A Detailed Analysis of Power Demand Compensation by Using Photovoltaic Power Generation

The available information on photovoltaics have a big selection of articles on the topic of photovoltaics. Most items are limited in scope, perhaps heralding a new discovery or discuss a particular project or application. The Internet offers a wealth of information as well, with sites sponsored by government agencies, industry groups and manufacturers. We had some trouble finding an overview of the topic. Most books on photovoltaics at least five years and cover the technical aspects of PV power without providing an assessment of the feasibility of using photovoltaics to generate energy. Why require a study of photovoltaic power generation The high cost of electricity by solar cells compared to conventional coal, gas and nuclear power generation has remained photovoltaic power generation to be in widespread use. Less than 1% of electricity is generated by photovoltaics. However, there are some applications where PV is economical. These applications include satellites, developing countries lack access to electricity, distribution infrastructure, and remote or rugged areas, is running distribution lines are not practical. As the cost of PV systems drops, more applications are economically viable. The clean look of photovoltaics can make it an attractive option, even when conventional power generation systems are more economical. The manufacture of photovoltaic systems has increased steadily over the past 25 years. It is inevitable that engineers will be called to develop photovoltaic technology or will be involved in projects using this technology. Many of the existing reports on photovoltaics covers only one facet of the technology, and writers sometimes inflate their reports on behalf of the company. There is a need for an up-to-date, objective understanding of photovoltaic power generation. With this in mind, we created this report. Photovoltaic technology scientists have known of the photovoltaic effect for more than 150 years. The photovoltaic power generation was not considered practical until the advent of the space program. The first satellites require a power source and the solution was not expensive. The development of solar cells for this purpose led to their eventual use in other applications. Output power and efficiency rating Figures for the power and efficiency of photovoltaic cells, modules and systems may be misleading. It is important to understand what these numbers mean and how they relate to the power output of installed photovoltaic generation systems. Ratings Photovoltaic power generation systems are rated in kilowatts peak (kWp). This is the amount of electricity that a new cleaning system is expected to produce when the sun is directly overhead on a clear day. We can safely assume that the actual output will never reach this value. The output of the system is compromised by sun angle, atmospheric conditions, dust collectors, and deterioration of components. When comparing conventional photovoltaic systems for power generation, we must bear in mind that PV systems are only productive during the day. Therefore, a 100 kW photovoltaic system can produce only a fraction of the daily production of a conventional generator of 100 kW. Rating of effectiveness The effectiveness of a photovoltaic system is the percentage of solar energy converted into electrical energy. The efficiency of the figures most often are the results of laboratory tests with small cells. A small cell has a lower internal resistance and lead to greater efficiency than large cells used in practical applications. In addition, PV modules are made up of many cells connected in series to provide a usable voltage. Because the internal resistance of each cell, increasing the total resistance and the efficiency is reduced to about 70% of the value of a single cell. The efficiency is greater at lower temperatures. The temperatures used in laboratory measurements may be lower than those of a practice facility. The conversion of sunlight into electricity A typical PV cell consists of semiconducting material (usually silicon) with a pn junction as shown in Figure 1. Figure 1. Application of solar cells solar light that reaches the cell increases the energy level of electrons and release them from their atomic layers. The electric field at the pn junction drives the electrons in the n region, while positive charges are taken to the p region A metal grid on the surface of the cell collects the electrons while a metal back plate contains positive charges. Light generates electrons and p-Type Hole-n type thin-film technology thin film solar cells are manufactured by applying thin layers of semiconductor material to a solid support material. The composition of a typical thin film cell is shown in Figure 2. Sunlight entering the intrinsic layer generates free electrons. The p-type and n-type layers create an electric field across the intrinsic layer. The electric field drives the free electrons in the layer of ntype while positive charges accumulate in the p-type layer The total thickness of p-type, intrinsic, and n-type layers is about one micron. Although less efficient than a single and polycrystal silicon thin film solar cells offer greater promise for large-scale generation of energy due to the ease of mass production and low cost of materials. Thin film is also suitable for building integrated systems, because the semiconductor films can be applied to building materials such as glass ceilings and walls. Fig 2. Using thin film instead of silicon wafers reduces the amount of semiconductor material required for each cell and therefore reduces the cost reduction of photovoltaic cells. Gallium arsenide (GaAs), copper indium diselenide (CuInSe2), cadmium telluride (CdTe) and titanium dioxide (TiO2) are materials that have been used for thin film photovoltaic cells. Thin films of titanium dioxide have been developed recently and are interesting because the material is transparent and can be used for windows. Tin oxide is a tin oxide conductive material which is transparent when in a thin layer. Tin oxide is used instead of a wire mesh for the upper layer of thin film photovoltaic sheets. Amorphous silicon (a-Si) amorphous (not crystalline) silicon technology is the most popular thin film. It is prone to degradation and efficiency of the cell produces 5-7%. Double and triple-junction designs improve efficiency of 8-10%. Extra layers capture different wavelengths of light. The top cell captures light blue, cell capture half light green, and the bottom cell captures red light. Variations include amorphous silicon carbide (a-SiC), silicongermanium amorphous (a-SiGe), microcrystalline silicon (mc-Si) and amorphous silicon nitride (a-SIN). Cadmium Telluride (CdTe) and cadmium sulfide (CdS) photovoltaic cells using these materials are being developed by BP Solar and Solar Cells Inc. polycrystalline silicon poly-crystalline silicon offers improved efficiency in amorphous silicon while using only a small amount of material. By concentrating collectors use a lens or mirror to concentrate sunlight on a small area, you can reduce the amount of photovoltaic material needed. A second advantage is that greater cell efficiency can be achieved with higher concentrations of light. To accommodate the higher currents in the photocells, a wire mesh is used more. For example, in a system with a concentration ratio of 22X, the network covers 20% of the solar cell surface. To prevent this blocks 20% of sunlight, a prism is used to redirect sunlight into the photovoltaic material, as shown in Figure 3. A second problem is that the high temperatures of a system of concentration. The cells can be cooled with a heat sink or heat can be used to heat water. Fig 3. Only direct sunlight, not scattered by clouds or fog, can be concentrated. Therefore, the concentrating collectors are less effective in places that are often cloudy, as coastal areas. How much power is available from the sun? Sunlight reaches the Earth's outer atmosphere on the strength of 1367 watts per square meter, which is defined as AM0, or "zero air mass." Atmospheric losses reduce the power of the sun to about 1000 W/m2 when the sun is directly overhead on a clear day. Figure 4 shows the average daily sunlight falling on a surface of square feet that has shifted toward the southern horizon at an angle equal to the latitude. Note that diffuse and direct sunlight means, which makes this map applies to flat plate collectors. Fig 4. The average daily sunlight kWh/m2 most efficient conversion efficiency of PV modules usually employ monocrystalline silicon cells with efficiencies up to 15%. Poly-crystalline cells are less expensive to manufacture, but the performance of module efficiency of about 11%. Thin-film cells are less expensive yet, but give the efficiency at around 8% and suffer the greatest losses of deterioration. Considerations of production in the past, low-grade silicon was purchased from semiconductor manufacturers for use in the construction of solar cells. With improvements in the manufacturing process, silicon manufacturers are able to consistently produce the most profitable semiconductor grade silicon. As a result, it is increasingly difficult to buy low-grade silicon. It has been much discussion about building a production facility dedicated to the production of silicon for solar cells. Photovoltaic applications photovoltaic power generation has been very useful in remote applications with small power requirements where the cost of operation of distribution lines is prohibitive. As PV becomes more affordable, the use of photovoltaics for grid connection applications is increasing. However, the high cost of photovoltaic modules and require large barriers remain to the use of photovoltaic power to supplement the existing electric utilities. An interesting approach to both of these problems is the integration of photovoltaics in building materials. Building integrated systems for building integrated PV (BIPV) offers advantages in cost and appearance by integrating photovoltaic properties of construction materials such as roofing, siding, and glass. When BIPV materials are substituted for conventional materials in new construction, the savings involved in the purchase and installation of conventional materials are applied to the cost of the photovoltaic system. BIPV installations are architecturally more attractive than the roof mounted structures PV. For example, United Solar Corporation produces photovoltaic roof tiles that replace the normal asphalt shingles. Each tile PV replaces seven-foot long row of asphalt shingles, and any repair you can install. Normally, only one third of a roof needs to be covered with photovoltaic panels to produce enough power for the average household. Glass photovoltaic properties made available for use in skylights and windows. The architect may choose from several colors of transparent photovoltaic glass. The dye color and depth is controlled by the type and amount of semiconductor material used in the construction of photovoltaic glass. Outside the grid Applications Most applications of photovoltaic power generation are remote, off-grid applications. These include communication satellites, ground communication sites, homes and remote villages, and water pumps. These are hybrid systems sometimes involve an engine-driven generator to charge the battery when solar energy is insufficient. Networked applications in network-connected application, the DC power from solar cells run through an inverter and fed back into the distribution system. Grid-connected systems have proved an advantage in natural disasters, providing emergency power capabilities when they interrupted the public. Although PV is generally more expensive than the utility provided by the power, the use of networked systems is increasing. The economics of photovoltaic energy efficiency of photovoltaic generation and manufacturing costs have not reached the point that photovoltaic power generation can compete with conventional coal, gas, nuclear energy and facilities. The cost of photovoltaic power (when storage is not required) is two to four times that of conventionally produced energy. It is difficult to define this relationship precisely due to variations in the cost of producing and distributing conventional electrical power and other variables. Because of the wide range of these variables, some applications of photovoltaics are economically superior to conventional systems. Conclusion However, large variations in the cost of conventional electricity, and other factors, such as the cost of distribution, to situations where the use of photovoltaics is economically viable. Photovoltaic energy is used in remote applications such as communications, homes and villages in developing countries, water pumping, camping, and boating. Grid connected applications such as power generation facilities use and residential rooftop installations comprise a segment smaller but rapidly expanding use of photovoltaics. Moreover, as technological advances reduce the cost difference, the applications are increasingly viable economically at a rapid pace.