Chapter 17 Energy: Some Basics

History of Energy Crisis’ Greece & Rome – 2500 yrs ago –Energy source ---- WOOD local forests depleted - imported wood from as far as 1000 miles away –Turned to solar energy Built houses facing south Romans – used glass windows to increase effectiveness of solar heat Greenhouses were built to grow veg. in the winter Illegal to build a structure that shaded another TURNED TOWARD SUSTAINABILITY

U. S. Energy History Use of wood in US peaked in 1880’s (coal was widespread and also needed to be burned) Coal use decreased in 1920’s when oil and natural gas became available.

Energy Basics Energy: the ability to do work Potential Energy: energy that is stored (or due to position) Kinetic Energy: energy of motion - All energy is either potential or kinetic

1 st Law of Thermodynamics Energy is neither created nor destroyed, it is transformed Total energy in a system is ALWAYS conserved Types of energy: KE, PE, thermal, chemical, electrical, electrochemical, electromagnetic (light), sound and nuclear.

Example – Tire Swing PE transforms to KE transforms to Heat Energy The QUALITY of energy has also changed The availability of the energy to “do work” has changed. –Increase energy quality = easily does work (ie- oil, n.gas, coal) –Decrease energy quality = more difficult to do work ( heat)

2 nd Law of Thermodynamics Energy always tends to transform from a high quality energy to a lower quality energy –** When you USE energy, you lower its quality

POWER Energy – the ability to do work (W = Fd) Power – the rate at which work is done –Unit for power = Watt –Kilo (1000), Mega (mill.), Giga ( bill.) –A nuclear power plant produces electricity at a rate of 1000 MW or 1GW Power = work/time or energy/time –Therefore energy = power x time –Unit for energy is Watt-hour (Wh) – electricity is sold in KWh (kilowatt-hours)

Energy used annually (KWh/yr) = Power rating X time used in a year –(convert Watts to KW) –READ “A Closer Look 17.1” on page 351 in text – interpret Table 17.2

Energy Efficiency First Law Efficiency –Ratio of amount of energy delivered to amount of energy supplied Ex. A natural gas burning furnace delivers 1 Unit of heat to the house for every 1.5 Units of energy extracted from the burning of the fuel. 1/1.5 =.67 = 67% efficiency Second Law Efficiency –How well matched the energy end use is with the quality of the energy source Compare minimum energy necessary to heat a home with the energy actually used Ex. You could use an acetylene torch to light a candle or a match. The match is more efficient !!!

Energy Sources & Consumption Energy consumption is directly related to a countries “standard of living” – ^ standard of living = ^ energy consumption –US (5% of the world’s pop.) used 25% of all energy consumed in the world –90% of energy consumed in US is fossil fuels –Energy consumption has risen steadily form 1950 to today – with a dip in the 1980’s when energy conservation became popular

Energy Conservation, Increased Efficiency and Cogeneration Conservation: getting by with less demand for energy Energy Efficiency: designing equipment to yield more energy output from a given amount of input energy Cogeneration: a number of processes designed to capture and use waste heat rather than simply to release it into the atmosphere Ex. N.Gas powerplant – produces electricity in two ways: 1- burning gas (gas cycle) 2- heat energy given off by the gas cycle is used to create steam which produces electricity (steam cycle)

Energy Policy Hard Path vs. Soft Path –Hard Path: finding greater amounts of fossil fuels and building larger power plants –Soft Path: involves energy alternatives that emphasize energy quality and flexibility Integrated, Sustainable Energy Management –Integrated Energy Management: no single energy source can provide all the energy required by the world –Sustainable Energy Management: provides reliable sources of energy without causing serious harm, all while ensuring that future generation inherit a fair share of Earth’s resources

Energy Policy Act of 2005 Recommends using coal & n.gas with the objective of reducing our reliance on energy from foreign countries Promotes nuclear power Encourages alternative energy sources Promotes conservation methods – increase efficiency standards in federal bldgs & household product. Promotes research & development – improve coal powerplant emissions Keep up energy infrastructure – dependable electric grids