A residential PV power system enables a homeowner to generate some or all their daily electrical energy demand on their own roof. PV systems can also include battery backup capability to operate selected circuits in the residence for hours or days during a utility outage. The purpose of this research is to design and provide a standalone PV system with rechargeable batteries to supply electricity for a rural area residence outside of Addis Ababa at Chancho. The daily energy Consumption, load tabulation has been done by considering the floor plan of the home and the daily power consumption and energy demand of the house. Rural home in Chancho can be electrified by Using PV modules, batteries charger, Inverter, Charge Controller and Copper conductor.
Solar energy is clean and available in abundance. The energy potential of the sun is immense. Despite the unlimited resource however, harvesting it presents a challenge because of the limited efficiency of the array cells. The best efficiency of most commercially available solar cells ranges between 10 and 20 percent . This project seeks the design of a PV system with rechargeable batteries to supply electricity for rural area residence outside of Addis Ababa by considering the power required for a home. There is a growing need for energy from such sources as solar, wind, ocean tidal waves geothermal and hydropower for the provision of sustainable and power. Solar panels directly convert radiation from the sun into electrical energy. The sun delivers its energy to us in two main forms: heat and light. There are two main types of power system, namely, solar thermal systems that trap heat to warm up water, and solar PV systems that converts Sun light directly into electricity.
There are two main types of solar PV systems: grid-connected (or grid-tied) and off-grid (or standalone) solar PV systems. Off-grid PV systems applicable for area without power grid. Currently, such solar PV systems are usually installed at isolated sites where the power grid is so far away, such as rural areas. But they may also be installed within the city in situation where it is inconvenient or too costly to tap electricity from the power grid. An off-grid solar PV system need deep cycle rechargeable battery .
Photovoltaic, and other renewable energy technologies, can significantly contribute to economic and social development. Ethiopia is both densely populated and has high solar insolation, providing an ideal combination for Solar Power in Ethiopia. Power is the lifeline of any development of the nation. At present the power requirement is being met by different main sources Thermal, Hydropower, Wind, Solar and Nuclear. Fortunately, our country lies in sunny regions of the world. Among the most renewables energy supply alternative that the privet sector and others involve with solar PV system contribute to sustainable energy development. The problem that is posed is the design and determine the energy requirement which is capable of a system. The PV systems in Ethiopia is small and the main applications are for telecom station and for off-grid lighting . Now a day, due to the expanding growth rate of electric demand in Ethiopia, the country is expected to have sufficient electric energy to feed whatever electrical load that will be found in the urban area. Since the EEU is not facilitate all area, there may be problem of getting Electric power from the grid to supply their loads. To overcome this problem, we expected to be able to design a stand-alone PV system for the different household electrical application and implement to use technology.
The main objective of the research is to design a stand-alone PV system by considering the daily power consumption and energy demand of the rural residential house.
The scope of this research covers (delimits) the design of a stand-alone PV system at Chancho which the specified area of the problem faced is in the absence of coverage electrical supply. Even if this type of problem is faced in many areas due to the lack of availability of electric power, this research best choice to improve this problem.
Permit and licensing from EEP and governmental is often a very bureaucratic process involving multiple agencies in the central and local governments which may not coordinate their procedure and requirements
There may be a shortage of supply material and its initial cost is expensive.
A photovoltaic system can supply electric energy to a given load by directly converting solar energy through the photovoltaic effect. The system structure is very flexible. PV modules are the main building blocks; this can be arranged in to arrays to increase electric energy production. Normally additional equipment is necessary to transform energy in to a useful form or store energy for future use. The resulting system will therefore be determined by the energy need (or load) application .
The photovoltaic effect is the basic physical process through which a PV cell converts sunlight in to electricity. Sunlight is composed of photons (like energy accumulations), or particles of solar energy. These photons contain various amounts of energy corresponding to the different wavelengths of the solar spectrum. When photons hit a PV cell, they may be reflected or absorbed. Only the absorbed photons generate electricity. When this happens, the energy of the photon is transferred to an electron in an atom of the cell (usually silicon atoms). The electron can escape from its normal position associated in the atom to become part of the current in an electrical circuit.
To produce the electric field within a PV cell, the manufactures create a function of two different semiconductors (types P and N). The most common way of making P or N type silicon material is adding an element that has an extra election or has a deficit of an electron. Silicon is the most common material used in manufacturing process of photovoltaic cells. Silicon atoms have 14 electrons, where the four electrons in the last layer are called electrons. In a crystal solid, each silicon atom normally shares one of its four valance electrons in covalent junction with another silicon atom. The silicon crystal molecule is formed of 5 silicon atoms in a covalent junction.
The process of doping introduces an atom of another element into the silicon crystal to alter its electrical properties. The element used for doping has three or five valence electrons. Usually phosphorus is used to make the N type (phosphorus has 5 valance electrons) and Boron the P type (Boron has 3 valance electron). In a polycrystalline thin- film cell the layer is made of a different semiconductor material than the bottom semiconductor layer .
Photovoltaic modules: the basic building block of a photovoltaic module is the photovoltaic cell; these convert solar energy into electricity. The power output will depend on the amount of energy incident on the surface of the cell and the operating temperature of the photovoltaic cell. The power output of a single cell can supply small load like calculator or watches, but to be useful for high energy demand projects these cells must be arranged in series and parallel connection. A photovoltaic module is an array of photovoltaic cells pre-arranged in a single mounting mold. The type of module is therefore determined by the cells that compose the module itself .
Inverters: Inverters are used to transform DC current into AC current. In the photovoltaic industry, inverters can be classified into two broad categories:
Stand-Alone Inverters-These inverter are meant to operate isolated from the electrical distribution network and batteries for proper operation. The batteries provide a constant voltage source at the DC input of the inverter.
Grid Tied Inverters- These inverters operate coupled to the electric distribution network and therefore must be able to produce almost perfect sinusoidal voltage and currents .
Batteries: These are most commonly used to store energy in stand-alone applications for use at times when no irradiance is available (e.g. night, rainy day). Batteries are also used for a diverse number of application including stand-alone power and utility interactive schemes. PV batteries require tolerance to deep discharges and irregular charging patterns. Some applications may require the batteries to remain at a random state of charge for a prolonged time. The most common technology used in PV systems is the lead-acid battery .
Charge controllers: The charge controller is a DC to DC converter whose main function is to control the current flow from the photovoltaic modules array with the purpose of charging batteries. Most of these devises can maintain the maximum charge of the battery without overcharging or reaching the design charge.
Copper conductor: the two common conductor materials used in residential and commercial solar installations are copper and aluminum. Copper has a greater conductivity than aluminum, thus it carries more current than aluminum at the same size and we are use the copper conductor in our project .
The project began with a literature review of solar photovoltaic systems. This was followed by a simple prefeasibility study (using RET Screen tools) [Table1A] to obtain an idea of the amount of energy that will be generated by the system .
A residential home in Chancho will contain one salon, two bedrooms, corridor, Terrace/veranda, one kitchen, one shower and one toilet. Usually the kitchens, the Toilets and the shower are separated from the main house as indicated by the following floor plan diagram. As it is tried to indicate on the floor plan diagram, circles are used to indicate the lamps that must be install in each room, Small circles indicate 11W lamps whereas bigger circles indicate 15 W lamps.
The first step to sizing a solar electric system is to determine the average daily energy consumption. The average daily energy consumption should be as accurate as possible, and ways to conserve power should be considered as well because the total energy consumption will determine the size of the system.
Two important factors in solar array sizing are the sunlight levels (i.e. insolation values) of the area and the daily power consumption of your electrical loads. Taking the peak insolation of 8 hours for Ethiopia, and assuming also that the battery efficiency is 80% and Panel Efficiency is also 80% then the Panel Catalogue Power was determined using the following relationship;
Panel Catalogue power =Average Daily Energy Utilization
Panel Loss Factor X Peak hours x Battery discharge efficiency
No. of Panels = Panel catalogue power
Panel rating x panel loss factor
The size of the battery bank required will depend on the storage capacity required, the maximum discharge rate, the maximum charge rate, and the minimum temperature at which the batteries will be used.
The battery should supply the required load plus the distribution losses. It should also supply the load for 3 days of autonomy in the absence of the sun. Therefore, the required battery Ampere-hour was also evaluated .
Battery Ampere /hour= No. of Days of autonomy x Battery Load
Depth of Discharge x Distribution Losses
For stand-alone systems, the inverter must be large enough to handle the total amount of Watts in the system. As a standard design procedure, the inverter size should be 25-30% bigger than total Watts of appliances . Inverter size = load size x safety factor (1.3/1.25)
The controller size was determined as follows: Current rating = panel catalogue power x panel efficiency 24hr.
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