Final Project for Photovoltaic Cell class<br /> A Proposal for Solar Grant<br />(Cost Estimation for Providing Electricity for 100 Village Houses in Tanzania)<br />Jonathan Kenneth Rhyne<br />Younes Sina<br />Huidong Zang<br />Sabina Nwamaka Ude<br />Mary Diane Waddle<br /> PROPOSAL FOR SOLAR GRANT<br />To produce electricity from the sun for domestic use requires a careful selection of materials to ensure reliability, dependability and affordability. Many factors need to be considered when choosing the right solar components to provide uninterrupted power. These factors include: the right choice of PV panels with good efficiency and low cost, knowledge of the sun insolation of the area in question and the best tilt to capture this energy, amount of batteries needed for back-up during cloudy days when the sun rays are blocked, the right inverters and controllers to work with your system, site selection to avoid shading, cost of labor for initial installation and subsequent maintenance, etc. Consideration of these factors entails careful calculations and wise selection of the appropriate type and number of components for optimum power production.<br />1. INTRODUCTION<br />1.1. Photovoltaic cells<br />Photovoltaic (PV) power systems convert sunlight directly into electricity. A residential PV power system enables a homeowner to generate some or all of their daily electrical energy demand on their own roof, exchanging daytime excess power for future energy needs (i.e. nighttime usage). The house remains connected to the electric utility at all times, so any power needed above what the solar system can produce is simply drawn from the utility. PV systems can also include battery backup or uninterruptible power supply (UPS) capability to operate selected circuits in the residence for hours or days during a utility outage. Photovoltaic power offers a proven and reliable source of electrical power for remote, small-scale facilities. PV systems turn sunlight directly into electricity for use. Since there are typically no moving parts in PV systems, they require minimal maintenance. While often more expensive than other renewable technologies, the modularity of PV systems and the broad availability of the solar resource, sunlight, often make PV the most technically and economically feasible power generation option for small installations in remote areas. The initial investment in a PV system typically accounts for most of its lifetime acquisition, operation and maintenance costs. The cost of a PV system rises in direct proportion to the total size of the loads. <br />1.2. Location<br />Due to energy losses when transporting electricity over distances, especially at the low voltages typical of small PV projects, PV systems should be located within a reasonable distance of the point of energy use. Fortunately, PV modules can be placed anywhere the sun shines, including the roof of a building. Care must be taken to secure the modules in areas of high winds to prevent loss or damage. PV modules are very sensitive to shading. The shading of 5% to 10% of the surface area of a module can lead to a drop in power output of 30% to 50% or more.<br />1.3. Operation and Maintenance (O&M)<br />The minimal O&M requirements of a PV system make this technology well suited for isolated locations and rural applications where assistance may be infrequently available. Preventive maintenance, such as routine system cleaning and inspection, are always recommended. The most common maintenance required for typical PV systems is the periodic addition of distilled water to the batteries when flooded batteries are used. More expensive systems, using sealed batteries, can run for extended periods (months) without user intervention. When PV systems are used and managed by community organizations or system owners, there is a critical ongoing need for training and/or assistance in system maintenance and troubleshooting. Sometimes the malfunctioning of a small fuse can be the reason for a system failure. In this case, a routine inspection by an experienced technician could reveal what caused the original problem that burned the fuse.<br />1.4. Environmental Impacts <br />A PV system produces negligible pollutants during normal operation. The main environmental impact associated with PV systems comes from the failure to properly dispose of batteries used in conjunction with the arrays. <br />1.5. Costs <br />The cost of a standalone PV system varies greatly depending on local market conditions and the quality of the equipment used. While the PV modules themselves may cost about US$7.00 per Watt, the total upfront investment cost of a PV system, including batteries, inverter, installation, etc., typically is about US$20.00 per Watt installed. Costs per installed Watt depend on system size, the installation site and component quality. Smaller systems (less than 1 kW) tend to be at the higher end of the cost range. O&M costs for small-scale PV systems are generally low, at less than 1% of initial investment costs annually. If poor quality BOS components are used, these may fail and lead to higher costs to diagnose the problem and replace the faulty components. <br />1.6. Viability<br />The PV option is most likely to be competitive when tens or hundreds of peak Watts are required in remote or hard-to-reach areas. Depending on the situation, PV may also be competitive when only a few kilowatts of energy are needed. In many rural areas, diesel or gas generators and PV systems are the only viable alternatives. Unlike generator sets, PV systems are quiet and do not generate pollution. With proper design, installation and maintenance practices, PV systems can be more reliable and longer lasting than generators. The modularity of PV systems enables systems to be well matched to the demand. When there are multiple small sites requiring electrification, PV is best installed in the form of independent systems sized to match each individual load.<br />PV systems are more likely to fail in areas that lack the commercial and technical infrastructures needed to ensure long-term sustainability. This infrastructure includes PV markets that are active enough to sustain the field over time, including suppliers of warranted PV system components, installers and maintenance technicians.<br />2. SYSTEM DESIGN CONSIDERATIONS <br />2.1. Basic Principles for Designing a Quality PV System<br />1. We selected a packaged system that meets the owner's needs. Customer criteria for a system may include reduction in monthly electricity bill, environmental benefits, desire for backup power, initial budget constraints, etc. The size and orientation of the PV array is adjusted to provide the required electrical power and energy. The off grid system selected for the village guarantees the people of the village electricity during the entire year including the rainy season. <br />2. We are ensured the roof area or other installation site is capable of handling the desired system size.<br />3. We specified sunlight and weather resistant materials for all outdoor equipment.<br />4. We located the array to minimize shading from foliage, vent pipes, and adjacent structures.<br />5. We designed the system in compliance with all applicable building and electrical codes.<br />6. We designed the system with a minimum of electrical losses due to wiring, fuses, switches, and inverters.<br />7. We properly housed and managed the batteries and inverter systems.<br />2.2. Basic Steps for Installing a PV System<br />1. We ensured the roof area or other installation site is capable of handling the desired system size.<br />2. We realized that roof mounting is better than a solar field; therefore we verified that the roof is capable of handling additional weight of PV system. <br />3. We properly sealed any roof penetrations with roofing industry approved sealing methods.<br />4. We Installed equipment according to manufacturers' specifications, using installation requirements and procedures from the manufacturers' specifications.<br />5. We properly grounded the system parts to reduce the threat of shock hazards and induced surges.<br />2.3. Typical System Designs and Options<br />There are two general types of electrical designs for PV power systems for homes; systems that interact with the utility power grid and have no battery backup capability; and systems that interact and include battery backup as well. The village has an off grid system with large battery banks so the people of the village have electricity during nights as well as the rainy season.<br />2.4. Typical System Components<br />The village has typical system components as follows:<br />
A PV Array is made up of PV modules, which are environmentally sealed collections of PV Cells- the devices that convert sunlight to electricity. Often sets of four or more smaller modules are framed or attached together by struts in what is called a panel. This panel is typically around 20-35 square feet in area for ease of handling on a roof. This allows some assembly and wiring functions to be done on the ground if called for by the installation instructions. The solar panel is consisted by series or parallel connected solar cells. Thus, the work principle of the solar panel is same as the principle of single solar cell which generates electricity by photovoltaic effect. The photovoltaic effect refers to photons of light knocking electrons into a higher state of energy to create electricity. Moreover, the materials presently used for photovoltaic include mono-crystalline silicon, polycrystalline silicon, microcrystalline silicon, cadmium telluride, and copper indium selenide/sulfide. And the efficiency is around 10%-20%.<br />The PV array used for each home in this village is a roof mounted system. The panels will be attached on the north side of each home flat against the roof. The angle on the roof is 20°, so this places the panels at 20° above the horizon facing the equator. The array on each house will be a total of 78 panels split between the two sections of the roof leaving one side with a 4x10 panel grid and the other a 4x10 grid that is lacking two panels at the top. The panel we chose was a 180W panel from China with a 16% efficiency. The panels cost $283 dollars each. A detailed price assessment will be discussed later.<br />
Balance of system equipment (BOS)
BOS includes mounting systems and wiring systems used to integrate the solar modules into the structural and electrical systems of the home. The wiring systems include disconnects for the DC and AC sides of the inverter, ground-fault protection, and overcurrent protection for the solar modules. Most systems include a combiner board of some kind since most modules require fusing for each module source circuit. Some inverters include this fusing and combining function within the inverter enclosure.<br />
This is the device that takes the dc power from the PV array and converts it into standard AC power used by the house appliances. It is a necessary component in the system, because the solar panels and the batteries are DC source power, but the load is AC mode. Basically, the inverter can be divided by two types, one is stand along inverter and the other is grid tie inverter. The off grid inverter is used in isolated solar power system. And the inverter has the following functions: Overload protection, Sort circuit protection, the over-voltage protection, overheating protection.<br />We chose a 220V 50Hz 3kW inverter/charge controller from China. This unit has the inverter and the charge controller built into one unit. Each unit costs $1,757. Every house will have one active unit and another deactivated united on site for a replacement after the 5 yr life of the active unit is exceeded. The peak load that each house will experience throughout the day is 1.6kW which is within the limits of the unit.<br />
This includes meters to provide indication of system performance. Some meters can indicate home energy usage.<br />
Battery backup system components
Because all of the energy produced by the solar modules at any given time need to be stored as chemical energy, thus a battery bank is installed to collect and store excess energy to use when needed. The batteries used in solar applications are usually specialized, deep-cycle lead acid batteries.
The battery backup system include of the following components:<br />1. Batteries and battery enclosures<br />2. Battery charge controller<br />3. Separate subpanels for critical load circuits<br />This by far is the most expensive section of the project. The batteries themselves are cheap, $168, however the quantity needed to sustain each house through the rainy season is tremendous, 862 batteries per house. This totals 86,200 batteries for the village at a cost of 14.5 million dollars! This number could be tripled if the batteries only last 3 yrs and the grant is to provide power for 10 yrs. Since we are only discharging the batteries to their rated depth of discharge once a year, we are hoping that the batteries will last longer than this.<br />
A charge controller, charge regulator or battery regulator is one of the necessary components in the solar power system. It limits the rate at which electric current is added to or drawn from electric batteries. The most important factor of charge controller is preventing the overcharging that may prevent against overvoltage, which can reduce battery performance or lifespan, and may pose a safety risk. It may also prevent completely draining ("
) a battery, or perform controlled discharges, depending on the battery technology, to protect battery’s lifetime. The terms "
may refer to either a stand-alone device, or to control circuitry integrated within a battery pack, battery-powered device, or battery recharger.<br />This photovoltaic system is designed as an off-grid system that will withstand extreme temperature variations. This off-grid system is in Africa where its proximity to the equator and height influences the intensity of the sun. The more intense the sunlight, the more watts the solar panels will produce. This effect will increase the voltage and will potentially damage the batteries. The batteries are of major economic concern for an off-grid system and their importance is paramount. A charge controller is used to regulate the charging voltage to the batteries.<br />Charge controllers use a three stage cycle as bulk, absorption, and float. The graph below will illustrate the relationship between amps and voltage.<br />Fig1. Relationship between amps and voltage through the charging cycle<br />There are two multistage charge controllers used in PV systems; pulse width controllers (PWM) and maximum power point tracking (MPPT). Pulse width controllers maintain the constant voltage need, while the mppt match the battery voltage to the output of the solar array. The controller’s primary purpose in a PV system is to handle the maximum current produced by the solar array. The considerations in selecting a controller are as follows:<br />High/Low voltage disconnect<br />Temperature Compensation<br />Low voltage warning<br />Voltage meters/reverse current protection<br />These considerations must be analyzed to insure the batteries and the PV system is protected.<br />
Fuse, wire and switches
The function of fuse is to protect the solar power system and the standard of choosing fuse, wire and switches need to consider the value of current used in the situation of maximum output. The wire chosen for this project was tin plated copper wire that costs $0.805 per meter. We will require 5000m of wire for the complete system in the village.<br />
Utility switch <br /> 2.5. PV Installation<br />There are several ways to install a PV array at a residence. Often the most convenient and appropriate place to put the PV array is on the roof of the building. The PV array may be mounted above and parallel to the roof surface with a standoff of several inches for cooling purposes. In this project we decided to install the PV arrays on the roof of the houses to reduce the cost of wiring and also to reduce the risk of damage from accidental human and animal interference. The batteries and inverter/charge controller will be housed in a 25ftx25ftx8ft basement to the right of each house shown in figures 2.5.1 and 2.5.2. <br />Figure 2.5.1 black square is the house, the red the basement, the blue lines are the distance between houses, and the arrows say there are ten rows with ten columns.<br />Figure 2.5.2 gray is the walking space, the blue is the battery rows and the green is the inverter<br />There will be five rows of batteries that are that are 7 batteries high and 25 batteries long. The inverter will be in the lower corner depicted by the green square. This space also gives extra space for the spare inverters and panels.<br />3. Estimating System Output<br />PV systems produce power in proportion to the intensity of sunlight striking the solar array surface. The intensity of light on a surface varies throughout a day, as well as day to day, so the actual output of a solar power system can vary substantial. There are other factors that affect the output of a solar power system. These factors are standard test condition for modules, temperature, dirt and dust, mismatch and wiring losses, and DC to AC conversion losses. <br />The first step in estimating the power required for the village was to calculate the load each house has per day. This number was figured from the numbers below.<br />Lights<br />25W*10lamps*12h/day = 3kWh/day<br />Refrigerator<br />700kWh/yr*yr/365days = 1.91781kWh/day<br />Television<br />125W*5h/day + 15W*19h/day = 0.91kWh/day<br />Air Conditioner<br />750W*24h/day = 18kWh/day<br />Computer<br />200W*5h/day + 10W*19h/day = 1.19kWh/day<br />Washing Machine<br />0.25kWh/wk*wk/7days = 0.03572kWh/day<br />Total = 25.05353kWh/day/house <br />So each house uses ~25kWh/day. Next we found the insolation for the latitude and longitude of the village using the NASA surface meteorology and solar energy website. This site is very useful and gives virtually every parameter needed to perform any calculation and provides long term averages of 22 yrs for the data. The data we used is selected in red below in figure 3. <br />Figure 3 solar insolation at 18° averaged for each month<br />The slope of the roof is 20°, so we took the data for 18° above the horizontal facing the equator. We used the lowest insolation month to figure the number of panels. The lowest month is June with a value of 4.55kWh/sq.m/day which is in winter. The calculation was: 25.05353/(4.55*0.18*0.4) which gives 77 panels. The 0.18 is the watt rating of the panel in kilowatts and the 0.4 is for total system efficiency. The total be seen in table 3. <br />Table 3 the red numbers are the individual efficiencies used and the blue number is the total<br />Average PV System Component Efficiencies<br />PV array80-85%<br />Inverter80-90%<br />Wire97-98%<br />Disconnects, fuses98-99%<br />Total grid-tied PV system efficiency60-75%<br />New batteries (roundtrip efficiency)65-75%<br />Total off-grid PV system efficiency (AC)40-56%<br />The number of batteries was found by taking the total amount of charge required to sustain the house for the 3 month rainy season. It was given that each house receives 2 days of sunshine per week at random during the 3 months. Looking at the calendar, it is likely that there will be a total of 9 days total sunshine in both the months of Aug. and Sep. while Oct. will likely have 8. This results in a total of 26 days, the rest of the days will be discharging from the battery. The calculations for this can be seen in figure 3.1 below.<br />Figure 3.1 excel calculations used to determine the system size<br />The 2nd row is the insolation per month, the 3rd is the excess kWh produced, the 4th the sunny days in that month, and the 5th the total excess kWh produced during that month. The numbers in the 6th row are the sum of the corresponding color numbers above, the purple is the pre-spring months and the blue the post-spring ones. The pink numbers in the 7th row are the total kWh discharged from the batteries for that month and the total below them. The gray is the total kWh held in the 862 batteries at 80% depth of discharge. It is slightly above the pink total discharged over the spring months. The orange numbers in the last row are the kWh added back to the batteries. The middle number is a sum of the other two which is greater than the pink discharge total. This means that the batteries are fully recharged for the spring months every year. It turns out that the panels needed to be increased to 78 in order for this to happen. The batteries are fully discharged to 80% and recharged once a year.<br />4. Cost calculations<br />4.1. Cost of components<br />The cost for each components and the shipping information is listed in follow. Fig.4.1 shows the cost breakdown of components. <br />4.1.1. Controller and inverter (integrated system)<br />Company: Shanghai Jinxian Solar Tech Co. Ltd http://shayanjian.cn.alibaba.com/ <br />Tel: +86 21 5227 4750 (Mr. Jianghong Sha)<br />Model: HT22030J7<br />Output: 220V 50Hz 3000W<br />Price $1757<br />Size after packing 1m*1m*2m<br />Due to the peak hour power needed in a single house 1655Wh<br />The total controller and inverter integrated system would be<br />2 unit per house/ one active and one replacement with 4 spares <br />The total cost for controller and inverter integrated system: $1757*204=$358,428<br />4.1.2. Solar wires<br />Company: Shanghai Yingqiang Electronic Co. Ltd<br />http://liyoch.cn.alibaba.com/<br />Tel: +86 21 5947 0669 (Mr. Yongchun Li)<br />Model: PV1-F TIN PLATED COPPER WIRE<br />Brand: Yongben<br />Price: $0.805/m<br />The length of wire is calculated based on the map in the assignment, assuming the height of house is 4m. (5000m is needed)<br />So the total cost for wire is 5000m*0.805/m=$4025<br />4.1.3. Battery<br />Company: Shenzhen Haonaite Power Co. Ltd<br />http://detail.china.alibaba.com/company/detail/yhz9394.html<br />Model 12V200AH<br />Size: 522*238*218（mm）<br />Price: $158 plus $10 for box<br /># Batteries per house 862<br /> The total cost $168*862*100= $14,481,600<br />4.1.4. Fuse and switches<br />Fuse-Company: Shenzhen Weilangte Electronic Co. Ltd<br />http://shenzhenweilangte.manufacturer.globalsources.com.cn/si/6008828299332/Homepage.htm<br />Model: UDA/UDA-A<br />Max current: 10A; Max voltage: 250V<br />Size: 5mm*20mm<br />Price: $0.02<br /># fuses: 500 PCS<br />The total cost $0.02*500= $10<br />Switch-Company: Zhengtai electronic Co. Ltd.<br />http://www.chint.net/index.php<br />Model: NB1-63 220V 50Hz<br />Price: $3.5<br /># fuses: 300 PCS<br />The total cost $300*3.5= $1,050<br />4.1.5. Panels<br />Table4.1.5. shows some panel providers from different countries with deferent types, models, dimension efficiency and price. The GOD Company from China is selected as the panel provider for the village.<br />Panel Cost: $283x 7800=2,207,400 <br />4.2. Transportation Cost<br />4.2.1 Shipping from Shanghai to Tanga<br />40 gp container: 12.01m*2.33*2.38m Price: $630<br />Company: Sinotrans Container Lines Co., LTD<br />Website: http://www.sinolines.com/<br />
The size of panel after packing approx: 1.8m*0.9m*0.1m<br /># of panels 78*100=7800 pieces<br />So approx 300 panels per container<br /># of containers for panels: 7800/300=26<br /># cost for shipping panels = $630*26= $16,380<br />
Controller and inverters
The size of container is 12.01m*2.33*2.38m<br />The size of controller and inverter is 1m*1m*2m<br />So each container can load 12 systems<br /># Containers = 204/12 =17 containers<br />Cost for controller and inverter is $630*17 = $10,710<br />
Wires, Fuses and Switches
1 container is enough. <br /># Cost = $630<br />
According to the size of container and batteries<br />Each container can load 2400 batteries<br />So # container is 86200/2400= 36<br />Cost for shipping batteries<br /># 36*$630= $22680<br />Total cost for shipping <br />$16,380 + $10,710 + $630 + $22,680 + $1,060= $51,460<br />Fig.4.2. shows the cost breakdown for the shipping of the components.<br />
Transportation cost by truck
Total cost: $516,600<br />1300 trips/2$ per mile/ 216 miles<br />Fig.4.2.2 shows the distance from the port to the village that is the basis of shipping by truck.<br /> Fig.4.2.2. Distance from the port to the villageFig.4.Fig.<br />