar tracking system (Date 29-12-2008) 88
6. FURTHER DEVELOPMENT
7. SUMMARY
Bangladesh is a tropical country. We have sufficient sunlight all thorough the year. We can use this huge solar energy for power generation. Thus the solar power plant can be an excellent solution of existing power crisis in Bangladesh. Solar power plants are compact and less bulky compared to the conventional power plants, as it doesn‘t require boilers, turbines or other bulky components. In further development, the solar panel along with trackers and the control unit can be made a compact package, which can be used as mobile power generation unit. [11] This mobile power plant (Fig. 12) has the advantage of transportation from one place to another, in case of variation in solar intensity.
Investigation of the PV output power was carried out for tracking mode and fixed mode. An experimental study is done under local climate. During the experimental study PV output power with solar intensity is measured for both the tracking mode and fixed mode and the results were compared. The results indicate that PV output power is about 18-23% more for double-axis tracking PV panel compared to fixed PV panel. From the analysis, it is seen that some fluctuation of solar intensity occurred due to slight error in experimental setup. Simplicity, low cost and material availability has made the designed tracking system more effective. This system is more compact and efficient than any other tracking system with minimum cost [13]. This device does not need auxiliary power and may adjust automatically depending on the direction of the sun. With the designed Sun tracker, it is possible to get substantially more power from each PV panel and this increase in power results in lower cost per watt. From the result of the performance test of designed system the following conclusion can be drawn. 1) The designed solar tracker can follow the sun path preciously. 2) The efficiency of the tracking solar panel with respect to fixed panel was about 18-23% higher. 3) The software is highly beneficial for operating solar power plants. With the help of the software, the operator can control the movement of each individual solar panel from the control room. However, if the solar panels are subjected to environmental catastrophe or damaged, then the software apprises the operator in the control room about it.
Fig. 12 Mobile solar power plant
6.1Solar water purifying plant In hot arid regions (e.g. In Asian countries), scarcity of pure drinking water is a serious concern. A solar water purification plant [12] can be a great solution of this phenomenon. Moreover salt produced as a byproduct of salty water purification seems to be profitable. These plants may be used domestically (Fig. 13) or mass production can be achieved industrially (Fig. 14).
ACKNOWLEDGMENT This work was supported by Department of Mechanical Engineering, Bangladesh University of Engineering & Technology (BUET). REFERENCES [1]
[2]
[3]
[4]
Fig. 13 Domestic water purification by solar panels [5]
[6]
[7]
[8]
[9]
Fig. 14 Flow diagram of mass production of purified water by using solar panels
89
I. Vişa and M. Comşiţ, ―Tracking systems for solar energy conversion devices‖, in Proceedings of the 14-th ISES International Conference EUROSUN‘2004, pp. 783-788. S. Odeh a.o., ―Design of a single-axis tracking collector for moderate temperature applications‖, in Proceedings of the 14-th ISES Conference EUROSUN‘2004, pp. 527-532. S. Abdallah and S. Nijmeh, ―Design construction andoperating of one-axis sun tracker‖, Journal of Applied Science, Vol. 4, pp. 45-53, 2002. S. Abdallah and S. Nijmeh, ―Two-axis sun tracking with PLC control‖, Energy Conversion and Management, No. 45, pp. 31-39, 2004. C. Alexandru and M. Cosmit, ―Virtual Prototyping of The Solar Tracking Systems.‖ Published as M.Sc. thesis, University of Transsilvania, Romania. D. A. Pritchard, ―Sun tracking by peak power positioning for photovoltaic concentrator arrays,‖ IEEE Contr. Syst. Mag., vol. 3, no. 3, pp. 2-8, 1983. A. Konar and A. K. Mandal, ―Microprocessor based automatic sun tracker,‖ IEE Proc. Sci., Meas. Technol., vol. 138, no. 4, pp. 237-241, 1991. B. Koyuncu and K. Balasubramanian, ―A microprocessor controlled automatic sun tracker,‖ IEEE Trans. Consumer Electron., vol. 37, no. 4, pp. 913-917, 1991. J. D. Garrison, ―A program for calculation of solar energy collection by fixed and tracking collectors,‖ Sol. Energy, vol. 72, no. 4, pp. 241255, 2002.
[10] P. P. Popat ―Autonomous, low cost, automatic window covering system for day lighting Applications,‖ Renew. Energ., vol. 13, no. 1, pp. 146, 1998. [11] M. Berenguel, F. R. Rubio, A. Valverde, P. J. Lara, M. R. Arahal, E. F. Camacho, and M. López, ―An artificial vision-based control system for automatic heliostat positioning offset correction in a central receiver solar power plant,‖ Sol. Energy, vol. 76, no. 5, pp.563-575, 2004.
[12] J. Wen and T. F. Smith, ―Absorption of Solar Energy in a Room,‖ Sol. Energy, vol. 72, no. 4, pp. 283-297, 2002. [13] T.H. Mahdi, A. Morshed and Z.M. Hasib, ―Trackerbot-The Solar Tracker‖ undergraduate project, October 2007, Department of Mechanical Engineering, Bangladesh University of Engineering and Technology (BUET).
90
