Electrical Power System Technology - Assignment Example

Electrical Power System Technology Introduction Energy is a requirement of every living thing on this earth. Energy is directly related to power. The generation of power is usually done by converting any form of energy such as thermal energy is used to generate power in a thermal power plant and hydrodynamic energy in hydroelectric power plant. Most of these power plants make use of mechanical energy as its primary energy. With the passage of time, technology has brought much advancement in the generation, transmission and usage of power (Tester 2005). These ways are sometimes called as sustainable ways to generate, transmit and use electricity. TASK-1 A) Sustainable energy is defined as the energy that is required to fulfil the needs of the present as well as assuring the needs of the future (Tester 2005). As we know that the fossil fuel reservoirs in the world are emptying day by day, the generation of energy through the fossil fuel does not promise the future needs of energy. Sustainable sources of energy or renewable sources are plant matter, wind power, solar power, tidal power, geothermal power and wave power (Tester 2005). Solar power constitutes portions of heat and light, Electricity can be generated using both the components. The requirement of power of the world is approximately fifteen tera watts and the power provided by the sun to the earth is almost eighty six thousand tera watts (86000TW). Wind power has a potential of eight hundred and seventy tera watts (870TW). Geothermal has a potential of thirty-two tera watts (32TW) and hydro power has a potential of almost seven tera watts (7.2TW) (Jefferson 2006). The hydro power plant produces power by utilizing hydrodynamic energy of flowing water which is provided by the gravitational force of earth. The gravitational force creates a downstream of water which runs the turbine. A geothermal power plant is a thermal power plant but it does not involve fuel to boil the water. Water is pumped down the earth’s surface where the high temperature geothermal resources are available near the surface. A pipe line is drilled down the surface and water is passed through the pipe line. The same process is repeated several times till super heated steam is attained, which is further used to generate electrical power. Wind generator utilizes wind energy to generate electrical power. B) The above system uses fuel to move the turbine by boiling the water and then making a pressurized steam to strike the turbine blades, which produces a torque in the turbine. The system uses a gallon of fuel to generate a power of ten kilowatts for one hour with an efficiency of 33% to 48% (Han, Dutta and Ekkad 2000). The system can be upgraded to generate more power with an efficiency of 60%. The system uses thermal energy as input and produces mechanical or electrical energy. This system affects the environment by producing a large amount of carbon dioxide and some amount of carbon monoxide (Han, Dutta and Ekkad 2000). Both gases are involved in warming up the atmosphere producing a green house effect. Sulphur dioxide is also a by-product and a major pollutant of environment produced by the thermal power plants. As the system uses fossil fuel in the process, so it affects the cost of the product as day by day increase in petroleum products. Today the world depends on almost 25% natural gas and approximately 40% on coal to generate electrical power. Such large amounts of these sources used to generate electricity will eventually shorten us with these resources and also affect the price. C) I- The unit of electrical power is watt. Some conventional electric motors are rated to consume power in horsepower. Electrical horse power is approximately 745 watts or 0.745 kilo watts. One kilo watt is equal to 1000 watts. Electrical power is commonly measured in kilowatt/hour (kWh) at the consumption side or user side but at the production side megawatt (MWe). A single megawatt generator can generate 1000 kilowatts. The network, which supplies electricity from generation to its consumption, is called a grid (Weedy 1987). The grid contains the transmission lines and grid stations and holds the responsibility of providing uninterrupted electrical power to the user (Weedy 1987). The grid network can able to hold several mega watts. The transmission lines are made with an aluminium alloy because aluminium is lighter than copper but provides the same results. The best custodian for the system would be the government or some government department because government can deal with the system effectively. II An electrical system is incomplete without a transformer. Transformer plays a significant role in an electrical system. A transformer inductively couples two circuits transmitting the power from one circuit to the other. A basic transformer has two windings having a core between them. There may be an iron core or an air core between the two windings. The input winding is termed as the primary winding and the winding at the output of the transformer is termed as secondary winding. The number of turns in either primary or secondary winding can change the behaviour of a transformer. Transformers are used to step up or to step down the voltage using a ratio Vs/ Vp=Ns/Np, where Vs is the voltage in the secondary winding, Vp is the voltages in the primary winding, Ns is the number of turns in the secondary winding and Np is the number of turns in the primary winding. An oil cooling system is employed to lower the temperature of transformer. The generating plant produces electrical energy of about 2.3kV to 30kV (McLyman 2004). These voltages are much lesser to feed the transmission lines. So a transformer is used to step up the voltages to 115kV to 736kV. The reason for the stepping up of voltage is to reduce the losses in the transmission of the electrical power (McLyman 2004). These losses are due to the resistance in the transmission lines. Some customers are directly associated with transmission lines, these customers are known as transmission customers. These customers utilize high voltages which are of several hundred volts. At the user side, voltages are stepped down using a step down transformer, which steps the voltage down to 26kV to 69kV to be used by a sub-transmission customer (McLyman 2004). The sub-transmission customers may include larger factories. The voltages are stepped down again to 4kV to 13kV to be used by a primary customer. The voltages are stepped down to 240V-110V, which can be used to fulfil the requirements of residential units (McLyman 2004). TASK-2 A) I- The above system is a steam generator using thermal energy from coal. In a typical steam generator, water is boiled under pressure in a boiler resulting in the formation of pressurized steam. This steam is again heated to a temperature of 600 degree Celsius (Culp 1991). This type of steam is called super heated steam. This type of steam is highly under pressure. The super heated steam is then supplied to the turbine, which reacts and produces a torque in the rotor of the turbine generating a rotational motion. The rotational motion produced by the turbine is used to generate electrical energy. Another type or generator burns petroleum fuel or natural gas inside piston to provide a mechanical torque (Culp 1991). These types include diesel generators. An electrical generator converts mechanical energy to electrical energy. A basic electrical generator consists of two parts stator and a rotor (DiSalvo 1999). As the name indicates, stator is a part, which possesses stationary position and a rotor, which rotates when mechanical torque is applied. In electrical terms the two parts are armature and field. The winding part of a generator is termed as armature. The winding or armature can either be on rotor or on stator. The magnetic field of a generator is its field, mostly it is placed on rotor but it can be on stator. The magnetic field produces a magnetic flux. Faraday’s law of electromagnetic induction is used to produce the electric current as it states that varying magnetic flux makes electrons to flow in the external circuitry. Typically, stator contains the wiring and rotor holds the magnetic flux. When the rotor is rotated, it varies the magnetic flux along the stator winding, which results in the flow of electrons in the stator winding. The flow of the electrons is associated with the generation of electricity (DiSalvo 1999). II- A turbine converts mechanical energy into a useful mechanical energy as a hydrodynamics of water is converted by a turbine to a useful form of energy that is rotation; similar case is with the wind turbine (Han, Dutta and Ekkad 2000). Basically, a turbine converts hydrodynamic or aerodynamic energy into a rotational motion. A typical turbine has only one part that is its rotor. The rotor is made up of several blades. When the moving water or air strikes the blade of a turbine, the blades produces a torque in the turbine as they are shaped to do so (Han, Dutta and Ekkad 2000). This torque provides an adequate rotational motion in the shaft of the turbine. A combustion turbine or a gas turbine mixes fuel with air and ignites it. Such types of turbines are used where high rotational force is required and are commonly utilized in jet engines. III- The turbine and the generator are very much linked to each other. The rotational motion generated by the turbine can be used in a generator to produce electricity (Han, Dutta and Ekkad 2000). As the generator works by varying the magnetic flux, so a turbine can be used to rotate the magnetic flux in the generator to generate electricity (DiSalvo 1999). Such an example is very common in a hydro electricity generator. If the flow of water is reduced then there will be less rotational motion in turbine and so resulting less generation of electricity. In a thermal power plant super heated steam is produced to rotate the turbine, which then rotates the generator to generate electricity. A most common type of turbine generator combination can be seen in a wind generator, which uses wind to rotate a turbine. B) Modern utilities of electrical power depend on numerous electrical power generation systems to provide with an uninterrupted electrical power. These systems may include sustainable power generation systems as well as unsustainable power generation system. In order to achieve the best results, the grid network must be capable of dealing with the problems of synchronization i.e. phase, frequency and amplitude. Grid networks are equipped with numerous electrical and electronic component and devices, which are capable of dealing with the problems of frequency, phase, amplitude and synchronization between the frequency, phase and amplitude of two different electrical power generation systems (Weedy 1987). To eliminate the difference between the frequency generated by two different electrical power units, frequency changers or frequency convertors are utilized. Frequency convertors or frequency changers are devices, which employ different methods to convert the frequency from one A.C frequency to other A.C frequency. Conventionally frequency is converted using a motor generator set which is an electro mechanical device. In motor generator set motor is mechanically connected to a generator, which is capable of producing desired frequency (Weedy 1987). Another mechanism regarding frequency conversion is to convert the alternating current to direct current using a rectifier and then converting it back to alternating current of desired frequency through an inverter. This method is highly economical. The inverter may utilize the electronic devices such as IGCTs and IGBTs (Weedy 1987). IGBTs and IGCTs are power electronic devices which are capable of working with large power units. IGBTs are capable to operate with high frequency, voltage and current. If voltage conversion is required, the system may use a transformer. Amplitude can be converted by only with a utilization of step up or step down transformer or both of them. In a sine wave of an alternating current, amplitude represents the voltage of a system. The grid network is equipped with numerous transformers to step up and step down the voltages. The problems in the phase may usually be corrected by using phase convertors, which produce a delay in the phase. The delay in phase can make it in-phase or out of phase. C) I- Developing a power generation system using sustainable resources is not a difficult task. For my local community I will prefer a solar power generation system, which may utilize both photovoltaic cells and concentrated solar power. A concentrated solar power generation system applies a focused beam of sunbeam to boil water (Jefferson 2006). The system is also recognized as solar thermal power generation system. The system employs many lenses and concave mirrors to focus a sunbeam. Sometimes sterling engines are used to produce electrical power using a focused beam on a thermal tower. But in general solar thermal power generation system which focuses the sun beam to boil water is the best amongst all because it in more reliable amongst all (Jefferson 2006). Therefore, for my local community I will prefer to use solar thermal power generation system. However, what will happen at night. There will be no power without sun. So for continuous supply of power, molten salt is utilized. The system is capable of producing continuous power without any interruption. A linear parabolic reflector is positioned such that its focal point lies onto a receiver, which is able to trap heat energy from sun. The receiver duct is such that made that heat can enter the duct but unable to leave (Jefferson 2006). Vacuum construction is utilized to achieve the desired results. II- The system is highly economical is terms of power generation, capacity, consumption of fuel, no harmful gases. The system may also be known as green power generation system as the system is producing zero green house gases (Jefferson 2006). The system can able to generate large power units. A conventional power generation system consumes a large amount of fuel and pollutes the environment by producing tons of green house gases. The efficiency of such a power generation system is not greater than 48%. But, the solar thermal power generation system is capable of attaining the efficiency of 80% in terms of thermal efficiency and 100% in terms of inputs and outputs as the sun‘s energy costs nothing (Jefferson 2006). The system’s impact on power generation is very high because the system is so much effective that can be used for a single residential unit, a local community or a whole city. Photovoltaic cells are capable to fulfil the requirements of a single unit or a community. CONCLUSION The sustainable power generation systems have higher efficiency as compared to all conventional power generation systems. The conventional power generation system has a major contribution in the production of harmful gases or green house gases, which are responsible in rising the temperature of earth (Jefferson 2006). In order to maintain the environment of earth we should utilize the sustainable ways to generate power. All renewable resources involved in the generation of electrical power are capable of generating electrical power more than any of the conventional power generation systems. Geothermal power is restricted to some areas but other renewable resources are not restricted. Electrical energy can be generated using heat and light energy from sun and wind energy from wind. All sustainable resources are efficient and effective in generating electrical power and reducing in production of harmful gases. References Culp, A.W. Jr 1991, Principles of Energy Conversion, 2nd Ed, McGraw Hill, New York. DiSalvo, Francis J 1999, Thermoelectric Cooling and Power Generation, Science 30, pp. 703-706. Han, Je-Chen, Dutta, Sundip and Ekkad, Srinath 2000, Gas turbine heat transfer and cooling technology, Taylor and Francis, New York. Jefferson, M 2006. Sustainable energy development: performance and prospects. Elsevier, vol. 31, no. 5, pp. 571-582. McLyman, Colonel, Wm. T 2004, Transformer and Inductor Design Handbook, CRC, Chicago. Tester, Jefferson, W 2005, Sustainable Energy: Choosing Among Options, MIT Press, London. Weedy, B. M. 1987, Electricity Power Systems, Revised, 3rd Ed, John Wiley and Sons Inc., New York. Read More