Download
1 / 33
330 likes | 406 Vues
Energy. Energy and Work. Energy is the ability to do work. Work is that which causes change. Laws of Thermodynamics – Energy Conservation.
E N D
Energy and Work • Energy is the ability to do work. • Work is that which causes change.
Laws of Thermodynamics – Energy Conservation • Energy cannot be created or destroyed. The total amount of energy in the universe never changes. It can change from one form to another, but it never ceases to exist. • Eventually all energy, as it is used, becomes so random that it loses the ability to do work. This is also called entropy.
Types of Energy • Potential energy is energy that is waiting to happen. It is waiting to have motion. • Potential energy of position…gravity. • Potential energy of form…twisting, bending, stretching a material out of its natural shape. • Kinetic energy is described as energy in motion. Any object in motion has kinetic energy.
Forms of Energy • Light • Heat • Mechanical • Chemical • Electrical • Nuclear
Light Energy • Light energy is a small part of the electromagnet spectrum that we can see. • Light travels at about 186,000 miles per second. • Photosynthesis is the process plants use to convert light energy into food for growth.
Heat Energy • Heat energy, also called thermal energy, is the energy produced by movement of molecules in our surroundings. • One Btu is the amount of heat energy needed to raise the temperature of one pound of water one degree Fahrenheit. • Friction is a form of heat energy. Friction is created by two surfaces rubbing against each other.
How Heat Travels… • Radiation – heat energy through wavelengths. • Convection – is the movement within liquids and gases. The heat travels by circulation of heated liquid and air. • Conduction – is heat travel produced by molecular action. Warmer molecules bump into cooler ones and give some of their heat to slower moving cool molecules.
Mechanical Energy • Mechanical energy is the energy of motion. • Any object that can be observed in motion possesses mechanical energy. • All transportation systems are capable of, and rely on, mechanical energy.
Chemical Energy • Chemical energy is locked away in the molecules of many kinds of substances. • Gasoline, oil, food, are all examples of substances that contain chemical energy.
Electrical Energy • Electrical energy is the movement of electrons. • The negatively charged particles are electrons, the positively charged particles are protons. • The attraction between them causes a flow of electrons.
Nuclear Energy • Nuclear energy is that energy which is stored in atoms. • Nuclear energy is released when certain kinds of atoms are split or fused together. • Fission is the splitting of atoms. This is the type of reaction in current nuclear reactors. Uranium-235 is the most common fuel for nuclear fission. • Fusion involves the joining of atoms.
Sources of Energy • Renewable • Nonrenewable • Inexhaustible
Renewable • Renewable energy resources are those energy sources that can be replaced as needed. • Renewable energy resources can be grown and collected or harvested time after time. • Examples: Plants and Animals
Nonrenewable • Nonrenewable energy resources are those sources that cannot be replaced. • Nonrenewable energy resources have a limited supply. • Examples: Fossil Fuels and Uranium
Inexhaustible • Inexhaustible energy sources exist in such large quantities that they will never (in all practical purposes) run out. • Examples: Sun, Wind, Water
Modern Energy Conversions Some Examples… • Mechanical to electrical – generators and alternators. • Electrical to mechanical – electric motors. • Chemical to electrical – battery power to power a radio. • Electrical to chemical – when rechargeable batteries are recharged. • Light to electrical – photovoltaic cells.
Power and Power Systems • Power is the amount of work being done over a period of time. • A power system is a machine that does energy conversions. • Basic Power Systems • Electrical systems • Mechanical systems • Fluid systems • Heat systems
Elements of a Power System • A source of energy. • A conversion method. • A method of transmission. • A control system. • Measuring devices. • Output or load. • Losses.
Power System – Energy Source • Constant energy sources is one that is always on hand day or night. • Fossil Fuels • Changeable energy sources are available only some of the time. • Wind • Solar
Power System – Conversion of Energy • Energy may need to be converted from one form to another to become usable. • Automobile engine • Photovoltaic cells • Water turbines
Power System -- Transmission • Transmission is the act of moving the power from the source to the load. • Fluid linkage • Electrical linkage • Direct mechanical linkage
Power System -- Control Controls in power systems do three things: • Turn power on and off. • Regulate speed, stop movement, or cause some other change in the way power is applied. • Control direction. For Example • Switches • Throttles
Power System -- Measurement Measurement may: • Determine the amount of energy in the system. • Determine how much work the system is doing. • Determine how fast work is being done. Examples • Meters • Gauges
Power System – Output/Load • The load of the power system is the useful output. • A load is the work done by the system. • It is the goal of the system.
Power System -- Losses • Losses are the unwanted output of the power system. • Losses are the result of the conversion of energy from one form to another. Example: • Unwanted heat
Work = Distance x Force Power = work/time Horsepower = work/(time in minutes x 33,000) Torque = Force x Distance Velocity = Distance in the same direction/time Acceleration = Change in velocity/time Efficiency % = (Energy Out/Energy In) x 100 Pressure = Force/Area Voltage = Amperage x Resistance Wattage = Amperage x Voltage Some Useful Formulas
Energy is the ability to do work. Power is the amount of work being done. Watts is the measurement of power produced from a device or system. Amperage is the measure of the rate of electron flow (current). Voltage is the pressure pushing the current through the conductor. Resistance is the opposition to current flow through a conductor. Some Terms Explained
Energy • Sectors • Residential • Commercial • Industrial • Transportation
United States Energy Flow Schwaller, A. E. and Gilberti, A. F. (1996). Energy Technology: Sources of Power. Cincinnati, Ohio:TLT.
Energy Used in Transportation • Most of the energy used in the transportation sector comes from fossil fuels. • Over half of the oil in the U.S. is used in the transportation sector. • We need to start incorporating renewable and inexhaustible resources in the transportation sector.
