Energy Systems & Climate Change

1. Energy Systems &Climate Change Thursday 21 Jan. 2010 Ch.10: Wind, Water, Biomass Indirect from the Sun Dr. E.J. Zita zita@evergreen.edu http://academic.evergreen.edu/curricular/energy/0910

2. Overview Questions? Announcements? Logistics … Wind, Water, Biomass (Wolfson Ch.10 & Gore Ch.4, 6) 2:30: Brief Reports: Laura, Crystal, Torie 3:15: Seminar on 1st half of Laboratory Earth (upstairs)

3. Wind, Water, Biomass • Hydropower and hydrologic cycle • Wind power • How the sun drives winds • Coriolus force • Theoretical maxiumum • Biomass and biofuels

4. US net energy production

5. Hydrologic cycle

7. Hydro systems U=mgh

8. Hydropower 23% of incoming solar energy goes to evaporating water on Earth Hydropower is up to 90% efficient, very high energy quality – essentially no thermodynamic limit Hydropower is nearly fully developed in industrialized nations Potential for development x 5 worldwide – but it produces more GHG in tropical areas. + Clean, quiet, “non-polluting” + Pump water up high to store energy - DISCUSS environmental and human impacts

9. Power from Niagara falls 3. The average flow rate in the Niagara River is 6.0×106 kg/s, and the water drops 50 m over the Falls. If all this energy could be harnessed to generate hydro- electric power at 90 percent efficiency (e), what would be the electric power output? Solution: Power = e • Energy/time and Energy = mgh:

10. Wind power 1% of solar energy drives global winds via Temperature and pressure gradients Surface directions steered by Coriolus force

11. Uneven insolation causes…

12. →Warmer tropics …

13. Warmer tropics → lower pressure air by Sanjay Limaye and Rosalyn Pertzborn, University of Wisconsin (http://www.earthscape.org/t1/lis01/lis01aa.html)

14. Low pressure → rising air cools →condensation → precipitation

15. Hadley cells – atmospheric circulation

16. Coriolus force – winds deflect over rotating Earth

17. Total circulation pattern (play ≥)

18. Power in wind

19. Windpower across the US

20. Wind Speed and Power 6. By what factor must the wind speed increase in order for the power carried in the wind to double? Let the initial What happens to the velocity v if you double the power P? Solve for v/v0:

21. Optimal turbine speed

22. 10. (a) Estimate the total energy produced by a wind turbine with the power curve shown in Fig.10.15 during a day when the wind blows at 2 m/s for six hours, at 10m/s for six hours, at 15 m/s for six hours, and at 25 m/s for six hours. (b) What’s the turbine’s average power output over this day?

23. Wind power is rapidly growing

25. Discuss other considerations regarding windpower…

26. Energy payback time • Solar PV: 2 years • Wind: 2-3 months

27. Biomass and biofuels Biomass: wood, waste, plant-derived fuel … Photosynthesis: 6 H2O + 6 CO2 + energy → glucose + 6 O2 • less than 0.1% efficient, but stores 133 TW solar power in plant growth • Plants use half of gross: net primary productivity • Humans use 40% of net pp – too much already. Carbon neutrality requires: • Sustainable production/ harvest • No fossil fuel use (equivalent)

28. Environmental impacts of biofuels WVO?

29. Brief Reports Laura Crystal Torie

30. Ch. 10 HW for next week Questions 1, 2, 3, 5 Exercises 1, 2, 5, 6, 10, 12, 14 Research Problems: 1, 3 Please do Q and RP with your team, and turn in online in WinterWolfson forum. Turn in individual hardcopy exercises before class. Office hours next Wednesday: 3:15 in 3270 Lab II as usual

31. Break time See you at 3:15 upstairs

32. Wolfson Research Problems