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Hydroelectric Power

Hydroelectric Power. Overview Indirect solar power: rainfall at elevation Largest form of renewable energy in world – over 90% of renewable electricity Hydro not “renewable energy”? Virtually 100% of hydro power is for electricity generation 16% of global electricity supply in 2002.

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Hydroelectric Power

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  1. Hydroelectric Power • Overview • Indirect solar power: rainfall at elevation • Largest form of renewable energy in world – over 90% of renewable electricity • Hydro not “renewable energy”? • Virtually 100% of hydro power is for electricity generation • 16% of global electricity supply in 2002 PSE 104 Section 2: Lecture 9

  2. Energy from Biomass PSE 104 Section 2: Lecture 9

  3. Hydroelectric Power • Overview • Indirect solar power: rainfall at elevation • Largest form of renewable energy in world – over 90% of renewables • Hydro not “renewable energy”? • Virtually 100% of hydro power is for electricity generation • 16% of global electricity supply in 2002 PSE 104 Section 2: Lecture 9

  4. Hydroelectric Power • History • First ‘hydro power’ for pumping water and milling grain (similar to wind energy) – mechanical power • Waterwheel power used for shaft work: papermills, textiles mills, etc. • Rittenhouse papermill, Germantown, PA 1690 PSE 104 Section 2: Lecture 9

  5. Hydroelectric Power Waterwheels PSE 104 Section 2: Lecture 9

  6. Hydroelectric Power • History • First known use of hydro for electricity: 1881 in UK - waterwheel power on river River Wey • Very fast growth into 20th century: public power and power grid established • Recognized that hydro was tremendous resource for electricity generation • Key to growth: availability of hydraulic turbine • Fourneyron (UK): outward flow turbine • 80% efficiency • Francis (USA): inward flow turbine PSE 104 Section 2: Lecture 9

  7. Hydroelectric Power Fourneyron turbine PSE 104 Section 2: Lecture 9

  8. Hydroelectric Power Francis turbine PSE 104 Section 2: Lecture 9

  9. Hydroelectric Power • Hydro Power Fundamentals • Based on potential energy (pe) due to elevation and effect of gravity • For hydro power, need source of flowing water • pe = (masswater)(height)(gravity) = MgH • (kg)(m/sec2)(m) = (kg–m)(m) = (Newton)(m) = 1 Joule sec2 • Power must be a function of volume flow of water (Q) • Q = m3/sec • Power (P) = Energy per unit time • P = (ρ)(Q)(g)(H) = (kg/m3)(m3/sec)(m/sec2)(m) = N-m/sec = Joules/sec = watts PSE 104 Section 2: Lecture 9

  10. Hydroelectric Power • Hydro Power Fundamentals • For water where ρ= 1000 kg/m3 , P = (1000)(Q)(H) • Efficiency (η) = electrical output < 100% mechanical input Efficiency = 75% – +95% for hydroelectric turbines • Effective Power using water = (η)(1000)(Q)(H) = W • Power in kW = (η)(10)(Q)(H) PSE 104 Section 2: Lecture 9

  11. Hydroelectric Power • Hydro Power Fundamentals • Available Head = usable height of water in reservoir • Related to pressure energy of stored water = (ρ)(g)(H) • Presure = Force per unit area, i.e. lb/in2 = psi • (ρ)(g)(H)= (kg/m3) (m/sec2)(m) = N/m2 • Turbine types and efficiencies vary with head PSE 104 Section 2: Lecture 9

  12. Hydroelectric Power • Hydro Power Fundamentals PSE 104 Section 2: Lecture 9

  13. Hydroelectric Power • Hydro Power Fundamentals • “High Head” dam: high usable potential energy • Does not necessarily need high water flowrates (Q) for sufficient power generation • High pressures at outflow requires high construction costs • “Low Head” dam: low usable potential energy • Must have high water flowrates for reasonable power generation • Difference between tidal barrage and low head dam: variable water head in tidal barrage • Causes periodic power “spikes” as opposed to continuous power generation PSE 104 Section 2: Lecture 9

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