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Solar powered internet methods

2,894 bytes added, 17:11, 22 April 2012
===Design Methodology===
The following design methodology was created, employed and demonstrated in an example system. The system includes three units to demonstrate the mesh network and its functionality with one unit connected directly to a broadband source and the other two functioning as relays. It was decided that the system use ultracapacitors where possible to demonstrate their potential in such an application and the feasibility of implementing such a system. The sizing of the electronic components was determined using PVSyst. The associated converters and controllers were selected to optimize efficiency while minimizing cost and necessary components.
Mechanical components including the structural elements, mounting hardware, and fasteners were selected based upon the following criteria: cost, weight, strength, component life, transportability, ease of use, and maintenance. The structural support system was designed to hold the solar array at the optimum angle for the latitude at which the system will be utilized. Using the design methodology, several example systems were built for testing.
Include here exactly how this The following design methodology was created, employed and demonstrated in a prototype system. The system initially includes one unit connected directly to a broadband source to demonstrate the feasibility of using ultracapacitors as the only energy storage devices. In the future, two other units will be constructed to desmonstrate thier functionality acting as relays to the initial unit. It was done - edecided that the system use only ultracapacitors for energy storage to demonstrate their potential in such an application and the feasibility of implementing such a system.gThe sizing of the electronic components was determined using PVSyst. screen shots explanationsThe associated converters and controllers were selected to optimize efficiency while minimizing cost and necessary components. For  Mechanical components including the structural elements, mounting hardware, and fasteners were selected based upon the following criteria: cost, strength, component life, weight, transportability, ease of use, and maintenance. The structural support system was designed to hold the solar array at the optimum angles of 30ͦ and 60ͦ for the latitude at which the system will be demonstrated. The layout of the mechanical design show how components was designed using a rapid prototyping approach. Using this method, parts were kept to a minimum while the focus was doneplaced on function and simplicity. For Ultimately, the design shown below prevailed and can easily switch between the components - give a list optimum summer angle of 30ͦ and a weblinks to all partsthe optimum winter angle of 60ͦ. The entire support structure was constructed for roughly $30.
===Sizing of system parts===
The frame is constructed of 2x4s for the initial prototype with a field quality prototype being constructed from 1in (1/16th in) aluminum angles. A simple plastic storage container functioned as a waterproof housing to protect all necessary electronic components. This was done using a simple container and waterproofing it with silicone glue on the seams. The chosen container is a Sterilite 25-quart modular latch box. A rack to hold the ultracapcitors in the waterproof housing was designed using UniGraphics NX 7.5 and printed using a reprap machine. The profile for the part can be seen below. The final product was printed to a thickness of 1/2in.
[[File:Reprap part.jpg]]
 
The .stl file can be found here – Maxwell 3,000 Farad ultracapcitor holder.
 
Each mechanical component was modeled using UniGraphics NX 7.5 and is shown in the image below.
Material properties for each mechanical component were assessed to ensure all components could withstand the loading conditions including wind loads and snow loads (PV Systems Engineering 2006). The wind load was calculated to be 46psf 55psf using the following equations.
Velocity pressure (q) = 0.00256*Kz*Kzt*Kd*V2*I (1)
Where Kz = celocity pressure exposure coefficient at height z
I = importance factor
Design Wind Pressure (p) = q *G*Cf (1)
Where G = gust effect factor = 0.85
The snow load was assumed to be less than 8 psf as is recommended in Photovoltaic Systems Engineering by Roger Messenger and Jerry Ventre. This yields a combined load force of 56 71 psf. Each mechanical component was then sized using a factor of safety of 2 as is recommended by the American Society of Civil Engineers. The factor of safety was determined using the following equation.   Factor of Safety = Factor of Safety = Material Strength / Design Load
Using 6061 aluminum angles with a yield strength of 34,000 and a max stress of 16,600 psi under the design loading conditions results in a factor of safety of 2.
 A finite element analysis was also performed on the frame members using Abaqus 6.11. The analysis confirmed that 1in aluminum angles to be used on the field testing prototype will withstand the loading conditions while accounting for the safety factor of 2. A tetrahedral mesh was used and seeded every 20 mm along the edges as can be seen in the picture below.   [[File:Mesh.jpg]]
The boundary conditions set secured the bottom of the frame to the roof preventing and displacement or rotation. The applied load was placed on the frame of the module which is directly attached to the support structure itself. The applied load of 56 71 psf was distributed around the module frame. The boundary and loading conditions for each position can be seen below.  Boundary and loading conditions at the 30ͦ tilt angle. [[File:FEA - 30 - bc and loading.jpg]] 
Boundary and loading conditions at the 60ͦ tilt angle.
[[File:FEA - 30 - bc and loading.jpg]]
 
The stress and deflection distribution for the 30ͦ tilt angle can be seen in the picture pictures below. The greatest amount of stress equated to 18,600 psi.
[[File:FEA - 30 - stress analysis.jpg]]
 
[[File:FEA - 30 - deflection analysis.jpg]]
 
 
The stress and deflection distribution for the 60ͦ tilt angle can be seen in the pictures below.
[[File:FEA - 60 - stress analysis.jpg]]
 
[[File:FEA - 60 - deflection analysis.jpg]]
 
 
===Hardware Implementation:===
 The implementation of the electronic hardware is going to be made using DC/DC converters as shown in the schematic shown below. <center>[[Image:schematic1.jpeg|500px]]</center> Describe what The firing of the MOSFET’s is controlled by the Arduino Uno and the control code is available online. The incremental inductance algorithm is going on used for MPPT control as it is It is easy to implement, robust in structure, and has efficiencies >97% in operation  The MPPT algorithm is implemented as shown belowin the flow chart. <center>[[Image:solarinternetincrementalconductance.pngjpg.jpeg|600px500px]]</center> 
The firing of the MOSFET’s is done using a Micro controller based circuit, it has been proposed to use the Arduino Uno to implement this circuit. The Perturb and Observe algorithm being considered to be used to implement the MPPT control [http://ieeexplore.ieee.org/search/freesrchabstract.jsp?tp=&arnumber=1461481&openedRefinements%3D*%26filter%3DAND%28NOT%284283010803%29%29%26searchField%3DSearch+All%26queryText%3DPerturb+And+Observe+.LB.P.AND.O.RB.].The advantage of this method is , it is easy to implement and robust in structure which increases the efficiency of the system.
The Arduino Uno micro-controller was chosen to control the converters. Using PVSyst, it was determined that the system required a 24Ah capacity battery and a 190 Wp capacity photovoltaic module to provide enough power during operation and store sufficient energy for nights and low light situations. An ultracapacitor bank of 12, 3000F of Maxwell make (BCAP3000-P270-K04) ultracapacitors with 2.25 Ah each, is being used as the storage and provides 27Ah total. The router chosen is a Cisco Linksys WRT54, because it is among the least power consuming routers, drawing only 6W. We can also calculate the sizing using simple calculations as shown below (Equation 1) the total Ultra capacitors required is around 11, but to balance the voltage across the series connected capacitors we are taking 12 with 4 ultracapacitors in series and three such series connected arrays in parallel. The ultracapacitor has specifications of DOD=0.97, Efficiency=0.95[24], and an operating voltage of 9V. The router chosen is a Cisco Linksys WRT54 drawing 6W. Now considering the losses in the converters a total load of 8.5W (as the boost converter efficiency is usually in the range of 70-80%) can be considered. Going with autonomy of 1 day and a maximum Loss of Load of 5% we can arrive at the size of the system as follows:  The electric system was simulated in MATLAB/Simulink (7.13.0.564), taking into consideration the real time parameters of the PV. The Design of Ultracapacitor bank is done as follows: <center>[[Image:ultracapbank.jpg|500px]]</center> A resistor is placed in series with the capacitor bank in order to limit the current flowing into the bank initially as it acts as short-circuit. During the time of discharge the resistance gives rise to voltage drop and there is considerable power loss across it so a Schottky diode is placed in parallel to it which has a forward voltage drop of 0.25V only and acts as a short circuit during discharge and open circuit while charging.The 24 hour simulation has been done on a simplified model of the system where the components are modeled mathematically.The modeling of ultracapacitor bank in Simulink is done as follows: <center>[[Image:simplified.jpg|500px]]</center> The voltage across the capacitor bank and there by the SOC for 24 hour period is as fol-lows:<center>[[Image:p&oSOCultracap.pngjpg|500px]]</center>
===Economic viability===
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