Energy system_2018_10_31.pdf - Ajou University Energy System Engineering 2018 10 31 Prof Hui Joon Park(박 희 준 Department of Energy Systems Research

Energy system_2018_10_31.pdf - Ajou University Energy...

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Unformatted text preview: Ajou University Energy System Engineering 2018. 10. 31 Prof. Hui Joon Park (박 희 준) Department of Energy Systems Research Department Electrical and Computer Engineering Office: 에너지센터 206호 Tel: 031‐219‐2577 Email: [email protected] Research group web page: Energy? World: war for energy now ! Energy? What is the Energy? the capacity to do work Human Life with Energy Firepower: fire heat, light Development of energy conversion devices Development of electrical energy Fossil Fuel Depletion of petroleum → cheap petroleum was already depleted. The amount of energy per unit price Petroleum: chemical energy → heat energy ‐ Most efficient energy conversion medium ‐ Various factors affecting the usage of petroleum ‐ Environmental pollution Development of science according to economical issues Alternative energy? ‐ Wind, tidal energy, hydroelectric power ‐ Nuclear energy, solar energy ‐ Natural gas, shale gas, coal ‐ Fuel cell, hydrogen ‐ Energy storage media Gross Understanding on Energy Why gasoline? Any conspiracy? ‐ Gasoline has 15 times higher energy than TNT having the same weight. ‐ Gasoline has 720 times higher energy than bullet (e.g. 20g) 10 kcal/g X 20 g = 836000 J E=1/2mv2 =0.5 x 0.02 (kg) x 340 (m/s)2=1156J [bullet accelerated by explosion of gunpowder (1/720 energy of gasoline) & loss by heat] ‐ Gasoline has 1000 times higher energy than portable battery having the same weight, and 100 times higher energy than battery in laptop. ‐ Commercialization of electric car? energy storage issue → no conspiracy in physics point of view ‐ Coal is 20 times cheaper than gasoline to generate the same amount of energy. ‐ Food → Gasoline: 4 times higher than steak / 2 times than choco‐chip cookie / 1.4 times than butter fluttering of humming bird / difficulty of diet (e.g. 350ml sprite 150 kcal ‐> need exercise 30 min) ‐ Gasoline: 2 times higher energy than coal / 2 times methanol / 1.5 time ethanol / 1.1 time butanol (as biofuel) ‐ Replace gasoline? Natural gas: 1.3 times higher than gasoline / H2 gas: 2.6 times higher than gasoline (but separation issue, burning is cheaper)/ nuclear fission: 2 million times higher than gasoline / H2 nuclear fusion: 6 million times higher than gasoline Alternative Energy Purpose: replace fossil fuel ‐ Utilization of fossil fuel: transportation 25% (gasoline, air fuel), electricity generation 40%, heating (natural gas, coal) 20%, fuel for industry 20%, chemical process 5% ‐ Energy source (in US): petroleum (40%), coal (20%), natural gas (20%), nuclear power (10%), solar/wind etc. 10% Unit price of energy ‐ Coal: 0.4 cents ($ 40/t) ‐ Natural gas: 3.4 cents ($10/280,000m3) ‐ gasoline: 7.5 cents ($ 2.5/gallon) ‐ Battery for car: 21 cents ($50/exchange) ‐ Battery for laptop: 4 dollars ($100/exchange) ‐ AAA battery: 1,000 dollars ($1.5/EA) High price difference: efficiency of utilization (e.g. AAA battery & coal) Alternative energy should be more practical than coal. Coal: cheap ‐> in developing country, not focusing on other factors such as welfare, health, and education Various States of Energy (1) Alternative Energy Resources due to Lack of Fossil Fuel “Nothing Lost, Nothing Created” Antoine Lavoisier (2) Functional Use of Various Energy Forms: Effective Conversion Devices Loss is due to a conversion to unwanted energy state Many State‐of‐ the Art Devices are based on Energy Conversions Thermal Loss CLEFS CEA – No 50/51 Winter 2004‐2005 Energy • Energy conversion engineering has been one of the central themesin the development of the engineering profession. • It is concerned with the transformation of energy from sources such as fossil and nuclear fuels and the sun into conveniently used forms such as electrical energy, rotational and propulsive energy, and heating and cooling. • Then came the oil embargo of the 1970s, high fuel prices….. • The limitations of the Earth’s resources and environment started to come into clearer focus. • The public and legislatures began to recognize that air pollution. • Produced by factories, power plants, and automobiles and other forms of environmental pollution were harmful. Energy • These and other influences have been helping to create a more favorable climate for consideration, if not total acceptance, of energy conversion alternatives and new concepts. • Examples are combined steam and gas turbine cycles, rotary combustion engines, solar and windmill power farms, stationary and vehicular gas turbine power plants, cogeneration, photovoltaic solar power, turbocharged engines, fluidized‐bed combustors, and coal‐gasification power plants. • Some Significant Events in the History of Energy Conversion Energy Energy Energy • Since energy conversion engineering is deeply rooted in thermodynamics, fluid mechanics, heat transfer, and electromagnetics, these disciplines are necessary for understanding, analysis, and design in the field of energy conversion. Energy Energy: Forms and Changes What is energy: Energy is the power to change things. It is the ability to do work. Energy lights our cities, powers our vehicles, and runs machinery in factories. It warms and cools our homes, cooks our food, plays our music, and gives us pictures on television. Joule ‐ A unit of energy. One joule equals 0.2388 calories Nature of Energy ‐ Energy is all around you! You can hear energy as sound. You can see energy as light. And you can feel it as wind. Energy ‐ You use energy when you: hit a softball. lift your book bag. ‐…………... Living organisms need energy for growth and movement ‐ What is energy that it can be involved in so many different activities? Energy can be defined as the ability to do work. If an object or organism does work (exerts a force over a distance to move an object) the object or organism uses energy. ‐ Because of the direct connection between energy and work, energy is measured in the same unit as work: joules (J). ‐ In addition to using energy to do work, objects gain energy because work is being done on them. Energy Heat and Work Heat and Work Are Not Properties Mechanics teaches that work can change the kinetic energy of mass and can change the elevation or potential energy of mass in a gravitational field. Thus work performed by an outside agent on the system boundary can change the energy associated with the particles that make up the system. Likewise, heat is energy crossing the boundary of a system, increasing or decreasing the energy of the molecules within. Thus heat and work are not properties of state but forms of energy that are transported across system boundaries to or from the environment. They are sometimes referred to as energy in transit. Energy conversion engineering is vitally concerned with devices that use and create energy in transit. Energy The main forms of energy are: • Heat : The internal motion of the atoms is called heat energy, because moving particles produce heat. Heat energy can be produced by friction. Heat energy causes changes in temperature and phase of any form of matter. • Chemical: Chemical Energy is required to bond atoms together. And when bonds are broken, energy is released. Fuel and food are forms of stored chemical energy. • Electromagnetic: Power lines carry electromagnetic energy into your home in the form of electricity. Light is a form of electromagnetic energy. Each color of light represents a different amount of electromagnetic energy. Electromagnetic Energy is also carried by X‐rays, radio waves, and laser light. • Nuclear • Mechanical: When work is done to an object, it acquires energy. The energy it acquires is known as mechanical energy. When you kick a football, you give mechanical energy to the football to make it move Energy Energy Conversion: Energy can be changed from one form to another. Changes in the form of energy are called energy conversions. ‐ All forms of energy can be converted into other forms. The sun’s energy through solar cells can be converted directly into electricity. Green plants convert the sun’s energy (electromagnetic) into starches and sugars (chemical energy). ‐ In an automobile engine, fuel is burned to convert chemical energy into heat energy. The heat energy is then changed into mechanical energy. Chemical → Heat → Mechanical ‐ In an electric motor, electromagnetic energy is converted to mechanical energy. ‐ In a battery, chemical energy is converted into electromagnetic energy. ‐ The mechanical energy of a waterfall is converted to electrical energy in a generator. Energy The Law of Conservation of Energy ‐ ‐ Energy can be neither created nor destroyed by ordinary means. It can only be converted from one form to another. If energy seems to disappear, then scientists look for it – leading to many important discoveries. In 1905, Albert Einstein said that mass and energy can be converted into each other. He showed that if matter is destroyed, energy is created, and if energy is destroyed mass is created. (E = MC2) The different sources of energy 1. Fossil fuels 2. Hydro power plant 3. Biomass 4. Wind energy 5. Solar energy 6. Geo thermal energy 7. Ocean thermal energy 8. Tidal energy 9. Wave energy 10. Nuclear energy Energy Energy Energy Energy Energy RENEWABLE‐ NON‐RENEWABLE • RENEWABLE: ‐‐CAN BE REGENERATED IN A RELATIVELY SHORT PERIOD OF TIME; UNLIMITED • NON‐RENEWABLE: ‐‐CAN NOT BE REPLACED IN A SHORT AMOUNT OF TIME; LIMITED Energy Fossil fuels ‐ Coal, oil and gas are called "fossil fuels" because they have been formed from the organic remains of prehistoric plants and animals. ‐ Crude oil (called "petroleum") is easier to get out of the ground than coal, as it can flow along pipes. This also makes it cheaper to transport. ‐ Natural gas provides around 20% of the world's consumption of energy, and as well as being burnt in power stations, is used by many people to heat their homes. It is easy to transport along pipes, and gas power stations produce comparatively little pollution. ‐ Fossil fuels are not a renewable energy resource. Once we've burned them all, there isn't any more, and our consumption of fossil fuels has nearly doubled every 20 years since 1900. This is a particular problem for oil, because we also use it to make plastics and many other products. Energy Biomass • Biomass is a renewable energy resource derived from the carbonaceous waste of various human and natural activities. It is derived from numerous sources, including the by‐products from the timber industry, agricultural crops, raw material from the forest, major parts of household waste and wood. • Biomass does not add carbon dioxide to the atmosphere as it absorbs the same amount of carbon in growing as it releases when consumed as a fuel. Its advantage is that it can be used to generate electricity with the same equipment or power plants that are now burning fossil fuels. • At present, biogas technology provides an alternative source of energy in rural India for cooking. It is particularly useful for village households that have their own cattle. Through a simple process cattle dung is used to produce a gas, which serves as fuel for cooking. The residual dung is used as manure. ‐cIVJuDks Energy Wind energy • Wind energy is the kinetic energy associated with the movement of atmospheric air. It has been used for hundreds of years for sailing, grinding grain, and for irrigation. Wind energy systems convert this kinetic energy to more useful forms of power. • Wind turbines transform the energy in the wind into mechanical power, which can then be used directly for grinding etc., or further converting to electric power to generate electricity. Wind turbines can be used singly or in clusters called ‘wind farms’. Small wind turbines called aero‐generators can be used to charge large batteries. Energy Solar • A solar cell or photovoltaic cell is a machine that converts sunlight directly into electricity by the photovoltaic effect. • Photovoltaics is the field of technology and research related to the application of solar cells in producing electricity for practical use. • Solar heating: Solar heating systems are generally composed of solar thermal collectors, a fluid system to move the heat from the collector to its point of usage. ( ) ‐ The system may use electricity for pumping the fluid, and have a reservoir or tank for heat storage and subsequent use. ‐ The systems may be used to heat water for a wide variety of uses, including home, business and industrial uses. ‐ In many climates, a solar heating system can provide up to 85% of domestic hot water energy. ‐ In many northern European countries, combined hot water and space heating systems are used to provide 15 to 25% of home heating energy. ‐ Energy Ocean Thermal Energy • The main objective of ocean thermal energy or Ocean Thermal Energy Conversion (OTEC) is to turn the solar energy trapped by the ocean into useable energy. • This kind of energy is found in tropical oceans where the water temperature differs from surface to deeper into the sea. On the ocean surface it can be at least 20 oC hotter or cooler than the temperature at a deeper sea level. • Three approaches, open cycle OTEC, closed cycle OTEC and hybrid cycle OTEC have been created in the past fifty years. • The variety of products and services are the major advantage of OTEC plants. Ocean thermal is also relatively clean and will not produce more pollutants that contribute to global warming. • OTEC plants are most suitable for islands around the tropical region of the east Pacific Ocean. This is because OTEC plants can provide both energy and pure water at the same time with a relatively low cost. It is also because the ocean in that region has greater temperature differences, which is about 24 oC. ‐MVg ...
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