Lesson 1 Energy Conversion PDF

LESSON 1 – INTRODUCTION TO ENERGY CONVERSION ELT-42 ENERGY CONVERSION JAY-R M. BALLON, EdD Lecturer  2. Define terms used in the study of energy...

LESSON 1 – INTRODUCTION TO ENERGY CONVERSION ELT-42 ENERGY CONVERSION JAY-R M. BALLON, EdD Lecturer  2. Define terms used in the study of energy conversion Specific Objectives 1. Describe the basic 3. Describe various concepts, theory, and sources of energy and principles of energy governing laws for conversion energy Energy Energy is defined as the “capacity of a system to do work”.  common unit used for energy is joule, abbreviated J. Electric utilities bill the energy in kilowatt hours (kWh). A kWh represents “one kW being used for one hour”, and it equals 3.6 MJ of energy. Energy Energy can exist in many forms like heat, light, sound, mechanical, and electrical It cannot be consumed but can be converted from one form to another. Energy? The law of conservation of energy states that energy can neither be created nor be destroyed. Although, it What is the Law of may be transformed from one form to another. If you take all forms of energy Conservation of into account, the total energy of an isolated system always remains In a closed system, i.e., a system that constant. All the forms of energy follow is isolated from its the law of conservation of energy. In surroundings, the total energy of the brief, the law of conservation of energy system is conserved. states that Law of Conservation of Energy Examples: In Physics, most of the inventions rely on the fact that energy is conserved when it is transferred from one form to another. Several electrical and mechanical devices operate solely on the law of conservation of energy. In hydroelectric power plants, waterfalls on the turbines from a height. This, in turn, rotates the turbines and generates electricity. Hence, the potential energy of water is converted into the kinetic energy of the turbine, which is further converted into electrical energy. In a loudspeaker, electrical energy is converted into sound energy.  In a microphone, sound energy is converted into electrical energy. In a generator, mechanical energy is converted into electrical energy. When fuels are burnt, chemical energy is converted into heat and light energy. Chemical energy from food is converted to thermal energy when it is broken down in the body and is used to keep it warm. First Law of Thermodynamics “The First Law of Thermodynamics states that heat is a form of energy, and thermodynamic processes are therefore subject to the principle of conservation of energy.” This means that heat energy cannot be created or destroyed. It can, however, be transferred from one location to another and converted to and from other forms of energy. The second law of  thermodynamics The second law of thermodynamics says that “nature has a tendency towards disordered forms of energy”. This means that converting heat to electricity will not be as efficient as converting electricity to heat. About 60% of the heat energy input to power plants is lost as waste. Conservation of Mechanical Energy According to the principle of conservation of mechanical energy, The total mechanical energy of a system is conserved i.e., “the energy can neither be created nor be destroyed”; it can only be internally converted from one form to another if the forces doing work on the system are conservative in nature.  travelling down the hill, or it can be in the form of “potential energy” as Energy in the case of a skier standing at the Energy can be in the form of “kinetic top of a hill energy” as in the case of a truck  and distance would give the amount of work done or the energy spent during this process. An important thing to remember about gravitational potential energy “mgh”, where m is Potential Energy the mass, g is the gravitational In more general terms, we can defineconstant, and h is the height, is that energy as the work done in moving an the amount of energy stored by object to a certain distance x under a moving a mass to a higher altitude is certain force F. The product of force independent of how (through which path) the mass got to its final position  mass is given by For Kinetic Energy linear motion → E = The kinetic energy mv2/2 stored in a moving motion →E =lω2 /2 Kinetic Energy For rotational  Example When customers demand more power, the rotors of the generators slow down, thus reducing their stored kinetic energy (Figure 1.6). This drop in kinetic energy is converted to electricity to meet the increased load. Eventually, the control system reacts, releasing more steam or water into the turbines driving the generators, which then return to their normal speed. The opposite happens when loads are removed from the system.  Power Station Flywheel Sometimes, a flywheel on the shaft of the generator is intentionally included in the power systems to store energy and meet the sudden load changes without losing much speed (Figure 1.7). Flywheel  Nuclear Energy Nuclear energy is the massive  energy hidden in the nucleus (core) of an atom. Every object in the universe is made of atoms. There is enormous energy in the bonds that hold atoms together (Figure 1.8). If nuclear energy is released, it can be used to generate electricity. From physics, we all know the famous equation of Einstein which relates mass (m) with energy (E) and speed of light (c): E = mc2 This equation describes that if mass can be destroyed, immense amount of energy can be released. When heavy atoms like uranium 235 split under neutron bombardment (process is named fission), the mass of the fragments is less than the mass of the original atom. This way energy is created by the destruction of some of the original mass. This is the principle of operation of all current nuclear power plants (Figure 1.8). Terms to Remember Power - Power is the rate of flow of energy per second, and its unit is watts, which is given by Torque - Force is when you push or pull on an object, whereas torque involves the rotation of the object. Torque is the application of force on an object at a distance so that the object turns (Figure 1.9):  Basic of Torque Torque Application  Torque Torque makes use of the lever principle. It is easier to turn a longer wrench than a shorter  one. That is because less force is needed when it is applied at a larger distance (Figure 1.10). To avoid confusion, the units of torque are usually given as newton meters (Nm) instead of joules. Power is related to torque by the angular speed of rotation: Forms of Energy and Energy Conversions One of the basic types of energy is associated with an object’s motion: kinetic energy. A moving car or a rotating shaft has kinetic energy. Another type of energy, associated with an object’s position, is called potential energy. A stretched spring or a ball positioned above a table has potential energy. Kinetic and potential energy can be classified as forms of mechanical energy. Other forms of energy are listed here:  Nuclear energy. The energy found within the atomic nucleus is nuclear energy. Chemical energy. The fossil fuels as well as food possess chemical energy. Electrical energy. Electrical energy is produced at an electrical power plant or from the batteries in your iPod. Thermal energy. A hot object possesses thermal energy (a function of its mass and its temperature). Light (or radiant) energy. Radiant energy is also called electromagnetic radiation and covers everything from radio and television  waves to infrared radiation to visible light to X-rays. The electromagnetic radiation received from the sun is usually referred to as solar energy. On a microscopic level, all these kinds of energy are examples of kinetic energy or potential energy. The chemical energy stored within oil may be considered as potential energy associated with molecular bonds, which are changed or broken during combustion. Radiant energy and electrical energy may be loosely thought of as related to the kinetic energy of light or electrons, respectively. The thermal energy of an object consists primarily of the sum of the kinetic energy of all the molecules of that object. The transformation of energy from primary sources to end uses usually occurs through one or more energy conversion processes. Electrical energy is not a primary energy source but is the result of a conversion process that began with chemical, nuclear, or solar energy sources. For example, the chemical energy contained in oil is converted into other forms (thermal, electrical, and/or mechanical energy) beginning with combustion. The heat energy released by burning coal in a boiler turns water into steam, which drives a turbine that is connected to a generator to produce electrical energy. Another example of energy conversion occurs in a solar cell. Sunlight impinging on a solar cell produces electricity, which in turn can be used to run an electric motor. Energy is converted from the primary source of solar energy into electrical energy and then into mechanical energy.  FORMS OF ENERGY ENERGY CONVERSIONS  THE ENERGY SOURCES ARE GENERALLY CLASSIFIED INTO TWO CATEGORIES: 1. Non-Renewable Energy Sources  A non-renewable energy source can be defined as a resource that is not replaced on a continuous basis or is replaced only very slowly, but dependent completely on natural processes. - Fossil fuels that are considered non renewable may continually be produced by the decay of plant and animal matter, the rate of their production is so slow that they are not going to be replaced in the next hundred million years, therefore, should be considered “used up”, not available to us again. The following energy sources are considered non-renewable: Petroleum (Oil) Coal Uranium and Natural Gas Thorium (Nuclear Energy 2. Renewable Energy Sources  RESOURCE THAT IS AVAILABLE NATURALLY ON A CONTINUOUS BASIS OR CAN BE CONTINUALLY GENERATED OVER A SHORT PERIOD OF TIME; WHICH MAY BE ON A DAILY BASIS, OR OVER SEVERAL DAYS, OR SEVERAL YEARS. - THE RENEWABLE ENERGY SOURCES ARE DERIVED DIRECTLY FROM THE SUN (SUCH AS THERMAL, PHOTOCHEMICAL, AND PHOTOELECTRIC), INDIRECTLY FROM THE SUN (SUCH AS WIND, HYDROPOWER, AND PHOTOSYNTHETIC ENERGY STORED IN BIOMASS), OR FROM OTHER NATURAL PHENOMENA OF THE ENVIRONMENT (SUCH AS GEOTHERMAL AND TIDAL ENERGY). RENEWABLE ENERGY IS CONSIDERED AS ANY ENERGY - The most common renewable energy sources are: SOLAR ENERGY WIND ENERGY GEOTHERMAL ENERGY HYDROPOWER ENERGY  ENERGY BIOMASS ENERGY OCEAN ELECTRICAL POWER SYSTEMS Electricity usually cannot be generated where it is used. Thus, electric power must be transmitted over the electric power networks. An electrical  power network (Figure 1.20) consists of the following stages: Electricity Transmission Transmission generation (the power must first be generated) transmission (it must then Electricity be transmitted to where it will be used)  distribution (and finally, it must be transmission line, distributed to the users). the received voltage (V) at the load Consider the simple direct current (DC) resistor will be lower than the generator system shown in Figure 1.21 which conveys voltage (E) electrical power to a load R at a distant some power will be lost in the lines. location. If R is the resistance of the L line As can be seen, it is advantageous to convey electrical  power at high voltage levels. This way we can decrease the voltage drop and power loss in the lines. If the voltage E is alternating current (AC), we can raise or lower it by using transformers. If the voltage E is DC, we cannot change the voltage level E with a transformer. That is the main reason why AC is preferred to DC in transmitting electrical power to distant locations. electricity Ability to transmit Why AC is preferred over longer distances with lower losses by vs DC in using transformers. transmitting AC generators are cheaper to build and provides a very cheap, maintain than DC reliable, and rugged generators. motor for the industry. AC induction motor Subtransmission is part of an electric power transmission system that runs at relatively lower voltages compared to transmission voltages. It is uneconomical to connect all distribution substations to the high main transmission voltage, because the equipment would then be larger be more expensive.  VOLTAGE LEVELS IN ELECTRICAL POWER SYSTEMS Transmission voltages between 245 and 765 kV are called extra high voltages (EHVs) Transmission voltages between 115 and 230 kV are called high voltages (HVs). Voltages between 2.4 and 69 kV are called medium voltages (MVs). There is no fixed cutoff between subtransmission and transmission voltages, or sub-transmission and distribution voltages. The voltage ranges may overlap somewhat.  transmission = usually HV or EHV subtransmission = usually HV or MV distribution = usually MV consumer = low voltage (220 V)