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All power point images are only for the exclusive use of Phys3070/Envs3070 Spring term 2014

All power point images are only for the exclusive use of Phys3070/Envs3070 Spring term 2014. Web page. //www.colorado.edu/physics/phys3070 /phys3070_sp2014. Today. How much energy do we (the US) consume? In what form? How much of this energy is your share?.

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All power point images are only for the exclusive use of Phys3070/Envs3070 Spring term 2014

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  1. All power point images are only for the exclusive use of Phys3070/Envs3070 Spring term 2014

  2. Web page //www.colorado.edu/physics/phys3070 /phys3070_sp2014

  3. Today How much energy do we (the US) consume? In what form? How much of this energy is your share?

  4. HW #1 due at the beginning of class Wednesday January 22. All further homework is due in class or by CAPA every Monday. 1. ( 8 points) R and K Problem 1.8, amplified A bicyclist on a flat road expends energy at the rate of 60 Watts while traveling at a steady speed of 20 km/hour. a) How many Joules of energy are expended in a ten minute ride? b) How many kilocalories (Cal -the dieticians’ kind) are expended in that ten minutes? c) The rider’s lunch can provide 4 kcal(Cal)/gram. How much lunch was consumed in that ten minutes? Assume 100% efficiency in converting food to biking, which is not the case. d) Where did that energy go? Why did I have to specify a flat road and a steady SPEED? 2. (12 points) R and K problem 11, altered. A windmill on a stormy day with 25 mph winds generates 1500 watts of electrical power that is used to heat water. A bathtub holds 40 gallons of water at 10 deg. C, and you wish to heat that water to 40 deg C. How long will you have to wait? Assume that 100% of the electrical power is converted into heat and that the tub holds all the heat energy you put in without loss.

  5. USA

  6. Table 1.2US Energy Consumption per Person in 2003 Coal 3.7 tons Gas 74,900 ft3 (about ½ of G1B20) Petroleum 23.2 bbl (each bbl = 42 gal) Nuclear 2600 kWh * Renewables 1986 kWh * * ’equivalent thermal energy’

  7. coal 3.7 tons x 2.81 x 10 10 J / ton = 10.397 x 1010 J

  8. Gas • 74,900 ft3 x 1.09 x 109 J/thousand ft3 = 74.9 thousand ft3x 1.09 x 109 J/thousand ft3 =81.641 x 109 J =8.1641 x 10 10 J

  9. Oil 23.2 bbl x 6.12 x 109 Joule/bbl = 141.984 x 10 9 J =14.1984 x 10 10 J

  10. Nuclear 2600 kwh x 3.60 x 106 J/kwh =9360 x 106 J =0.936 x 1010 Joule Ditto renewables 0.717 x 10 10 Joule

  11. So, in 2003--- • Coal gave you 10 x 10 10 J • Gas gave you 8 x 10 10 J • Oil gave you 14 x 1010 J • Nuclear gave you 0.9 x 10 10 J • Renewables gave you 0.7 x 10 10 J (Pencil those onto Table 1.2)

  12. Where did this energy go? Table 1.3 (in 2003) • Electricity 39.0% • Transportation 27.3% • Industrial 22.1% • Residential and commercial 11.6% ( eg: oil/gas heating)

  13. Process heat Heat energy used as heat itself, not electricity or transportation • Smelting iron • Drying grain • Making cement • Heating tar sands to liquify the oil • Heating petroleum to separate the components

  14. The other way around • Almost all transportation uses petroleum • Electicity comes from a wide range of sources

  15. Sources of 2011 US electricitywww.eia.gov, in million kW-hr • Coal 1,733,430 • Gas 1,013,689 • Nuclear 790,204 total 4,047,765 • Hydro 276,240 • Wind 150,822 • Wood 37,799 • Petroleum 30,182 • Waste 19,823 • Geothermal 15,562 • Solar PV 4328

  16. Or, use for numerical answers How many tons of coal did we have to burn to generate that 1,733,430 million kW-hrs?

  17. method Energy content of coal=7800 kW-hr/ton (text) Usage=1,733,430 million kW-hr=1.73x1012 kW-hr Tons = (kW-hr) / (kW-hr/ton) =1.73x1012/7800 =0.0002218 x1012 =2.218 x10-4x1012 =2.218 x108 tons =221.8 million tons of coal (text Fig. 2.7 shows 1060 million tons in 2005) Something is wrong or missing!

  18. Next week Wednesday, HW #1 is due Usages and trends of US energy. Friday, costs and benefits of energy. Using energy to get energy.

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