PV Mounting System - Dissertation Example

? PV Mounting System Lecturer Photovoltaic (PV) Mounting System The mechanical mounting system for the Photovoltaic (PV)System will be designed for: Maximum PV performance; Low cost; Durability; Ease of installation; Portability; and Security of the PV system Concept Generation Concept generation is aimed at coming up with a suitable mounting system based aforementioned design criteria. The concept generation strives at pinpointing the best mounting system to adopt, the best material to use and the security system to be employed to fulfill the design criteria already mentioned. PV Mounting There are two distinct methods of mounting PV solar systems, which enable installation of systems in different locations depending on systems energy output ratings and weight characteristics of cells and support systems. The two PV mounting methods include fixed tilt mounting and the azimuth (sun tracking) PV mounting systems. 1. Fixed Tilt Mounting System PV panels are installed at permanent angles. The angle is usually predetermined so that there is an optimum solar radiation being received, by the panel, throughout the year. Efficiency can be increased by mounting the PV panels on a double axis, where two panels are mounted in such a way that they face away from each other, at an angle, as shown in figure 1 (Sampson 2009). This is opposed to a single axis mounting where the panel (or panels) is mounted on one side of the mounting structure as shown in figure 2. Double fixed tilt mounting system is usually more expensive than single fixed tilt mounting system because double fixed tilt mounting structures require more materials than their single mounting counterparts do. However, double fixed tilt mounting system results to higher PV performance since the panels’ exposure to solar radiation is higher than in single fixed tilt mounting systems. Figure 1: Double axis fixed tilt mounting system Figure 2: Single axis fixed tilt PV mounting system (Sampson 2009) 2. Azimuth (Sun Tracking) PV Mounting System This mounting system aims at maximizing panel’s exposure to the sun, which results into an increase in power output. It is essentially a combination of the single and doubles axis fixed tilt mounting systems whereby an automatic adjustment system makes a single axis fixed tilt mounting system operate like a double axis mounted fixed tilt mounting system. The automatic adjustment system changes the panel’s angle with respect to the sun’s position, in the sky, and the PV array as shown in figure 3. There are two mounting arrangements under the azimuth mounting system: single axis and double axis tracking system. In the single axis sun tracking system, the panel is adjusted with respect to the sun’s East-West movement only (single axis). On the other hand, in double axis tracking system, the panel is usually adjusted along two axes, the east-west sun’s movement and the seasonal shifts in sun’s position. In other words, the double axis tracking system adjusts the panels with respect to sun’s position in the sky throughout the year (Sampson 2009). Figure 3: Azimuth PV mounting system (Sampson 2009) The azimuth PV mounting system offers power advantages compared to the fixed tilt mounting system although it is much more expensive than the fixed tilt mounting system due to its complexity. Due to their low initial and operation costs, single axis fixed tilt PV mounting systems are often used for home application (Glasnovic and Margeta 2009: 1144). In addition, single axis fixed tilt mounting systems are easy to install because they only require a mounting frame that is tilted at an angle and a PV securing system. However, power output is usually minimal, which may require people to use panels that are of a higher capacity than their domestic needs to ensure that enough power is collected during the exposure time, which is often a fraction of the daylight (Glasnovic and Margeta 2009: 1144). Otherwise, power collected during the day may not be sufficient to run basic domestic application at night. Double axis fixed tilt may be an alternative PV mounting system that can overcome the power disadvantages of single axis fixed tilt mounting system usually used. However, double axis fixed tilt mounting system requires at least two panels, which interprets to increased initial cost. Therefore, a system that adjusts a single axis fixed tilt mounting system to perform like a double axis fixed tilt system is required. Such a system, which will be designed, will enable a user to adjust the tilt angle of the panel, at least two times in a day, to maximize PV’s power output, like a double axis fixed tilt mounting, but at a reduced initial cost. The user can adjust the panel’s angle as many times as possible. The new system will be a manual version of the single axis azimuth mounting system, which will result to higher PV’s power output than the fixed tilt mounting system, but lower than the azimuth tracking system. However, power output will highly depend on the availability of a person to adjust the angle at least twice a day, when the sun changes its position in the sky. The adjustment system will be calibrated in such a way a person can adjust the mounting angle at one-hour intervals as shown in figure 4. Figure 4: The manual tracking PV mounting system Materials The materials used should be readily available at reduced prices. PV panels are usually exposed to harsh weather conditions including, high temperatures variations and rain. Therefore, the material used in making the frame, securing system and the adjustment system must withstand such conditions. In other words, they must be durable at their application to avoid frequent repairs, adjustment and replacements, which may lead to PV destruction- PVs are usually delicate as they can easily break. The mounting and securing system should avoid excessive, if any, shading or obstruction of PV exposure to sun to ensure maximum performance. Aluminum has characteristics that make it suitable for the frame, especially due to its corrosion resistant property (Hasan 2007: 17). However, aluminum is usually expensive and not readily available. In addition, aluminum has a high thermal expansion property that makes it unsuitable. Further, aluminum requires special processing, especially when welding it (Hasan 2007: 19). Steel is readily available at reasonable prices and various shapes. However, it is easily attacked by rust, which makes it necessary to apply protective coats to ensure durability. It is easily machine-able and does not require special treatment during processing, especially when welding (Ashby and Jones 1992: 87). Therefore, steel will be used for the frame and adjustment system. L-bar will be used for the frame. Durability will be ensured through painting of all parts that are exposed to water. Adjustment System The adjustment system shall employ a system that connects the mounting frame on the roof with an adjustment wheel located inside the house. A rope (nylon, sisal or steel) can be used to transmit the motion from the wheel to the frame. The material used should be durable. The system will not be exposed to the sun, which means that temperature is not an issue. However, the material should avoid excessive extensions, due to the load associated with the adjustment, which will result into inaccuracy. Sisal is readily available at reduced cost, but it can easily wear out especially in places where abrasion is involved. Nylon is also readily available at reasonable cost, but it easily wears under abrasion and it extents under weight. Therefore, the two materials shall not be used. Steel rope is readily available but at a relatively high price. However, it is durable and extends far much less than nylon rope. Therefore, steel rope shall be used for the adjusting system. Security To ensure security of the PV panels, and ensure that thieves will not run away with the panels, a padlock shall be used to secure the panel by locking up the upper and lower sections of the frame. The upper section, which shall be removable, will be slid into slots made in the lower section and then locked up. The padlock shall be prevented from rain by a cover. The entire design is as shown on the figures that follow. High temperatures usually lead to reduced PV performance since they reduce the power output of a panel (Boxwell 2011: 42). Therefore, the mounting system should allow for air circulation to cool the panels during hot days. This shall be facilitated by ensuring that enough space is available between the roof and the bottom of the mounting system. Further, the bottom of the mounting system shall be as clear as possible to avoid obstruction to air flow. The mounting system shall rest on the roof via a shaft, which will facilitate rotation motion (for angle adjustment). The shaft shall be designed for 60 kilograms, which will comprise the weight of the PV, the mounting system and any other unexpected weight. Further, design will be based on a full shaft and a torque of 2 Nm, which is the optimum torque that a person can produce when tilting the PV. Figure 5: Free Body Diagram Maximum bending moment at the centre, The Equivalent twisting moment, = 11.772 Nm Equivalent twisting moment (Te), Where t is the Yield strength = 250 mPa for steel = 6.21 mm A shaft of diameter 6.21 mm would be sufficient. Two (20 mm long) pieces of steel shaft of standard diameter steel shaft of 25 mm will be used. They shall be attached to the mounting frame as shown in figure 10. Figure 6: Lower PV locking frame Figure 7: Upper PV locking frame Figure 8: PV locked by upper and lower locking systems. The upper part slides into a slot provided in the lower part, and the two are locked with a padlock that is protected from rain by a steel plate Figure 9: tracking system Figure 10: The PV mounting system complete Figure 11: Detailed drawing Figure 12: Detailed drawing Bibliography Ashby, M.F. & Jones, R.H. 1992. Engineering Materials 2. Oxford, UK: Pergamon Press. Boxwell, M. 2011. Solar Electricity Handbook: A Simple, Practical Guide to Solar Energy- Designing and Installing Photovoltaic Solar Electric Systems. Warwickshire, UK: Greenstream Publishing. Glasnovic, Z. & Margeta, J. 2009. “The Features of Sustainable Solar Hydroelectric Power Plant”, Renewable Energy, vol 34, no. 7, pp. 1742-1751. Hasan, H. 2007. Understanding the Elements of the Periodic Table: Aluminum. East 21st Street, NY: The Rosen Publishing Group, Inc. Sampson, G. 2009. “Solar Power Installation on Closed Landfills: Technical and Regulatory Considerations.” U. S. Environmental Protection Agency. From Accessed July 18, 2012. Read More