chapter 17 energy: some basics. history of energy crisis’ greece & rome – 2500 yrs ago...
TRANSCRIPT
Chapter 17
Energy: Some Basics
History of Energy Crisis’• Greece & Rome – 2500 yrs ago
– Energy source ---- WOODlocal 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
1st 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)
2nd 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