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This week---

This week---. Monday: New ideas in transportation- hydrogen, fuel cells, electric cars, hybrid cars Wednesday: Exam 2—Chapters 5-8 Friday: Chapter 9, Air Pollution. Electric car-8.3.1. Run from the burning of coal. ( Exam 1, need to quadruple US coal mining)

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This week---

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  1. This week--- Monday: New ideas in transportation- hydrogen, fuel cells, electric cars, hybrid cars Wednesday: Exam 2—Chapters 5-8 Friday: Chapter 9, Air Pollution

  2. Electric car-8.3.1 • Run from the burning of coal. ( Exam 1, need to quadruple US coal mining) • Multiply efficiency at coal plant x efficiency of car engine • Range • Battery weight • Battery charging time • Battery cycles

  3. Example 15 gallon fuel tank holds 15 x 36.6 kWhr =549 kWhr of energy. a 12 volt battery, charging at 10 amperes, rate 120 W, holding the same energy needs 549 x 103 kW hr = 120 watts x time Time =4575 hours to charge.

  4. The good part At $2.50/gallon, the tank costs $37.50 The electricity at $0.07/kW hr costs $38.43 The gasoline engine has 20% efficiency An electric motor has 80% efficiency.

  5. Hybrid car-8.3.3 • Gasoline engine– for energy density, range • Run at constant speed to generate electricity—greater efficiency • Electric motor runs wheels • Motor=generator, collect energy when slowing or going downhill. • Battery to store the electricity. Enough for a short trip without gasoline.

  6. Direct conversion of fuel to electricity The fuel cell.

  7. Fuel cell efficiency=electric energy out/fuel energy in Burn hydrogen at 25 deg Cmax 83%, useful 50% x motor 80% =40% Internal combustion engine Max (theory) 58 %, useful 20% Battery 90% x motor 80%=72%

  8. Hydrogen 2H2 +O2 2 H2O + energy We can make H2, from coal C +H2OCO + H2 Or natural gas CH4+2H2O CO2 + H2 Or water 2H2O  2H2 + O2 (electrolysis)

  9. Energy density (Table 8.4) • Hydrogen 38,000 Watt hr/kg • Gasoline 13,000 • Battery 25 So the 549 KW-hr example above would require a battery mass of 549,000 /25 Watt-hr/kg = 21,960 kg=22 tonnes !!

  10. Energy densities H2 gas LH2 methane gasoline 10.2 9553 38.5 24,500 MJ/m3 • 114 50.5 34 MJ/kg H2 gas has 1/8 density of natural gas LH2 has 1/10 density of gasoline LH2 – liquid at -253 deg C at atmo. pressure H2 gas tank- 10,000 psi (700 atmospheres)

  11. SWOT Electric car • Strength—short trips • Weakness- heavy, no long trips • Opportunity—battery technology • Threat-accidents

  12. Hybrid • S- combines short range and long range options • W-twice as much machinery • O- fuel cells for efficiency • T- Fragility of fuel cells

  13. Hydrogen S- moves the CO2 problem elsewhere W-no hydrogen mines, energy density O- cheaper hydrogen, fuel cells T- pressures

  14. Exam 2 • Wednesday March 17, Chapters 5-8 • Office hours all day today • See web site for tutorials, old exam, exam 1 key, homework solutions, class slides.

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