TEL322 — Electrical Energy Systems: Lecture Note

About this lecture note

This is the complete lecture note for TEL322 Electrical Energy Systems. You can read it online below, open it in the full viewer, or download the PDF for offline study. It pairs with the course's video lectures, so you can read and watch together.

Preview: opening of the note

Course code: TEL 322 Course title: Electrical Energy Systems Course credit load: 2 Units Series 1: Generation of Electric Energy and Economics of Power Supply • Part 1.1: Introduction to Power Generation o Sub Part 1.1.1: Sources of Energy o Sub Part 1.1.2: Heat Value of Fuels o Sub Part 1.1.3: Thermal Stations: Principle of Operation • Part 1.2: Power Generation Stations o Sub Part 1.2.1: Thermal Stations: Major Components and Efficiency o Sub Part 1.2.2: Hydroelectric Stations o Sub Part 1.2.3: Nuclear Stations • Part 1.3: Economics of Power Supply I o Sub Part 1.3.1: Fixed and Running Charges in Electric Power Production o Sub Part 1.3.2: Load Curves o Sub Part 1.3.3: Load Duration Curves • Part 1.4: Economics of Power Supply II o Sub Part 1.4.1: Base, Intermediate, and Peak Load o Sub Part 1.4.2: Load Factor and Maximum Demand o Sub Part 1.4.3: Diversity Factor and Its Effect on Generation Introduction This is the opening Series of TEL 322: Electrical Energy Systems. This Series lays the foundation for the entire course, introducing how electric energy is generated from various

primary energy sources, before turning to the basic economic concepts used throughout the power industry to plan, operate, and cost electricity generation. The aim of this Series is to equip you with a sound understanding of sources of energy, the heat value of fuels, and thermal stations; hydroelectric and nuclear stations; fixed and running charges, load curves, and load duration curves; and base, intermediate, and peak load, load factor, maximum demand, and diversity factor. We shall commence this Series by examining sources of energy, the heat value of fuels, and the principle of operation of a thermal station. Next, we will consider a thermal station's major components and efficiency, together with hydroelectric and nuclear stations. Following that, our attention turns to fixed and running charges, load curves, and load duration curves. Finally, we will conclude by examining base, intermediate, and peak load, load factor, maximum demand, and diversity factor. Series Learning Outcomes Upon completing this Series, you should be able to: • SLO 1.1: identify sources of energy and calculate the heat value of fuels, • SLO 1.2: describe the principle of operation of a thermal power station, • SLO 1.3: describe the major components and efficiency of a thermal station, • SLO 1.4: describe hydroelectric and nuclear power stations, • SLO 1.5: describe fixed and running charges in electric power production, • SLO 1.6: describe load curves and load duration curves, • SLO 1.7: define base, intermediate, and peak load, and calculate load factor and maximum demand, • SLO 1.8: define diversity factor and explain its effect on generation. 1.1 Introduction to Power Generation 1.1.1 Sources of Energy Electric energy is generated by converting some other, primary form of energy into electrical form, and the sources of this primary energy are broadly classified as conventional sources, such as coal, oil, natural gas, and falling water, which have historically supplied the great majority of the world's electricity, and non-conventional (renewable) sources, such as solar,

wind, geothermal, and tidal energy, whose contribution has grown considerably in recent decades. Conventional sources are further divided into exhaustible (non-renewable) sources, such as coal, oil, and natural gas (collectively called fossil fuels) and nuclear fuel, which exist in a finite, depleting quantity, and renewable sources, such as falling water, which are naturally replenished and can, in principle, supply energy indefinitely without depletion. Worked example: A power utility compares two candidate energy sources for a new generating station: coal, an exhaustible fossil fuel requiring continuous purchase and transport, and a nearby river's falling water, a renewable source requiring only the initial dam and turbine investment, illustrating the fundamental economic trade-off between exhaustible and renewable energy sources. Application: Understanding the classification of energy sources as conventional or non-conventional, and exhaustible or renewable, is the essential starting point for national energy policy and long-term power system planning, since the balance chosen directly affects a country's energy security, cost of electricity, and environmental impact. Fill in the blank: Coal, oil, and natural gas are collectively called ________ fuels. Falling water is a ________ source, naturally replenished over time. 1.1.2 Heat Value of Fuels The heat value (or calorific value) of a fuel is the quantity of heat energy released when a unit mass (or unit volume, for a gas) of that fuel is completely burned, conventionally expressed in kilojoules per kilogram (kJ/kg) for solid and liquid fuels, and is the essential quantity used to compare different fuels' energy content and to calculate the fuel required to generate a given amount of electrical energy. A fuel's heat value is measured as either its higher heating value (HHV), which includes the additional heat recovered by condensing the water vapour produced during combustion, or its lower heating value (LHV), which excludes this condensation heat since it is not normally recoverable in a conventional power station, with the LHV consequently always somewhat lower than the HHV for the same fuel. Worked example: A thermal station burns coal with a heat value of 25,000 kJ/kg to generate 100,000,000 kJ of heat energy. The mass of coal required is 100,000,000 kJ / 25,000 kJ/kg = 4000 kg. Application: A fuel's heat value is the essential quantity used throughout thermal power station design and operation to calculate fuel consumption rates, fuel storage and transport requirements, and the overall cost of fuel per unit of electricity generated.

Fill in the blank: Heat value is conventionally expressed in ________ per kilogram for solid and liquid fuels. The lower heating value excludes the heat recoverable from condensing ________ vapour. 1.1.3 Thermal Stations: Principle of Operation A thermal power station generates electricity by burning a fuel to produce heat, which converts water into high-pressure steam in a boiler, with that steam then expanded through a turbine to produce mechanical rotational energy, which finally drives a synchronous generator to produce electrical energy, a sequence of energy conversions following what is known as the Rankine thermodynamic cycle. After passing through the turbine, the low-pressure exhaust steam is cooled and condensed back into liquid water in a condenser, typically using water drawn from a nearby river or sea, before being pumped back into the boiler to repeat the cycle, and the overall thermal efficiency of this complete cycle, the ratio of electrical energy output to fuel heat energy input, is fundamentally limited by the laws of thermodynamics to well below 100%. Worked example: A thermal station burns fuel releasing 1000 MJ of heat energy and produces 350 MJ of electrical energy output. The station's thermal efficiency is 350/1000 = 35%, a typical figure for a conventional coal-fired thermal station. Application: Understanding the Rankine cycle's sequence, boiler, turbine, generator, and condenser, is essential for identifying where efficiency losses occur within a thermal station, and for understanding why the condenser's cooling water supply is as critical to a thermal station's siting as its fuel supply. Fill in the blank: In a thermal station, steam produced in the boiler is expanded through a ________ to produce mechanical energy. The condenser converts low-pressure exhaust steam back into ________ water. Figure 1.1: The Rankine cycle of a thermal power station.

Pilot questions 1.1 1. Distinguish between conventional and non-conventional energy sources. (Linked to SLO 1.1) 2. Define the heat value of a fuel. (Linked to SLO 1.1) 3. Distinguish between higher and lower heating value. (Linked to SLO 1.1) 4. Describe the Rankine cycle. (Linked to SLO 1.2) 5. State the function of a condenser in a thermal station. (Linked to SLO 1.2) 1.2 Power Generation Stations 1.2.1 Thermal Stations: Major Components and Efficiency A thermal power station's major components include the boiler (or steam generator), which burns fuel to produce steam; the turbine, which extracts mechanical energy from the expanding steam; the alternator (synchronous generator), which converts this mechanical energy into electrical energy; the condenser, which recovers the exhaust steam as water; and the feedwater and fuel handling systems, which support the continuous operation of the entire cycle. A thermal station's overall efficiency is reduced not only by the fundamental thermodynamic limits of the Rankine cycle itself, but also by auxiliary power consumption, the electrical power the station itself consumes to run its own pumps, fans, and control systems, so that the station's net efficiency, based on power actually delivered to the grid, is somewhat lower than its gross efficiency, based on the alternator's total output. Worked example: A thermal station's alternator produces a gross output of 500 MW, of which 25 MW is consumed by the station's own auxiliary equipment. The net power delivered to the grid is 500 − 25 = 475 MW. Application: Distinguishing between a thermal station's gross and net efficiency, and correctly accounting for auxiliary power consumption, is essential for accurately calculating a station's true fuel cost per unit of electricity actually delivered to consumers. Fill in the blank: A thermal station's boiler burns fuel to produce ________. Net efficiency accounts for ________ power consumption, unlike gross efficiency. 1.2.2

This is the opening of the note. Read the full note or download the PDF to continue.