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Energy, Society, and the Environment

Energy, Society, and the Environment. Unit I: Units, Energy Types, Energy Consumption, Back-of-the-Envelope Estimates. We use A LOT of energy. It is a measure of wealth. It is a measure of wealth. And a measure of attitude. Total Consumption and Sources. Units of Energy.

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Energy, Society, and the Environment

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  1. Energy, Society, and the Environment Unit I: Units, Energy Types, Energy Consumption, Back-of-the-Envelope Estimates

  2. We use A LOT of energy Phys 202 Spring 2009

  3. It is a measure of wealth Phys 202 Spring 2009

  4. It is a measure of wealth Phys 202 Spring 2009

  5. And a measure of attitude Phys 202 Spring 2009

  6. Total Consumption and Sources Phys 202 Spring 2009

  7. Units of Energy • 5 figures from 5 different sources; 4 different units!!! ENERGY • Joule: the energy unit in the meter-kilogram-second system • Calorie: amount of energy needed to heat 1 g of water by 1 degree Celsius (1.8 degrees Fahrenheit) • BTU (British Thermal Unit) -- ACs, furnaces, stoves typically labeled with Btus • Electron-Volt -- important for batteries etc. • Other Frequently Used Energy Units: Barrels of oil equivalent (bboe), kWh Phys 202 Spring 2009

  8. Power • Power = Energy / time Watt = W = Joule/s = J/s You can use energy at a slow rate or a fast rate Any unit of power x any unit of time = energy One such “mixed” unit: kWh Phys 202 Spring 2009

  9. 3600 s 3600 s x x 1 hr = 2 hr = 216 x 103 J = 216 kJ 288 x 103 J = 288 kJ x x 40 60 1 hr 1 hr J J s s Example • Which uses more energy? A 40 W bulb on for two hours or a 60 W bulb on for an hour? How many kWh is each usage? Phys 202 Spring 2009

  10. Energy Consumption, again Phys 202 Spring 2009

  11. Getting Used to Energy Units 1 barrel (bbl) of crude oil = 42 gallons = 6.12 x 109 joules 1 MToe = million tons of oil, equivalent = 1013 joules A useful unit calculator http://www.iea.org/statist/calcul.htm Inside cover of your book is also useful Phys 202 Spring 2009

  12. Unit Conversions Phys 202 Spring 2009

  13. Announcements 1/21 • Assignment 1 is up on the website ice.as.arizona.edu/~fozel/Phys202.html • Please send me e-mail asap if you have any problems accessing it • It is due a week from today! • Get started on your reading • D2L page still not up despite multiple requests • You will be assigned to a Friday discussion section as soon as that happens • We’ll meet in class this Friday Phys 202 Spring 2009

  14. bbl Btu x x 300 x106 people = 58 5.8x106 yrperson bbl 1 x 1017 Btu = 100 QBtu Example • US Oil Consumption: In one source, the per capita consumption for the US is quoted as the equivalent of 58 bbl/yr. In another, we see that the total annual consumption is about 103 QBtus. (That is Quadrillion Btus, as in a million billion, or 1015 Btus.) Are these numbers consistent? Phys 202 Spring 2009

  15. Things to watch out for • Units!!! • If it is energy or power • Whether the source is talking about electricity or total energy consumption • The source of the energy: Different energy generation mechanisms have different outputs Phys 202 Spring 2009

  16. bbl 42 gal $ 3 x = $ 7300 / (yr xperson) x 58 Yr x person bbl gal Example • US Oil Consumption: Estimate the dollar value of the equivalent amount of oil we use annually. Look also at Problem #5 on the handout. Phys 202 Spring 2009

  17. An Electricity Bill Phys 202 Spring 2009

  18. A Natural Gas Bill About $14.00 / 103 ft3 (Some utilities now use therms = 105 Btu) Phys 202 Spring 2009

  19. Example • Economic comparison of energy sources: Using a natural gas bill, electricity bill, and a gas station receipt, find the ratio of the energy cost of electricity to that of natural gas and gasoline. List the three in order of cost. A couple of givens: Natural gas is usually measured in a thousand cubic feet (103 ft3), an amount that produces 1.035 x 106 Btu of energy. 1 gallon of gasoline yields 1.25 x 105 Btu. You may find the conversions listed inside the book cover useful. Phys 202 Spring 2009

  20. US Energy Consumption Energy flow in 2007 from the Department of Energy Petroleum: 39.82 Imported Petroleum: 28.70 Transportation: 29.10 Units: QBtu Phys 202 Spring 2009

  21. Forms of Energy • Potential energy (due to gravity) More energy the higher you lift: h (height) More energy the heavier the rock: m (mass) More energy the stronger the pull: g (gravity) Energy = mass x height x gravity Phys 202 Spring 2009

  22. Gravitational Energy • Hydropower What keeps the cycle going in a dam? (a) Tidal energy (b) The sun’s energy (c) Pumps (d) Winds • Tidal energy: Gravitational interaction between the Earth and the moon Phys 202 Spring 2009

  23. The Water Cycle Phys 202 Spring 2009

  24. Forms of Energy • Kinetic energy: Energy of Moving Things More energy the faster you go: v (velocity) More energy the heavier the man: m (mass) Energy = 0.5 x mass x velocity x velocity Phys 202 Spring 2009

  25. Forms of Energy • Chemical energy: For example, energy of food (or energy from burning a log or burning oil) Generating/Releasing/Storing Chemical Energy: Combustion, batteries, food digestion Phys 202 Spring 2009

  26. Example • Daily calorie needs: How many donuts do you need to eat to meet your daily calorie requirements? A donut has about 34 g carbs (4 cal/g) and 16 g fat (9 cal/g). NOTE: Do not take this as a sound nutritional advice! Phys 202 Spring 2009

  27. Light Energy (a.k.a. electromagnetic radiation) Phys 202 Spring 2009

  28. Nuclear Energy E = mc2 c = 3 x 108 m/s Huge energy release from small mass! Phys 202 Spring 2009

  29. The World Population Phys 202 Spring 2009

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