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Hydroelectricity

Hydroelectricity. Hydro Power. Hydro power is the most widely used renewable resource in the world. In US we got 2.9 quad in 2006 (versus 2.6 quad in 1970) This is about 3% of total US energy, about 9% of electricity.

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Hydroelectricity

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  1. Hydroelectricity

  2. Hydro Power Hydro power is the most widely used renewable resource in the world. In US we got 2.9 quad in 2006 (versus 2.6 quad in 1970) This is about 3% of total US energy, about 9% of electricity. Worldwide hydro dominates for some countries (TWh for 2006): Canada (352, 59%), Brazil (345, 84%), Norway (118, 98%), China (431, 16%), Worldwide (2998, 16.6%) South America is about 2/3 hydro (639.6/951.0) http://www.eia.doe.gov/emeu/international/RecentElectricityGenerationByType.xls

  3. Largest Hydro US: Grand Coulee, WA Largest hydro in US is on Columbia River Opened in 1942, expanded through 1974, capacity is 6.8 GW 380 feet hydraulic head; 125 sq miles reservoir 33 turbines, 112 MW to 800 MW size Can do pumped storage (6 x 50 MW units)

  4. Grand Coulee Francis Turbine

  5. Current World’s largest: Three Gorges Dam (14,000 MW)

  6. What Could be Coming: Grand Inga, DR Congo Present Inga dams: 351 MW, 1,424 MW. Under development, Inga III 4,500 MW and Grand Inga 39,000 MW World Bank pledged support on 9/11/09 (est. $80 billion) Total electric consumption in Africa for 2006 is 547 TWh (Canada = 594 TWh) Take out RSA (228TWh) and Egypt (109TWh) 257 TWh for ca. 800 million people (321 kWh per capita)

  7. Hydropower without dam (run of river) Niagara Falls: 50m head, 1.6 MW

  8. The Dalles (2000 MW run of river)

  9. Hydroelectric systems Impoundment involving dams eg. Hoover Dam, Grand Coulee, Three Gorges Diversion or run-of-river systems, e.g. Niagara Falls Pumped storage? two way flow: water pumped up to a storage reservoir and returned for power generation

  10. Hydropower is without opponents, right? Environmental damage? Large reservoirs result in submersion of extensive areas upstream E.g. Three Gorges project displaced 106 people… Increase evaporative losses (big deal at Grand Aswan Dam) Effects of natural flooding removed from system Aquatic ecology: fish (esp. salmon in PNW?), plants, mammals. Health hazards? Water chemistry changes (Mercury, nitrates, oxygen), bacterial and viral infections (malaria, schitosomiasis) Relicensing of dams in question (or breaching actually proposed – see “Lower Snake River” issue) Limited Service Life… Slower/low turbulence water created by dams will cause sedimentation Can reduce usefulness for flood control E.g., Three Gorges Dam has about 70 years lifetime for flood control at current rate of siltation

  11. Hydroelectric facility schematic

  12. Racoon mountain = 1,532 megawatts (4 x 400MW) Z=100m

  13. Micro Hydro (less than 100 kW)

  14. Hydro Setup At top (station A): gross head (HG) = ZA At bottom: net head (HN) Losses: HN=HG-HL Potential Energy A ZA Pressure Kinetic Energy B

  15. Energy in Hydro

  16. Power conversion

  17. Losses… Main losses: • Residual head at turbine (small, see book) • Fluid friction with walls

  18. Hazen-Williams Loss Equation Empirical frictional head loss calculation Q = flow rate [m3s-1] L = length of pipe [m] d = diameter of pipe [m] C = roughness coefficient (PVC = 150, steel = 100)

  19. Pelton Wheel The original impulse turbine by Lester Pelton Water squirts out of nozzles onto sets of “buckets” attached to the rotating wheel Best for high pressure, low flow

  20. Francis Turbine Developed in 1848 High efficiency conversion of high flow rate water

  21. Kaplan • For low head, very high flow (e.g., run of river)

  22. Application of turbines

  23. Turbines Principal concepts in turbine operation: • Kinetic energy of a moving fluid is converted to rotational motion of a shaft • Momentum of fluid lost equals momentum applied to turbine blade • if arranged in cylindrical symmetry, rate of change of angular momentum is torque transferred • Turbine blades deflect fluid • Impulse: energy transferred from “impact” of water on surface • Reaction: energy transferred by “lift” effect

  24. Impulse vs. reaction turbine Images nabbed from F. Gunnerson, M.E., U Idaho

  25. Turbine Design - 2 Approaches 1. Impulse turbines - most common for micro-hydro systems - capture kinetic energy of high-speed jets - high head, low flow 2. Reaction turbines - pressure difference of blades creates a torque - low head, high flow

  26. Usual analysis: Euler’s equation Fluid in at radius r1 with velocity q1 Fluid exits at r2 with velocity q2 Tangential velocity at r1 is Tangential velocity at r2 is For momentum transfer need mass Use density r and flow rate Q Then power transferred is (This is known as Euler’s Turbine Equation)

  27. Pelton Turbine Only possible if space around turbine is not filled with water… Need high pressure (head) to create jet at nozzle

  28. Pelton Turbine (Pleton Wheel) General principle: Water hits cups such that water is deflected backwards

  29. Francis Turbine P is large if the second term disappears i.e., fluid comes in tangentially, leaves radially (makes 90o turn)

  30. Francis control vanes Closed Open Note how vanes guide water flow in direction opposite flow through turbine (but same as turbine rotation direction)

  31. Francis Turbine Developed in 1848 High efficiency conversion of high flow rate water

  32. Midterm • Good work! • Plan for remainder of term: • HW + 1 “project” + Final • GS: (1 talk + 1 paper)=(HW) + Final

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