Steam energy: Usage and potential - Research Paper Example

? Steam Energy: Usage and Potential Introduction For generations, steam turbine power generators have been used to generate electricpower. In its conventional form, burning fossil fuels such as oil, coal or natural gas are normally used to heat water. The heated water is then turned into steam, which can be used turn power turbines for the generation of electric energy. A celebrated English physicist, Michael Faraday (1791-1867), did the first discovery of electric generation. His discovery suggested that electricity could be generated by rotating a wire coil near a strong magnet. Numerous applications utilizing a generator for the production of electrical power were formed on this basis. This is the same principle of electromagnetism that works for in a spinning turbine. Combine Cycle gas Turbine Power Plant also referred to as a gas-fired combined cycle power plant is a system that combines the capabilities of two different thermal processes in a unique way. The two thermal processes that are combined include a steam turbine together with the gas turbine to produce electricity. Normally, CCGT is the acronym that is used to describe this kind of system (Doty, 2009). In this system, close to a third of the power generated is electrical energy. This is achieved by combusting a mixture of compressed air and fuel. A generator coupled with the hot gases created in the combustion process drives the turbine. The remaining one third of the generated electrical power is produced by the steam turbine through the utilization of the hot exhaust gases that leave the gas turbine. The exhaust gases in the heat recovery steam generator (the HRSG) transfer their heat into water that is circulating. In the process, the pressure in the system rises due to the vaporizing pressurized water. The steam turbine is driven by the steam coupled by a generator. Combine Cycle gas Turbine Power Plant are technologically advance and are nowadays used all over the world. These plants are highly efficient when compared to other types of power plants. For instance, in Italy, the EGL state of the art plants achieve approximately 56 percent, which implies that the fuel energy supplied is efficiently and technically converted into electricity(Doty, 2009).. In terms of investment, the costs incurred are comparatively very low. This is attributed to the fact that the main components used in these systems are very standardized. It is possible for a compact power plant that would take approximately two or more years to construct because of the extremely powerful gas turbines. Combine Cycle gas Turbine Power Plants (CCGT) are built modular with several blocks. Each of these blocks looks like it is practically an independent, self-contained power plant. These standardized EGL power plants are made up of two blocks with approximately 760 megawatts and one of them could cover over 10 percent the annual energy needs of Switzerland. The emission of exhaust gases that are harmful can be controlled and minimized. The emissions of nitric oxide and carbon dioxide are at the lowest when natural gas is used to fire these plants. This is one advantage of coal-fired power plants when compared with the traditional thermal plants. The Working of a Combine Cycle gas Turbine Power Plant In order to ensure efficient generation of electricity, Combine Cycle gas Turbine Power Plant combines two thermal processes. One third of the produced electricity comes from the steam turbine whereas the remaining two thirds are produced by the gas turbine. A mechanical rotation occurs in the two turbines when the steam (steam turbine) or the expanding fuel gases (gas turbine) power these plants. This is then converted into electrical energy by the generators. The design of EGL power plants are such that they are multi-shaft installations in nature. This implies that, the two turbines are coupled to different generators, which is in contrast to installations considered as single-shafts. In single-shaft installations, both the turbines power the same generator. In Italy, the EGL power plants are made up of two blocks such that each of the have four drive machines, two steam and two gas turbines, and generators (four driven machines. Figure 1: Gas Turbine Figure 2: End winding of generator The Combined Cycle gas Turbine Power Plant Model Illustration Figure 3: Combine Cycle gas Turbine Power Plant Model 1. Ambient air is compressed in the compressor and drawn via the filter gases 2. In the gas turbine, natural gas is mixed in and air is compressed. Hot gases are generated under high-pressure when combustion takes place. The turbine powers the compressor and the generator. 3. Using the hot exhaust gases from the gas turbine are used to vaporize water in the heat recovery steam generator. 4. In the steam turbine, the turbine is powered by the steam and the resultant mechanical energy is transferred into the generator. 5. From the steam turbine, exhaust steam is converted back into water by the means of cooling air in the condenser. 6. These are the generators where electricity is generated by the conversion of mechanical energy. The gas turbine: the heart of the power plant In the process of producing electricity in the Combine Cycle gas Turbine Power Plant, the gas turbine is the very first stage. It draws air in via a filter, which is labeled 1 on the model from the environment. In the compressor (labeled 2 on the model), air is compressed. This implies that, air is elevated to a higher pressure. It is then directed into the chamber where combustion takes place. In the form of natural gas, fuel is fed into the combustion chamber, and then combustion begins. As a result of this process, hot gases are produced which are allowed to relax inside the turbine. This implies that, they are brought to near virtual ambient pressure. The gas then expands and spreads out. Therefore, the energy released through this process is then converted into a mechanical rotation just like when air is escaping from a toy balloon. In this scenario too, the expansion of pressure also results into motion, what is called darting off in the case of the balloon. The generator and the compressor are thus powered by the mechanical rotation. The generator into electricity then converts this energy. The hot gases exiting the turbine as exhaust gases are at a temperature of about 600°C. The heat energy generated is then transferred into the heat recovery steam generator to the water. The second stage of the generation of electricity is then put in motion. This is the steam/water cycle where pressurized water is heated and then vaporized. The gas turbine is thus considered the heart of the Combine Cycle gas Turbine Power Plant. This is because it gives the power plant its name and at the same time produces about two thirds of the electricity produced In the Combine Cycle gas Turbine Power Plant, diesel oil could also be utilized as possible fuel. However, diesel oil results in very high exhaust gas emissions compared to natural gas, which have very low exhaust gas emissions. In addition to this shortcoming of diesel fuel being used, the effort and cost required to service and maintain the turbines powered by diesel fuel are far much higher when compared to turbines powered with natural gas that have very low maintenance and service costs. Moreover, general overhauls, where the replacement of heavily used parts need replacement tend to be essential only after about three years. It is very efficient when a power plant normally has more than a single block especially during maintenance and inspection times. This is because; one part of the pant could be utilized for continued electricity production as the other block is under inspection or maintenance and is out of order. Most Combine Cycle gas Turbine Power Plants use gas turbines of the type V94.3A2. These are manufactured under a license provided by Siemens to an Italian company known as Ansaldo. The weight of the turbines is about 300 tons and a nominal output of about 260 megawatts of electricity is produced. In comparison, over 3500 VW would be required to ensure the production of this kind of output. The water/steam cycle The remaining one third of the total electricity produced by this system is from the part labeled number 4 in the Combine Cycle gas Turbine Power Plant model (Figure 3.). The steam/water cycle utilizes the heat energy from the exhaust gases that otherwise would have gone to waste in the gas turbine process. Water vapor generated by heat is used in the production of electricity with the assistance of the steam turbine. Always the same water is heated in the steam/water cycle since the steam/water cycle is always closed. This heated water is then vaporized and converted back into water in the condenser. In the Combine Cycle gas Turbine Power Plant model (Figure 3.), the part labeled 3 is the heat recovery steam generator. It is a very large and complex configuration made up of numerous bundles of drums and pipes. It is made up of three areas, each of which has different levels of pressure. One has a medium pressure level, one has low-pressure level, and the other has high-pressure level. It is thus possible to harness aremarkable amount of energy enclosed in the exhaust gas by simply dividing the heat recovery steam generator into these three pressure levels. Overall, almost all Combine Cycle gas Turbine Power Plants have a boiler that is roughly seventeen meters wide and forty-five meters high. On the Combine Cycle gas Turbine Power Plant, the part labeled 4, represents the steam turbine. The steam turbine just like the boiler is divided into three different pressure levels including one medium pressure level, one high-pressure level, and one low-pressure level. Each respective level of the steam boiler supplies the steam turbine with the right amount of steam. The supplied steam is then allowed to relax and release pressure. The steam energy is then converted into mechanical rotation, which is then transferred into the generator. Once in the generator, the mechanical energy from the mechanical rotation is the transformed into electricity. The turbine converts the steam energy into a mechanical rotation that is then transferred to the generator where it is transformed into electricity. Almost all generators have a nominal output of about 132 megawatts According to the model above, the condenser labeled 5, is the most striking of all the components of the power plants in terms of its size. Under vacuum or at negative pressure, the steam exits the turbine. It then flows into the condenser through pipes, which are a few meters in diameter where it is then cooled by air. Ambient air is added via large ventilators, which ensures that the steam becomes water again by cooling it right down. The condensate resulting from the cooling by ambient air is then pumped and returned by feed-water to the boiler. This cycle then starts afresh and continues repeatedly. The high-voltage system Another striking thing about these plants is that the generated alternating current cannot be stored. Therefore, it is imperative that these power plants are fitted with electrical systems that can convey the produced electricity reliably to consumers. The power plants have transformers, which are responsible for converting the produced electricity in a way that it can be directly fed into the high-voltage network. The plant spontaneously starts running down in a safe mode when the high-voltage network is interrupted. The power plant supplies the required output after it has spontaneously linked itself to the grid. This happens immediately after the corresponding demand exists and the electricity grid is available again. The Control System Control and Security This is the Combine Cycle gas Turbine Power Plant’s central control room. It controls, steers and monitors all the operations and processes in the power plant. All process variables and major sequences are recorded. It also assists in human intervention and can draw the relationships and differences between actual, and target conditions on its own and respond to them. In addition, the automatic responses triggered in the power plant are as a result of the numerous and continuous feedback that are sent. In a normal setting within the power plant, all the standard operation sequences are from start to finish completely automated. However, the staff operating the power plant can purposefully intervene whenever necessary to make improvements and changes. The system is capable of collecting and storing large volumes of operational data that are significant for certain important analyses. The stored data also enables the plant’s staff members to be able to determine and precisely schedule inspection and maintenance times. A Potential Alternative of Steam Turbines and Steam in Production of Energy As a potential alternative to steam turbines and steam in production of energy, solar steam turbine is a method in which solar energy can be harnessed and used in the generation of power, which involves heating water by use of solar energy from the sun. Today, the use of smaller home steam turbines is in an acute rise. They have the potential of doing more than just supplying electrical power. Solar power electricity production has today become a very common activity. Many people who own homes as well as industries can take advantage of the benefits of solar energy by the installation of PV (Photovoltaic) solar panels on the ground nearby or by mounting them on their rooftops to generate electrical power for them. However, using specialized power panel s could ensure the delivery of concentrated solar power, which can be a potential alternative for steam turbine, generated electric power. Solar heated water also produces steam, which can be used to power the blades of a turbine. In the process there is much less pollution produced. In comparison with other fossil fuel dependent steam production methods, which produce much more pollution, they are far much better and environmentally clean. However, there is an obstacle associated with solar energy powered steam turbines, which is getting the water hot enough so that it can vaporize into steam. Therefore, solar powered steam turbine engines are better alternatives for the generation of electrical energy compared to a fossil fuel powered steam turbine or natural gas powered steam turbine. The Positive Aspects of a Combine Cycle gas Combined-Cycle Power Plant The Matter of Effectiveness The key to cost efficiency of a plant is its availability. This is implied in the sense of what extent the power plant can readily operate after unscheduled and scheduled downtimes. If well maintained, Combine Cycle gas Turbine Power Plant can achieve very high upward values of up to about 95 percent. This implies that, on average, they are connected to the grid for approximately three hundred and forty five days in a year. In comparison with other types of power plants, Combine Cycle gas Turbine Power Plant boasts of a very high level of efficiency. During production of electricity by conversion of energy introduced in form of natural gas, Combine Cycle gas Turbine Power Plant loses little or very insignificant amount of energy that is technically feasible. However, achieving zero losses is impossible because of the amount of heat transfer and friction that cause some energy loss. The gas turbines manage around or close to thirty-five percent level of efficiency. The steam/water cycled when coupled to the gas turbines raises the efficiency significantly for the entire Combine Cycle gas Turbine Power Plant. This is done through the use of the heat energy from the exhaust gases, which are emitted by the gas turbines when producing steam, and thus, generates electricity. This way Combine Cycle gas Turbine Power Plants can achieve excellent values of about 58 percent. Power plants that are coal-fired, are on the other hand, between ten to fifteen percent points below the level achieved by Combine Cycle gas Turbine Power Plant. Plant efficiency is slightly lower when cooling is done with air as opposed when it is done with water. However, this offers better freedom for the operation of the plant as well as protecting natural water resources. It is worth noting that, the features of the plant are not the only guarantors and contributors to the efficiency in costs of the plants. Other contributors and decisive factors that influence the efficiency of Combine Cycle gas Turbine Power Plant also include the professionalism of the plant operation and the location of the plant. Another important feature of location that influences the efficiency of Combine Cycle gas Combined-Cycle Power Plant is its proximity to a very high-voltage power line (over three hundred and eighty kilovolts). This is because, if the Combine Cycle gas Turbine Power Plant is located close to a high voltage power line, the distance of transmission is short and thus implying very insignificant amount of energy are lost. Transmission losses can be greatly minimized. It is also important that, the capacities of the line to the consumer centers should be enough. As much as the connection to a very high voltage power line is important, connection to the natural gas supply is also significant. For this reason, an ideal location for a Combine Cycle gas Turbine Power Plant is one close to a natural gas pipeline as well as to a high-voltage power line. In order to achieve reliable operation of a Combine Cycle gas Turbine Power Plant, experienced and well-trained personnel are a basic and important requirement. Combine Cycle gas Turbine Power Plant staff should be recruited early and continuous training should be offered for them to understand their specialized duties. Normally, availability of the plant is dependent and is the responsibility of the employees’ in-charge of the sites operation. Matters such as production volumes and the use of the power plant are the responsibilities of the specialists situated at the Combine Cycle gas Turbine Power Plant head office. Cost Matters For Combine Cycle gas Turbine Power Plant, the costs of investments are far much lower when compared to other conventional thermal plants and coal-fired power plants. Currently, the costs stands at about half a million euros per megawatt of installed capacity. For coal-fired power plants, the costs of investment are almost double the amount of the investment incurred in the case of Combine Cycle gas Turbine Power Plants. The reasons for this can be attributed to the huge standardization of the major or main components of Combine Cycle gas Turbine Power Plants as well as the shorter time taken to construct these plants, which as earlier stated is about two and a half years. It is also very possible for operations on a Combine Cycle gas Turbine Power Plant to begin with only the gas turbine ready depending on the design. Later complete the steam/water cycle in parallel.The reasons for this can be attributed to the huge standardization of the major or main components of Combine Cycle gas Turbine Power Plants as well as the shorter time taken to construct these plants, which as earlier stated is about two and a half years. It is also very possible for operations on a Combine Cycle gas Turbine Power Plant to begin with only the gas turbine ready depending on the design and later complete the steam/water cycle in parallel. Through this, an investor can start generating income early enough through the sale of electricity, thus achieving better returns. Combine Cycle gas Turbine Power Plant has about twenty five to thirty years of useful life which is almost similar to other type of power plants. The costs of electricity production depend heavily on the costs of fuel. It is measured in euros per megawatt hour. With the prices of natural gas sky rocketing in the recent years, their share accounts to almost over seventy percent. Due to this huge dependency, it is far much better to use Combine Cycle gas Turbine Power Plants for the production of medium load electricity. This implies making use of the benefits of their flexibility and only making them operational when the market prices of electricity are attractive. Three hundred and eighty megawatts block size per each Combine Cycle gas Turbine Power Plant guarantees attractive economies of scale, which is measured on the costs of production. When the units are smaller, more specific investment expenditure is required thereby leading very low profits being generated. Modern Combustion Technology This is a plus for Combine Cycle gas Turbine Power Plant.Combine Cycle gas Turbine Power Plant compared to other types of energy generating plants emits greenhouse gases. Compared to all other energygenerating plants, fossil-thermal plants, which are plants that all have combustion processes, the emission of nitrogen oxide and carbon dioxide are at the lowest in plants that are powered and operated with natural gases. For coal-fired power plants, the values are almost two times the values of Combine Cycle gas Turbine Power Plant. As opposed to coal-fired power plants, natural gas is usually regarded as a very clean fuel thus implying very low emissions. To minimize and control emissions, continuous monitoring of combustion is very helpful. References Babcock and Wilcox Company (2005). Steam Its Generation and Use. Kissinger Publishing. Bell, D. R. (). Solar Steam Turbine. 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