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Today. US and global energy trends, with a lot of graphical information. HW #1 is due HW #1 solutions www.colorado.edu/physics/phys3070/phy3070_sp14/ All power point images are only for the exclusive use of Phys3070/Envs3070 Spring term 2014. Reporting Energy.

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Today

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  1. Today US and global energy trends, with a lot of graphical information. HW #1 is due HW #1 solutions www.colorado.edu/physics/phys3070/phy3070_sp14/ All power point images are only for the exclusive use of Phys3070/Envs3070 Spring term 2014

  2. Reporting Energy Primary energy, the first fire. Compiled by the IEA=International Energy Agency //www.iea.org 2. End user, where the final benefit of the energy is found. Compiled by the EIA=Energy Information Agency. Text figures, probably. //www.eia.gov (most of the difference is in the generation of electricity)

  3. US Wolfson/Energy,Environment and Climate 2d edition

  4. Primary energy USA World

  5. USA (end use) EIA

  6. = end use Much like text Fig. 1.1

  7. Your Table 1.2=33.6x1010J=319 million BTU

  8. US ‘Nominal’ dollars?

  9. USA—Table 1.2, in J =336 GJ

  10. Getting TWO end usesRecycling an aluminum can Mass of Rolling Rock can = 14.1 grams Wikipedia says the electrical energy needed to turn bauxite ore to the aluminum is 227-342 MJ/kg. 300 MJ/kg * 14.1 grams* 0.001 kg/gram =4.23x106 J Coal holds 2.81 x10 10 Joules/ton, So we need 4.23 x106J/2.81 x1010J/ton =1.51x10-4 ton=1.51 x 10-4ton x 2000 pounds/ton =0.30 pounds of coal (before considering efficiency)

  11. Homework #1 1a) Energy (Joules)=Power (60 Watts) * Time (seconds)=60 J/sec * 10 min * 60 sec/min= 36,000 J b) One calorie (note the lower case) = 4.184 Joules (text, inside front cover),so convert ‘languages’ for energy units--- Energy expended=36,000 J / 4.184 J/cal =8604 cal = 8.604 Cal (kilocal) (ok to say 8.6 Cal) c) Lunch consumed = M(grams) *4 Cal/gram = that energy burned=8.6 Cal, so M=8.6 Cal /( 4 Cal/gram)=2.15 grams (in fact, the process is not very efficient, so the real food energy burned is much larger) d) Level, implies no change in (gravitational) potential energy Constant speed, implies no change in kinetic energy The forces of friction opposing the motion do work equal to that force times the distance travelled. The work to do that mechanical work came from burning lunch.

  12. 2) The total wind energy (power * time) is converted to the same amount of heat energy DQ in the water, which raises the temperature of the water by DT, DQ=mass*DT*specific heat. DQ=1500 Joule/sec * t (unknown time, in seconds) = energy in Joules mass= 40 gallons *3.7854 liter/gallon * 1 kg/liter =151.416 kg of water (the typo in the original table on the inside cover of the text said 3.885 liter/gal, which would make an answer of m=155.4 kg) C=specific heat of water = 1 cal/gram = 1 kcal (Cal)/kg The water heated by 40 -10 = 30 deg C DQ and DT are related by DQ=mass * DT * C, using metric units here, so 1500 * t = 151.416 kg * 30 deg C * 1 kcal/kgdeg C *1000 cal/kcal * 4.184 Joule/cal =19005736 Joules = 1.90 * 107 Joules =1.9E7 in CAPA (note that only metric units enter this, for full orthodoxy, so t will also be in metric units, seconds) t=1.90 * 107 /1500 =12670 sec =3.52 hours. (with the original text conversion of liters per gallon t=13004 sec = 3.61 hr)

  13. Next homework Monday 0900CAPA Pick up your personalpaper copy in the second basement 2. or- go online to find it, at //capa.colorado.edu 3. Work out the answer, clearly, on a piece of paper you can keep. 4. Check that your units are the same as those requested. Translate if necessary 5. Enter your answer 6. Wrong? Go over, rewrite, until you get it right. 7. Save for reference.

  14. CAPA • Go to http://capa.colorado.edu • Select course (phys3070) • Sign in with student ID = 9 digits • Sign in with your personal weekly PIN=4 digits • Select ‘current set’ • From your work sheet, enter your answers in the boxes. No commas. 3.2 x 10-5 = 3.2E-5. If units, use MKS • Press ‘submit all answers’, as many times as you want. If you refresh your page, all answers you entered will vanish, and you will use up one of your tries.

  15. Friday Energy intensity, not in the text. Energy costs of getting energy. New word “EMERGY” Please look this up. //www.greatchange.org/footnotes-emergy.html Cost/benefit ratios Then, next week, specific fossil fuels

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