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

2. Unit IPhys 202 Spring 2009 We use A LOT of energy

3. Unit IPhys 202 Spring 2009 It is a measure of wealth

4. Unit IPhys 202 Spring 2009 It is a measure of wealth

5. Unit IPhys 202 Spring 2009 And a measure of attitude

6. Unit IPhys 202 Spring 2009 Total Consumption and Sources

7. Unit IPhys 202 Spring 2009 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

8. Unit IPhys 202 Spring 2009 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

9. Unit IPhys 202 Spring 2009 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? 60 J s x 3600 s 1 hr x1 hr =216 x 10 3 J = 216 kJ 40 J s x 3600 s 1 hr x2 hr =288 x 10 3 J = 288 kJ

10. Unit IPhys 202 Spring 2009 Energy Consumption, again

11. Unit IPhys 202 Spring 2009 Getting Used to Energy Units 1 barrel (bbl) of crude oil = 42 gallons = 6.12 x 10 9 joules 1 MToe = million tons of oil, equivalent = 10 13 joules A useful unit calculator http://www.iea.org/statist/calcul.htm Inside cover of your book is also useful

12. Unit IPhys 202 Spring 2009 Unit Conversions

13. Unit IPhys 202 Spring 2009 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

14. Unit IPhys 202 Spring 2009 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 10 15 Btus.) Are these numbers consistent? 58 bbl yr  person xx300 x10 6 people = 1 x 10 17 Btu = 100 QBtu 5.8x10 6 Btu bbl

15. Unit IPhys 202 Spring 2009 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

16. Unit IPhys 202 Spring 2009 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. 58 bbl Yr x person x 42 gal bbl x= $ 7300 / (yr xperson) $ 3 gal

17. Unit IPhys 202 Spring 2009 An Electricity Bill

18. Unit IPhys 202 Spring 2009 A Natural Gas Bill About $14.00 / 10 3 ft 3 (Some utilities now use therms = 10 5 Btu)

19. Unit IPhys 202 Spring 2009 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 (10 3 ft 3 ), an amount that produces 1.035 x 10 6 Btu of energy. 1 gallon of gasoline yields 1.25 x 10 5 Btu. You may find the conversions listed inside the book cover useful.

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

21. Unit IPhys 202 Spring 2009 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

22. Unit IPhys 202 Spring 2009 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

23. Unit IPhys 202 Spring 2009 The Water Cycle

24. Unit IPhys 202 Spring 2009 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

25. Unit IPhys 202 Spring 2009 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

26. Unit IPhys 202 Spring 2009 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!

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

28. Unit IPhys 202 Spring 2009 Nuclear Energy E = mc 2 c = 3 x 10 8 m/s Huge energy release from small mass!

29. Unit IPhys 202 Spring 2009 The World Population