Power Station/ Rinecopo
Chapter
Station design and layout
1 Introduction
Power stations are complex arrangements of individual plant items, equipment and mechanical and electrical engineering systems. The term ‘station’ in its widest sense can be taken to include all the plant equipment, engineering systems and buildings which are normally accommodated within the confines of the site boundary, but it is often convenient to consider the design process as being sub-divided into two areas. Firstly, the main station buildings which contain the major plant items and systems such as the steam raising process and turbine-generators, and secondly, the auxiliary supporting systems and services such as the coal handling plant, ash handling plant, cooling water pumps, etc., which are often located around the site outside the main buildings. Whereas the design of the main building is, in the main, independent of site-related factors above foundation level, the design and layout of the major auxiliary systems is often influenced to a significant extent by site-specific features.
The content of this chapter follows this philosophy where, following a review of the major factors influencing the design process and the types of power stations operated by the CEGB, details of the layout considerations, which influence the design of the main plant areas, are given. The following sections of this chapter describe the features which have a major influence on auxiliary equipment and systems.
Chapter
Station design and layout
Publisher Summary
Power stations are complex arrangements of individual plant items, equipment, and mechanical and electrical engineering systems. The term station in its widest sense can be taken to include all the plant equipment, engineering systems, and buildings that are normally accommodated within the confines of the site boundary; however, it is often convenient to consider the design process as being sub-divided into two areas: (1) the main station buildings that contain the major plant items and systems such as the steam raising process and turbine-generators and (2) the auxiliary supporting systems and services such as the coal handling plant, ash handling plant, and cooling water pumps, which are often located around the site outside the main buildings. Coal, oil, and dual-fired (either coal or oil) stations have many similar design features, with the main difference being the type of fuel used to generate steam in the boiler. Coal-fired stations require extensive fuel storage and handling facilities, ash collection, disposal facilities, and larger boilers than oil-fired ones because of the generally lower calorific value of the fuel.
2.1 Basic site requirements
A power station is simply a factory for the conversion of the energy stored in the fuel into electrical energy. The basic requirements for a power station are, therefore, similar to those of any other factory:
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A supply of raw material at a competitive cost (fuel).
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Access to the markets for its products (transmission).
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A labour force of the size and quality required.
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Means of disposal for any trade effluent or byproduct.
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Land for construction and operation.
The raw material from which electricity is made in a thermal power station can be coal, oil, uranium or natural gas. Electricity, the main product, has its own access to centres of consumption through the transmission and distribution system. By-products are ash or irradiated uranium fuel elements and the economic disposal of the former is often a major consideration. The trade effluents are the large quantities of heat, the disposal of which generally requires very large quantities of water which, for cost reasons, must be available close to the site. The products of combustion, in the form of large volumes of flue gases, must also be dispersed without contravening the national clean air policy or causing atmospheric pollution.
The main technical requirements of sites for nuclear and coal-fired stations of the size being considered currently are summarised in Table 1.1.
Power stations that make electricity from renewable sources (wind, waves, sun) can make electricity continuously, so that it is available all the time.
3 Power plants classifications and development
3.1 Power plant classifications
A power station (also called a generating station, powerhouse, generating plant, or power plant) refers to industrial equipment for electric power generation. The classification of TPPs is normally based on the fuel type, types of the thermodynamic cycle, as well as the type of installed prime mover [31,32].
3.1.1 Classifications of power plants based on the types of thermodynamics cycles.
Power plants are classified based on the type of thermodynamics cycle into Carnot Cycle, Atkinson Cycle, Ericsson Cycle, Dual Cycle, Diesel Cycle, Otto Cycle, Brayton Cycle, and Rankine Cycle.
3.1.2 Classifications of power plants based on the fuel types.
Power plants are classified according to the fuel types into conventional and non-conventional. The conventional types include gas turbine PP, steam PP, diesel PP, hydro-electric PP, nuclear PP, while non-conventional types include solar PP, geothermal PP, tidal & wave PP, and wind PP.
3.1.3 Classifications of power plants based on the prime mover types
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Steam turbine plants: The generated dynamic pressure by the expanding steam is channeled to the blades of a turbine. This system is used in almost all large non-hydro plants; steam turbines are used to generate almost 80% of all global electric power [33].
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Gas turbine plants: Turbines are directly operated using the dynamic pressure generated by the flowing gases [34]. Being that natural gas-fired turbine plants can start rapidly, they are normally used to provide “peak” power during high periods of energy demand but at a higher cost compared to the base-loaded plants. As they may be small units compared to other power plants, they are sometimes completely unmanned and operated remotely.
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Combined cycle plants: These power plants are equipped with both a natural gas-fired turbine and a steam boiler & steam turbine. This steam system produces electricity from the hot exhaust gas emitted by the gas turbine, thereby increasing the overall systems’ efficiency. Most of the new baseload power plants are natural gas-fired combined-cycle plants[34].
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Internal combustion reciprocating engines: These are used to generate energy for isolated communities and normally employed for small cogeneration plants. They are also used as a backup power source in public places like hospitals, industrial plants, office buildings, and other critical facilities. They are usually fired by diesel oil, natural gas, landfill gas, and heavy oil [35].
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Microturbines, Stirling engine, and internal combustion reciprocating engines represent cost-effective alternatives for energy generation from opportunity fuels, such as digester gas from wastewater plants and oil production-related waste gas [36].
3.2 Historical development of thermal power Plants.
Thermal power plant development started in 1866 when Werner von Siemens built the first dynamo for power generation. Years later in 1882, Thomas Edison developed the first central power station in New York [37]. In the first steam generators, the generated steam to drive the DC dynamos is either low-pressure saturated or slightly superheated. Table 1 presents the historical trend of thermal power plant development. The thermal efficiency of the first steam turbine-generator developed by Sir Charles Parsons in 1884 was only 1.6%. However, he improved the performance of the steam turbine by incorporating the first condensing turbine to drive the AC generator. His commitment towards building a larger system with more turbines efficiency led to the development of 5-MW condensing steam turbines with 21 thermal efficiencies at the turn of the century, translating to about 15 net power plant efficiency. Nicola Tesla introduced the AC generator technology which paved the way to the emergence of larger central power stations. These larger power stations can be remotely located because of the possibility of transforming and transmitting their AC power-efficient via high-voltage transmission lines [38].
Improvement in the thermal power plant cycle was achieved in the 1910 s with the arrival of turbines with steam extractions for feedwater heating and steam generators equipped with air preheaters. In steam turbines, steam extraction reduces the exhaust flow, and to further increase the unit sizes, larger last-stage blades became available. Two casing turbines were also built with a 2-flow low-pressure (LP) turbine section. The heating of the feedwater with the extracted steam from the turbine improves the performance of the plant cycle, while the use of low-temperature flue gas heat energy in air preheaters to raise the combustion air temperature improves the steam generator efficiency. With the migration to pulverized-coal combustion, it becomes possible to establish a large air preheating temperature difference by simultaneously increasing the combustion air temperature to at least 450℃ [39].
The first once-through boiler applications and reheat steam power plants were introduced in the 1920 s. The once-through boilers were built in the 1940 s by raising the temperature of the main steam to about 610℃, thereby improving the efficiency of the power plant designs. Power plants with dark smoking stacks were considered a sign of prosperity in the 1920 s, but the 1940 s witnessed the initial efforts towards cleaning the flue gas by mechanically removing the dust. Electrostatic precipitators are used for this purpose today with a dust removal efficiency of up to 99.9%. The emergence of more efficient thermal power plants began in the 1950 s through 1960 s with the building of the first once-through steam generator with supercritical main steam pressure. Several pilot plants with main steam pressures and temperature exceeding the supercritical limits of 221 bar and 593℃ respectively, were built [40]. The use of large pulverized coal-fired steam generators and large reheat steam turbines has improved the output of power plants. The once-through boiler technology gained wide acceptance and reheat steam turbines were designed as either tandem or cross-compound units. Some double reheat steam power plants were also built. In the early 1960 s, the first 1000-MW reheat steam turbine was commissioned in New York and its maximum unit ratings of 1300 MW achieved in the early 1970 s. The improvement of the steam condition gave rise to the power plant technology. Hence, there is no much difference in the basics of engineering designs & operation from conventional power plants [13].
With the launch of the first TPPs, great improvements have been achieved on the performance of all power plant components. The thermal efficiency of the first turbine-generator developed by Sir Charles Parsons was only 1.6% and because of this low performance, the system was called “the steam eater”. However, the thermal efficiency of 21% was achieved by a 5-MW Parsons turbine-generator in 1903, translating into a power plant net efficiency of about 15%. This level of power plant efficiency can only be achieved with a condensing steam turbine efficiency of almost 60%. The increase in power plant net efficiency from 15 to 45% is due to the improvements in the Rankine process of power plants, as well as the improvements in the performance of the components of power plants. Table 2 presents the major improvements in power plant performance which has led to this overall level of improvement in performance [51]. The table also presents the major factors that result in improvements in the efficiency of TPPs. Evidently, all the major plant components have experienced certain levels of improvement; however, the adoption of the emission-cleanup systems evidently had negative impacts on the performance of power plants due to the increase in heat and power consumption.
Chapter
Telecommunications
13.2.1 Power station zones
For the purpose of public address broadcasting (and also for operation of the sirens via the siren system described elsewhere), the power station is divided into eight internal zones and one external zone. This facility may be used to minimise interference by public address messages in zones of the power station not affected.
2 Site selection and investigation
2.1 Basic site requirements
A power station is simply a factory for the conversion of the energy stored in the fuel into electrical energy. The basic requirements for a power station are, therefore, similar to those of any other factory:
- •
-
A supply of raw material at a competitive cost (fuel).
- •
-
Access to the markets for its products (transmission).
- •
-
A labour force of the size and quality required.
- •
-
Means of disposal for any trade effluent or byproduct.
- •
-
Land for construction and operation.
The raw material from which electricity is made in a thermal power station can be coal, oil, uranium or natural gas. Electricity, the main product, has its own access to centres of consumption through the transmission and distribution system. By-products are ash or irradiated uranium fuel elements and the economic disposal of the former is often a major consideration. The trade effluents are the large quantities of heat, the disposal of which generally requires very large quantities of water which, for cost reasons, must be available close to the site. The products of combustion, in the form of large volumes of flue gases, must also be dispersed without contravening the national clean air policy or causing atmospheric pollution.
The main technical requirements of sites for nuclear and coal-fired stations of the size being considered currently are summarised in Table 1.1.
5.1 Introduction
Power generating systems are generally treated as heat engines to convert heat input into work, hence to produce electricity at a sustained rate. Heat input is supplied by burning fossil fuels (coal, oil and natural) and biomass, or processing nuclear fuel, or harvesting thermal energy from renewable energy sources. For example, in a conventional coal-fired power plant (the term power station is also used), the energy of coal is eventually converted into power. In general, conventional power stations comprise multiple generating units which are designed to operate at their nominal load when they function optimally.
There are a number of well-known power generating systems denoted as conventional, namely the spark ignition engine, compression-ignition engine, steam Rankine or organic Rankine power plant, combustion turbine power plant, combined cycle power station, nuclear power station, and hydroelectric power station. All these conventional power generating systems (CPGSs) primarily produce mechanical work which is transferred to subsequent systems in the form of shaft rotation. In vehicles, shaft power developed by engines is transferred to the traction system for propulsion. In stationary power plants or generators the shaft power developed by the prime mover is used to rotate an electrical generator which converts the rotational mechanical power to electrical power.
The key component of a CPGS is the prime mover or the organ that produces shaft power. Two types of prime movers are used in CPGSs: positive displacement machines (e.g., reciprocating engines) and turbomachines. Reciprocating machines generally consist of piston-and-cylinder assemblies where the pressure force of an expanding gas is transformed in a reciprocating movement which subsequently is converted into shaft rotation. Turbomachines (turbines) convert kinetic energy of a fluid directly into shaft rotation.
Small-scale CPGS use in general reciprocating prime movers; these are the spark ignition engine and the compression-ignition engine. Large-scale CPGS use turbines as prime movers. The only CPGS which does not use heat as an energy source is the hydroelectric power plant, where hydraulic energy is the input. All other CPGS represent thermomechanical converters and operate based on a specific thermodynamic cycle. The steam Rankine cycle is used in coal-fired, gas-fired, and oil-fired power stations and conventional nuclear power plants. The Brayton cycle is used in gas turbine power plants. A diesel cycle is specific to compression-ignition engines, whereas the spark ignition engine operates based on the Otto cycle.
Any CPGS has its distinct type of equipment. As already mentioned, the most important equipment is the prime mover: steam power plants develop power with the help of steam turbines, gas turbine power plants develop power using specific turbomachinery as the prime mover (this is the gas turbine), hydropower plants use various types of hydraulic turbines, and internal combustion engines use reciprocating piston–cylinder systems for their admission, combustion, compression, and expansion processes, thus generating net work output.
In steam power plants the second major piece of equipment after the steam turbine is the steam generator. Conventional steam generators use to be fired with coal, oil, or natural gas. In a nuclear power plant the steam generator is more specialized, as it is heated using various types of systems aimed at transferring heat from the nuclear reactor to the boiling water in a controlled and safe manner. The specific nuclear-based power generating systems and their power cycles, conventional and advanced, are introduced in Chapter 6 of this book.
In this chapter, the CPGSs are presented in the following order: vapor cycle power plants, gas turbine cycle power plants, gas engines, and hydroelectric power stations. For steam power plants the thermodynamic cycle of steam Rankine type is presented first with various arrangements. Coal-fired power stations with their specific steam generators are then introduced. Organic Rankine cycle (ORC) systems are discussed as a variant of Rankine cycles using an organic working fluid instead of steam. The focus is then shifted to gas turbine cycle power plants with analyses of the air-standard Brayton cycle. The section on internal combustion power generating systems covers information about the Diesel, Otto, Stirling, and Ericson cycles. The last section before chapter’s conclusion discusses hydro power plants. More importantly, the CPGSs and their components are analyzed thermodynamically by writing all balance equations for mass, energy, entropy and exergy, and the performance assessments of these systems and components are carried out by energy and exergy efficiencies as well as other energetic and exergetic performance evaluation criteria.
Power station units with and without on-load tap-changers (factors KS; KG,S; KT,S; and KSO; KG,SO; KT,SO)
A power station unit is defined as the combined generator and its step-up transformer is shown in Figure 7.1. Two cases are considered: the first where the step-up transformer is equipped with an on-load tap-changer and the second where it is not.
2 Problem statement
Given are regions r ∈ R, with power stations k ∈ Kr, parallel generators j ∈ Jk, and discretized capacities of generator p ∈ Pk. There are two types of power stations: existing and potential (power stations. A set of power station designs h ∈ Hk and corresponding operation modes m ∈ Mk,h, time periods (year) t ∈ T, and sub-periods (season) in each year n ∈ N are also given. Specifically, h = 1 indicates that one generator is available in power stations k and h = H means all generators that can be installed in power stations k are available. Likewise, m = 1 represents one generator is operated, m = M refers to the mode in which all generators are operated. Each power station k has different failure states s ∈ Sm,k,h depending on the design h and operation mode m. The failure states can also be classified into successful operation states and partial operation states. ‘Successful operation states’ indicate the operation modes in which the power generation capacity is sufficient to satisfy the load demand, whereas ‘Partial operation states’ refer to the operation modes in which the power generation capacity is insufficient to meet the load demand as it can only produce electric power at a limited level. The major assumptions in this model are: (i) Each power station has a maximum number of available power generators, (ii) Storage systems are not included, (iii) Operational problems such as unit commitment are not included.
